linux-kernel - Re: Doubts about listen backlog and tcp_max_syn

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Message-ID: <CAGK4HS_2=b3gJmDeBTbSmFYk4PB2epMUQE6nkr1XMGfFgmfHvw@mail.gmail.com>
Date:	Sun, 27 Jan 2013 21:21:32 -0800
From:	Vijay Subramanian <subramanian.vijay@...il.com>
To:	Nivedita Singhvi <niveditasinghvi@...il.com>
Cc:	Leandro Lucarella <leandro.lucarella@...iomantic.com>,
	Rick Jones <rick.jones2@...com>,
	Eric Dumazet <eric.dumazet@...il.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: Doubts about listen backlog and tcp_max_syn_backlog

> +    { "ListenDrops", N_("%u SYNs to LISTEN sockets dropped"), opt_number },
>
> (see the file debian/patches/CVS-20081003-statistics.c_sync.patch
>  in the net-tools src)
>
> i.e., the netstat pkg is printing the value of the TCPEXT MIB counter
> that's counting TCPExtListenDrops.
>
> Theoretically, that number should be the same as that printed by nstat,
> as they are getting it from the same kernel stats counter. I have not
> looked at nstat code (I actually almost always dump the counters from
> /proc/net/{netstat + snmp} via a simple prettyprint script (will send
> you that offline).
>

nstat pretty much does what you describe which is to parse the
/proc/net files(s) and
print the contents. This is one advantage of nstat over netstat. When
you add a new MIB, you
do not need to update nstat.

> If the nstat and netstat counters don't match, something is fishy.
> That nstat output is broken.
>
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