[klibc] PATCH: ipconfig may discard useful packets

Άλκης Γεωργόπουλος alkisg at gmail.com
Mon Jun 16 02:14:52 PDT 2008

I'm sending same debug output samples to demonstrate the problem.
In the places where I say "the older version lost an ACK", I had
wireshark running on the ltsp server to see it.

I think there's ***ANOTHER*** problem as well, ipconfig considers
receiving IGMP or ARP packets an error, and this causes rare but
large delays (I got about 5 of them in 30 minutes of testing).
I'll look into that afterwards, if you'll allow me.

The debug output files are from 3 different versions:
ipconfig-1.5.10  = the original unmodified version,
ipconfig-git = the one in git right now,
ipconfig-1.5.10-patched = with the patch proposed in this thread.

Test environment:
an adsl router/dhcp server =,
a laptop/LTSP server/dhcp server =

Because of many attachments, I uploaded elsewhere the output, and
I only enter the links and the description here.

Output of ipconfig-1.5.10 losing an ACK, receiving an ARP
packet, considering it an error and delaying for 1 sec:

Output of ipconfig-git losing an ACK, receiving 2 ARP packets,
considering them as errors and delaying for *** 96 + 75 ***
seconds. I think it shouldn't consider them as errors, it
should just discard the packets.

Output of ipconfig-1.5.10-patched receiving an ARP packet,
considering it an error and delaying for 10 secs. It didn't drop any
packets before the error (as the other versions did), the error
happend before the offer (rare - took me many minutes to reproduce).
So this ARP error is on all versions. The delay depends on the errors
received, I've seen all versions needing from 1 sec to some minutes.

Output of ipconfig-1.5.10 accepting a DHCPOFFER as DHCPNAK:

Output of ipconfig-1.5.10-patched ignoring the above DHCPOFFER:

(Usual) output of correct address aquisition with

Sample output from dhclient:

Kind regards,
Alkis Georgopoulos

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