[systemd-devel] [PATCH 4/6] make in_addr_from_string() accept ipv4 addresses even when using AF_INET6

[Zbigniew Jędrzejewski-Szmek]

On Sun, Mar 15, 2015 at 01:28:05PM -0700, Shawn Landden wrote:
> On Sun, Mar 15, 2015 at 1:07 PM, Zbigniew Jędrzejewski-Szmek <
> zbyszek at in.waw.pl> wrote:
> 
> > On Wed, Mar 11, 2015 at 08:13:47AM -0700, Shawn Landden wrote:
> > > if we are going to have a function to fix up the deficiencies of
> > > inet_pton(), better go all the way.
> > > ---
> > >  src/shared/in-addr-util.c | 17 +++++++++++++++++
> > >  src/shared/in-addr-util.h |  1 +
> > >  2 files changed, 18 insertions(+)
> > >
> > > diff --git a/src/shared/in-addr-util.c b/src/shared/in-addr-util.c
> > > index ade4012..b7532a6 100644
> > > --- a/src/shared/in-addr-util.c
> > > +++ b/src/shared/in-addr-util.c
> > > @@ -206,7 +206,18 @@ int in_addr_to_string(int family, const union
> > in_addr_union *u, char **ret) {
> > >          return 0;
> > >  }
> > >
> > > +struct in6_addr in_addr_to_in6_addr(struct in_addr ipv4) {
> > > +        struct in6_addr r = { { {
> > > +                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xFF, 0xFF, 0, 0, 0, 0
> > > +        } } };
> > > +
> > > +        r.s6_addr32[3] = ipv4.s_addr;
> > > +
> > > +        return r;
> > > +}
> > > +
> > >  int in_addr_from_string(int family, const char *s, void *ret) {
> > > +        struct in_addr v4mapped;
> > >
> > >          assert(s);
> > >          assert(ret);
> > > @@ -214,6 +225,12 @@ int in_addr_from_string(int family, const char *s,
> > void *ret) {
> > >          if (!IN_SET(family, AF_INET, AF_INET6))
> > >                  return -EAFNOSUPPORT;
> > >
> > > +        if (family == AF_INET6)
> > > +                if (inet_pton(AF_INET, s, &v4mapped) == 1) {
> > > +                        *((struct in6_addr *)ret) =
> > in_addr_to_in6_addr(v4mapped);
> > > +                        return 0;
> > > +                }
> > > +
> > Hm, IIUC, an ipv6 address was specified, but the user gave an ipv4 address.
> > Automatically converting seems like a way to entice confusion...
> >
> > Except that the linux kernel supports binding to ipv4 this way, (see
> ipv6(7)).
> 
> In the inet_pton man page:
> 
> BUGS
>        AF_INET6 does not recognize IPv4 addresses.  An explicit IPv4-mapped
> IPv6 address must be supplied in src instead.
Right, but looking at how in_addr_from_string is used, we usually call it
with an explicit family, and if it parses as ipv4, assume the family is ipv4,
otherwise parse it as ipv6. So your change would either be a noop (if
the check for ipv4 syntax was already done before), or would mess up this
detection.

What scenario are you trying to solve?

Zbyszek

> 
> 
> Zbyszek
> >
> > >          errno = 0;
> > >          if (inet_pton(family, s, ret) <= 0)
> > >                  return errno ? -errno : -EINVAL;
> > > diff --git a/src/shared/in-addr-util.h b/src/shared/in-addr-util.h
> > > index 8b3a07c..f140ec9 100644
> > > --- a/src/shared/in-addr-util.h
> > > +++ b/src/shared/in-addr-util.h
> > > @@ -37,6 +37,7 @@ int in_addr_equal(int family, const union
> > in_addr_union *a, const union in_addr_
> > >  int in_addr_prefix_intersect(int family, const union in_addr_union *a,
> > unsigned aprefixlen, const union in_addr_union *b, unsigned bprefixlen);
> > >  int in_addr_prefix_next(int family, union in_addr_union *u, unsigned
> > prefixlen);
> > >  int in_addr_to_string(int family, const union in_addr_union *u, char
> > **ret);
> > > +struct in6_addr in_addr_to_in6_addr(struct in_addr ipv4) _const_;
> > >  int in_addr_from_string(int family, const char *s, void *ret);
> > >  int in_addr_from_string_auto(const char *s, int *family, union
> > in_addr_union *ret);
> > >  unsigned char in_addr_netmask_to_prefixlen(const struct in_addr *addr);
> > > --
> > > 2.2.1.209.g41e5f3a
> > >
> > > _______________________________________________
> > > systemd-devel mailing list
> > > systemd-devel at lists.freedesktop.org
> > > http://lists.freedesktop.org/mailman/listinfo/systemd-devel
> > _______________________________________________
> > systemd-devel mailing list
> > systemd-devel at lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/systemd-devel
> >
> 
> 
> 
> -- 
> Shawn Landden