[squid-users] Squid Source Code: What files/functions receive/send packets from/to hardware

[Amos Jeffries]

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On 6/01/2015 6:01 a.m., Priya Agarwal wrote:
> Thank you for the reply.
> 
> I do not intend to change its functionality. I just want to make it
> run on a processor (Freescale's T4240). For that it has to use some
> new architectural features (Data Path Acceleration Architecture)
> which are a part of the processor.
> 
> For e.g. suppose squid was merely swapping ipv4/mac src and dest
> addresses( just an example! ) in the packet header and sends it
> back. So I don't want to change what it does, I just want squid to
> send whatever data it has prepared to a memory location. Basically
> instead of receiving and sending to OS Stack, I want to it read and
> write from memory.  (Further details : This memory is basically a
> memory-mapped device which is further responsible for transmitting
> the frame to a network interface, ethernet)
> 
> So maybe if I could know where in the source code does it
> communicate with the OS stack.

Ah, that kind of packet handling is all much, much lower level than Squid.

Squid uses functions provided by the POSIX system API with socket
handles/"filedescriptors".

http://man7.org/linux/man-pages/man7/socket.7.html
http://man7.org/linux/man-pages/man2/read.2.html
http://man7.org/linux/man-pages/man2/write.2.html

The functions in src/fd.cc are where that happens, the lowest
networking-I/O level of Squid.


NP: If you want to take this further and/or discuss any other feature
additions/changes I encourage you to sign up to squid-dev mailing list
and discuss it with the whole dev team. This list is for general user
discussions, (though sometimes code talk from someone doing bug
investigations does slip in).

Amos
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