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From: | Jonathan Larmour |
Subject: | Re: [lwip-devel] IP fragmentation |
Date: | Wed, 09 May 2007 10:23:15 +0100 |
User-agent: | Mozilla Thunderbird 1.0.8-1.1.fc3.4.legacy (X11/20060515) |
Goldschmidt Simon wrote:
I'm looking at the code to do the IP reassembly, and notice that itappearsthat it is only able to handle a single fragmented payload at a time.Isthis really true, or am I seeing things again? If so, theimplementationis somewhat problematic in that if one of the fragments of an IPdatagram islost, then the ip_reass_tmr has to expire before the stack can handle a fragment belonging to a new IP datagram. By default, this timer is settoexpire every seconds.As far as I can see, you're right. What also disturbs me is that, because there is only one reassembly-buffer, you can only receive fragmented IP-packets from one host at a time. That's because I didn't enable IP_REASSEMBLY... Or am I wrong and this would never happen??
This is correct and intentional - more frags to reassemble means more memory, it's as simple as that. You should try and avoid getting fragmented packets in the first place!
Of course if lwIP could implement path MTU discovery, it could keep up its side of the bargain.
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