Re: [Qemu-devel] [PATCH 1/2] socket: treat ipv4=on, ipv6=on uniformly

[Gerd Hoffmann]

On Fr, 2014-02-28 at 11:16 +0100, Paolo Bonzini wrote:
> In some cases, "ipv4=on,ipv6=on" means "try both kinds of address";
> in others, it means "try IPv6 only" just by virtue of how the code
> is structured.

> @@ -127,10 +127,13 @@ int inet_listen_opts(QemuOpts *opts, int port_offset, 
> Error **errp)

> -    if (qemu_opt_get_bool(opts, "ipv4", 0))
> -        ai.ai_family = PF_INET;
> -    if (qemu_opt_get_bool(opts, "ipv6", 0))
> -        ai.ai_family = PF_INET6;
> +    if (qemu_opt_get_bool(opts, "ipv4", 0) != qemu_opt_get_bool(opts, 
> "ipv6", 0)) {
> +        if (qemu_opt_get_bool(opts, "ipv4", 0)) {
> +            ai.ai_family = PF_INET;
> +        } else {
> +            ai.ai_family = PF_INET6;
> +        }
> +    }

This is wrong for the listening side.

ipv6 sockets can listen on both ipv4 and ipv6.  qemu configures ipv6
sockets to do that, unconditionally.

So ipv4=yes,ipv6=no works correctly.
ipv4=yes,ipv6=yes works too.
ipv4=no,ipv6=yes doesn't work, but to fix that you have to set the
IPV6_V6ONLY socket option according to the ipv4 option.

Canevat: Listening on both ipv4+ipv6 with a single file handle works for
the wildcard address only.  Specifying -- say --
host=localhost,ipv4=yes,ipv6=yes, then expect qemu to listen on both
127.0.0.1 and ::1 doesn't work.

This can only be fixed by allowing multiple listening filehandles.
Which is a non-trivial change as this also affects the public api (which
will have to report a list of listening addresses instead of a single
address).
 
> @@ -319,11 +322,12 @@ static struct addrinfo 
> *inet_parse_connect_opts(QemuOpts *opts, Error **errp)

> -    if (qemu_opt_get_bool(opts, "ipv4", 0)) {
> -        ai.ai_family = PF_INET;
> -    }
> -    if (qemu_opt_get_bool(opts, "ipv6", 0)) {
> -        ai.ai_family = PF_INET6;
> +    if (qemu_opt_get_bool(opts, "ipv4", 0) != qemu_opt_get_bool(opts, 
> "ipv6", 0)) {
> +        if (qemu_opt_get_bool(opts, "ipv4", 0)) {
> +            ai.ai_family = PF_INET;
> +        } else {
> +            ai.ai_family = PF_INET6;
> +        }

For connect this change is fine I think.

> @@ -418,10 +422,13 @@ int inet_dgram_opts(QemuOpts *opts, Error **errp)

> -    if (qemu_opt_get_bool(opts, "ipv4", 0))
> -        ai.ai_family = PF_INET;
> -    if (qemu_opt_get_bool(opts, "ipv6", 0))
> -        ai.ai_family = PF_INET6;
> +    if (qemu_opt_get_bool(opts, "ipv4", 0) != qemu_opt_get_bool(opts, 
> "ipv6", 0)) {
> +        if (qemu_opt_get_bool(opts, "ipv4", 0)) {
> +            ai.ai_family = PF_INET;
> +        } else {
> +            ai.ai_family = PF_INET6;
> +        }
> +    }

Not fully sure, but I think this is fine too.

cheers,
  Gerd