<myipaddress>

1.2.3.4

$ whoami

# whoami

0:0:0:0:0:ffff:a.b.c.d/96

::ffff:a.b.c.d/96

::ffff:1.2.3.4

0:0:0:0:0:0:a.b.c.d/96

::a.b.c.d/96

3ffe:

3ffe:ffff:100:f102::1

3ffe:ffff: 

2002:

2002:c0a8:0101:5::1

ipv4="1.2.3.4"; sla="5"; printf "2002:%02x%02x:%02x%02x:%04x::1" `echo $ipv4
¬ | tr "." " "` $sla

2001:

3fff:ffff::/32
2001:0DB8::/32   EXAMPLENET-WF

ff02::1:ff00:1234

2001:db8:100:f101:210:a4ff:fee3:9566/64  <- Node's address

2001:db8:100:f101::/64  <- subnet-router anycast address

alias net-pf-10 ipv6  # automatically load IPv6 module on demand

alias net-pf-10 off   # disable automatically load of IPv6 module on demand

# ping6 fe80::212:34ff:fe12:3456 
connect: Invalid argument

# ping6 -I eth0 -c 1 fe80::2e0:18ff:fe90:9205 
PING fe80::212:23ff:fe12:3456(fe80::212:23ff:fe12:3456) from
¬ fe80::212:34ff:fe12:3478 eth0: 56 data bytes 
64 bytes from fe80::212:23ff:fe12:3456: icmp_seq=0 hops=64 time=445 usec

--- fe80::2e0:18ff:fe90:9205 ping statistics --- 
1 packets transmitted, 1 packets received, 0% packet loss round-trip
¬ min/avg/max/mdev = 0.445/0.445/0.445/0.000 ms

# ping6 -I eth0 ff02::1
PING ff02::1(ff02::1) from fe80:::2ab:cdff:feef:0123 eth0: 56 data bytes
64 bytes from ::1: icmp_seq=1 ttl=64 time=0.104 ms
64 bytes from fe80::212:34ff:fe12:3450: icmp_seq=1 ttl=64 time=0.549 ms (DUP!) 

# tcpdump -t -n -i eth0 -s 512 -vv ip6 or proto ipv6 
tcpdump: listening on eth0 
2001:0db8:100:f101:2e0:18ff:fe90:9205 > 2001:0db8:100:f101::1: icmp6: echo
¬ request (len 64, hlim 64) 
2001:0db8:100:f101::1 > 2001:0db8:100:f101:2e0:18ff:fe90:9205: icmp6: echo
¬ reply (len 64, hlim 64)

# tcpdump -t -n -i ppp0 -s 512 -vv ip6 or proto ipv6 
tcpdump: listening on ppp0 
1.2.3.4 > 5.6.7.8: 2002:ffff:f5f8::1 > 2001:0db8:100::1: icmp6: echo request
¬ (len 64, hlim 64) (DF) (ttl 64, id 0, len 124) 
5.6.7.8 > 1.2.3.4: 2001:0db8:100::1 > 2002:ffff:f5f8::1: icmp6: echo reply (len
¬ 64, hlim 61) (ttl 23, id 29887, len 124) 
1.2.3.4 > 5.6.7.8: 2002:ffff:f5f8::1 > 2001:0db8:100::1: icmp6: echo request
¬ (len 64, hlim 64) (DF) (ttl 64, id 0, len 124) 
5.6.7.8 > 1.2.3.4: 2001:0db8:100::1 > 2002:ffff:f5f8::1: icmp6: echo reply (len
¬ 64, hlim 61) (ttl 23, id 29919, len 124)

$ ssh -6 ::1 
user@::1's password: ****** 
[user@ipv6host user]$

# ip -6 route show | grep ^default
default via fe80::212:34ff:fe12:3450 dev eth0 proto kernel metric 1024 expires
¬ 29sec mtu 1500 advmss 1440

|   3+13   |    32     |    16  |            64 bits             | 
+---+------+-----------+--------+--------------------------------+ 
|  FP+TLA  |  V4ADDR   | SLA ID |           Interface ID         | 
|  0x2002  |           |        |                                | 
+---+------+-----------+--------+--------------------------------+

# /sbin/ip tunnel add <device> mode sit ttl <ttldefault> remote
¬ <ipv4addressofforeigntunnel> local <ipv4addresslocal>

# /sbin/ip tunnel add sit1 mode sit ttl <ttldefault> remote
¬ <ipv4addressofforeigntunnel1> local <ipv4addresslocal>
# /sbin/ip link set dev sit1 up
# /sbin/ip -6 route add <prefixtoroute1> dev sit1 metric 1

# /sbin/ip tunnel add sit2 mode sit ttl <ttldefault>
¬ <ipv4addressofforeigntunnel2> local <ipv4addresslocal>
# /sbin/ip link set dev sit2 up
# /sbin/ip -6 route add <prefixtoroute2> dev sit2 metric 1

# /sbin/ip tunnel add sit3 mode sit ttl <ttldefault>
¬ <ipv4addressofforeigntunnel3> local <ipv4addresslocal>
# /sbin/ip link set dev sit3 up
# /sbin/ip -6 route add <prefixtoroute3> dev sit3 metric 1

# /sbin/ifconfig sit0 up

# /sbin/ifconfig sit0 tunnel <ipv4addressofforeigntunnel1>
# /sbin/ifconfig sit1 up
# /sbin/route -A inet6 add <prefixtoroute1> dev sit1

# /sbin/ifconfig sit0 tunnel <ipv4addressofforeigntunnel2>
# /sbin/ifconfig sit2 up
# /sbin/route -A inet6 add <prefixtoroute2> dev sit2

# /sbin/ifconfig sit0 tunnel <ipv4addressofforeigntunnel3>
# /sbin/ifconfig sit3 up
# /sbin/route -A inet6 add <prefixtoroute3> dev sit3

# /sbin/ifconfig sit0 up

# /sbin/route -A inet6 add <prefixtoroute1> gw
¬ ::<ipv4addressofforeigntunnel1> dev sit0
# /sbin/route -A inet6 add <prefixtoroute2> gw
¬ ::<ipv4addressofforeigntunnel2> dev sit0
# /sbin/route -A inet6 add <prefixtoroute3> gw
¬ ::<ipv4addressofforeigntunnel3> dev sit0

# /sbin/ip tunnel del <device>

# /sbin/ip -6 route del <prefixtoroute1> dev sit1
# /sbin/ip link set sit1 down
# /sbin/ip tunnel del sit1

# /sbin/ip -6 route del <prefixtoroute2> dev sit2
# /sbin/ip link set sit2 down
# /sbin/ip tunnel del sit2

# /sbin/ip -6 route del <prefixtoroute3> dev sit3
# /sbin/ip link set sit3 down
# /sbin/ip tunnel del sit3

# /sbin/route -A inet6 del <prefixtoroute3> dev sit3
# /sbin/ifconfig sit3 down

# /sbin/route -A inet6 del <prefixtoroute2> dev sit2
# /sbin/ifconfig sit2 down

# /sbin/route -A inet6 add <prefixtoroute1> dev sit1
# /sbin/ifconfig sit1 down

# /sbin/ifconfig sit0 down

# /sbin/route -A inet6 del <prefixtoroute1> gw
¬ ::<ipv4addressofforeigntunnel1> dev sit0
# /sbin/route -A inet6 del <prefixtoroute2> gw
¬ ::<ipv4addressofforeigntunnel2> dev sit0
# /sbin/route -A inet6 del <prefixtoroute3> gw
¬ ::<ipv4addressofforeigntunnel3> dev sit0

# /sbin/ifconfig sit0 down

# /sbin/ip tunnel add tun6to4 mode sit ttl <ttldefault> remote any local
¬ <localipv4address> 

# /sbin/ip link set dev tun6to4 up 

# /sbin/ip -6 addr add <local6to4address>/16 dev tun6to4 

# /sbin/ip -6 route add 2000::/3 via ::192.88.99.1 dev tun6to4 metric 1

# /sbin/ip -6 route add 2000::/3 via 2002:c058:6301::1 dev tun6to4 metric 1

# /sbin/ifconfig sit0 up 

# /sbin/ifconfig sit0 add <local6to4address>/16

# /sbin/route -A inet6 add 2000::/3 gw ::192.88.99.1 dev sit0

# /sbin/ip -6 route flush dev tun6to4

# /sbin/ip link set dev tun6to4 down

# /sbin/ip tunnel del tun6to4 

# /sbin/route -A inet6 del 2000::/3 gw ::192.88.99.1 dev sit0

# /sbin/ifconfig sit0 del <local6to4address>/16

# /sbin/ifconfig sit0 down 

# cat /proc/sys/net/ipv6/conf/all/forwarding
0

# echo "1" >/proc/sys/net/ipv6/conf/all/forwarding

# sysctl net.ipv6.conf.all.forwarding
net.ipv6.conf.all.forwarding = 0

# sysctl -w net.ipv6.conf.all.forwarding=1
net.ipv6.conf.all.forwarding = 1

# sysctl -w net.ipv4.ip_local_port_range="32768 61000"
net.ipv4.ip_local_port_range = 32768 61000

ZEBRA: netlink-listen error: No buffer space available, type=RTM_NEWROUTE(24),
¬ seq=426, pid=0

15:43:49.484751 fe80::212:34ff:fe12:3450 > ff02::1: icmp6: router
¬ advertisement(chlim=64, router_ltime=30, reachable_time=0,
¬ retrans_time=0)(prefix info: AR valid_ltime=30, preffered_ltime=20,
¬ prefix=2002:0102:0304:1::/64)(prefix info: LAR valid_ltime=2592000,
¬ preffered_ltime=604800, prefix=2001:0db8:0:1::/64)(src lladdr:
¬ 0:12:34:12:34:50) (len 88, hlim 255)

15:44:21.152646 fe80::212:34ff:fe12:3456 > ff02::2: icmp6: router solicitation
¬ (src lladdr: 0:12:34:12:34:56) (len 16, hlim 255)

15:44:17.712338 :: > ff02::1:ff12:3456: icmp6: neighbor sol: who has
¬ fe80::212:34ff:fe12:3456(src lladdr: 0:12:34:12:34:56) (len 32, hlim 255)

15:44:21.905596 :: > ff02::1:ff12:3456: icmp6: neighbor sol: who has
¬ 2002:0102:0304:1:212:34ff:fe12:3456(src lladdr: 0:12:34:12:34:56) (len 32,
¬ hlim 255)

15:44:22.304028 :: > ff02::1:ff12:3456: icmp6: neighbor sol: who has
¬ 2001:0db8:0:1:212:34ff:fe12:3456(src lladdr: 0:12:34:12:34:56) (len 32, hlim
¬ 255)

13:07:47.664538 2002:0102:0304:1:2e0:18ff:fe90:9205 > ff02::1:ff00:10: icmp6:
¬ neighbor sol: who has 2001:0db8:0:1::10(src lladdr: 0:e0:18:90:92:5) (len 32,
¬ hlim 255)

13:11:20.870070 fe80::2e0:18ff:fe90:9205 > ff02::1:ff00:10: icmp6: neighbor
¬ sol: who has fe80::10(src lladdr: 0:e0:18:90:92:5) (len 32, hlim 255)

IP6ADDR="<ipv6-address>/<prefix>"

IPADDR="<ipv6-address>/<prefix>"

# ip6tables -L 

# ip6tables -n -v --line-numbers -L 

# ip6tables -n -v --line-numbers -L INPUT 

# ip6tables --table filter --append INPUT  -j LOG --log-prefix "INPUT:"
¬ --log-level 7 

# ip6tables --table filter --append INPUT  -j DROP 

# ip6tables --table filter --delete INPUT 1 

# ip6tables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

# ip6tables -A INPUT -i sit+ -p icmpv6 -j ACCEPT 

# ip6tables -A OUTPUT -o sit+ -p icmpv6 -j ACCEPT 

# ip6tables -A INPUT -p icmpv6 --icmpv6-type echo-request -j ACCEPT

# ip6tables -A INPUT --protocol icmpv6 --icmpv6-type echo-request
¬ -j ACCEPT --match limit --limit 30/minute

# ip6tables -A INPUT -i sit+ -p tcp -s 2001:0db8:100::1/128 --sport 512:65535
¬ --dport 22 -j ACCEPT 

# ip6tables -A OUTPUT -o sit+ -p tcp -d 2001:0db8:100::1/128 --dport 512:65535
¬ --sport 22 ! --syn -j ACCEPT 

# iptables -A INPUT -i ppp0 -p ipv6 -j ACCEPT 

# iptables -A OUTPUT -o ppp0 -p ipv6 -j ACCEPT 

# iptables -A INPUT -i ppp0 -p ipv6 -s 192.0.2.2 -j ACCEPT 

# iptables -A OUTPUT -o ppp0 -p ipv6 -d 192.0.2.2 -j ACCEPT 

# ip6tables -I INPUT -i sit+ -p tcp --syn -j DROP 

# ip6tables -I FORWARD -i sit+ -p tcp --syn -j DROP 

# ip6tables -I INPUT -i sit+ -p udp ! --dport 32768:60999 -j DROP 

# ip6tables -I FORWARD -i sit+ -p udp ! --dport 32768:60999 -j DROP 

File: /etc/sysconfig/ip6tables

*filter :INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
:RH-Firewall-1-INPUT - [0:0]
-A INPUT -j RH-Firewall-1-INPUT
-A FORWARD -j RH-Firewall-1-INPUT
-A RH-Firewall-1-INPUT -i lo -j ACCEPT
-A RH-Firewall-1-INPUT -p icmpv6 -j ACCEPT
-A RH-Firewall-1-INPUT -p 50 -j ACCEPT
-A RH-Firewall-1-INPUT -p 51 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp --dport 5353 -d ff02::fb -j ACCEPT
-A RH-Firewall-1-INPUT -p udp -m udp --dport 631 -j ACCEPT 
-A RH-Firewall-1-INPUT -p tcp -m tcp --dport 631 -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state NEW -p tcp --dport 22 -j ACCEPT
-A RH-Firewall-1-INPUT -j REJECT --reject-with icmp6-adm-prohibited
COMMIT 

