netdev - Re: What causes these TCP packet getting lost in linux kernel

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Date:	Mon, 14 Apr 2014 11:32:55 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Sharat Masetty <sharat04@...il.com>
Cc:	chptx y <chptxy@...il.com>, David Newall <davidn@...idnewall.com>,
	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: What causes these TCP packet getting lost in linux kernel

On Mon, 2014-04-14 at 11:58 -0600, Sharat Masetty wrote:
> Thats a good find.. Is this drop count documented in netstat stats?


Sure  : LINUX_MIB_PAWSESTABREJECTED

nstat -a | grep PAWSEstab

> 
> On Mon, Apr 14, 2014 at 8:13 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> > On Mon, 2014-04-14 at 17:20 +0800, chptx y wrote:
> >> i don't know why, no matter I capture packets on my Ubuntu PC or
> >> Android device with tcpdump,  open the output file with wireshark, all
> >> output packets are marked with "incorrect checksum", but it seems that
> >> this problem don't affect  subsequent packets interaction. why?
> >
> > Checksums are filled by the NIC on TX packets, some tcpdump/wireshark
> > versions do not really know of this.
> >
> > packet 30 (which is accepted) has TSval=4054079470 & TSecr=22894,
> > but packet 32 has TSval=4054078149 & TSecr=22863, while its sequence is
> > correct (coming after the prior packet)
> >
> > Sender has a wrong implementation of TCP Timestamps (RFC 1323), or a
> > middlebox mangles timestamps badly.
> >
> > Receiver considers this as an old packet.
> >\

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