[lwip-users] Dont fragment (DF) bit in IP Header

[Martin Glunz]

In src/core/ipv4/ip.c ip_output_if() sets the
Don't fragment Flag (DF) in every IP Header:
  IPH_OFFSET_SET(iphdr, htons(IP_DF));

This caused problems when I tried to access an
embedded device via the internet (ADSL Router at
home and at work, port forwarding and dyndns.org service). 
Packets reached the device through the routers, then
the device replied with a maximum length packet and
the DF flag set. The router rejected this packet
because the ADSL mtu is smaller than the regular
ethernet mtu and the packet could not be fragmented.

So I just reset the DF flag in lwip and everthing worked fine.
Is there any reason why the DF flag is always set in lwip?


-- 
MfG
Martin Glunz

WANTED: Schrödinger's Cat. Dead or Alive.

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