[lwip-devel] [bug #17200] UDP not receiving broadcast subnet

[Tim Curran]

URL:
  <http://savannah.nongnu.org/bugs/?func=detailitem&item_id=17200>

                 Summary: UDP not receiving broadcast subnet
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: tgcmn
            Submitted on: Tuesday 07/25/2006 at 12:28
                Category: UDP
                Severity: 3 - Normal
              Item Group: Faulty Behaviour
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open

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Details:

Using LWIP as UDP client on a NIOS processor and static IP addresses (not
DHCP).  The subnet mask is 255.255.255.0.  Packets directed at the socket
with exact IP address work fine, but if the last dot quad address is .255,
the packet is ignored.  As an unverified patch, I altered line 216 of file
udp.c:
  ip_addr_cmp(&(pcb->local_ip), &(iphdr->dest)))) {
replaced with 2 lines
  ip_addr_cmp(&(pcb->local_ip), &(iphdr->dest))) ||
  ip_addr_isbroadcast(&iphdr->dest, inp) )  {

and now subnet broadcasts appear to work okay.  I do not know if this is
rigorously correct, but I wanted to report the behavior and suggest what
might be a solution.

Tim






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