File: /etc/sysconfig/iptables

*filter :INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
:RH-Firewall-1-INPUT - [0:0]
-A INPUT -j RH-Firewall-1-INPUT
-A FORWARD -j RH-Firewall-1-INPUT
-A RH-Firewall-1-INPUT -i lo -j ACCEPT
-A RH-Firewall-1-INPUT -p icmp --icmp-type any -j ACCEPT
-A RH-Firewall-1-INPUT -p 50 -j ACCEPT
-A RH-Firewall-1-INPUT -p 51 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp --dport 5353 -d 224.0.0.251 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp -m udp --dport 631 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m tcp --dport 631 -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT
-A RH-Firewall-1-INPUT -j REJECT --reject-with icmp-host-prohibited
COMMIT 

# service iptables start
# service ip6tables start

# chkconfig iptables on
# chkconfig ip6tables on

# ip6tables -n -v -L 
Chain INPUT (policy DROP 0 packets, 0 bytes) 
 pkts bytes target     prot opt in     out     source               destination
    0     0 extIN      all      sit+   *       ::/0                 ::/0 
    4   384 intIN      all      eth0   *       ::/0                 ::/0 
    0     0 ACCEPT     all      *      *       ::1/128              ::1/128 
    0     0 ACCEPT     all      lo     *       ::/0                 ::/0 
    0     0 LOG        all      *      *       ::/0                 ::/0       
¬        LOG flags 0 level 7 prefix `INPUT-default:' 
    0     0 DROP       all      *      *       ::/0                 ::/0 
 
Chain FORWARD (policy DROP 0 packets, 0 bytes) 
 pkts bytes target     prot opt in     out     source               destination
¬ 
    0     0 int2ext    all      eth0   sit+    ::/0                 ::/0 
    0     0 ext2int    all      sit+   eth0    ::/0                 ::/0 
    0     0 LOG        all      *      *       ::/0                 ::/0       
¬        LOG flags 0 level 7 prefix `FORWARD-default:' 
    0     0 DROP       all      *      *       ::/0                 ::/0 
 
Chain OUTPUT (policy DROP 0 packets, 0 bytes) 
 pkts bytes target     prot opt in     out     source               destination
¬ 
    0     0 extOUT     all      *      sit+    ::/0                 ::/0 
    4   384 intOUT     all      *      eth0    ::/0                 ::/0 
    0     0 ACCEPT     all      *      *       ::1/128              ::1/128 
    0     0 ACCEPT     all      *      lo      ::/0                 ::/0 
    0     0 LOG        all      *      *       ::/0                 ::/0       
¬        LOG flags 0 level 7 prefix `OUTPUT-default:' 
    0     0 DROP       all      *      *       ::/0                 ::/0 
 
Chain ext2int (1 references) 
 pkts bytes target     prot opt in     out     source               destination
¬ 
    0     0 ACCEPT     icmpv6    *      *       ::/0                 ::/0 
    0     0 ACCEPT     tcp      *      *       ::/0                 ::/0       
¬        tcp spts:1:65535 dpts:1024:65535 flags:!0x16/0x02 
    0     0 LOG        all      *      *       ::/0                 ::/0       
¬        LOG flags 0 level 7 prefix `ext2int-default:' 
    0     0 DROP       tcp      *      *       ::/0                 ::/0 
    0     0 DROP       udp      *      *       ::/0                 ::/0 
    0     0 DROP       all      *      *       ::/0                 ::/0 
 
Chain extIN (1 references) 
 pkts bytes target     prot opt in     out     source               destination
¬ 
    0     0 ACCEPT     tcp      *      *       3ffe:400:100::1/128  ::/0       
¬        tcp spts:512:65535 dpt:22 
    0     0 ACCEPT     tcp      *      *       3ffe:400:100::2/128  ::/0       
¬        tcp spts:512:65535 dpt:22 
    0     0 ACCEPT     icmpv6    *      *       ::/0                 ::/0 
    0     0 ACCEPT     tcp      *      *       ::/0                 ::/0       
¬        tcp spts:1:65535 dpts:1024:65535 flags:!0x16/0x02 
    0     0 ACCEPT     udp      *      *       ::/0                 ::/0       
¬        udp spts:1:65535 dpts:1024:65535 
    0     0 LOG        all      *      *       ::/0                 ::/0       
¬        limit: avg 5/min burst 5 LOG flags 0 level 7 prefix `extIN-default:' 
    0     0 DROP       all      *      *       ::/0                 ::/0 
 
Chain extOUT (1 references) 
 pkts bytes target     prot opt in     out     source               destination
¬ 
    0     0 ACCEPT     tcp      *      *       ::/0                
¬ 2001:0db8:100::1/128tcp spt:22 dpts:512:65535 flags:!0x16/0x02 
    0     0 ACCEPT     tcp      *      *       ::/0                
¬ 2001:0db8:100::2/128tcp spt:22 dpts:512:65535 flags:!0x16/0x02 
    0     0 ACCEPT     icmpv6    *      *       ::/0                 ::/0 
    0     0 ACCEPT     tcp      *      *       ::/0                 ::/0       
¬        tcp spts:1024:65535 dpts:1:65535 
    0     0 ACCEPT     udp      *      *       ::/0                 ::/0       
¬        udp spts:1024:65535 dpts:1:65535 
    0     0 LOG        all      *      *       ::/0                 ::/0       
¬        LOG flags 0 level 7 prefix `extOUT-default:' 
    0     0 DROP       all      *      *       ::/0                 ::/0 
 
Chain int2ext (1 references) 
 pkts bytes target     prot opt in     out     source               destination
¬ 
    0     0 ACCEPT     icmpv6    *      *       ::/0                 ::/0 
    0     0 ACCEPT     tcp      *      *       ::/0                 ::/0       
¬        tcp spts:1024:65535 dpts:1:65535 
    0     0 LOG        all      *      *       ::/0                 ::/0       
¬        LOG flags 0 level 7 prefix `int2ext:' 
    0     0 DROP       all      *      *       ::/0                 ::/0 
    0     0 LOG        all      *      *       ::/0                 ::/0       
¬        LOG flags 0 level 7 prefix `int2ext-default:' 
    0     0 DROP       tcp      *      *       ::/0                 ::/0 
    0     0 DROP       udp      *      *       ::/0                 ::/0 
    0     0 DROP       all      *      *       ::/0                 ::/0 
 
Chain intIN (1 references) 
 pkts bytes target     prot opt in     out     source               destination
¬ 
    0     0 ACCEPT     all      *      *       ::/0                
¬ fe80::/ffc0:: 
    4   384 ACCEPT     all      *      *       ::/0                 ff02::/16 
 
Chain intOUT (1 references) 
 pkts bytes target     prot opt in     out     source               destination
¬ 
    0     0 ACCEPT     all      *      *       ::/0                
¬ fe80::/ffc0:: 
    4   384 ACCEPT     all      *      *       ::/0                 ff02::/16 
    0     0 LOG        all      *      *       ::/0                 ::/0       
¬        LOG flags 0 level 7 prefix `intOUT-default:' 
    0     0 DROP       all      *      *       ::/0                 ::/0 

#!/sbin/setkey -f
flush;
spdflush;
spdadd 2001:db8:1:1::1 2001:db8:2:2::2 any -P out ipsec esp/transport//require;
spdadd 2001:db8:2:2::2 2001:db8:1:1::1 any -P in  ipsec esp/transport//require;

#!/sbin/setkey -f
flush;
spdflush;
spdadd 2001:db8:1:1::1 2001:db8:2:2::2 any -P out ipsec
¬ esp/tunnel/2001:db8:1:1::1-2001:db8:2:2::2/require;
spdadd 2001:db8:2:2::2 2001:db8:1:1::1 any -P in  ipsec
¬ esp/tunnel/2001:db8:2:2::2-2001:db8:1:1::1/require;

# Racoon IKE daemon configuration file.
# See 'man racoon.conf' for a description of the format and entries.
path include "/etc/racoon";
path pre_shared_key "/etc/racoon/psk.txt";

listen
{
        isakmp 2001:db8:1:1::1;
}

remote 2001:db8:2:2::2
{
        exchange_mode main;
        lifetime time 24 hour;
        proposal
        {
                encryption_algorithm 3des;
                hash_algorithm md5;
                authentication_method pre_shared_key;
                dh_group 2;
        }
}

# gateway-to-gateway
sainfo address 2001:db8:1:1::1 any address 2001:db8:2:2::2 any
{
        lifetime time 1 hour;
        encryption_algorithm 3des;
        authentication_algorithm hmac_md5;
        compression_algorithm deflate;
}

sainfo address 2001:db8:2:2::2 any address 2001:db8:1:1::1 any
{
        lifetime time 1 hour;
        encryption_algorithm 3des;
        authentication_algorithm hmac_md5;
        compression_algorithm deflate;
} 

# file for pre-shared keys used for IKE authentication
# format is: 'identifier' 'key'

2001:db8:2:2::2 verysecret 

# racoon -F -v -f /etc/racoon/racoon.conf
Foreground mode. 
2005-01-01 20:30:15: INFO: @(#)ipsec-tools 0.3.3
¬ (http://ipsec-tools.sourceforge.net)
2005-01-01 20:30:15: INFO: @(#)This product linked
¬ OpenSSL 0.9.7a Feb 19 2003 (http://www.openssl.org/)
2005-01-01 20:30:15: INFO: 2001:db8:1:1::1[500] used as isakmp port (fd=7)
2005-01-01 20:31:06: INFO: IPsec-SA request for 2001:db8:2:2::2
¬ queued due to no phase1 found.
2005-01-01 20:31:06: INFO: initiate new phase 1 negotiation:
¬ 2001:db8:1:1::1[500]<=>2001:db8:2:2::2[500]
2005-01-01 20:31:06: INFO: begin Identity Protection mode.
2005-01-01 20:31:09: INFO: ISAKMP-SA established
¬ 2001:db8:1:1::1[500]-2001:db8:2:2::2[500] spi:da3d3693289c9698:ac039a402b2db401
2005-01-01 20:31:09: INFO: initiate new phase 2 negotiation:
¬ 2001:6f8:900:94::2[0]<=>2001:db8:2:2::2[0]
2005-01-01 20:31:10: INFO: IPsec-SA established:
¬ ESP/Tunnel 2001:db8:2:2::2->2001:db8:1:1::1 spi=253935531(0xf22bfab) 
2005-01-01 20:31:10: INFO: IPsec-SA established:
¬ ESP/Tunnel 2001:db8:1:1::1->2001:db8:2:2::2 spi=175002564(0xa6e53c4) 

20:35:55.305707 2001:db8:1:1::1 > 2001:db8:2:2::2: ESP(spi=0x0a6e53c4,seq=0x3)
20:35:55.537522 2001:db8:2:2::2 > 2001:db8:1:1::1: ESP(spi=0x0f22bfab,seq=0x3)

