Thanks Mulyadi, Yeah that a final alternative. Actually I was looking for some optimized way of getting packet filtered at kernel level using BPF filter. On 21 December 2011 06:22, Mulyadi Santosa <mulyadi.santosa@gmail.com>wrote:
Hi Mukesh..
On Wed, Dec 21, 2011 at 01:38, Mukesh Yadav <mukesh.fkd@gmail.com> wrote:
BPF filters used are: Even IP filter :-> tcpdump -i interface 'ether dst <dest mac> && ip[19] & 0x01 = 0' Odd IP filter :-> tcpdump -i interface 'ether dst <dest mac> && ip[19] & 0x01 = 1'
There is a packet loss for odd IP thread even when CPU is available. Reason being packet drop due recv buffer full. Same amount of traffic is well handled by even IP thread(user code being same in both), scaling CPU to full 100%.
In odd IP thread, If filter is changed to "tcpdump -i interface 'ether dst <dest mac> && ip proto 17' ", all goes fine. Also CPU usage at kernel drops from 50% to 4 % for a particular amount of traffic.
I have zero experience with BPF, so this is just my theory.
In kernel level, (or maybe between kernel and user level), by putting your odd and even filter, kernel work too hard to separate the packets into different "queue" or "channel"...or something like that. While in the mean time, incoming packets are bursting .... This makes buffers filled up fast.
How about this... just filter anything that match your target MAC....fed this up to the user level application and let your application do the odd and even IP filtering?
-- regards,
Mulyadi Santosa Freelance Linux trainer and consultant
blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com
-- Cheers Mukesh Yadav Senior Software Engineer Plot6 Sector 18 Aricent Gurgaon Mob: 9953024169