On 05/19/2017 01:03 PM, Daniel P. Berrange wrote: > When binding to an IPv6 socket we currently force the > IPV6_V6ONLY flag to off. This means that the IPv6 socket > will accept both IPv4 & IPv6 sockets when QEMU is launched > with something like > > -vnc :::1 > > While this is good for that case, it is bad for other > cases. For example if an empty hostname is given, > getaddrinfo resolves it to 2 addresses 0.0.0.0 and ::, > in that order. We will thus bind to 0.0.0.0 first, and > then fail to bind to :: on the same port. The same > problem can happen if any other hostname lookup causes > the IPv4 address to be reported before the IPv6 address. > > When we get an IPv6 bind failure, we should re-try the > same port, but with IPV6_V6ONLY turned on again, to > avoid clash with any IPv4 listener. > > This ensures that > > -vnc :1 > > will bind successfully to both 0.0.0.0 and ::, and also > avoid > > -vnc :1,to=2 > > from mistakenly using a 2nd port for the :: listener. > > Signed-off-by: Daniel P. Berrange <berra...@redhat.com> > --- > util/qemu-sockets.c | 31 +++++++++++++++++++++++-------- > 1 file changed, 23 insertions(+), 8 deletions(-) >
> for (p = port_min; p <= port_max; p++) {
> +#ifdef IPV6_V6ONLY
> + /* listen on both ipv4 and ipv6 */
> + int v6only = 0;
> +#endif
> inet_setport(e, p);
> +#ifdef IPV6_V6ONLY
> + rebind:
> + if (e->ai_family == PF_INET6) {
The rebind: label could go here with no change in semantics and one less
conditional when compiled without optimization. But hopefully the
compiler is smart enough to see that under -O2, so I don't see a reason
for you to change the code.
> + qemu_setsockopt(slisten, IPPROTO_IPV6, IPV6_V6ONLY, &v6only,
> + sizeof(v6only));
> + }
> +#endif
> if (bind(slisten, e->ai_addr, e->ai_addrlen) == 0) {
> goto listen;
> }
> +
> +#ifdef IPV6_V6ONLY
> + /* If we got EADDRINUSE from an IPv6 bind & V6ONLY is unset,
> + * it could be that the IPv4 port is already claimed, so retry
> + * with V6ONLY set
> + */
> + if (e->ai_family == PF_INET6 && errno == EADDRINUSE && !v6only) {
> + v6only = 1;
> + goto rebind;
> + }
> +#endif
> +
Reviewed-by: Eric Blake <ebl...@redhat.com>
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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