Re: [lwip-users] netif error

[David Empson]

----- Original Message ----- 
From: "Adam Fullerton" <address@hidden>
To: <address@hidden>
Sent: Saturday, June 26, 2010 7:25 AM
Subject: [lwip-users] netif error


> Hi All,
>
> Has anyone got any idea of what is going wrong in this Wireshark capture?
>
> The client sent the character + in frame 6, frame 7 is expected data
> and the server's reply is in frame 9.

What problem are you observing? I can't see anything wrong with the TCP 
headers, and I don't know what you expect in the way of data in frame 7.

Frame 7's data does look peculiar - it seems to be a repeat of the data in 
frame 4, with the data received in frame 6 overwriting the first character, 
and some binary data appended.

This looks suspiciously like reuse of a pbuf before LWIP had finished with 
it. Somehow incoming data overwrote data in a previously transmitted 
segment, and the entire previously transmitted segment is being treated as 
new data, resulting in it being transmitted again in frame 7 with some new 
data from the application appended, and an updated TCP header indicating the 
sequence number has advanced.

A threading issue (multiple allocation of the same pbuf chain) seems most 
likely.