[lwip-devel] [bug #43028] IP_MULTICAST_TTL affects unicast datagrams

[Joel Cunningham]

URL:
  <http://savannah.nongnu.org/bugs/?43028>

                 Summary: IP_MULTICAST_TTL affects unicast datagrams
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: jcunningham
            Submitted on: Tue 19 Aug 2014 07:59:55 PM GMT
                Category: UDP
                Severity: 3 - Normal
              Item Group: Faulty Behaviour
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: 
            lwIP version: 1.4.1

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Details:

When setting the IP_MULTICAST_TTL socket option via setsockopt(), all
transmitted datagrams from that socket now use the TTL value specified in the
setsockopt() call regardless of whether the destination of the datagram is
unicast or multicast.  My understanding of the socket option is that it should
only affect datagrams sent (on that socket) to a multicast group.

Taking a look at the implementation, IP_MULTICAST_TTL sets the 
sock->conn->pcb.udp->ttl which is used for every call to ip_output_if from
udp.c

Further, the getsockopt() returns sock->conn->pcb.ip->ttl (as opposed to
pcb.udp->ttl for the setter)




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