[lwip-devel] [bug #31367] Cannot send a UDP datagram to a different valid subnet

[Bill Auerbach]

URL:
  <http://savannah.nongnu.org/bugs/?31367>

                 Summary: Cannot send a UDP datagram to a different valid
subnet
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: billauerbach
            Submitted on: Mon 18 Oct 2010 03:27:34 PM EDT
                Category: ARP
                Severity: 3 - Normal
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: 
            lwIP version: CVS Head

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Details:

Example:

UDP Broadcast from 192.168.1.100.  A device at 169.254.1.100 sees the
broadcast and responds with a source of 169.254.1.100 and a destination of
192.168.1.100.  This is acceptable because the destination is on the subnet of
the receiver.

The test at the end of etharp_output blocks the send. lwIP returns ERR_RTE.

There's a secondary issue as well - I don't think the broadcast received made
an ARP entry.  I say this because etharp_query complains if I let it try to
handle the output directly.  The complaint is an ICMP destination unreachable
which isn't true.

lwIP appears to be based on RFC 950.  RFC 1122 changes and adds quite a bit
to RFC 950 and doesn't add that allowing the above example is an error.




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