# setkey -D
2001:db8:1:1::1 2001:db8:2:2::2
        esp mode=tunnel spi=175002564(0x0a6e53c4) reqid=0(0x00000000)
        E: 3des-cbc  bd26bc45 aea0d249 ef9c6b89 7056080f 5d9fa49c 924e2edd
        A: hmac-md5  60c2c505 517dd8b7 c9609128 a5efc2db
        seq=0x00000000 replay=4 flags=0x00000000 state=mature
        created: Jan  1 20:31:10 2005   current: Jan  1 20:40:47 2005
        diff: 577(s)    hard: 3600(s)   soft: 2880(s)
        last: Jan  1 20:35:05 2005      hard: 0(s)      soft: 0(s)
        current: 540(bytes)     hard: 0(bytes)  soft: 0(bytes)
        allocated: 3    hard: 0 soft: 0
        sadb_seq=1 pid=22358 refcnt=0
2001:db8:2:2::2 2001:db8:1:1::1
        esp mode=tunnel spi=253935531(0x0f22bfab) reqid=0(0x00000000)
        E: 3des-cbc  c1ddba65 83debd62 3f6683c1 20e747ac 933d203f 4777a7ce
        A: hmac-md5  3f957db9 9adddc8c 44e5739d 3f53ca0e
        seq=0x00000000 replay=4 flags=0x00000000 state=mature
        created: Jan  1 20:31:10 2005   current: Jan  1 20:40:47 2005
        diff: 577(s)    hard: 3600(s)   soft: 2880(s)
        last: Jan  1 20:35:05 2005      hard: 0(s)      soft: 0(s)
        current: 312(bytes)     hard: 0(bytes)  soft: 0(bytes)
        allocated: 3    hard: 0 soft: 0
        sadb_seq=0 pid=22358 refcnt=0 

# /etc/ipsec.conf - Openswan IPsec configuration file
#
# Manual:     ipsec.conf.5
version 2.0     # conforms to second version of ipsec.conf specification

# basic configuration
config setup
        # Debug-logging controls:  "none" for (almost) none, "all" for lots.
        # klipsdebug=none
        # plutodebug="control parsing"

#Disable Opportunistic Encryption
include /etc/ipsec.d/examples/no_oe.conf

conn ipv6-p1-p2
        connaddrfamily=ipv6       # Important for IPv6!
        left=2001:db8:1:1::1
        right=2001:db8:2:2::2
        authby=secret
        esp=aes128-sha1
        ike=aes128-sha-modp1024
        type=transport
        #type=tunnel
        compress=no
        #compress=yes
        auto=add
        #auto=start

2001:db8:1:1::1 2001:db8:2:2::2 : PSK      "verysecret"

# /etc/rc.d/init.d/ipsec start

# ipsec auto --up ipv6-peer1-peer2
104 "ipv6-p1-p2" #1: STATE_MAIN_I1: initiate
106 "ipv6-p1-p2" #1: STATE_MAIN_I2: sent MI2, expecting MR2
108 "ipv6-p1-p2" #1: STATE_MAIN_I3: sent MI3, expecting MR3
004 "ipv6-p1-p2" #1: STATE_MAIN_I4: ISAKMP SA established
112 "ipv6-p1-p2" #2: STATE_QUICK_I1: initiate
004 "ipv6-p1-p2" #2: STATE_QUICK_I2: sent QI2,
¬ IPsec SA established {ESP=>0xa98b7710 <0xa51e1f22} 

# setkey -D
2001:db8:1:1::1 2001:db8:2:2::2
        esp mode=transport spi=2844489488(0xa98b7710) reqid=16385(0x00004001)
        E: aes-cbc  082ee274 2744bae5 7451da37 1162b483
        A: hmac-sha1  b7803753 757417da 477b1c1a 64070455 ab79082c
        seq=0x00000000 replay=64 flags=0x00000000 state=mature
        created: Jan  1 21:16:32 2005   current: Jan  1 21:22:20 2005
        diff: 348(s)    hard: 0(s)      soft: 0(s)
        last:                           hard: 0(s)      soft: 0(s)
        current: 0(bytes)       hard: 0(bytes)  soft: 0(bytes)
        allocated: 0    hard: 0 soft: 0
        sadb_seq=1 pid=23825 refcnt=0
2001:db8:2:2::2 2001:db8:1:1::1
        esp mode=transport spi=2770214690(0xa51e1f22) reqid=16385(0x00004001)
        E: aes-cbc  6f59cc30 8d856056 65e07b76 552cac18
        A: hmac-sha1  c7c7d82b abfca8b1 5440021f e0c3b335 975b508b
        seq=0x00000000 replay=64 flags=0x00000000 state=mature
        created: Jan  1 21:16:31 2005   current: Jan  1 21:22:20 2005
        diff: 349(s)    hard: 0(s)      soft: 0(s)
        last:                           hard: 0(s)      soft: 0(s)
        current: 0(bytes)       hard: 0(bytes)  soft: 0(bytes)
        allocated: 0    hard: 0 soft: 0
        sadb_seq=0 pid=23825 refcnt=0 

# tc qdisc add dev eth1 root handle 1: cbq avpkt 1000 bandwidth 1000Mbit

# tc class add dev eth1 parent 1: classid 1:1 cbq rate   1Mbit allot 1500 bounded 

# tc class add dev eth1 parent 1: classid 1:2 cbq rate  50Mbit allot 1500 bounded

# tc class add dev eth1 parent 1: classid 1:3 cbq rate  10Mbit allot 1500 bounded

# tc class add dev eth1 parent 1: classid 1:4 cbq rate 200kbit allot 1500 bounded

# tc filter add dev eth1 parent 1: protocol ip   u32 match ip  protocol 6 0xff match ip dport 5001 0xffff flowid 1:1

# tc filter add dev eth1 parent 1: protocol ipv6 u32 match ip6 protocol 6 0xff match ip6 dport 5001 0xffff flowid 1:2

# tc filter add dev eth1 parent 1: protocol ipv6 u32 match ip6 flowlabel 12345 0x3ffff flowid 1:3 

# tc filter add dev eth1 parent 1: protocol ipv6 handle 32 fw flowid 1:4

# ip6tables -A POSTROUTING -t mangle -p tcp --dport 5003 -j MARK --set-mark 32 

# iperf -V -s -p 5001
# iperf -V -s -p 5002
# iperf -V -s -p 5003

# iperf -V -c SERVER-IPv4 -p 5001    (expected:      1 MBit/s)
# iperf -V -c SERVER-IPv6 -p 5001    (expected:     50 MBit/s)
# iperf -V -c SERVER-IPv4 -p 5002    (expected:  >> 50 MBit/s && <= 1000 MBit/s)
# iperf -V -c SERVER-IPv6 -p 5002    (expected:  >> 50 MBit/s && <= 1000 MBit/s)
# iperf -V -c SERVER-IPv4 -p 5003    (expected:  >> 50 MBit/s && <= 1000 MBit/s)
# iperf -V -c SERVER-IPv6 -p 5003    (expected:    200 kBit/s)

options {
        # sure other options here, too
        listen-on-v6 { any; };
};

# netstat -lnptu |grep "named\W*$" 
tcp 0 0 :::53         :::*      LISTEN 1234/named
¬ # incoming TCP requests
udp 0 0 1.2.3.4:53    0.0.0.0:*        1234/named
¬ # incoming UDP requests to IPv4 1.2.3.4
udp 0 0 127.0.0.1:53  0.0.0.0:*        1234/named
¬ # incoming UDP requests to IPv4 localhost
udp 0 0 0.0.0.0:32868 0.0.0.0:*        1234/named
¬ # dynamic chosen port for outgoing queries
udp 0 0 :::53         :::*             1234/named
¬ # incoming UDP request to any IPv6

# dig localhost @::1

options {
        # sure other options here, too
        listen-on-v6 { none; };
};

transfer-source-v6 <ipv6addr|*> [port port];

notify-source-v6 <ipv6addr|*> [port port];

$ host -t aaaa www.6bone.net 2001:0db8:200:f101::1 
Using domain server: 
Name: 2001:0db8:200:f101::1 
Address: 2001:0db8:200:f101::1#53 
Aliases:

Host www.6bone.net. not found: 5(REFUSED)

Jan 3 12:43:32 gate named[12347]: client
¬ 2001:0db8:200:f101:212:34ff:fe12:3456#32770: 
 query denied

$ host -t aaaa www.6bone.net 2001:0db8:200:f101::1 
Using domain server: 
Name: 2001:0db8:200:f101::1 
Address: 2001:0db8:200:f101::1#53 
Aliases:

www.6bone.net. is an alias for 6bone.net. 
6bone.net. has AAAA address 3ffe:b00:c18:1::10

Listen [2001:0db8:100::1]:80
<VirtualHost [2001:0db8:100::1]:80>
        ServerName ipv6only.yourdomain.yourtopleveldomain
        # ...sure more config lines
</VirtualHost>

Listen [2001:0db8:100::2]:80 
Listen 1.2.3.4:80
<VirtualHost [2001:0db8:100::2]:80 1.2.3.4:80>
        ServerName ipv6andipv4.yourdomain.yourtopleveldomain
        # ...sure more config lines
</VirtualHost>

# netstat -lnptu |grep "httpd2\W*$" 
tcp 0 0 1.2.3.4:80          0.0.0.0:* LISTEN 12345/httpd2 
tcp 0 0 2001:0db8:100::1:80 :::*      LISTEN 12345/httpd2 
tcp 0 0 2001:0db8:100::2:80 :::*      LISTEN 12345/httpd2

interface eth0 { 
        AdvSendAdvert on;
        MinRtrAdvInterval 3; 
        MaxRtrAdvInterval 10;
        prefix 2001:0db8:0100:f101::/64 { 
                AdvOnLink on; 
                AdvAutonomous on; 
                AdvRouterAddr on; 
        };
};

# ip -6 addr show eth0 
3: eth0: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 100 
    inet6 2001:0db8:100:f101:2e0:12ff:fe34:1234/64 scope global dynamic 
       valid_lft 2591992sec preferred_lft 604792sec 
    inet6 fe80::2e0:12ff:fe34:1234/10 scope link

interface eth0 { 
        AdvSendAdvert on;
        MinRtrAdvInterval 3; 
        MaxRtrAdvInterval 10;
        prefix 0:0:0:f101::/64 { 
                AdvOnLink off; 
                AdvAutonomous on; 
                AdvRouterAddr on; 
                Base6to4Interface ppp0;
                AdvPreferredLifetime 20; 
                AdvValidLifetime 30;
        };
};

# /sbin/ip -6 addr show eth0 
3: eth0: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 100 
   inet6 2002:0102:0304:f101:2e0:12ff:fe34:1234/64 scope global dynamic 
      valid_lft 22sec preferred_lft 12sec
   inet6 fe80::2e0:12ff:fe34:1234/10 scope link

# /sbin/ip -6 route add 2002:0102:0304:f101::/64 dev eth0 metric 1

interface eth0 {
        server-preference 255;
        renew-time 60;
        rebind-time 90;
        prefer-life-time 130;
        valid-life-time 200;
        allow rapid-commit;
        option dns_servers 2001:db8:0:f101::1 sub.domain.example;
        link AAA {
                range 2001:db8:0:f101::1000 to 2001:db8:0:f101::ffff/64;
                prefix 2001:db8:0:f101::/64;
        };
};

interface eth0 {
        send rapid-commit;
        request domain-name-servers;
}; 

# service dhcp6s start

# dhcp6c -f eth0

# dhcp6s -d -D -f eth0

# ping6 -I eth0 ff02::1:2

# dhcp6c -d -f eth0
Oct/03/2005 17:18:16 dhcpv6 doesn't support hardware type 776 
Oct/03/2005 17:18:16 doesn't support sit0 address family 0 
Oct/03/2005 17:18:16 netlink_recv_rtgenmsg error 
Oct/03/2005 17:18:16 netlink_recv_rtgenmsg error 
Oct/03/2005 17:18:17 status code for this address is: success 
Oct/03/2005 17:18:17 status code: success 
Oct/03/2005 17:18:17 netlink_recv_rtgenmsg error 
Oct/03/2005 17:18:17 netlink_recv_rtgenmsg error 
Oct/03/2005 17:18:17 assigned address 2001:db8:0:f101::1002 prefix len is not
¬ in any RAs prefix length using 64 bit instead 
Oct/03/2005 17:18:17 renew time 60, rebind time 9

default-lease-time 600;
max-lease-time 7200; 
log-facility local7; 
subnet6 2001:db8:0:1::/64 {
        # Range for clients
        range6 2001:db8:0:1::129 2001:db8:0:1::254;
        # Additional options
        option dhcp6.name-servers fec0:0:0:1::1;
        option dhcp6.domain-search "domain.example";
        # Prefix range for delegation to sub-routers
        prefix6 2001:db8:0:100:: 2001:db8:0:f00:: /56;
        # Example for a fixed host address
        host specialclient {
    		host-identifier option dhcp6.client-id 00:01:00:01:4a:1f:ba:e3:60:b9:1f:01:23:45;
        	fixed-address6 2001:db8:0:1::127;
    	} 
} 

# hexdump -e '"%07.7_ax " 1/2 "%04x" " " 14/1 "%02x:" "\n"' /var/lib/dhcpv6/dhcp6c_duid 0000000 000e 00:01:00:01:4a:1f:ba:e3:60:b9:1f:01:23:45:

