[CentOS] packet traversal

Fri Dec 6 19:43:05 UTC 2013
John R Pierce <pierce at hogranch.com>

On 12/6/2013 11:28 AM, m.roth at 5-cent.us wrote:
>> I don't know whether i am asking on a correct list or not i have a query
>> >that how to know that what system call are called when packet enters the
>> >system or when we send a packet from a system?
> Hi, there. Sounds like you want to do a tcpdump, or some such, on eth0 (or
> whatever).

um, no, that wouldn't answer his question.

when a packet is recieved by a NIC, it generates a hardware interrupt, 
which triggers a kernel driver interrupt handler, this will use various 
kernel level APIs which aren't visible to user space, and bubbles 
through the various layers of the network stack, before its finally 
presented to the user mode application which is waiting for it via a 
read or select call.

the specifics of the kernel mode stuff is outside the scope of this 
list.   actually, this whole question is outside the scope of this list 
as its really not centos specific at all, its a general Linux kernel 
question.    I don't know what the appropriate forum for such might be, 

john r pierce                                      37N 122W
somewhere on the middle of the left coast