[lwip-users] Fast retransmit

[Samuel Thomas Jansen]

I've got lwip going in a testing context and during a small amount of 
loss lwip correctly attempts Fast Retransmit.

However, it seems to retransmit the entire window rather than the packet 
than the sequence number the duplicate acks are refering to. You can see 
this in the output from tcptrace (www.tcptrace.org) I've put on the web: 
http://www.wand.net.nz/~stj2/900/random/lwip-fast-retransmit.png

In the middle of the above picture, at time 2.3, we see the entire 
window (11 packets) being retransmitted in response to 3 duplicate acks!

Has anyone else noticed this error? I guess it is still possible that 
part of my implementation has produced this bug, though that seems 
rather unlikely; the rest of TCP seems to work perfectly.

I had a cursory glance at the code and couldn't narrow the problem down 
easily. If someone can confirm this behaviour I'll have a look in a bit 
more depth sometime this week.