# /usr/sbin/dhcpd -6 -f -cf /etc/dhcp/dhcpd.conf eth1 
Internet Systems Consortium DHCP Server 4.1.0 
Copyright 2004-2008 Internet Systems Consortium. 
All rights reserved. 
For info, please visit http://www.isc.org/sw/dhcp/ 
Not searching LDAP since ldap-server, ldap-port and ldap-base-dn were not specified in the config file 
Wrote 0 leases to leases file. 
Bound to *:547 
Listening on Socket/5/eth1/2001:db8:0:1::/64 
Sending on   Socket/5/eth1/2001:db8:0:1::/64

log-level 8 
log-mode short 
preference 0 
iface "eth1" {
 // also ranges can be defines, instead of exact values  t1 1800-2000  t2 2700-3000
  prefered-lifetime 3600
  valid-lifetime 7200
  class {
    pool 2001:6f8:12d8:1::/64
  }
  option dns-server fec0:0:0:1::1
  option domain domain.example
} 

# dibbler-server run 
| Dibbler - a portable DHCPv6, version 0.7.3 (SERVER, Linux port) 
| Authors : Tomasz Mrugalski<thomson(at)klub.com.pl>,Marek Senderski<msend(at)o2.pl> 
| Licence : GNU GPL v2 only. Developed at Gdansk University of Technology. 
| Homepage: http://klub.com.pl/dhcpv6/ 
2009.05.28 10:18:48 Server Notice    My pid (1789) is stored in /var/lib/dibbler/server.pid 
2009.05.28 10:18:48 Server Notice    Detected iface eth0/3, MAC=54:52:00:01:23:45. 
2009.05.28 10:18:48 Server Notice    Detected iface eth1/2, MAC=54:52:00:67:89:ab. 
2009.05.28 10:18:48 Server Notice    Detected iface lo/1, MAC=00:00:00:00:00:00. 
2009.05.28 10:18:48 Server Debug     Skipping database loading. 
2009.05.28 10:18:48 Server Debug     Cache:server-cache.xml file: parsing started, expecting 0 entries. 
2009.05.28 10:18:48 Server Notice    Parsing /etc/dibbler/server.conf config file... 
18:48 Server Debug     Setting 0 generic option(s). 
18:48 Server Debug     0 per-client configurations (exceptions) added. 
18:48 Server Debug     Parsing /etc/dibbler/server.conf done. 
18:48 Server Info      0 client class(es) defined. 
18:48 Server Debug     1 interface(s) specified in /etc/dibbler/server.conf 
18:48 Server Info      Mapping allow, deny list to class 0:0 allow/deny entries in total. 
18:48 Server Info      Interface eth1/2 configuration has been loaded. 
18:48 Server Notice    Running in stateful mode. 
18:48 Server Info      My DUID is 00:01:00:01:11:aa:6d:a7:54:52:00:67:89:ab. 
18:48 Server Notice    Creating multicast (ff02::1:2) socket on eth1/2 (eth1/2) interface. 
18:48 Server Debug     Cache: size set to 1048576 bytes, 1 cache entry size is 87 bytes, so maximum 12052 address-client pair(s) may be cached. 
18:48 Server Notice    Accepting connections. Next event in 4294967295 second(s).

sshd:           1.2.3. [2001:0db8:100:200::]/64
daytime-stream: 1.2.3. [2001:0db8:100:200::]/64

ALL: ALL

ALL: ALL: spawn (echo "Attempt from %h %a to %d at `date`" 
 | tee -a /var/log/tcp.deny.log | mail root@localhost)

Jan 2 20:40:44 gate xinetd-ipv6[12346]: FAIL: daytime-stream libwrap
¬ from=::ffff:1.2.3.4
Jan 2 20:32:06 gate xinetd-ipv6[12346]: FAIL: daytime-stream libwrap 
 from=2001:0db8:100:200::212:34ff:fe12:3456

Jan 2 20:24:17 gate sshd[12345]: refused connect from ::ffff:1.2.3.4
¬ (::ffff:1.2.3.4)
Jan 2 20:39:33 gate sshd[12345]: refused connect 
 from 2001:0db8:100:200::212:34ff:fe12:3456
¬ (2001:0db8:100:200::212:34ff:fe12:3456)

Jan 2 20:37:50 gate xinetd-ipv6[12346]: START: daytime-stream pid=0
¬ from=::ffff:1.2.3.4 
Jan 2 20:37:56 gate xinetd-ipv6[12346]: START: daytime-stream pid=0 
 from=2001:0db8:100:200::212:34ff:fe12:3456

Jan 2 20:43:10 gate sshd[21975]: Accepted password for user from ::ffff:1.2.3.4
¬ port 33381 ssh2
Jan 2 20:42:19 gate sshd[12345]: Accepted password for user 
 from 2001:0db8:100:200::212:34ff:fe12:3456 port 33380 ssh2

struct sockaddr_in
{
   sa_family_t    sin_family;
   in_port_t      sin_port;
   struct in_addr sin_addr;
   /* Plus some padding for alignment */
};

struct sockaddr_in6
{
   sa_family_t     sin6_family;
   in_port_t       sin6_port;
   uint32_t        sin6_flowinfo;
   struct in6_addr sin6_addr;
   uint32_t        sin6_scope_id;
};

Host A (fe80::1) ---- eth0 ---- Host B ---- eth1 ---- Host C (fe80::1)

ssize_t recvfrom( int              s,
                  void            *buf,
                  size_t           len,
                  int              flags,
                  struct sockaddr *from,
                  socklen_t       *fromlen );

/*
** Read a message from a remote peer, and return a buffer pointer to
** the caller.
**
** 's' is the file descriptor for the socket.
*/
char *rcvMsg( int s )
{
   static char             bfr[ 1025 ];  /* Where the msg is stored. */
   ssize_t                 count;
   struct sockaddr_storage ss;           /* Where the peer adr goes. */
   socklen_t               sslen;
   sslen = sizeof( ss );
   count = recvfrom( s,
                     bfr,
                     sizeof( bfr ) - 1,
                     0,
                     (struct sockaddr*) &ss,
                     &sslen );
   bfr[ count ] = '\0';   /* Null-terminates the message. */
   return bfr;
}  /* End rcvMsg() */

::ffff:192.0.2.1

        ::1                        localhost
        127.0.0.1                  localhost
        fe80::2c0:8cff:fe01:2345   pt141
        192.0.2.1                  pt141

tod6d [-v] [service]

