(usagi-users 02113) Re: multiproto bind() ?

["Eva M. Castro" <ecastro@xxxxxxxxxx>]

Notice that IN6_IS_ADDR_V4MAPPED macro only
checks the octects 1 to 10 of the IPv6 address are set to 0
and, octects 11 and 12 are all set to 1, following the
IPv4-mapped IPv6 address:
::FFFF:a.b.c.d

#define IN6_IS_ADDR_V4MAPPED(a) \
        ((((__const uint32_t *) (a))[0] == 0)                                 \
         && (((__const uint32_t *) (a))[1] == 0)                              \
         && (((__const uint32_t *) (a))[2] == htonl (0xffff)))

eva

Abdul Basit wrote:

> i thought the same, but unaware of such a macro,
> thanks for identifying the macro though
>
> definately this helps.
>
> -- basit
>
> On Sun, 19 Jan 2003, Eva M. Castro wrote:
>
> > Abdul Basit wrote:
> >
> > > i want to distinguish between clients coming to ipv4 or ipv6
> > > and print client address ? if i would get sa_family correct
> > > i can switch(family) { and case for AF_INET and AF_INET6 and
> > > use inet_ntop to print address ? but i am getting same family
> > > always (28c/bsd and 10c/linux --> AF_INET6)
> > >
> > > any hints?
> >
> > When an IPv4 client connects to your server, the connection is established
> > using an IPv4-mapped IPv6 address, for instance, if your IPv4 client
> > is running at host using a.b.c.d IPv4 address, the IPv4-mapped IPv6
> > address will be:
> > ::FFFF:a.b.c.d
> >
> > Then, your IPv6 server will always use IPv6 addresses,
> > IPv6 addresses when connections come from IPv6 hosts and
> > IPv4-mapped IPv6 addresses when connections come from IPv4 hosts.
> > This is the reason you always print AF_INET6.
> >
> > You can see how it works:
> > http://jungla.dit.upm.es/~ecastro/IPv6-web/ipv6.html
> > in the figure "IPv6 server on dual stack".
> >
> > There is a macro definition to check if an address is IPv4-mapped IPv6
> > address:
> >
> > IN6_IS_ADDR_V4MAPPED
> >
> > Using this macro you can check if the client connections come from
> > IPv4 or IPv6 host.
> >
> > I hope it helps,
> >
> > eva
> >
> >
> >
> >