[lwip-devel] [patch #9645] Fragmentation of packets where MF=1

[Joe Takagi]

URL:
  <http://savannah.nongnu.org/patch/?9645>

                 Summary: Fragmentation of packets where MF=1
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: joetakagi
            Submitted on: Fri 01 Jun 2018 09:35:12 AM UTC
                Category: IPv4
                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:

If an LwIP instance has multiple interfaces and is performing IP routing
between them it may receive, and need to fragment, packets which have already
been fragmented by an upstream device. 

Currently LwIP asserts when attempting fragmentation of such packets which is
a reliability and potential DoS issue in my application.

This patch aims to improve fragmentation behaviour by:
 1. correctly populating the MF flag of fragments generated from packets where
MF was set: 
    a. all packets generated from fragmentation of a packet with MF set should
have MF set
    b. all except the last packet generated from fragmentation of a packet
with MF cleared should have MF set.
 2. removing the LWIP_ASSERT on fragmentation of packets where MF is set.

Joe T





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File Attachments:


-------------------------------------------------------
Date: Fri 01 Jun 2018 09:35:12 AM UTC  Name: frag-patch.txt  Size: 595B   By:
joetakagi
patch to ip4_frag.c 
<http://savannah.nongnu.org/patch/download.php?file_id=44267>

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