/******************************************************************************
* File: tod6d.c
* Description: Contains source code for an IPv6-capable 'daytime' server.
* Author: John Wenker, Sr. Software Engineer,
*         Performance Technologies, San Diego, USA
******************************************************************************/
/*
** System header files.
*/
#include <errno.h>        /* errno declaration & error codes.            */
#include <netdb.h>        /* getaddrinfo(3) et al.                       */
#include <netinet/in.h>   /* sockaddr_in & sockaddr_in6 definition.      */
#include <stdio.h>        /* printf(3) et al.                            */
#include <stdlib.h>       /* exit(2).                                    */
#include <string.h>       /* String manipulation & memory functions.     */
#include <sys/poll.h>     /* poll(2) and related definitions.            */
#include <sys/socket.h>   /* Socket functions (socket(2), bind(2), etc). */
#include <time.h>         /* time(2) & ctime(3).                         */
#include <unistd.h>       /* getopt(3), read(2), etc.                    */
/*
** Constants.
*/
#define DFLT_SERVICE "daytime"   /* Default service name.                    */
#define INVALID_DESC -1          /* Invalid file descriptor.                 */
#define MAXCONNQLEN  3           /* Max nbr of connection requests to queue. */
#define MAXTCPSCKTS  2           /* One TCP socket for IPv4 & one for IPv6.  */
#define MAXUDPSCKTS  2           /* One UDP socket for IPv4 & one for IPv6.  */
#define VALIDOPTS    "v"         /* Valid command options.                   */
/*
** Simple boolean type definition.
*/
typedef enum { false = 0, true } boolean;
/*
** Prototypes for internal helper functions.
*/
static int  openSckt( const char *service,
                      const char *protocol,
                      int         desc[ ],
                      size_t     *descSize );
static void tod( int    tSckt[ ],
                 size_t tScktSize,
                 int    uSckt[ ],
                 size_t uScktSize );
/*
** Global (within this file only) data objects.
*/
static char        hostBfr[ NI_MAXHOST ];   /* For use w/getnameinfo(3).    */
static const char *pgmName;                 /* Program name w/o dir prefix. */
static char        servBfr[ NI_MAXSERV ];   /* For use w/getnameinfo(3).    */
static boolean     verbose = false;         /* Verbose mode indication.     */
/*
** Usage macro for command syntax violations.
*/
#define USAGE                                       \
        {                                           \
           fprintf( stderr,                         \
                    "Usage: %s [-v] [service]\n",   \
                    pgmName );                      \
           exit( 127 );                             \
        }  /* End USAGE macro. */
/*
** Macro to terminate the program if a system call error occurs.  The system
** call must be one of the usual type that returns -1 on error.  This macro is
** a modified version of a macro authored by Dr. V. Vinge, SDSU Dept. of
** Computer Science (retired)... best professor I ever had.  I hear he writes
** great science fiction in addition to robust code, too.
*/
#define CHK(expr)                                                   \
        do                                                          \
        {                                                           \
           if ( (expr) == -1 )                                      \
           {                                                        \
              fprintf( stderr,                                      \
                       "%s (line %d): System call ERROR - %s.\n",   \
                       pgmName,                                     \
                       __LINE__,                                    \
                       strerror( errno ) );                         \
              exit( 1 );                                            \
           }   /* End IF system call failed. */                     \
        } while ( false )
/******************************************************************************
* Function: main
*
* Description:
*    Set up a time-of-day server and handle network requests.  This server
*    handles both TCP and UDP requests.
*
* Parameters:
*    The usual argc and argv parameters to a main() function.
*
* Return Value:
*    This is a daemon program and never returns.  However, in the degenerate
*    case where no sockets are created, the function returns zero.
******************************************************************************/
int main( int   argc,
          char *argv[ ] )
{
   int         opt;
   const char *service   = DFLT_SERVICE;
   int         tSckt[ MAXTCPSCKTS ];     /* Array of TCP socket descriptors. */
   size_t      tScktSize = MAXTCPSCKTS;  /* Size of uSckt (# of elements).   */
   int         uSckt[ MAXUDPSCKTS ];     /* Array of UDP socket descriptors. */
   size_t      uScktSize = MAXUDPSCKTS;  /* Size of uSckt (# of elements).   */
   /*
   ** Set the program name (w/o directory prefix).
   */
   pgmName = strrchr( argv[ 0 ], '/' );
   pgmName = pgmName == NULL  ?  argv[ 0 ]  :  pgmName + 1;
   /*
   ** Process command options.
   */
   opterr = 0;   /* Turns off "invalid option" error messages. */
   while ( ( opt = getopt( argc, argv, VALIDOPTS ) ) >= 0 )
   {
      switch ( opt )
      {
         case 'v':   /* Verbose mode. */
         {
            verbose = true;
            break;
         }
         default:
         {
            USAGE;
         }
      }  /* End SWITCH on command option. */
   }  /* End WHILE processing options. */
   /*
   ** Process command line arguments.
   */
   switch ( argc - optind )
   {
      case 0:  break;
      case 1:  service = argv[ optind ]; break;
      default: USAGE;
   }  /* End SWITCH on number of command line arguments. */
   /*
   ** Open both a TCP and UDP socket, for both IPv4 & IPv6, on which to receive
   ** service requests.
   */
   if ( ( openSckt( service, "tcp", tSckt, &tScktSize ) < 0 ) ||
        ( openSckt( service, "udp", uSckt, &uScktSize ) < 0 ) )
   {
      exit( 1 );
   }
   /*
   ** Run the time-of-day server.
   */
   if ( ( tScktSize > 0 ) || ( uScktSize > 0 ) )
   {
      tod( tSckt,         /* tod() never returns. */
           tScktSize,
           uSckt,
           uScktSize );
   }
   /*
   ** Since tod() never returns, execution only gets here if no sockets were
   ** created.
   */
   if ( verbose )
   {
      fprintf( stderr,
               "%s: No sockets opened... terminating.\n",
               pgmName );
   }
   return 0;
}  /* End main() */
/******************************************************************************
* Function: openSckt
*
* Description:
*    Open passive (server) sockets for the indicated inet service & protocol.
*    Notice in the last sentence that "sockets" is plural.  During the interim
*    transition period while everyone is switching over to IPv6, the server
*    application has to open two sockets on which to listen for connections...
*    one for IPv4 traffic and one for IPv6 traffic.
*
* Parameters:
*    service  - Pointer to a character string representing the well-known port
*               on which to listen (can be a service name or a decimal number).
*    protocol - Pointer to a character string representing the transport layer
*               protocol (only "tcp" or "udp" are valid).
*    desc     - Pointer to an array into which the socket descriptors are
*               placed when opened.
*    descSize - This is a value-result parameter.  On input, it contains the
*               max number of descriptors that can be put into 'desc' (i.e. the
*               number of elements in the array).  Upon return, it will contain
*               the number of descriptors actually opened.  Any unused slots in
*               'desc' are set to INVALID_DESC.
*
* Return Value:
*    0 on success, -1 on error.
******************************************************************************/
static int openSckt( const char *service,
                     const char *protocol,
                     int         desc[ ],
                     size_t     *descSize )
{
   struct addrinfo *ai;
   int              aiErr;
   struct addrinfo *aiHead;
   struct addrinfo  hints    = { .ai_flags  = AI_PASSIVE,    /* Server mode. 
¬ */
                                 .ai_family = PF_UNSPEC };   /* IPv4 or IPv6.
¬ */
   size_t           maxDescs = *descSize;
   /*
   ** Initialize output parameters.  When the loop completes, *descSize is 0.
   */
   while ( *descSize > 0 )
   {
      desc[ --( *descSize ) ] = INVALID_DESC;
   }
   /*
   ** Check which protocol is selected (only TCP and UDP are valid).
   */
   if ( strcmp( protocol, "tcp" ) == 0 )        /* TCP protocol.     */
   {
      hints.ai_socktype = SOCK_STREAM;
      hints.ai_protocol = IPPROTO_TCP;
   }
   else if ( strcmp( protocol, "udp" ) == 0 )   /* UDP protocol.     */
   {
      hints.ai_socktype = SOCK_DGRAM;
      hints.ai_protocol = IPPROTO_UDP;
   }
   else                                         /* Invalid protocol. */
   {
      fprintf( stderr,
               "%s (line %d): ERROR - Unknown transport "
               "layer protocol \"%s\".\n",
               pgmName,
               __LINE__,
               protocol );
      return -1;
   }
   /*
   ** Look up the service's well-known port number.  Notice that NULL is being
   ** passed for the 'node' parameter, and that the AI_PASSIVE flag is set in
   ** 'hints'.  Thus, the program is requesting passive address information.
   ** The network address is initialized to :: (all zeros) for IPv6 records, or
   ** 0.0.0.0 for IPv4 records.
   */
   if ( ( aiErr = getaddrinfo( NULL,
                               service,
                               &hints,
                               &aiHead ) ) != 0 )
   {
      fprintf( stderr,
               "%s (line %d): ERROR - %s.\n",
               pgmName,
               __LINE__,
               gai_strerror( aiErr ) );
      return -1;
   }
   /*
   ** For each of the address records returned, attempt to set up a passive
   ** socket.
   */
   for ( ai = aiHead;
         ( ai != NULL ) && ( *descSize < maxDescs );
         ai = ai->ai_next )
   {
      if ( verbose )
      {
         /*
         ** Display the current address info.   Start with the protocol-
         ** independent fields first.
         */
         fprintf( stderr,
                  "Setting up a passive socket based on the "
                  "following address info:\n"
                  "   ai_flags     = 0x%02X\n"
                  "   ai_family    = %d (PF_INET = %d, PF_INET6 = %d)\n"
                  "   ai_socktype  = %d (SOCK_STREAM = %d, SOCK_DGRAM = %d)\n"
                  "   ai_protocol  = %d (IPPROTO_TCP = %d, IPPROTO_UDP = %d)\n"
                  "   ai_addrlen   = %d (sockaddr_in = %d, "
                  "sockaddr_in6 = %d)\n",
                  ai->ai_flags,
                  ai->ai_family,
                  PF_INET,
                  PF_INET6,
                  ai->ai_socktype,
                  SOCK_STREAM,
                  SOCK_DGRAM,
                  ai->ai_protocol,
                  IPPROTO_TCP,
                  IPPROTO_UDP,
                  ai->ai_addrlen,
                  sizeof( struct sockaddr_in ),
                  sizeof( struct sockaddr_in6 ) );
         /*
         ** Now display the protocol-specific formatted socket address.  Note
         ** that the program is requesting that getnameinfo(3) convert the
         ** host & service into numeric strings.
         */
         getnameinfo( ai->ai_addr,
                      ai->ai_addrlen,
                      hostBfr,
                      sizeof( hostBfr ),
                      servBfr,
                      sizeof( servBfr ),
                      NI_NUMERICHOST | NI_NUMERICSERV );
         switch ( ai->ai_family )
         {
            case PF_INET:   /* IPv4 address record. */
            {
               struct sockaddr_in *p = (struct sockaddr_in*) ai->ai_addr;
               fprintf( stderr,
                        "   ai_addr      = sin_family:   %d (AF_INET = %d, "
                        "AF_INET6 = %d)\n"
                        "                  sin_addr:     %s\n"
                        "                  sin_port:     %s\n",
                        p->sin_family,
                        AF_INET,
                        AF_INET6,
                        hostBfr,
                        servBfr );
               break;
            }  /* End CASE of IPv4. */
            case PF_INET6:   /* IPv6 address record. */
            {
               struct sockaddr_in6 *p = (struct sockaddr_in6*) ai->ai_addr;
               fprintf( stderr,
                        "   ai_addr      = sin6_family:   %d (AF_INET = %d, "
                        "AF_INET6 = %d)\n"
                        "                  sin6_addr:     %s\n"
                        "                  sin6_port:     %s\n"
                        "                  sin6_flowinfo: %d\n"
                        "                  sin6_scope_id: %d\n",
                        p->sin6_family,
                        AF_INET,
                        AF_INET6,
                        hostBfr,
                        servBfr,
                        p->sin6_flowinfo,
                        p->sin6_scope_id );
               break;
            }  /* End CASE of IPv6. */
            default:   /* Can never get here, but just for completeness. */
            {
               fprintf( stderr,
                        "%s (line %d): ERROR - Unknown protocol family (%d).\n",
                        pgmName,
                        __LINE__,
                        ai->ai_family );
               freeaddrinfo( aiHead );
               return -1;
            }  /* End DEFAULT case (unknown protocol family). */
         }  /* End SWITCH on protocol family. */
      }  /* End IF verbose mode. */
      /*
      ** Create a socket using the info in the addrinfo structure.
      */
      CHK( desc[ *descSize ] = socket( ai->ai_family,
                                       ai->ai_socktype,
                                       ai->ai_protocol ) );
      /*
      ** Here is the code that prevents "IPv4 mapped addresses", as discussed
      ** in Section 22.1.3.1.  If an IPv6 socket was just created, then set the
      ** IPV6_V6ONLY socket option.
      */
      if ( ai->ai_family == PF_INET6 )
      {
#if defined( IPV6_V6ONLY )
         /*
         ** Disable IPv4 mapped addresses.
         */
         int v6Only = 1;
         CHK( setsockopt( desc[ *descSize ],
                          IPPROTO_IPV6,
                          IPV6_V6ONLY,
                          &v6Only,
                          sizeof( v6Only ) ) );
#else
         /*
         ** IPV6_V6ONLY is not defined, so the socket option can't be set and
         ** thus IPv4 mapped addresses can't be disabled.  Print a warning
         ** message and close the socket.  Design note: If the
         ** #if...#else...#endif construct were removed, then this program
         ** would not compile (because IPV6_V6ONLY isn't defined).  That's an
         ** acceptable approach; IPv4 mapped addresses are certainly disabled
         ** if the program can't build!  However, since this program is also
         ** designed to work for IPv4 sockets as well as IPv6, I decided to
         ** allow the program to compile when IPV6_V6ONLY is not defined, and
         ** turn it into a run-time warning rather than a compile-time error.
         ** IPv4 mapped addresses are still disabled because _all_ IPv6 traffic
         ** is disabled (all IPv6 sockets are closed here), but at least this
         ** way the server can still service IPv4 network traffic.
