Packet drop while using BPF filter

[Mukesh Yadav]

Hi  Raghavendra,

" /proc/sys/net/core/bpf_jit_**enable " is not present on machine. Seems
kernel need to be configured for these.
Btw CPU scaling issue is resolved. Packet drop was because all interrupt
handling was happening on core where packets were getting drop. Tuning
system for interrupt handling using smp_affinity resolved the issue.

Thanks
Mukesh

On 22 December 2011 19:18, Raghavendra D Prabhu <raghu.prabhu13 at gmail.com>wrote:

> Hi,
>
>    Have you tried enabling -- /proc/sys/net/core/bpf_jit_**enable --
>    provides JIT compiled BPF  on 64 bit linux.
>
>
> * On Wed, Dec 21, 2011 at 12:08:04AM +0530, Mukesh Yadav <
> mukesh.fkd at gmail.com> wrote:
>
>> Hi Guys,
>>
>> I am working on user level code which uses BPF filter.
>> Solution has two threads and  BPF filter for incoming packets to raw
>> socket
>> dedicated to each thread.
>> Intent is to divide ingress traffic between two thread based on whether
>> dest IP is even or odd.
>>
>> 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.
>>
>> Would appreciate any I/ps for reducing load at kernel for packet
>> filtering(Odd/Even IP distribution)
>>
>>
>> Cheers
>> Mukesh
>>
>
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>
> --------------------------
> Raghavendra Prabhu
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-- 
Cheers
Mukesh Yadav
Senior Software Engineer
Plot6 Sector 18
Aricent
Gurgaon
Mob: 9953024169
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