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Re: [Qemu-devel] Patch to improve handling of server sockets
From: |
Daniel P. Berrange |
Subject: |
Re: [Qemu-devel] Patch to improve handling of server sockets |
Date: |
Wed, 5 May 2010 09:29:45 +0100 |
User-agent: |
Mutt/1.4.1i |
On Tue, May 04, 2010 at 03:49:50PM +0200, Reinhard Max wrote:
> Hi,
>
> I am maintaining the tightvnc package for openSUSE and was recently
> confronted with an alleged vnc problem with QWMU that turned out to be
> a shortcoming in QEMU's code for handling TCP server sockets, which is
> used by the vnc and char modules.
>
> The problem occurs when the address to listen on is given as a name
> which resolves to multiple IP addresses the most prominent example
> being "localhost" resolving to 127.0.0.1 and ::1 .
>
> The existing code stopped walking the list of addresses returned by
> getaddrinfo() as soon as one socket was successfully opened and bound.
> The result was that a qemu instance started with "-vnc localhost:42"
> only listened on ::1, wasn't reachable through 127.0.0.1. The fact
> that the code set the IPV6_V6ONLY socket option didn't help, because
> that option only works when the socket gets bound to the IPv6 wildcard
> address (::), but is useless for explicit address bindings.
This seems to be something we overlooked in the initial impl. I don't
see any alternative but to make QEMU listen on multiple sockets in
the scenario you describe. An even clear example is to consider binding
QEMU to a machine with multiple non-localhost addresses, eg
myserver.com resolving to 192.168.122.41 + 2a00:123:456::1
because there's no way that the kernel can know/decide to automatically
listen on 192.168.122.41, when given the address 2a00:123:456::1 and if
the machine has many NICs, you can't assume the wildcard address is
suitable either.
> The attached patch against QEMU 0.11.0 extends inet_listen() to create
> sockets for as many addresses from the address list as possible and
> adapts its callers and their data structures to deal with a linked
> list of socket FDs rather than a single file descriptor.
The approach looks reasonable, though the patch is somewhat mangled
by the mix of tabs + spaces
Regards,
Daniel
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- Re: [Qemu-devel] Patch to improve handling of server sockets, (continued)
- Re: [Qemu-devel] Patch to improve handling of server sockets, Gerd Hoffmann, 2010/05/04
- Re: [Qemu-devel] Patch to improve handling of server sockets, Reinhard Max, 2010/05/04
- Re: [Qemu-devel] Patch to improve handling of server sockets, Gerd Hoffmann, 2010/05/05
- Re: [Qemu-devel] Patch to improve handling of server sockets, Reinhard Max, 2010/05/05
- Re: [Qemu-devel] Patch to improve handling of server sockets, Gerd Hoffmann, 2010/05/05
- Re: [Qemu-devel] Patch to improve handling of server sockets, Daniel P. Berrange, 2010/05/05
Re: [Qemu-devel] Patch to improve handling of server sockets,
Daniel P. Berrange <=