Disable Mozilla IPv6?

[Richard Bejtlich]

Hello,

Is it possible to compile Mozilla without IPv6
support?   Can this be made the standard for
installing Mozilla through the ports tree?

Mozilla 1.6 has the annoying habit of doing queries
for IPv6 AAAA records before trying IPv4 A record
queries.  Many name servers do not handle these AAAA
queries properly, causing Mozilla to time out before
doing the A query.  For example, this query shows a
name server cooperating.  Mozilla asks for the AAAA
record, gets a zero answer reply, and then makes the A
query.

18:24:04.604363 192.168.2.5.49203 > 172.27.20.1.53: 
56494+ AAAA? xlonhcld.xlontech.net. (39)
18:24:04.611197 172.27.20.1.53 > 192.168.2.5.49203: 
56494 0/1/0 (104)
18:24:04.611474 192.168.2.5.49204 > 172.27.20.1.53: 
56495+ A? xlonhcld.xlontech.net. (39)
18:24:04.619886 172.27.20.1.53 > 192.168.2.5.49204: 
56495 18/7/0 A[|domain]

This is what happens with sites that don't answer AAAA
queries properly:

Mozilla asks for the AAAA record four times

18:20:11.292864 192.168.2.5.49188 > 172.27.20.1.53: 
4329+ AAAA? dclkcorp.rpts.net. (35)
18:20:16.304730 192.168.2.5.49189 > 172.27.20.1.53: 
4329+ AAAA? dclkcorp.rpts.net. (35)
18:20:26.319837 192.168.2.5.49190 > 172.27.20.1.53: 
4329+ AAAA? dclkcorp.rpts.net. (35)
18:20:46.334627 192.168.2.5.49191 > 172.27.20.1.53: 
4329+ AAAA? dclkcorp.rpts.net. (35)

After 75 seconds it gives up and asks for the A
record.  The name server promptly responds and the
page loads.

18:21:26.345147 192.168.2.5.49192 > 172.27.20.1.53: 
4330+ A? dclkcorp.rpts.net. (35)
18:21:26.378344 172.27.20.1.53 > 192.168.2.5.49192: 
4330 2/6/6[|domain]

Here are the replies for the AAAA record requests.  I
haven't figured out the purpose of the ICMP port
unreachable messages.

18:21:59.533098 172.27.20.1.53 > 192.168.2.5.49190: 
4329 ServFail 0/0/0 (35)
18:21:59.533170 192.168.2.5 > 172.27.20.1: icmp:
192.168.2.5 udp port 49190 unreachable
18:22:00.197621 172.27.20.1.53 > 192.168.2.5.49189: 
4329 ServFail 0/0/0 (35)
18:22:00.197688 192.168.2.5 > 172.27.20.1: icmp:
192.168.2.5 udp port 49189 unreachable
18:22:11.193955 172.27.20.1.53 > 192.168.2.5.49188: 
4329 ServFail 0/0/0 (35)
18:22:11.194029 192.168.2.5 > 172.27.20.1: icmp:
192.168.2.5 udp port 49188 unreachable
18:22:44.194926 172.27.20.1.53 > 192.168.2.5.49191: 
4329 ServFail 0/0/0 (35)
18:22:44.195000 192.168.2.5 > 172.27.20.1: icmp:
192.168.2.5 udp port 49191 unreachable

This issue was discussed on -current recently:

http://unix.derkeiler.com/Mailing-Lists/FreeBSD/current/2004-02/0485.html

There's a long-running Mozilla bug report too:

http://bugzilla.mozilla.org/show_bug.cgi?id=68796

Thank you,

Richard Bejtlich
http://www.taosecurity.com

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