         */
         fprintf( stderr,
                  "%s (line %d): WARNING - Cannot set IPV6_V6ONLY socket "
                  "option.  Closing IPv6 %s socket.\n",
                  pgmName,
                  __LINE__,
                  ai->ai_protocol == IPPROTO_TCP  ?  "TCP"  :  "UDP" );
         CHK( close( desc[ *descSize ] ) );
         continue;   /* Go to top of FOR loop w/o updating *descSize! */
#endif /* IPV6_V6ONLY */
      }  /* End IF this is an IPv6 socket. */
      /*
      ** Bind the socket.  Again, the info from the addrinfo structure is used.
      */
      CHK( bind( desc[ *descSize ],
                 ai->ai_addr,
                 ai->ai_addrlen ) );
      /*
      ** If this is a TCP socket, put the socket into passive listening mode
      ** (listen is only valid on connection-oriented sockets).
      */
      if ( ai->ai_socktype == SOCK_STREAM )
      {
         CHK( listen( desc[ *descSize ],
                      MAXCONNQLEN ) );
      }
      /*
      ** Socket set up okay.  Bump index to next descriptor array element.
      */
      *descSize += 1;
   }  /* End FOR each address info structure returned. */
   /*
   ** Dummy check for unused address records.
   */
   if ( verbose && ( ai != NULL ) )
   {
      fprintf( stderr,
               "%s (line %d): WARNING - Some address records were "
               "not processed due to insufficient array space.\n",
               pgmName,
               __LINE__ );
   }  /* End IF verbose and some address records remain unprocessed. */
   /*
   ** Clean up.
   */
   freeaddrinfo( aiHead );
   return 0;
}  /* End openSckt() */
/******************************************************************************
* Function: tod
*
* Description:
*    Listen on a set of sockets and send the current time-of-day to any
*    clients.  This function never returns.
*
* Parameters:
*    tSckt     - Array of TCP socket descriptors on which to listen.
*    tScktSize - Size of the tSckt array (nbr of elements).
*    uSckt     - Array of UDP socket descriptors on which to listen.
*    uScktSize - Size of the uSckt array (nbr of elements).
*
* Return Value: None.
******************************************************************************/
static void tod( int    tSckt[ ],
                 size_t tScktSize,
                 int    uSckt[ ],
                 size_t uScktSize )
{
   char                     bfr[ 256 ];
   ssize_t                  count;
   struct pollfd           *desc;
   size_t                   descSize = tScktSize + uScktSize;
   int                      idx;
   int                      newSckt;
   struct sockaddr         *sadr;
   socklen_t                sadrLen;
   struct sockaddr_storage  sockStor;
   int                      status;
   size_t                   timeLen;
   char                    *timeStr;
   time_t                   timeVal;
   ssize_t                  wBytes;
   /*
   ** Allocate memory for the poll(2) array.
   */
   desc = malloc( descSize * sizeof( struct pollfd ) );
   if ( desc == NULL )
   {
      fprintf( stderr,
               "%s (line %d): ERROR - %s.\n",
               pgmName,
               __LINE__,
               strerror( ENOMEM ) );
      exit( 1 );
   }
   /*
   ** Initialize the poll(2) array.
   */
   for ( idx = 0;     idx < descSize;     idx++ )
   {
      desc[ idx ].fd      = idx < tScktSize  ?  tSckt[ idx ]
                                             :  uSckt[ idx - tScktSize ];
      desc[ idx ].events  = POLLIN;
      desc[ idx ].revents = 0;
   }
   /*
   ** Main time-of-day server loop.  Handles both TCP & UDP requests.  This is
   ** an interative server, and all requests are handled directly within the
   ** main loop.
   */
   while ( true )   /* Do forever. */
   {
      /*
      ** Wait for activity on one of the sockets.  The DO..WHILE construct is
      ** used to restart the system call in the event the process is
      ** interrupted by a signal.
      */
      do
      {
         status = poll( desc,
                        descSize,
                        -1 /* Wait indefinitely for input. */ );
      } while ( ( status < 0 ) && ( errno == EINTR ) );
      CHK( status );   /* Check for a bona fide system call error. */
      /*
      ** Get the current time.
      */
      timeVal = time( NULL );
      timeStr = ctime( &timeVal );
      timeLen = strlen( timeStr );
      /*
      ** Indicate that there is new network activity.
      */
      if ( verbose )
      {
         char *s = malloc( timeLen+1 );
         strcpy( s, timeStr );
         s[ timeLen-1 ] = '\0';   /* Overwrite '\n' in date string. */
         fprintf( stderr,
                  "%s: New network activity on %s.\n",
                  pgmName,
                  s );
         free( s );
      }  /* End IF verbose. */
      /*
      ** Process sockets with input available.
      */
      for ( idx = 0;     idx < descSize;     idx++ )
      {
         switch ( desc[ idx ].revents )
         {
            case 0:        /* No activity on this socket; try the next. */
               continue;
            case POLLIN:   /* Network activity.  Go process it.         */
               break;
            default:       /* Invalid poll events.                      */
            {
               fprintf( stderr,
                        "%s (line %d): ERROR - Invalid poll event (0x%02X).\n",
                        pgmName,
                        __LINE__,
                        desc[ idx ].revents );
               exit( 1 );
            }
         }  /* End SWITCH on returned poll events. */
         /*
         ** Determine if this is a TCP request or UDP request.
         */
         if ( idx < tScktSize )
         {
            /*
            ** TCP connection requested.  Accept it.  Notice the use of
            ** the sockaddr_storage data type.
            */
            sadrLen = sizeof( sockStor );
            sadr    = (struct sockaddr*) &sockStor;
            CHK( newSckt = accept( desc[ idx ].fd,
                                   sadr,
                                   &sadrLen ) );
            CHK( shutdown( newSckt,       /* Server never recv's anything. */
                           SHUT_RD ) );
            if ( verbose )
            {
               /*
               ** Display the socket address of the remote client.  Begin with
               ** the address-independent fields.
               */
               fprintf( stderr,
                        "Sockaddr info for new TCP client:\n"
                        "   sa_family = %d (AF_INET = %d, AF_INET6 = %d)\n"
                        "   addr len  = %d (sockaddr_in = %d, "
                        "sockaddr_in6 = %d)\n",
                        sadr->sa_family,
                        AF_INET,
                        AF_INET6,
                        sadrLen,
                        sizeof( struct sockaddr_in ),
                        sizeof( struct sockaddr_in6 ) );
               /*
               ** Display the address-specific fields.
               */
               getnameinfo( sadr,
                            sadrLen,
                            hostBfr,
                            sizeof( hostBfr ),
                            servBfr,
                            sizeof( servBfr ),
                            NI_NUMERICHOST | NI_NUMERICSERV );
               /*
               ** Notice that we're switching on an address family now, not a
               ** protocol family.
               */
               switch ( sadr->sa_family )
               {
                  case AF_INET:   /* IPv4 address. */
                  {
                     struct sockaddr_in *p = (struct sockaddr_in*) sadr;
                     fprintf( stderr,
                              "   sin_addr  = sin_family: %d\n"
                              "               sin_addr:   %s\n"
                              "               sin_port:   %s\n",
                              p->sin_family,
                              hostBfr,
                              servBfr );
                     break;
                  }  /* End CASE of IPv4. */
                  case AF_INET6:   /* IPv6 address. */
                  {
                     struct sockaddr_in6 *p = (struct sockaddr_in6*) sadr;
                     fprintf( stderr,
                              "   sin6_addr = sin6_family:   %d\n"
                              "               sin6_addr:     %s\n"
                              "               sin6_port:     %s\n"
                              "               sin6_flowinfo: %d\n"
                              "               sin6_scope_id: %d\n",
                              p->sin6_family,
                              hostBfr,
                              servBfr,
                              p->sin6_flowinfo,
                              p->sin6_scope_id );
                     break;
                  }  /* End CASE of IPv6. */
                  default:   /* Can never get here, but for completeness. */
                  {
                     fprintf( stderr,
                              "%s (line %d): ERROR - Unknown address "
                              "family (%d).\n",
                              pgmName,
                              __LINE__,
                              sadr->sa_family );
                     break;
                  }  /* End DEFAULT case (unknown address family). */
               }  /* End SWITCH on address family. */
            }  /* End IF verbose mode. */
            /*
            ** Send the TOD to the client.
            */
            wBytes = timeLen;
            while ( wBytes > 0 )
            {
               do
               {
                  count = write( newSckt,
                                 timeStr,
                                 wBytes );
               } while ( ( count < 0 ) && ( errno == EINTR ) );
               CHK( count );   /* Check for a bona fide error. */
               wBytes -= count;
            }  /* End WHILE there is data to send. */
            CHK( close( newSckt ) );
         }  /* End IF this was a TCP connection request. */
         else
         {
            /*
            ** This is a UDP socket, and a datagram is available.  The funny
            ** thing about UDP requests is that this server doesn't require any
            ** client input; but it can't send the TOD unless it knows a client
            ** wants the data, and the only way that can occur with UDP is if
            ** the server receives a datagram from the client.  Thus, the
            ** server must receive _something_, but the content of the datagram
            ** is irrelevant.  Read in the datagram.  Again note the use of
            ** sockaddr_storage to receive the address.
            */
            sadrLen = sizeof( sockStor );
            sadr    = (struct sockaddr*) &sockStor;
            CHK( count = recvfrom( desc[ idx ].fd,
                                   bfr,
                                   sizeof( bfr ),
                                   0,
                                   sadr,
                                   &sadrLen ) );
            /*
            ** Display whatever was received on stdout.
            */
            if ( verbose )
            {
               ssize_t rBytes = count;
               fprintf( stderr,
                        "%s: UDP datagram received (%d bytes).\n",
                        pgmName,
                        count );
               while ( count > 0 )
               {
                  fputc( bfr[ rBytes - count-- ],
                         stdout );
               }
               if ( bfr[ rBytes-1 ] != '\n' )
                  fputc( '\n', stdout );   /* Newline also flushes stdout. */
               /*
               ** Display the socket address of the remote client.  Address-
               ** independent fields first.
               */
               fprintf( stderr,
                        "Remote client's sockaddr info:\n"
                        "   sa_family = %d (AF_INET = %d, AF_INET6 = %d)\n"
                        "   addr len  = %d (sockaddr_in = %d, "
                        "sockaddr_in6 = %d)\n",
                        sadr->sa_family,
                        AF_INET,
                        AF_INET6,
                        sadrLen,
                        sizeof( struct sockaddr_in ),
                        sizeof( struct sockaddr_in6 ) );
               /*
               ** Display the address-specific information.
               */
               getnameinfo( sadr,
                            sadrLen,
                            hostBfr,
                            sizeof( hostBfr ),
                            servBfr,
                            sizeof( servBfr ),
                            NI_NUMERICHOST | NI_NUMERICSERV );
               switch ( sadr->sa_family )
               {
                  case AF_INET:   /* IPv4 address. */
                  {
                     struct sockaddr_in *p = (struct sockaddr_in*) sadr;
                     fprintf( stderr,
                              "   sin_addr  = sin_family: %d\n"
                              "               sin_addr:   %s\n"
                              "               sin_port:   %s\n",
                              p->sin_family,
                              hostBfr,
                              servBfr );
                     break;
                  }  /* End CASE of IPv4 address. */
                  case AF_INET6:   /* IPv6 address. */
                  {
                     struct sockaddr_in6 *p = (struct sockaddr_in6*) sadr;
                     fprintf( stderr,
                              "   sin6_addr = sin6_family:   %d\n"
                              "               sin6_addr:     %s\n"
                              "               sin6_port:     %s\n"
                              "               sin6_flowinfo: %d\n"
                              "               sin6_scope_id: %d\n",
                              p->sin6_family,
                              hostBfr,
                              servBfr,
                              p->sin6_flowinfo,
                              p->sin6_scope_id );
                     break;
                  }  /* End CASE of IPv6 address. */
                  default:   /* Can never get here, but for completeness. */
                  {
                     fprintf( stderr,
                              "%s (line %d): ERROR - Unknown address "
                              "family (%d).\n",
                              pgmName,
                              __LINE__,
                              sadr->sa_family );
                     break;
                  }  /* End DEFAULT case (unknown address family). */
               }  /* End SWITCH on address family. */
            }  /* End IF verbose mode. */
            /*
            ** Send the time-of-day to the client.
            */
            wBytes = timeLen;
            while ( wBytes > 0 )
            {
               do
               {
                  count = sendto( desc[ idx ].fd,
                                  timeStr,
                                  wBytes,
                                  0,
                                  sadr,        /* Address & address length   */
                                  sadrLen );   /*    received in recvfrom(). */
               } while ( ( count < 0 ) && ( errno == EINTR ) );
               CHK( count );   /* Check for a bona fide error. */
               wBytes -= count;
            }  /* End WHILE there is data to send. */
         }  /* End ELSE a UDP datagram is available. */
         desc[ idx ].revents = 0;   /* Clear the returned poll events. */
      }  /* End FOR each socket descriptor. */
   }  /* End WHILE forever. */
}  /* End tod() */

