Re: [Qemu-devel] [PATCH] slirp: Add explanation for hostfwd parsing failure

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Philippe Mathieu-Daudé (f4bug@amsat.org) wrote:
> Hi David,
> 
> On 09/08/2017 12:53 PM, Dr. David Alan Gilbert (git) wrote:
> > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> > 
> > e.g.
> > ./x86_64-softmmu/qemu-system-x86_64 -nographic -netdev 'user,id=vnet,hostfwd=:555.0.0.0:0-:22'
> > qemu-system-x86_64: -netdev user,id=vnet,hostfwd=:555.0.0.0:0-:22: Invalid host forwarding rule ':555.0.0.0:0-:22' (Bad host address)
> > 
> > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > ---
> >   net/slirp.c | 13 ++++++++++++-
> >   1 file changed, 12 insertions(+), 1 deletion(-)
> > 
> > diff --git a/net/slirp.c b/net/slirp.c
> > index 01ed21c006..d87664d42e 100644
> > --- a/net/slirp.c
> > +++ b/net/slirp.c
> > @@ -496,9 +496,11 @@ static int slirp_hostfwd(SlirpState *s, const char *redir_str,
> >       char buf[256];
> >       int is_udp;
> >       char *end;
> > +    const char *fail_reason = "";
> 
> Isn't it better not initialize this? So if one add a new failed syntax case
> the build with abort with -Werror=uninitialized

I never quite trust compilers to spot it or not-moan even though
every route to failure will have set it.

> Anyway:
> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

Thanks.

Dave

> 
> >       p = redir_str;
> >       if (!p || get_str_sep(buf, sizeof(buf), &p, ':') < 0) {
> > +        fail_reason = "No : separators";
> >           goto fail_syntax;
> >       }
> >       if (!strcmp(buf, "tcp") || buf[0] == '\0') {
> > @@ -506,35 +508,43 @@ static int slirp_hostfwd(SlirpState *s, const char *redir_str,
> >       } else if (!strcmp(buf, "udp")) {
> >           is_udp = 1;
> >       } else {
> > +        fail_reason = "Bad protocol name";
> >           goto fail_syntax;
> >       }
> >       if (!legacy_format) {
> >           if (get_str_sep(buf, sizeof(buf), &p, ':') < 0) {
> > +            fail_reason = "Missing : separator";
> >               goto fail_syntax;
> >           }
> >           if (buf[0] != '\0' && !inet_aton(buf, &host_addr)) {
> > +            fail_reason = "Bad host address";
> >               goto fail_syntax;
> >           }
> >       }
> >       if (get_str_sep(buf, sizeof(buf), &p, legacy_format ? ':' : '-') < 0) {
> > +        fail_reason = "Bad host port separator";
> >           goto fail_syntax;
> >       }
> >       host_port = strtol(buf, &end, 0);
> >       if (*end != '\0' || host_port < 0 || host_port > 65535) {
> > +        fail_reason = "Bad host port";
> >           goto fail_syntax;
> >       }
> >       if (get_str_sep(buf, sizeof(buf), &p, ':') < 0) {
> > +        fail_reason = "Missing guest address";
> >           goto fail_syntax;
> >       }
> >       if (buf[0] != '\0' && !inet_aton(buf, &guest_addr)) {
> > +        fail_reason = "Bad guest address";
> >           goto fail_syntax;
> >       }
> >       guest_port = strtol(p, &end, 0);
> >       if (*end != '\0' || guest_port < 1 || guest_port > 65535) {
> > +        fail_reason = "Bad guest port";
> >           goto fail_syntax;
> >       }
> > @@ -547,7 +557,8 @@ static int slirp_hostfwd(SlirpState *s, const char *redir_str,
> >       return 0;
> >    fail_syntax:
> > -    error_setg(errp, "Invalid host forwarding rule '%s'", redir_str);
> > +    error_setg(errp, "Invalid host forwarding rule '%s' (%s)", redir_str,
> > +               fail_reason);
> >       return -1;
> >   }
> > 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK