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Date: Wed, 16 Mar 2011 22:06:05 +0000
Message-ID: <AANLkTi=dvpTHhP8f8FdxOObFCjSszcuD+X5hCyYRhfsH@mail.gmail.com>
Subject: Re: [Qemu-devel] [PATCH 1/2] Use getaddrinfo for migration
From: Peter Maydell <peter.maydell@linaro.org>
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To: Juan Quintela <quintela@redhat.com>
Cc: qemu-devel@nongnu.org

On 16 March 2011 21:01, Juan Quintela <quintela@redhat.com> wrote:
> +static int tcp_server_bind(int fd, struct addrinfo *rp)
> +{
> + =C2=A0 =C2=A0int val =3D 1;
> + =C2=A0 =C2=A0int ret;
> +
> + =C2=A0 =C2=A0/* allow fast reuse */
> + =C2=A0 =C2=A0setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, (const char *)&va=
l,
> + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 sizeof(val));
> +
> + =C2=A0 =C2=A0ret =3D bind(fd, rp->ai_addr, rp->ai_addrlen);
> +
> + =C2=A0 =C2=A0if (ret =3D=3D -1) {
> + =C2=A0 =C2=A0 =C2=A0 =C2=A0ret =3D -socket_error();
> + =C2=A0 =C2=A0}
> + =C2=A0 =C2=A0return ret;
> +
> +}

I know this is just moved code, but does this do the right thing
on Windows? Windows semantics for SO_REUSEADDR are completely
different from the Unix ones:
http://blogs.msdn.com/b/wndp/archive/2005/08/03/anthony-jones.aspx
http://msdn.microsoft.com/en-us/library/ms740618%28VS.85%29.aspx

Roughly, Unix default behaviour is like Windows SO_EXCLUSIVEADDRUSE;
Unix SO_REUSEADDR is like Windows default behaviour; and Windows
SO_REUSEADDR behaviour is really weird and you don't want it.

(I think Cygwin has a workaround for this to give unix semantics,
but Windows qemu builds as a mingw app, so we get the MS semantics,
right?)

> +static int tcp_start_common(const char *str, int *fd, bool server)
> +{
[...]
> + =C2=A0 =C2=A0s =3D getaddrinfo(name, service, &hints, &result);
> + =C2=A0 =C2=A0if (s !=3D 0) {
> + =C2=A0 =C2=A0 =C2=A0 =C2=A0fprintf(stderr, "qemu: getaddrinfo: %s\n", g=
ai_strerror(s));
> + =C2=A0 =C2=A0 =C2=A0 =C2=A0return -EINVAL;
> + =C2=A0 =C2=A0}

It seems a bit odd to have a low level utility routine printing
diagnostics to stderr rather than just returning the error
details to its caller somehow. Ditto the other fprintf later.

-- PMM