Public bug reported:
When calling getaddrinfo and specifying AF_UNSPEC and AI_PASSIVE it
returns both IPv4 and IPv6 addresses when the sysctl net.ipv6.bindv6only
= 0. Proper app behavior for AI_PASSIVE should be to bind and listen to
all returned addresses, but the kernel does not allow binding to a V4
and V6 address with the same port. In this case getaddrinfo should
return only a IPv4 or only a IPv6 address.
Illustrated with python because I'm lazy:
>>> resx =
>>> socket.getaddrinfo(None,'1234',0,socket.SOCK_STREAM,0,socket.AI_PASSIVE)
>>> print resx
[(2, 1, 6, '', ('0.0.0.0', 1234)), (10, 1, 6, '', ('::', 1234, 0, 0))]
>>> res = resx[0]
>>> fd = socket.socket(res[0],res[1],res[2])
>>> fd.bind(res[4]);
>>> res = resx[1]
>>> fd2 = socket.socket(res[0],res[1],res[2])
>>> fd2.bind(res[4]);
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<string>", line 1, in bind
socket.error: [Errno 98] Address already in use
At least in earlier Ubuntu releases this case returned the IPv6 address
first, so most apps which don't properly use all addresses 'worked' but
it was still wrong to return both addresses. The new behavior breaks
IPv6 in various cases, with no possible app work-around!
Apps should not be expected to 'sense' if the system is bindv6only.
getaddrinfo AF_UNSPEC/AI_PASSIVE should return v6 only for an IPv6
enabled bindv6only = 0 host and both IPv6 and IPv4 (in any order) for an
IPv6 enabled bindv6only= host.
At a minimum the old sorting behavior of putting v6 first should be
restored! Real apps depend on this!
I've noted various other bugs in this same theme:
http://sources.redhat.com/bugzilla/show_bug.cgi?id=9981
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=573456
So here is one for Ubuntu with a bit more clarity on the exact problem.
ProblemType: Bug
DistroRelease: Ubuntu 10.10
Package: libc6 2.12.1-0ubuntu8
ProcVersionSignature: Ubuntu 2.6.35-22.35-generic 2.6.35.4
Uname: Linux 2.6.35-22-generic x86_64
Architecture: amd64
Date: Wed Nov 10 12:52:08 2010
InstallationMedia: Ubuntu 10.10 "Maverick Meerkat" - Release amd64 (20101007)
ProcEnviron:
PATH=(custom, no user)
LANG=C
SHELL=/bin/bash
SourcePackage: eglibc
** Affects: eglibc (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug maverick
--
getaddrinfo and AI_PASSIVE is broken for net.ipv6.bindv6only=0
https://bugs.launchpad.net/bugs/673708
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