Re: [RFC PATCH 0/2] Add AF_VSOCK support to getnameinfo(3) and getaddrinfo(3)

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Thu, Sep 29, 2016 at 03:25:55PM +0200, Florian Weimer wrote:
> * Stefan Hajnoczi:
> 
> > Many existing programs use getnameinfo(3) and getaddrinfo(3).
> > Porting programs to support AF_VSOCK is easy if the library
> > functions can handle this address family.  Without support in glibc
> > each program needs to duplicate address parsing code and it becomes
> > harder to port programs.
> 
> What has changed since the previous discussion?
> 
>   <https://sourceware.org/ml/libc-help/2015-08/msg00004.html>
> 
> How do you expect that applications will know that they have to pass
> AF_VSOCK to getaddrinfo instead of AF_UNSPEC?

For example ncat(1) has --unixsock and --udp command-line options.  A
--vsock option can be added.  At that point the program knows to use
AF_VSOCK and the same getaddrinfo(3) code path can be used by TCP, UDP,
UNIX, and vsock.

The AF_UNSPEC approach where getaddrinfo(3) parses an arbitrary string
and figures out the address family can't be supported for the security
reasons you explained previously.  But the other getnameinfo(3) and
getaddrinfo(3) use cases still make sense and simplify porting existing
applications to AF_VSOCK.

One note about the previous discussion: I had proposed a [vsock:<cid>]
syntax for the host.  It's not implement in this patch but I will do it
for the next revision because it fits better into IPv4/IPv6 and URL
parsing.

Stefan

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