Re: [lwip-users] Sending 2 packets with same sequence number

[Simon Goldschmidt]

Since you are completely bypassing tcp here (or so it seems), there is nothing 
that even knows about sequence numbers (only the tcp code handles them). Being 
like that, the problem lies somewhere else, and I'd suspect the NAT code first, 
since it doesn't belong to the lwip core code and I so not know of a problem 
like that so far.

Simon


Am 21.07.2010 um 17:37 schrieb Marco Jakobs <address@hidden>:

> Hi @all,
> 
> i'm actually testing with a PPP connection to a GPRS network, using LwIP as a 
> small NAT router. I see incoming packets from the PPP interface, which have 
> different ID numbers (counting up), but the same sequence numbers - seems to 
> be retransmissions.
> 
> After rewriting the headers for NAT, the packets are sent to the ethernet 
> interface with:
> 
> err = nat_entry.cmn->cfg->in_if->output( nat_entry.cmn->cfg->in_if, q, &( 
> iphdr->dest ) )
> 
> What i see in wireshark, connected to the ethernet port, is every packet is 
> transferred fine on the ethernet - as long as the sequence number is 
> different. The retransmissions with same sequence numbers are not put out on 
> the ethernet, only the first of the packets with that sequence number is sent 
> out, the following packets are not.
> 
> Is there any mechanism in LwIP prevent it sending out packets with the same 
> sequence number as the previously sent packet?
> 
> Marco
> 
> 
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