[Openvpn-devel] Does OpenVPN get IP_PKTINFO in the correct manner?

[Yang Zhe]

Let's say openvpn 2.2.0

In function link_socket_read_udp_posix_recvmsg() writes:

     struct cmsghdr *cmsg;
     fromlen = mesg.msg_namelen;
     cmsg = CMSG_FIRSTHDR (&mesg);
     if (cmsg != NULL
         && CMSG_NXTHDR (&mesg, cmsg) == NULL
#ifdef IP_PKTINFO
         && cmsg->cmsg_level == SOL_IP
         && cmsg->cmsg_type == IP_PKTINFO
#elif defined(IP_RECVDSTADDR)
         && cmsg->cmsg_level == IPPROTO_IP
         && cmsg->cmsg_type == IP_RECVDSTADDR
#else
#error ENABLE_IP_PKTINFO is set without IP_PKTINFO xor IP_RECVDSTADDR (fix
syshead.h)
#endif
         && cmsg->cmsg_len >= sizeof (struct openvpn_in4_pktinfo))
       {
#ifdef IP_PKTINFO
         struct in_pktinfo *pkti = (struct in_pktinfo *) CMSG_DATA (cmsg);
         from->pi.in4.ipi_ifindex = pkti->ipi_ifindex;
         from->pi.in4.ipi_spec_dst = pkti->ipi_spec_dst;
#elif defined(IP_RECVDSTADDR)
         from->pi.in4 = *(struct in_addr*) CMSG_DATA (cmsg);
#else
#error ENABLE_IP_PKTINFO is set without IP_PKTINFO xor IP_RECVDSTADDR (fix
syshead.h)
#endif
       }

I looked up manpages and other web resources, normally they iterated in the
cmsghdr list then find the required information by

for (cmsg = CMSG_FIRSTHDR(&mesg); cmsg; cmsg = CMSG_NXTHDR(&mesg, cmsg))
  if (cmsg->cmsg_level == SOL_IP && cmsg->cmsg_type == IP_PKTINFO
      && ... ) {
  }

In the openvpn's code, it only examine the FIRSTHDR, and assuming CMSG_NXTHDR =
NULL, which is odd.

Anybody get "--multihome" worked?

-- 
Sincerely,
    Yang Zhe