Making net.inet6.ip6.v6only=0 default

[Hiroki Sato]

JINMEI Tatuya / 神明達哉 <jinmei at isc.org> wrote
  in <m2ppv5k988.wl%jinmei at isc.org>:

ji> > So I guess the question is: what do we do? It looks like we're in
ji> > violation of both RFC 3493, Section 5.3 and POSIX 2008, Volume 2, Section
ji> > 2.10.20*.
ji>
ji> ...aside from what FreeBSD should do for ip6.v6only, I personally
ji> believe that realistically this issue should be resolved at the
ji> application side, i.e., explicitly set the IPV6_V6ONLY socket option
ji> to 1 and use both AF_INET (for IPv4) and AF_INET6 (for IPv6, and only
ji> for IPv6) sockets.  As far as I know this is the most portable
ji> behavior.  Regarding the rwhois case, I'd first suggest updating the
ji> patch with this socket option setting.  Hopefully it can be accepted
ji> by the upstream because it's most portable.  If they still reject it
ji> because "it's against the standard" (and even if it's less portable in
ji> reality), my next suggestion is to explicitly set the IPV6_V6ONLY
ji> socket option to 0.  This setting is "redundant" in the sense of
ji> standard purity, but hopefully less controversial for those preferring
ji> the standard compliance as it only requires a small change and will
ji> make it still more portable.
ji>
ji> Going back to the question of what FreeBSD should do for ip6.v6only:
ji> Personally, I'd still suggest keeping the same default because I agree
ji> this behavior is sufficiently safer (as noted above) *and* there'll
ji> be portability issues anyway (OSes using the different default
ji> "religiously" will never change it).  But I also understand the
ji> argument that standard compliance is more important than debatable
ji> safety.  In either case, it would help if we provide detailed
ji> discussion for the description of this sysctl knob.

 Agreed.  Honestly my patch was not intended for upstream because it
 was too aggressive (for them).  Explicitly dropping IPV6_V6ONLY may
 be acceptable.

 I am also for keeping the sysctl knob.  Except for Java, most of
 applications which run on FreeBSD have survived with it.  In addition
 to the points already mentioned, I do not like s/AF_INET/AF_INET6/
 replacement like rwhoisd does, and I believe this kind of network
 programs should be implemented in an AF-independent fashion, not
 depending on AF_INET6, and handle each available AF separately.  It
 prevents issues in corner cases.

-- Hiroki
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