tod6tc [-v] [-s scope_id] [host [service]]

/******************************************************************************
* File: tod6tc.c
* Description: Contains source code for an IPv6-capable 'daytime' TCP client.
* Author: John Wenker, Sr. Software Engineer
*         Performance Technologies, San Diego, USA
******************************************************************************/
/*
** System header files.
*/
#include <errno.h>        /* errno declaration and error codes.             */
#include <net/if.h>       /* if_nametoindex(3).                             */
#include <netdb.h>        /* getaddrinfo(3) and associated definitions.     */
#include <netinet/in.h>   /* sockaddr_in and sockaddr_in6 definitions.      */
#include <stdio.h>        /* printf(3) et al.                               */
#include <stdlib.h>       /* exit(2).                                       */
#include <string.h>       /* String manipulation and memory functions.      */
#include <sys/socket.h>   /* Socket functions (socket(2), connect(2), etc). */
#include <unistd.h>       /* getopt(3), read(2), etc.                       */
/*
** Constants & macros.
*/
#define DFLT_HOST      "localhost"   /* Default server name.              */
#define DFLT_SCOPE_ID  "eth0"        /* Default scope identifier.         */
#define DFLT_SERVICE   "daytime"     /* Default service name.             */
#define INVALID_DESC   -1            /* Invalid file (socket) descriptor. */
#define MAXBFRSIZE     256           /* Max bfr sz to read remote TOD.    */
#define VALIDOPTS      "s:v"         /* Valid command options.            */
/*
** Type definitions (for convenience).
*/
typedef enum { false = 0, true } boolean;
typedef struct sockaddr_in       sockaddr_in_t;
typedef struct sockaddr_in6      sockaddr_in6_t;
/*
** Prototypes for internal helper functions.
*/
static int  openSckt( const char   *host,
                      const char   *service,
                      unsigned int  scopeId );
static void tod( int sckt );
/*
** Global (within this file only) data objects.
*/
static const char *pgmName;           /* Program name (w/o directory). */
static boolean     verbose = false;   /* Verbose mode.                 */
/*
** Usage macro.
*/
#define USAGE                                                            \
        {                                                                \
           fprintf( stderr,                                              \
                    "Usage: %s [-v] [-s scope_id] [host [service]]\n",   \
                    pgmName );                                           \
           exit( 127 );                                                  \
        }  /* End USAGE macro. */
/*
** This "macro" (even though it's really a function) is loosely based on the
** CHK() macro by Dr. V. Vinge (see server code).  The status parameter is
** a boolean expression indicating the return code from one of the usual system
** calls that returns -1 on error.  If a system call error occurred, an alert
** is written to stderr.  It returns a boolean value indicating success/failure
** of the system call.
**
** Example: if ( !SYSCALL( "write",
**                         count = write( fd, bfr, size ) ) )
**          {
**             // Error processing... but SYSCALL() will have already taken
**             // care of dumping an error alert to stderr.
**          }
*/
static __inline boolean SYSCALL( const char *syscallName,
                                 int         lineNbr,
                                 int         status )
{
   if ( ( status == -1 ) && verbose )
   {
      fprintf( stderr,
               "%s (line %d): System call failed ('%s') - %s.\n",
               pgmName,
               lineNbr,
               syscallName,
               strerror( errno ) );
   }
   return status != -1;   /* True if the system call was successful. */
}  /* End SYSCALL() */
/******************************************************************************
* Function: main
*
* Description:
*    Connect to a remote time-of-day service and write the remote host's TOD to
*    stdout.
*
* Parameters:
*    The usual argc & argv parameters to a main() program.
*
* Return Value:
*    This function always returns zero.
******************************************************************************/
int main( int   argc,
          char *argv[ ] )
{
   const char   *host     = DFLT_HOST;
   int           opt;
   int           sckt;
   unsigned int  scopeId  = if_nametoindex( DFLT_SCOPE_ID );
   const char   *service  = DFLT_SERVICE;
   /*
   ** Determine the program name (w/o directory prefix).
   */
   pgmName = (const char*) strrchr( argv[ 0 ], '/' );
   pgmName = pgmName == NULL  ?  argv[ 0 ]  :  pgmName+1;
   /*
   ** Process command line options.
   */
   opterr = 0;   /* Turns off "invalid option" error messages. */
   while ( ( opt = getopt( argc, argv, VALIDOPTS ) ) != -1 )
   {
      switch ( opt )
      {
         case 's':   /* Scope identifier (IPv6 kluge). */
         {
            scopeId = if_nametoindex( optarg );
            if ( scopeId == 0 )
            {
               fprintf( stderr,
                        "%s: Unknown network interface (%s).\n",
                        pgmName,
                        optarg );
               USAGE;
            }
            break;
         }
         case 'v':   /* Verbose mode. */
         {
            verbose = true;
            break;
         }
         default:
         {
            USAGE;
         }
      }  /* End SWITCH on command option. */
   } /* End WHILE processing command options. */
   /*
   ** Process command arguments.  At the end of the above loop, optind is the
   ** index of the first NON-option argv element.
   */
   switch ( argc - optind )
   {
      case 2:   /* Both host & service are specified on the command line. */
      {
          service = argv[ optind + 1 ];
          /***** Fall through *****/
      }
      case 1:   /* Host is specified on the command line. */
      {
          host = argv[ optind ];
          /***** Fall through *****/
      }
      case 0:   /* Use default host & service. */
      {
          break;
      }
      default:
      {
         USAGE;
      }
   }  /* End SWITCH on number of command arguments. */
   /*
   ** Open a connection to the indicated host/service.
   **
   ** Note that if all three of the following conditions are met, then the
   ** scope identifier remains unresolved at this point.
   **    1) The default network interface is unknown for some reason.
   **    2) The -s option was not used on the command line.
   **    3) An IPv6 "scoped address" was not specified for the hostname on the
   **       command line.
   ** If the above three conditions are met, then only an IPv4 socket can be
   ** opened (connect(2) fails without the scope ID properly set for IPv6
   ** sockets).
   */
   if ( ( sckt = openSckt( host,
                           service,
                           scopeId ) ) == INVALID_DESC )
   {
      fprintf( stderr,
               "%s: Sorry... a connection could not be established.\n",
               pgmName );
      exit( 1 );
   }
   /*
   ** Get the remote time-of-day.
   */
   tod( sckt );
   /*
   ** Close the connection and terminate.
   */
   (void) SYSCALL( "close",
                   __LINE__,
                   close( sckt ) );
   return 0;
}  /* End main() */
/******************************************************************************
* Function: openSckt
*
* Description:
*    Sets up a TCP connection to a remote server.  Getaddrinfo(3) is used to
*    perform lookup functions and can return multiple address records (i.e. a
*    list of 'struct addrinfo' records).  This function traverses the list and
*    tries to establish a connection to the remote server.  The function ends
*    when either a connection has been established or all records in the list
*    have been processed.
*
* Parameters:
*    host    - A pointer to a character string representing the hostname or IP
*              address (IPv4 or IPv6) of the remote server.
*    service - A pointer to a character string representing the service name or
*              well-known port number.
*    scopeId - For IPv6 sockets only.  This is the index corresponding to the
*              network interface on which to set up the connection.  This
*              parameter is ignored for IPv4 sockets or when an IPv6 "scoped
*              address" is specified in 'host' (i.e. where the colon-hex
*              network address is augmented with the scope ID).
*
* Return Value:
*    Returns the socket descriptor for the connection, or INVALID_DESC if all
*    address records have been processed and a connection could not be
*    established.
******************************************************************************/
static int openSckt( const char   *host,
                     const char   *service,
                     unsigned int  scopeId )
{
   struct addrinfo *ai;
   int              aiErr;
   struct addrinfo *aiHead;
   struct addrinfo  hints;
   sockaddr_in6_t  *pSadrIn6;
   int              sckt;
   /*
   ** Initialize the 'hints' structure for getaddrinfo(3).
   **
   ** Notice that the 'ai_family' field is set to PF_UNSPEC, indicating to
   ** return both IPv4 and IPv6 address records for the host/service.  Most of
   ** the time, the user isn't going to care whether an IPv4 connection or an
   ** IPv6 connection is established; the user simply wants to exchange data
   ** with the remote host and doesn't care how it's done.  Sometimes, however,
   ** the user might want to explicitly specify the type of underlying socket.
   ** It is left as an exercise for the motivated reader to add a command line
   ** option allowing the user to specify the IP protocol, and then process the
   ** list of addresses accordingly (it's not that difficult).
   */
   memset( &hints, 0, sizeof( hints ) );
   hints.ai_family   = PF_UNSPEC;     /* IPv4 or IPv6 records (don't care). */
   hints.ai_socktype = SOCK_STREAM;   /* Connection-oriented byte stream.   */
   hints.ai_protocol = IPPROTO_TCP;   /* TCP transport layer protocol only. */
   /*
   ** Look up the host/service information.
   */
   if ( ( aiErr = getaddrinfo( host,
                               service,
                               &hints,
                               &aiHead ) ) != 0 )
   {
      fprintf( stderr,
               "%s (line %d): ERROR - %s.\n",
               pgmName,
               __LINE__,
               gai_strerror( aiErr ) );
      return INVALID_DESC;
   }
   /*
   ** Go through the list and try to open a connection.  Continue until either
   ** a connection is established or the entire list is exhausted.
   */
   for ( ai = aiHead,   sckt = INVALID_DESC;
         ( ai != NULL ) && ( sckt == INVALID_DESC );
         ai = ai->ai_next )
   {
      /*
      ** IPv6 kluge.  Make sure the scope ID is set.
      */
      if ( ai->ai_family == PF_INET6 )
      {
         pSadrIn6 = (sockaddr_in6_t*) ai->ai_addr;
         if ( pSadrIn6->sin6_scope_id == 0 )
         {
            pSadrIn6->sin6_scope_id = scopeId;
         }  /* End IF the scope ID wasn't set. */
      }  /* End IPv6 kluge. */
      /*
      ** Display the address info for the remote host.
      */
      if ( verbose )
      {
         /*
         ** Temporary character string buffers for host & service.
         */
         char hostBfr[ NI_MAXHOST ];
         char servBfr[ NI_MAXSERV ];
         /*
         ** Display the address information just fetched.  Start with the
         ** common (protocol-independent) stuff first.
         */
         fprintf( stderr,
                  "Address info:\n"
                  "   ai_flags     = 0x%02X\n"
                  "   ai_family    = %d (PF_INET = %d, PF_INET6 = %d)\n"
                  "   ai_socktype  = %d (SOCK_STREAM = %d, SOCK_DGRAM = %d)\n"
                  "   ai_protocol  = %d (IPPROTO_TCP = %d, IPPROTO_UDP = %d)\n"
                  "   ai_addrlen   = %d (sockaddr_in = %d, "
                  "sockaddr_in6 = %d)\n",
                  ai->ai_flags,
                  ai->ai_family,
                  PF_INET,
                  PF_INET6,
                  ai->ai_socktype,
                  SOCK_STREAM,
                  SOCK_DGRAM,
                  ai->ai_protocol,
                  IPPROTO_TCP,
                  IPPROTO_UDP,
                  ai->ai_addrlen,
                  sizeof( struct sockaddr_in ),
                  sizeof( struct sockaddr_in6 ) );
         /*
         ** Display the protocol-specific formatted address.
         */
         getnameinfo( ai->ai_addr,
                      ai->ai_addrlen,
                      hostBfr,
                      sizeof( hostBfr ),
                      servBfr,
                      sizeof( servBfr ),
                      NI_NUMERICHOST | NI_NUMERICSERV );
         switch ( ai->ai_family )
         {
            case PF_INET:   /* IPv4 address record. */
            {
               sockaddr_in_t *pSadrIn = (sockaddr_in_t*) ai->ai_addr;
               fprintf( stderr,
                        "   ai_addr      = sin_family: %d (AF_INET = %d, "
                        "AF_INET6 = %d)\n"
                        "                  sin_addr:   %s\n"
                        "                  sin_port:   %s\n",
                        pSadrIn->sin_family,
                        AF_INET,
                        AF_INET6,
                        hostBfr,
                        servBfr );
               break;
            }  /* End CASE of IPv4 record. */
            case PF_INET6:   /* IPv6 address record. */
            {
               pSadrIn6 = (sockaddr_in6_t*) ai->ai_addr;
               fprintf( stderr,
                        "   ai_addr      = sin6_family:   %d (AF_INET = %d, "
                        "AF_INET6 = %d)\n"
                        "                  sin6_addr:     %s\n"
                        "                  sin6_port:     %s\n"
                        "                  sin6_flowinfo: %d\n"
                        "                  sin6_scope_id: %d\n",
                        pSadrIn6->sin6_family,
                        AF_INET,
                        AF_INET6,
                        hostBfr,
                        servBfr,
                        pSadrIn6->sin6_flowinfo,
                        pSadrIn6->sin6_scope_id );
               break;
            }  /* End CASE of IPv6 record. */
            default:   /* Can never get here, but just for completeness. */
            {
               fprintf( stderr,
                        "%s (line %d): ERROR - Unknown protocol family (%d).\n",
                        pgmName,
                        __LINE__,
                        ai->ai_family );
               break;
            }  /* End DEFAULT case (unknown protocol family). */
         }  /* End SWITCH on protocol family. */
      }  /* End IF verbose mode. */
      /*
      ** Create a socket.
      */
      if ( !SYSCALL( "socket",
                     __LINE__,
                     sckt = socket( ai->ai_family,
                                    ai->ai_socktype,
                                    ai->ai_protocol ) ) )
      {
         sckt = INVALID_DESC;
         continue;   /* Try the next address record in the list. */
      }
      /*
      ** Connect to the remote host.
      */
      if ( !SYSCALL( "connect",
                     __LINE__,
                     connect( sckt,
                              ai->ai_addr,
                              ai->ai_addrlen ) ) )
      {
         (void) close( sckt );   /* Could use SYSCALL() again here, but why? */
         sckt = INVALID_DESC;
         continue;   /* Try the next address record in the list. */
      }
   }  /* End FOR each address record returned by getaddrinfo(3). */
   /*
   ** Clean up & return.
   */
   freeaddrinfo( aiHead );
   return sckt;
}  /* End openSckt() */
/******************************************************************************
* Function: tod
*
* Description:
*    Receive the time-of-day from the remote server and write it to stdout.
*
* Parameters:
*    sckt - The socket descriptor for the connection.
*
* Return Value: None.
******************************************************************************/
static void tod( int sckt )
{
   char bfr[ MAXBFRSIZE+1 ];
   int  inBytes;
   /*
   ** The client never sends anything, so shut down the write side of the
   ** connection.
   */
   if ( !SYSCALL( "shutdown",
                  __LINE__,
                  shutdown( sckt, SHUT_WR ) ) )
   {
      return;
   }
   /*
   ** Read the time-of-day from the remote host.
   */
   do
   {
      if ( !SYSCALL( "read",
                     __LINE__,
                     inBytes = read( sckt,
                                     bfr,
                                     MAXBFRSIZE ) ) )
      {
         return;
      }
      bfr[ inBytes ] = '\0';   /* Null-terminate the received string. */
      fputs( bfr, stdout );    /* Null string if EOF (inBytes == 0).  */
   } while ( inBytes > 0 );
   fflush( stdout );
}  /* End tod() */

tod6uc [-v] [-s scope_id] [host [service]]

