tcp / ip stack and ip forwarding questions

tcp / ip stack and ip forwarding questions

Post by Miri Groentma » Fri, 20 Apr 2001 01:00:09

Im a newbe to Linux kernel, and Im trying to understand some networking
issues in kernel 2.4.
I will highly appreciate it if anyone could refer me to networking
documentation in general, and tcp / ip stack documentation in particular.
Ive been reading tcp/ip illustrated (vol. II), but it seems like in these
issues the 2.4 kernel version is quite different from BSD.
 Im especially looking for answers to questions such as where in the code a
host validates the packet ip?
Where in the code the a packet which is addressed to a different ip is
dropped / discarded  (when the kernel isnt configured as a router), and
where in the code a packet is forwarded when the kernel IS configured as a

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1. Packets from bottom of TCP/IP stack direct to application bypassing stack

Hello Everyone

I am working on a ADSL modem and have the following situation that I
would like to have some advice on.

I need to filter out some packages in the lower level of the network
stack. There are 2 types of packages: [eth | ppp | ip | udp] and [eth
| ip | udp], the data in these packages are the same and they can be
identified with the first 16 bits in the UDP data.

I have manage to catch these packages in the /net/core/dev.c file and
function netif_rx(...) with the 16 bit ID so I have the packages.

Now for my question: How do I in an easy way get these packages
directly to my application without using the network stack. I need
BOTH of these packages to reach there and if I use socket the one with
PPP get thrown away somewhere and that is not so good.

I know this is not a very specific question and a little vague but
some advice and pointers would be appreciated.


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