Re: [nft PATCH v2] src: use reentrant getprotobyname_r()/getprotobynumber_r()/getservbyport_r()

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Fri, Aug 18, 2023 at 06:10:23PM +0200, Pablo Neira Ayuso wrote:
> On Fri, Aug 18, 2023 at 04:14:01PM +0200, Thomas Haller wrote:
> > Hi Pablo,
> > 
> > On Fri, 2023-08-18 at 11:57 +0200, Pablo Neira Ayuso wrote:
> > > 
> > > > -       struct protoent *p;
> > > > -
> > > >         if (!nft_output_numeric_proto(octx)) {
> > > > -               p = getprotobynumber(mpz_get_uint8(expr->value));
> > > > -               if (p != NULL) {
> > > > -                       nft_print(octx, "%s", p->p_name);
> > > > +               char name[1024];
> > > 
> > > Is there any definition that could be used instead of 1024. Same
> > > comment for all other hardcoded buffers. Or maybe add a definition
> > > for
> > > this?
> > 
> > Added defines instead. See v3.
> > 
> > [...]
> > 
> > > >  #include <nftables.h>
> > > >  #include <utils.h>
> > > > @@ -105,3 +106,90 @@ int round_pow_2(unsigned int n)
> > > >  {
> > > >         return 1UL << fls(n - 1);
> > > >  }
> > > > +
> > > 
> > > Could you move this new code to a new file instead of utils.c? We are
> > > slowing moving towards GPLv2 or any later for new code. Probably
> > > netdb.c or pick a better name that you like.
> > 
> > This request leaves me with a lot of choices. I made them, but I guess
> > you will have something to say about it. See v3.
> > 
> > > 
> > > > +bool nft_getprotobynumber(int proto, char *out_name, size_t
> > > > name_len)
> > > > +{
> > > > +       const struct protoent *result;
> > > > +
> > > > +#if HAVE_DECL_GETPROTOBYNUMBER_R
> > > > +       struct protoent result_buf;
> > > > +       char buf[2048];
> > > > +       int r;
> > > > +
> > > > +       r = getprotobynumber_r(proto,
> > > > +                              &result_buf,
> > > > +                              buf,
> > > > +                              sizeof(buf),
> > > > +                              (struct protoent **) &result);
> > > > +       if (r != 0 || result != &result_buf)
> > > > +               result = NULL;
> > > > +#else
> > > > +       result = getprotobynumber(proto);
> > > > +#endif
> > > 
> > > I'd suggest wrap this code with #ifdef's in a helper function.
> > 
> > I don't understand. nft_getprotobynumber() *is* that helper function to
> > wrap the #if. This point is not addressed by v3 (??).
> 
> I mean, something like a smaller function:
> 
> static struct __nft_getprotobynumber(...)

static const struct protoent *__nft_getprotobynumber(...)

> that is wraps this code above and it returns const struct protoent.
> This helper function is called from nft_getprotobynumber().
> 
> But it is fine as it is, this is just a bit of bike shedding.