Re: [Qemu-devel] [PATCH v4 2/4] sockets: factor out create_fast_reuse_socket

[Knut Omang <knut.omang@oracle.com>]

On Mon, 2017-06-26 at 11:28 +0100, Daniel P. Berrange wrote:
> On Fri, Jun 23, 2017 at 12:31:06PM +0200, Knut Omang wrote:
> > 
> > First refactoring step to prepare for fixing the problem
> > exposed with the test-listen test in the previous commit
> > 
> > Signed-off-by: Knut Omang <knut.omang@oracle.com>
> > ---
> >  util/qemu-sockets.c | 24 +++++++++++++++++-------
> >  1 file changed, 17 insertions(+), 7 deletions(-)
> > 
> > diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c
> > index 852773d..699e36c 100644
> > --- a/util/qemu-sockets.c
> > +++ b/util/qemu-sockets.c
> > @@ -149,6 +149,20 @@ int inet_ai_family_from_address(InetSocketAddress
> > *addr,
> >      return PF_UNSPEC;
> >  }
> >  
> > +static int create_fast_reuse_socket(struct addrinfo *e, Error **errp)
> > +{
> > +    int slisten = qemu_socket(e->ai_family, e->ai_socktype, e-
> > >ai_protocol);
> > +    if (slisten < 0) {
> > +        if (!e->ai_next) {
> > +            error_setg_errno(errp, errno, "Failed to create socket");
> > +        }
> 
> I think that having this method sometimes report an error message, and
> sometimes not report an error message, depending on state of a variable
> used by the caller is rather unpleasant. I'd much rather see this
> error message reporting remain in the caller.
>
> > 
> > +        return -1;
> > +    }
> > +
> > +    socket_set_fast_reuse(slisten);
> > +    return slisten;
> > +}
> > +
> >  static int inet_listen_saddr(InetSocketAddress *saddr,
> >                               int port_offset,
> >                               bool update_addr,
> > @@ -210,21 +224,17 @@ static int inet_listen_saddr(InetSocketAddress *saddr,
> >          return -1;
> >      }
> >  
> > -    /* create socket + bind */
> > +    /* create socket + bind/listen */
> >      for (e = res; e != NULL; e = e->ai_next) {
> >          getnameinfo((struct sockaddr*)e->ai_addr,e->ai_addrlen,
> >  		        uaddr,INET6_ADDRSTRLEN,uport,32,
> >  		        NI_NUMERICHOST | NI_NUMERICSERV);
> > -        slisten = qemu_socket(e->ai_family, e->ai_socktype, e-
> > >ai_protocol);
> > +
> > +        slisten = create_fast_reuse_socket(e, &err);
> >          if (slisten < 0) {
> > -            if (!e->ai_next) {
> > -                error_setg_errno(errp, errno, "Failed to create socket");
> > -            }
> >              continue;
> 
> It isn't shown in this diff context, but at the end of the outer
> loop we have
> 
>    error_setg_errno(errp, errno, "Failed to find available port");
> 
> so IIUC, even this pre-existing code is wrong. If 'e->ai_next' is
> NULL, we report an error message here. Then, we continue to the
> next loop iteration, which causes use to terminate the loop
> entirely. At which point we'll report another error message
> over the top of the one we already have. So I think the error
> reporting does still need refactoring, but not in the way it
> is done here.

Yes, I did scratch my head about this but I tried to keep the original semantics
to avoid mixing unrelated changes.

With the split into separate refactoring commits we are beyond that anyway.

I'll have a second look at it..

Thanks,
Knut

> 
> > 
> >          }
> >  
> > -        socket_set_fast_reuse(slisten);
> > -
> >          port_min = inet_getport(e);
> >          port_max = saddr->has_to ? saddr->to + port_offset : port_min;
> >          for (p = port_min; p <= port_max; p++) {
> 
> Regards,
> Daniel