[lwip-users] handling packets with equal sequence number

[Thomas Richter (TCD - DE/Dresden)]

Hi,

in my tests the following problem occurs:
A packet with the same sequence number was sent to lwIP. Wireshark TCP
analysis says it was a TCP Retransmission with same sequence number and
same data (plus a little bit more data append to the earlier transmitted
data).

My question:
What will be happen in lwIP in tcp_receive() ?
I have seen in this function that a sequence analysis will be done. But
I do not understand it?
I will understand what is given by lwIP to my receive callback function?

For instance the following frames are sent by :
- Frame 1 with some data of length 100 bytes, e.g. AABBCCDD..YYZZ
- Frame 2 consists of data of Frame 1 (100 bytes) + new data (50 bytes)
= 150 bytes, e.g. AABBCCDD..YYZZ001122..

Can I ignore Frame 1 and take only Frame 2?
Give lwIP both frames or only the second frame?

Thanks for any help.

Best regards
Thomas