| Message ID | 20170519180342.19618-2-berrange@redhat.com |
|---|---|
| State | New |
| Headers | show |
On 05/19/2017 03:03 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 <berrange@redhat.com> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org> > --- > util/qemu-sockets.c | 31 +++++++++++++++++++++++-------- > 1 file changed, 23 insertions(+), 8 deletions(-) > > diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c > index d8183f7..397212b 100644 > --- a/util/qemu-sockets.c > +++ b/util/qemu-sockets.c > @@ -208,22 +208,37 @@ static int inet_listen_saddr(InetSocketAddress *saddr, > } > > socket_set_fast_reuse(slisten); > -#ifdef IPV6_V6ONLY > - if (e->ai_family == PF_INET6) { > - /* listen on both ipv4 and ipv6 */ > - const int off = 0; > - qemu_setsockopt(slisten, IPPROTO_IPV6, IPV6_V6ONLY, &off, > - sizeof(off)); > - } > -#endif > > port_min = inet_getport(e); > port_max = saddr->has_to ? saddr->to + port_offset : port_min; > 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) { > + 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 > + > if (p == port_max) { > if (!e->ai_next) { > error_setg_errno(errp, errno, "Failed to bind socket"); >
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 <berrange@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 <eblake@redhat.com>
On Mon, May 22, 2017 at 10:26:09AM -0500, Eric Blake wrote: > 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 <berrange@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. Also bear in mind the running time of this method is going to be dominated by the getaddrinfo() call most of the time, so I don't think there's any measurable perf difference to moving the label. > > + 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 <eblake@redhat.com> > > -- > Eric Blake, Principal Software Engineer > Red Hat, Inc. +1-919-301-3266 > Virtualization: qemu.org | libvirt.org > Regards, Daniel
diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c index d8183f7..397212b 100644 --- a/util/qemu-sockets.c +++ b/util/qemu-sockets.c @@ -208,22 +208,37 @@ static int inet_listen_saddr(InetSocketAddress *saddr, } socket_set_fast_reuse(slisten); -#ifdef IPV6_V6ONLY - if (e->ai_family == PF_INET6) { - /* listen on both ipv4 and ipv6 */ - const int off = 0; - qemu_setsockopt(slisten, IPPROTO_IPV6, IPV6_V6ONLY, &off, - sizeof(off)); - } -#endif port_min = inet_getport(e); port_max = saddr->has_to ? saddr->to + port_offset : port_min; 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) { + 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 + if (p == port_max) { if (!e->ai_next) { error_setg_errno(errp, errno, "Failed to bind socket");
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 <berrange@redhat.com> --- util/qemu-sockets.c | 31 +++++++++++++++++++++++-------- 1 file changed, 23 insertions(+), 8 deletions(-)