RE: [lwip-users] Bug in snd_buf calculation

[Jan Ulvesten]

Leon, Christian



from tcp_out.c
-------------
#if 0
  pcb->snd_buf -= ((len+1) & ~0x1); /* Even the send buffer */
#else
  pcb->snd_buf -= len;
#endif  



from tcp_in.c
-------------
#if 0
      pcb->snd_buf += ((pcb->acked+1) & ~0x1); /* Even the send buffer
*/
#else
      pcb->snd_buf += pcb->acked;
#endif      


This may happen:

len=3   ->      snd_buf -= 4
len=3 ->        snd_buf -= 4
ack=6 ->        snd_buf += 6 (and two bytes are "lost")

Remember that TCP does not ack every single packet (sliding window)

Test by transmitting odd length packets continuously.

I'm not sure why snd_buff must be even?  If I knew I might contribute
with a fix.


Jan Ulvesten
Sicom

-----Original Message-----
From: Christiaan Simons [mailto:address@hidden 
Sent: 24. februar 2006 09:50
To: address@hidden
Subject: Re: [lwip-users] Bug in snd_buf calculation



Leon wrote:

>Could you discuss how to proceed with a proper fix for this?

Is it possible to create a test-case to pin-point the problem?
E.g. using new or existing example code.

If I can reproduce and solve the problem here,
I'm more confident with applying such changes.

Bye,

Christiaan Simons

Hardware Designer
Axon Digital Design

http://www.axon.tv



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