[lwip-devel] [bug #36017] ARP might not support duplicate addresses on multiple netifs

[Simon Goldschmidt]

URL:
  <http://savannah.nongnu.org/bugs/?36017>

                 Summary: ARP might not support duplicate addresses on
multiple netifs
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: goldsimon
            Submitted on: Di 27 Mär 2012 19:00:24 GMT
                Category: ARP
                Severity: 3 - Normal
              Item Group: Faulty Behaviour
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: 
            lwIP version: CVS Head

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Details:

This is from reading the code only, I haven't observed this (as I don't use
multiple netifs).

This is somewhat related to bug #34683 (IPv4 routing doesn't consider source
IP address), where Amir also said that ARP entries should be-separated not
only by destination IP address.

Since we only have one global ARP table and we don't check the source address
or the netif when searching for ARP entries, duplicate IP addresses will
result in the address being resolved only once. For the 2nd netif, the same
MAC address will be used (although the packet will be sent on the correct
netif - i.e. noone will listen to it).

On good networks, this is probably only a problem for AutoIP - there shouldn't
be duplicate addresses otherwise.




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