netdev - Re: kernel BUG at net/core/dev.c:1383 skb_checksum_help: BUG

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Date:	Mon, 15 Oct 2007 13:54:42 +0300 (EEST)
From:	"Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi>
To:	Guillaume Chazarain <guichaz@...oo.fr>
cc:	Netdev <netdev@...r.kernel.org>
Subject: Re: kernel BUG at net/core/dev.c:1383 skb_checksum_help: BUG_ON(offset
 > (int)skb->len)

On Mon, 15 Oct 2007, Guillaume Chazarain wrote:

> Le Mon, 15 Oct 2007 13:15:05 +0300 (EEST),
> "Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi> a écrit :
>  
> > ...Never mind, noticed the fix later on.
> 
> Yes, but here is it anyway, in case you see something fishy.
>
> (gdb) p *(struct tcp_sock *)skb->sk
> $4 = {inet_conn = {icsk_inet = {sk = {__sk_common = {skc_family = 2, 

...snip...

>   mdev_max = 3080, rttvar = 3080, rtt_seq = 4014273285, packets_out = 16, 
>   retrans_out = 0, rx_opt = {ts_recent_stamp = 1192377268, 

...snip...

>   advmss = 1448, prior_ssthresh = 9, lost_out = 8, sacked_out = 8, 
>   fackets_out = 16, high_seq = 4014280275, retrans_stamp = 4946974, 
> 
> Thanks.

Hmm. Thanks.

Unlikely that there is something wrong. From values I counted that 
packets_out - (sacked_out + left_out) + retrans_out yields to zero,
so such large underflow is probably due to prior_inflight reused for 
something, though of course that particular state when prior_inflight
is collected is no longer available to us because tcp_clean_rtx_queue
was likely executed as packets_acked is 1. So I don't intend to do
further investigation on this one.

-- 
 i.