Better documentation related to IPv6.

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@280706 65c4cc65-6c06-0410-ace0-fbb531ad65f3

configs/sip.conf.sample

@@ -136,6 +136,28 @@ allowoverlap=no                 ; Disable overlap dialing support. (Default is y
                                 ; In this case Realm will be based on request 'From'/'To' header
                                 ; and should match one of domain names.
                                 ; Otherwise default 'realm=...' will be used.
+
+; With the current situation, you can do one of four things:
+;  a) Listen on a specific IPv4 address.      Example: bindaddr=192.0.2.1
+;  b) Listen on a specific IPv6 address.      Example: bindaddr=2001:db8::1
+;  c) Listen on the IPv4 wildcard.            Example: bindaddr=0.0.0.0
+;  d) Listen on the IPv4 and IPv6 wildcards.  Example: bindaddr=::
+; (You can choose independently for UDP, TCP, and TLS, by specifying different values for
+; "udpbindaddr", "tcpbindaddr", and "tlsbindaddr".)
+;
+; You may optionally add a port number. (The default is port 5060 for UDP and TCP, 5061
+; for TLS).
+;   IPv4 example: bindaddr=0.0.0.0:5062
+;   IPv6 example: bindaddr=[::]:5062
+;
+; The address family of the bound UDP address is used to determine how Asterisk performs
+; DNS lookups. In cases a) and c) above, only A records are considered. In case b), only
+; AAAA records are considered. In case d), both A and AAAA records are considered. Note,
+; however, that Asterisk ignores all records except the first one. In case d), when both A
+; and AAAA records are available, either an A or AAAA record will be first, and which one
+; depends on the operating system. On systems using glibc, AAAA records are given
+; priority.
+
 udpbindaddr=0.0.0.0             ; IP address to bind UDP listen socket to (0.0.0.0 binds to all)
                                 ; Optionally add a port number, 192.168.1.1:5062 (default is port 5060)
 
@@ -707,6 +729,8 @@ srvlookup=yes                   ; Enable DNS SRV lookups on outbound calls
 ;        stunaddr = foo.stun.com:3478
 ;        externrefresh = 15
 ;
+;      NOTE: STUN is only implemented for IPv4.
+;
 ;   Note that at the moment all these mechanism work only for the SIP socket.
 ;   The IP address discovered with externaddr/externhost/STUN is reused for
 ;   media sessions as well, but the port numbers are not remapped so you