On 04-01-16 18:58, Wietse Venema wrote: > Tom Hendrikx: >> >> Hi, >> >> I'm trying to setup a test environment using smtp-sink as a mail >> receiver. For ipv4 I'm running smtp-sink on random addresses in >> 127.0.0.0/8, and was looking for the same trick on ipv6. My OS allows me >> to (ab)use ::ffff:0:0/96 for this, but unfortunately, smtp-sink does not: >> >> $ smtp-sink -v ::ffff:127.1.2.3:12345 100 >> smtp-sink: name_mask: all >> smtp-sink: trying... [::ffff:127.1.2.3]:12345 >> smtp-sink: fatal: bind ::ffff:127.1.2.3 port 12345: Invalid argument > > The bind(2) system call rejects the address. Postfix is the messenger > of bad news. Don't blame the messenger. > > Wietse >
I did some rummaging in the source code to see what I'm doing wrong, and found out that inet_listen.c sets the IPV6_V6ONLY flag on the socket [1], which makes the bind(2) bail out. If I remove the setsockopt(2) call and recompile, smtp-sink works as I hoped: $ ./smtp-sink -v ::ffff:127.1.2.3:12345 100 ./smtp-sink: name_mask: all ./smtp-sink: trying... [::ffff:127.1.2.3]:12345 <waiting for connections> ./smtp-sink: connect (AF_INET6 ::ffff:127.0.0.1) ./smtp-sink: vstream_tweak_tcp: TCP_MAXSEG 21888 ./smtp-sink: fd=5: stream buffer size old=0 new=43776 ./smtp-sink: smtp_stream_setup: maxtime=100 enable_deadline=0 ./smtp-sink: helo test ./smtp-sink: quit ./smtp-sink: disconnect I can see the use of the setsockopt call, since leaving it out has the side effect that smtp-sink is also reachable on 127.1.2.3 (ipv4). On the other hand, that behaviour is sort of what I requested when I explicitly specified an IPv4-mapped IPv6 address. So this means IMHO that IPv4-mapped IPv6 listen addresses are not supported/explicitly disabled by postfix, it has nothing to do with bind(2). Would be nice if that was mentioned somewhere. [1]: https://github.com/vdukhovni/postfix/blob/master/postfix/src/util/inet_listen.c#L145 Regards, Tom
