[lwip-devel] [patch #9165] Allowing udp src port to be 0 in cases when we don't care about outgoing port

[Alex Moran]

URL:
  <http://savannah.nongnu.org/patch/?9165>

                 Summary: Allowing udp src port to be 0 in cases when we don't
care about outgoing port
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: alex081293
            Submitted on: Thu 17 Nov 2016 10:25:35 PM GMT
                Category: UDP
                Priority: 5 - Normal
                  Status: None
                 Privacy: Public
             Assigned to: None
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None

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Details:

In the case of knowing the senders IP address, the host running LWIP should be
able to open a socket on their known local port and be able to receive packets
from the known sender without caring about its source port. 

With the current implementation of the UDP stack, it is impossible to
receiving a packet from only the intended source without first knowing it's
outgoing port. I believe you should be able to specify if you do not care
about the outgoing port of the sender but only want to receive packets from
that address like so:

udp_bind(this->pcb, IP_ADDR_ANY, LocalPort);
udp_connect(this->pcb, &RecvIPAddress), 0);

The patch I'd like to add is to change line 278 of the current /src/core/udp.c
file to:
((pcb->remote_port == src) || (pcb->remote_port == 0)) &&
      

Without this change, the packet gets to the udp layer but is dropped. This
allows the packet to be passed up to the application layer regardless of what
the remote port is. 




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