RE: [lwip-users] Checksum Incorrect caused by Concatenation

[Hervé GARAT : Audemat]

Sorry, but yersteday I thought that my first mail adress does not work well, 
cause I did not get an answer and I wrote the same message with a new mail 
adress. I'm newbie in mailing list, sorry again!

My problem append when I use the pbuf_cat function, and I use this only if 
there is a communication problem. 

When I look for the execution code in debug mode, when my problem append, so 
LWIP go in pbuf_cat function and after inet_chksum calculate checksum with 
p->len but the message which is sent is p->tot_len long! And wireshark says TCP 
CHECKSUM INCORRECT and He's right!
When you go in pbuf_cat function, after the TCP Checksum is OK?

> -----Message d'origine-----
> De : address@hidden
> [mailto:address@hidden De la
> part de Simon Goldschmidt
> Envoyé : mardi 17 novembre 2009 10:11
> À : Mailing list for lwIP users
> Objet : Re: RE: [lwip-users] Checksum Incorrect caused by Concatenation
> 
> 
> Just sending a post a second time is normally not a way to attract much
> attention...
> 
> 
> "Hervé GARAT : Audemat" wrote:
> >
> > Kieran said:
> > >No, that's wrong.  p->len refers to the length of each individual pbuf.
> > >We've added another pbuf to the chain, but not changed the length of
> > >each pbuf.  Because the chain is longer, we increment the length of
> > >p->tot_len, but not the length of p->len.
> >
> > But in the inet_chksum_pseudo function,the len used to make checksum is
> > p->len and not p->tot_len. However the message sent is long as p-
> >tot_len,
> > therefore the TCP checksum is Incorrect!!
> >
> > All the other change that I made(queuelen--
> > ;pbuf_free(p->queuelen);...)are made to have a valid checksum if LWIP do
> a concatenation.
> 
> As Kieran also said, the pbuf_free() is *wrong*, too.
> 
> >
> > What's the best way to solve my problem?
> 
> To be able to tell you that I would have to get your problem first. In my
> software, the same code path is executed and there is no error.
> 
> Simon
> --
> DSL-Preisknaller: DSL Komplettpakete von GMX schon für
> 16,99 Euro mtl.!* Hier klicken: http://portal.gmx.net/de/go/dsl02
> 
> 
> _______________________________________________
> lwip-users mailing list
> address@hidden
> http://lists.nongnu.org/mailman/listinfo/lwip-users