[Bug network/16826] New: getaddrinfo() doesn't get scope ID for IPv6-only look-ups

[Bug network/16826] New: getaddrinfo() doesn't get scope ID for IPv6-only look-ups

[pub at craig dot mcqueen.id.au]

https://sourceware.org/bugzilla/show_bug.cgi?id=16826

            Bug ID: 16826
           Summary: getaddrinfo() doesn't get scope ID for IPv6-only
                    look-ups
           Product: glibc
           Version: 2.17
            Status: NEW
          Severity: normal
          Priority: P2
         Component: network
          Assignee: unassigned at sourceware dot org
          Reporter: pub at craig dot mcqueen.id.au

I'm trying to follow up on Ubuntu Launchpad bug #369008, in which mDNS IPv6
look-ups don't get the scope ID. There is a patch for nss-mdns which makes it
work by implementing _nss_gethostbyname4_r(), which is the only way to pass
through the IPv6 scope ID. However, while it works for lookups with family
AF_UNSPEC, it doesn't work for family AF_INET6.

It turns out that getaddrinfo() is calling _nss_gethostbyname4_r() only for
lookups with family AF_UNSPEC. But for family AF_INET6, it is calling
_nss_gethostbyname2_r() instead. It really should always call
_nss_gethostbyname4_r() for any IPv6 look-ups, in order to get the IPv6 scope
ID.

It used to work, however, I've traced the problem to glibc git commit
8479f23aa1.
http://repo.or.cz/w/glibc.git/commit/8479f23aa1d5e5477a37f46823856bdafaedfa46

In that commit, it was changed to only use _nss_gethostbyname4_r() for
AF_UNSPEC, and not AF_INET6. That breaks IPv6 scope ID retrieval. Can we revert
that change?

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[Bug network/16826] getaddrinfo() doesn't get scope ID for IPv6-only look-ups

[pub at craig dot mcqueen.id.au]

https://sourceware.org/bugzilla/show_bug.cgi?id=16826

--- Comment #1 from Craig McQueen <pub at craig dot mcqueen.id.au> ---
By the way, Ubuntu Launchpad bug #369008 "mdns lookups fail over ipv6" affects
look-ups of Zeroconf ".local" names through mDNS. Zeroconf is "zero
configuration networking" and that's the application in which IPv6 scope ID is
most important--where you want to plug things together and have it "just work".
On a network without assigned IPv6 addresses, IPv6 Unique Local Addresses (ULA)
are used, and it's necessary to have scope ID look-ups working to be able to
communicate to the IPv6 ULA.

With nss-mdns working (patched from the above Ubuntu Launchpad bug), it's
possible to do:

telnet mycomputername.local

(it uses a family AF_UNSPEC look-up, which works)

But due to this bug, on a network without assigned IPv6 addresses (ULA only)
it's not possible to do:
telnet -6 mycomputername.local
ping6 mycomputername.local

(it uses a family AF_INET6 look-up, which doesn't work with IPv6 ULA because
scope ID is missing)

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[Bug network/16826] getaddrinfo() doesn't get scope ID for IPv6-only look-ups

[schwab@linux-m68k.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=16826

Andreas Schwab <schwab@linux-m68k.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Blocks|                            |14505

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[Bug network/16826] getaddrinfo() doesn't get scope ID for IPv6-only look-ups

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=16826

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
              Flags|                            |security-

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[Bug network/16826] getaddrinfo() doesn't get scope ID for IPv6-only look-ups

[ott at mirix dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=16826

Matthias-Christian Ott <ott at mirix dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ott at mirix dot org

--- Comment #2 from Matthias-Christian Ott <ott at mirix dot org> ---
Are there any plans to address this issue? Is there any information missing
that blocks fixing this (5 year old) issue?

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[Bug network/16826] getaddrinfo() doesn't get scope ID for IPv6-only look-ups

[matthijsvanduin at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=16826

Matthijs van Duin <matthijsvanduin at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |matthijsvanduin at gmail dot com

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[Bug network/16826] getaddrinfo() doesn't get scope ID for IPv6-only look-ups

[sam at gentoo dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=16826

Sam James <sam at gentoo dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sam at gentoo dot org

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[Bug network/16826] getaddrinfo() doesn't get scope ID for IPv6-only look-ups

[sam at gentoo dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=16826

Sam James <sam at gentoo dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |toolchain at gentoo dot org

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