(usagi-users 02068) recvfrom ipv6

[Abdul Basit <basit@xxxxxxxx>]

Hello all,

 I was trying to catch icmpv6 stuff , but getting different behaviours
on other systems

like my code snippet is

-- start

  struct ip6_hdr *ip6;
  struct icmp6_hdr *icmp6;
  struct sockaddr_storage *s6;
  struct sockaddr_in6 *in6;
  static char src6host[128];
  socklen_t len6;
  struct icmp6_filter fil;


 ICMP6_FILTER_SETBLOCKALL (&fil);
 ICMP6_FILTER_SETPASS (ICMP6_ECHO_REQUEST, &fil);


  setsockopt (sock6fd, IPPROTO_ICMPV6, ICMP6_FILTER, &fil, sizeof (fil));

  for (;;)
    {
      n6 =
        recvfrom (sock6fd, buf6,
                  sizeof (struct ip6_hdr) + sizeof (struct icmp6_hdr), 0,
                  (struct sockaddr *) s6, &len6);
   if (n6 > 0)
        {
          ip6 = (struct ip6_hdr *) buf6;
          ip6_len = sizeof (struct ip6_hdr);
          icmp6 = (struct icmp6_hdr *) (buf6 + ip6_len);
          in6 = (struct sockaddr_in6 *) s6;

        // a tricky way, inet_ntoa doesn't support struct sockaddr_in6 ..
          inet_ntop (AF_INET6, &in6->sin6_addr, src6host, sizeof (src6host));

     if (icmp6->icmp6_type == 0)
            {
               printf("hello.. ipv6 icmp request");
 ......................


-- end

see, everytime if i write like if (icmp6->icmp6_type == ICMP6_ECHO_REQUEST)
{ , it never matches, everytime i am getting icmp6_type == 0 , 0 value in
icmp6.h is defined for more than one #define ,

#define ICMP6_DST_UNREACH_NOROUTE     0 /* no route to destination */
#define ICMP6_TIME_EXCEED_TRANSIT     0 /* Hop Limit == 0 in transit */
#define ICMP6_PARAMPROB_HEADER        0 /* erroneous header field */

Why its not matching ICMP6_ECHO_REQUEST and instead matching against 0

If i try to print next header value from ip6->ip6_nxt, it shows 118 ,
and 118 is not defined anywhere in headers ?

also  on some glibc 2.2.5 with stock linux(2.4.17) kernel , the above
recvfrom(... ) statement returns n6 == -1 , but on my system USAGI
snap 6'th jan. with glibc 2.3.1 , it pass things correclty.

seems the fifth argument in above recvfrom(..) is doing something wrong
if i set that to NULL, it will work everywhere(no matter what glibc , what
ipv6 implementation) but then how i'd be able to get source address of
icmp (from ip6 header?)

sorry for very long msg :(, i hope someone will reply

-- basit