Re: [lwip-users] tcp_listen_input: ACK in LISTEN, sending reset

[Leon Woestenberg]

Hello Johan,

On Wed, 2006-05-10 at 17:19 +0200, Johan Högberg wrote:
> Hi,
> 
> I have problems with the sequence number generated by the reset in
> listen state and wonder if "ackno + 1" is correct in the following sequence:
> 
> tcp_in.c:
> static err_t
> tcp_listen_input(struct tcp_pcb_listen *pcb)
> {
> .....
>   if (flags & TCP_ACK) {
>     /* For incoming segments with the ACK flag set, respond with a
>        RST. */
>     LWIP_DEBUGF(TCP_RST_DEBUG, ("tcp_listen_input: ACK in LISTEN, sending 
> reset\n"));
>     tcp_rst(ackno + 1, seqno + tcplen,
> ....
> 
> In my setup Ethereal report out of sequence error on this frame.
> I believe the "+ 1" should be omitted, is this correct?

Good call, but maybe first check this with a good book on TCP, or even
the RFC (if this describes this corner case unambiguously).

Regards,

Leon Woestenberg.