/******************************************************************************
* File: tod6uc.c
* Description: Contains source code for an IPv6-capable 'daytime' UDP client.
* Author: John Wenker, Sr. Software Engineer
*         Performance Technologies, San Diego, USA
******************************************************************************/
/*
** System header files.
*/
#include <errno.h>        /* errno declaration and error codes.             */
#include <net/if.h>       /* if_nametoindex(3).                             */
#include <netdb.h>        /* getaddrinfo(3) and associated definitions.     */
#include <netinet/in.h>   /* sockaddr_in and sockaddr_in6 definitions.      */
#include <stdio.h>        /* printf(3) et al.                               */
#include <stdlib.h>       /* exit(2).                                       */
#include <string.h>       /* String manipulation and memory functions.      */
#include <sys/socket.h>   /* Socket functions (socket(2), connect(2), etc). */
#include <unistd.h>       /* getopt(3), recvfrom(2), sendto(2), etc.        */
/*
** Constants & macros.
*/
#define DFLT_HOST      "localhost"   /* Default server name.              */
#define DFLT_SCOPE_ID  "eth0"        /* Default scope identifier.         */
#define DFLT_SERVICE   "daytime"     /* Default service name.             */
#define INVALID_DESC   -1            /* Invalid file (socket) descriptor. */
#define MAXBFRSIZE     256           /* Max bfr sz to read remote TOD.    */
#define VALIDOPTS      "s:v"         /* Valid command options.            */
/*
** Type definitions (for convenience).
*/
typedef enum { false = 0, true } boolean;
typedef struct sockaddr_in       sockaddr_in_t;
typedef struct sockaddr_in6      sockaddr_in6_t;
/*
** Prototypes for internal helper functions.
*/
static int  openSckt( const char   *host,
                      const char   *service,
                      unsigned int  scopeId );
static void tod( int sckt );
/*
** Global (within this file only) data objects.
*/
static const char *pgmName;           /* Program name (w/o directory). */
static boolean     verbose = false;   /* Verbose mode.                 */
/*
** Usage macro.
*/
#define USAGE                                                            \
        {                                                                \
           fprintf( stderr,                                              \
                    "Usage: %s [-v] [-s scope_id] [host [service]]\n",   \
                    pgmName );                                           \
           exit( 127 );                                                  \
        }  /* End USAGE macro. */
/*
** This "macro" (even though it's really a function) is loosely based on the
** CHK() macro by Dr. V. Vinge (see server code).  The status parameter is
** a boolean expression indicating the return code from one of the usual system
** calls that returns -1 on error.  If a system call error occurred, an alert
** is written to stderr.  It returns a boolean value indicating success/failure
** of the system call.
**
** Example: if ( !SYSCALL( "write",
**                         count = write( fd, bfr, size ) ) )
**          {
**             // Error processing... but SYSCALL() will have already taken
**             // care of dumping an error alert to stderr.
**          }
*/
static __inline boolean SYSCALL( const char *syscallName,
                                 int         lineNbr,
                                 int         status )
{
   if ( ( status == -1 ) && verbose )
   {
      fprintf( stderr,
               "%s (line %d): System call failed ('%s') - %s.\n",
               pgmName,
               lineNbr,
               syscallName,
               strerror( errno ) );
   }
   return status != -1;   /* True if the system call was successful. */
}  /* End SYSCALL() */
/******************************************************************************
* Function: main
*
* Description:
*    Connect to a remote time-of-day service and write the remote host's TOD to
*    stdout.
*
* Parameters:
*    The usual argc & argv parameters to a main() program.
*
* Return Value:
*    This function always returns zero.
******************************************************************************/
int main( int   argc,
          char *argv[ ] )
{
   const char   *host     = DFLT_HOST;
   int           opt;
   int           sckt;
   unsigned int  scopeId  = if_nametoindex( DFLT_SCOPE_ID );
   const char   *service  = DFLT_SERVICE;
   /*
   ** Determine the program name (w/o directory prefix).
   */
   pgmName = (const char*) strrchr( argv[ 0 ], '/' );
   pgmName = pgmName == NULL  ?  argv[ 0 ]  :  pgmName+1;
   /*
   ** Process command line options.
   */
   opterr = 0;   /* Turns off "invalid option" error messages. */
   while ( ( opt = getopt( argc, argv, VALIDOPTS ) ) != -1 )
   {
      switch ( opt )
      {
         case 's':   /* Scope identifier (IPv6 kluge). */
         {
            scopeId = if_nametoindex( optarg );
            if ( scopeId == 0 )
            {
               fprintf( stderr,
                        "%s: Unknown network interface (%s).\n",
                        pgmName,
                        optarg );
               USAGE;
            }
            break;
         }
         case 'v':   /* Verbose mode. */
         {
            verbose = true;
            break;
         }
         default:
         {
            USAGE;
         }
      }  /* End SWITCH on command option. */
   } /* End WHILE processing command options. */
   /*
   ** Process command arguments.  At the end of the above loop, optind is the
   ** index of the first NON-option argv element.
   */
   switch ( argc - optind )
   {
      case 2:   /* Both host & service are specified on the command line. */
      {
          service = argv[ optind + 1 ];
          /***** Fall through *****/
      }
      case 1:   /* Host is specified on the command line. */
      {
          host = argv[ optind ];
          /***** Fall through *****/
      }
      case 0:   /* Use default host & service. */
      {
          break;
      }
      default:
      {
         USAGE;
      }
   }  /* End SWITCH on number of command arguments. */
   /*
   ** Open a connection to the indicated host/service.
   **
   ** Note that if all three of the following conditions are met, then the
   ** scope identifier remains unresolved at this point.
   **    1) The default network interface is unknown for some reason.
   **    2) The -s option was not used on the command line.
   **    3) An IPv6 "scoped address" was not specified for the hostname on the
   **       command line.
   ** If the above three conditions are met, then only an IPv4 socket can be
   ** opened (connect(2) fails without the scope ID properly set for IPv6
   ** sockets).
   */
   if ( ( sckt = openSckt( host,
                           service,
                           scopeId ) ) == INVALID_DESC )
   {
      fprintf( stderr,
               "%s: Sorry... a connectionless socket could "
               "not be set up.\n",
               pgmName );
      exit( 1 );
   }
   /*
   ** Get the remote time-of-day.
   */
   tod( sckt );
   /*
   ** Close the connection and terminate.
   */
   (void) SYSCALL( "close",
                   __LINE__,
                   close( sckt ) );
   return 0;
}  /* End main() */
/******************************************************************************
* Function: openSckt
*
* Description:
*    Sets up a UDP socket to a remote server.  Getaddrinfo(3) is used to
*    perform lookup functions and can return multiple address records (i.e. a
*    list of 'struct addrinfo' records).  This function traverses the list and
*    tries to establish a connection to the remote server.  The function ends
*    when either a connection has been established or all records in the list
*    have been processed.
*
* Parameters:
*    host    - A pointer to a character string representing the hostname or IP
*              address (IPv4 or IPv6) of the remote server.
*    service - A pointer to a character string representing the service name or
*              well-known port number.
*    scopeId - For IPv6 sockets only.  This is the index corresponding to the
*              network interface on which to exchange datagrams.  This
*              parameter is ignored for IPv4 sockets or when an IPv6 "scoped
*              address" is specified in 'host' (i.e. where the colon-hex
*              network address is augmented with the scope ID).
*
* Return Value:
*    Returns the socket descriptor for the connection, or INVALID_DESC if all
*    address records have been processed and a socket could not be initialized.
******************************************************************************/
static int openSckt( const char   *host,
                     const char   *service,
                     unsigned int  scopeId )
{
   struct addrinfo *ai;
   int              aiErr;
   struct addrinfo *aiHead;
   struct addrinfo  hints;
   sockaddr_in6_t  *pSadrIn6;
   int              sckt;
   /*
   ** Initialize the 'hints' structure for getaddrinfo(3).
   **
   ** Notice that the 'ai_family' field is set to PF_UNSPEC, indicating to
   ** return both IPv4 and IPv6 address records for the host/service.  Most of
   ** the time, the user isn't going to care whether an IPv4 connection or an
   ** IPv6 connection is established; the user simply wants to exchange data
   ** with the remote host and doesn't care how it's done.  Sometimes, however,
   ** the user might want to explicitly specify the type of underlying socket.
   ** It is left as an exercise for the motivated reader to add a command line
   ** option allowing the user to specify the IP protocol, and then process the
   ** list of addresses accordingly (it's not that difficult).
   */
   memset( &hints, 0, sizeof( hints ) );
   hints.ai_family   = PF_UNSPEC;     /* IPv4 or IPv6 records (don't care). */
   hints.ai_socktype = SOCK_DGRAM;    /* Connectionless communication.      */
   hints.ai_protocol = IPPROTO_UDP;   /* UDP transport layer protocol only. */
   /*
   ** Look up the host/service information.
   */
   if ( ( aiErr = getaddrinfo( host,
                               service,
                               &hints,
                               &aiHead ) ) != 0 )
   {
      fprintf( stderr,
               "%s (line %d): ERROR - %s.\n",
               pgmName,
               __LINE__,
               gai_strerror( aiErr ) );
      return INVALID_DESC;
   }
   /*
   ** Go through the list and try to open a connection.  Continue until either
   ** a connection is established or the entire list is exhausted.
   */
   for ( ai = aiHead,   sckt = INVALID_DESC;
         ( ai != NULL ) && ( sckt == INVALID_DESC );
         ai = ai->ai_next )
   {
      /*
      ** IPv6 kluge.  Make sure the scope ID is set.
      */
      if ( ai->ai_family == PF_INET6 )
      {
         pSadrIn6 = (sockaddr_in6_t*) ai->ai_addr;
         if ( pSadrIn6->sin6_scope_id == 0 )
         {
            pSadrIn6->sin6_scope_id = scopeId;
         }  /* End IF the scope ID wasn't set. */
      }  /* End IPv6 kluge. */
      /*
      ** Display the address info for the remote host.
      */
      if ( verbose )
      {
         /*
         ** Temporary character string buffers for host & service.
         */
         char hostBfr[ NI_MAXHOST ];
         char servBfr[ NI_MAXSERV ];
         /*
         ** Display the address information just fetched.  Start with the
         ** common (protocol-independent) stuff first.
         */
         fprintf( stderr,
                  "Address info:\n"
                  "   ai_flags     = 0x%02X\n"
                  "   ai_family    = %d (PF_INET = %d, PF_INET6 = %d)\n"
                  "   ai_socktype  = %d (SOCK_STREAM = %d, SOCK_DGRAM = %d)\n"
                  "   ai_protocol  = %d (IPPROTO_TCP = %d, IPPROTO_UDP = %d)\n"
                  "   ai_addrlen   = %d (sockaddr_in = %d, "
                  "sockaddr_in6 = %d)\n",
                  ai->ai_flags,
                  ai->ai_family,
                  PF_INET,
                  PF_INET6,
                  ai->ai_socktype,
                  SOCK_STREAM,
                  SOCK_DGRAM,
                  ai->ai_protocol,
                  IPPROTO_TCP,
                  IPPROTO_UDP,
                  ai->ai_addrlen,
                  sizeof( struct sockaddr_in ),
                  sizeof( struct sockaddr_in6 ) );
         /*
         ** Display the protocol-specific formatted address.
         */
         getnameinfo( ai->ai_addr,
                      ai->ai_addrlen,
                      hostBfr,
                      sizeof( hostBfr ),
                      servBfr,
                      sizeof( servBfr ),
                      NI_NUMERICHOST | NI_NUMERICSERV );
         switch ( ai->ai_family )
         {
            case PF_INET:   /* IPv4 address record. */
            {
               sockaddr_in_t *pSadrIn = (sockaddr_in_t*) ai->ai_addr;
               fprintf( stderr,
                        "   ai_addr      = sin_family: %d (AF_INET = %d, "
                        "AF_INET6 = %d)\n"
                        "                  sin_addr:   %s\n"
                        "                  sin_port:   %s\n",
                        pSadrIn->sin_family,
                        AF_INET,
                        AF_INET6,
                        hostBfr,
                        servBfr );
               break;
            }  /* End CASE of IPv4 record. */
            case PF_INET6:   /* IPv6 address record. */
            {
               pSadrIn6 = (sockaddr_in6_t*) ai->ai_addr;
               fprintf( stderr,
                        "   ai_addr      = sin6_family:   %d (AF_INET = %d, "
                        "AF_INET6 = %d)\n"
                        "                  sin6_addr:     %s\n"
                        "                  sin6_port:     %s\n"
                        "                  sin6_flowinfo: %d\n"
                        "                  sin6_scope_id: %d\n",
                        pSadrIn6->sin6_family,
                        AF_INET,
                        AF_INET6,
                        hostBfr,
                        servBfr,
                        pSadrIn6->sin6_flowinfo,
                        pSadrIn6->sin6_scope_id );
               break;
            }  /* End CASE of IPv6 record. */
            default:   /* Can never get here, but just for completeness. */
            {
               fprintf( stderr,
                        "%s (line %d): ERROR - Unknown protocol family (%d).\n",
                        pgmName,
                        __LINE__,
                        ai->ai_family );
               break;
            }  /* End DEFAULT case (unknown protocol family). */
         }  /* End SWITCH on protocol family. */
      }  /* End IF verbose mode. */
      /*
      ** Create a socket.
      */
      if ( !SYSCALL( "socket",
                     __LINE__,
                     sckt = socket( ai->ai_family,
                                    ai->ai_socktype,
                                    ai->ai_protocol ) ) )
      {
         sckt = INVALID_DESC;
         continue;   /* Try the next address record in the list. */
      }
      /*
      ** Set the target destination for the remote host on this socket.  That
      ** is, this socket only communicates with the specified host.
      */
      if ( !SYSCALL( "connect",
                     __LINE__,
                     connect( sckt,
                              ai->ai_addr,
                              ai->ai_addrlen ) ) )
      {
         (void) close( sckt );   /* Could use SYSCALL() again here, but why? */
         sckt = INVALID_DESC;
         continue;   /* Try the next address record in the list. */
      }
   }  /* End FOR each address record returned by getaddrinfo(3). */
   /*
   ** Clean up & return.
   */
   freeaddrinfo( aiHead );
   return sckt;
}  /* End openSckt() */
/******************************************************************************
* Function: tod
*
* Description:
*    Receive the time-of-day from the remote server and write it to stdout.
*
* Parameters:
*    sckt - The socket descriptor for the connection.
*
* Return Value: None.
******************************************************************************/
static void tod( int sckt )
{
   char bfr[ MAXBFRSIZE+1 ];
   int  inBytes;
   /*
   ** Send a datagram to the server to wake it up.  The content isn't
   ** important, but something must be sent to let it know we want the TOD.
   */
   if ( !SYSCALL( "write",
                  __LINE__,
                  write( sckt, "Are you there?", 14 ) ) )
   {
      return;
   }
   /*
   ** Read the time-of-day from the remote host.
   */
   if ( !SYSCALL( "read",
                  __LINE__,
                  inBytes = read( sckt,
                                  bfr,
                                  MAXBFRSIZE ) ) )
   {
      return;
   }
   bfr[ inBytes ] = '\0';   /* Null-terminate the received string. */
   fputs( bfr, stdout );    /* Null string if EOF (inBytes == 0).  */
   fflush( stdout );
}  /* End tod() */