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Old 06-12-2009, 07:06 AM   #1
pcarey
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Question netstat : packets directly received from backlog


Hi

Does anyone know what the following entry from the netstat output actually mean?

55413462 packets directly received from backlog

Where can I find the most comprehensive information about each line of the netstat output (don't suggest info or man)?

Peter
 
Old 06-12-2009, 08:15 AM   #2
unSpawn
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stracing -v -eopen netstat -s shows that /proc/net/netstat is read. net-tools source shows reading is done with MIB item named TCPDirectCopyFromBacklog. /proc means kernel, so in LXR (http://lxr.linux.no/linux+v2.6.30/) this is referenced in include/linux/snmp.h, net/ipv4/proc.c and net/ipv4/tcp.c. In the latter, checking at aprox line 1470 where it reads "Ugly... If prequeue is not empty, we have to process it before releasing socket, otherwise order will be broken at second iteration", and if I understand this correctly, it reads that TCP backlog receive queue data does not need to be queued more but is processed directly, hence "TCP Direct Copy From Backlog".

Last edited by unSpawn; 06-12-2009 at 08:16 AM.
 
  


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