RE: [PATCH V2 2/7] tcp: use limited socket backlog

[Eric Dumazet <eric.dumazet@gmail.com>]

Le jeudi 04 mars 2010 à 13:21 +0800, Zhu, Yi a écrit :
> Eric Dumazet <eric.dumazet@gmail.com> wrote:
> 
> > Then its a separate bug. MD5 support added so many bugs its not even
> > funny.
> 
> > Existing bugs are not an excuse for adding new ones, we try the reverse.
> > No ?
> 
> Can you show me where sk_drops is used by TCP and what SNMP MIB value
> should I use for backlog dropping? TCP_MIB_INERRS doesn't seem correct.

sk_drop is not yet used by TCP, because when backlog processing is
performed, TCP state machine has much finer grain capabilities to show
why a packet is dropped. In our backlog drop, we dont examine details of
packet and drop it at a lower level.

Please add a new counter, say LINUX_MIB_TCPBACKLOGDROP :

3 added lines:
- one in "include/linux/snmp.h" to define the MIB name
- one to define its string
- one to perform the increment when actual drop occurs)

A good starting point would be to study recent commit
72032fdbcde8b333e65b3430e1bcb4358e2d6716 from Jamal
(xfrm: Introduce LINUX_MIB_XFRMFWDHDRERROR)

For sk_drop, just increment it and we can get it at generic sock level.

Thanks !