How to create an icmp request call in the kernel?

joblack · 07-17-2008, 02:50 PM

I'm experimenting with two experimental icmp messages.

I want to create an icmp_request in the kernel, but I have only found icmp replies (icmp_reply in icmp.c) and icmp error messages.

How can I create an icmp request without using external userspace programs (in fact I can't use the icmp_send function)? Does the icmp_reply function has some side effects?

My kernel is the 2.6.25.2 ...

Greetings and thanks
Tobias

storkus · 07-18-2008, 04:34 AM

Wow, you're talking kernel programming, which is known to be something of a black art!

Instead of Linux Questions, you should probably try places like:

www.kerneltrap.org Kernel news
www.osdever.net General kernel development
www.kernelnewbies.org Maybe t00 n00bish for you
www.linuxfoundation.org The authoritative source, but maybe not technical enough for you--I just skimmed it
www.linuxchix.org What it says. You might find something useful there...

There are undoubtedly more. In addition, talking to the people who develop the code you're trying to hook into is probably a really good idea as well.

Mike

resetreset · 07-19-2008, 04:36 AM

i maybe completely wrong about all this, but from what i remember from a long time ago, you'd have to do that in userspace. icmp uses udp. linux itself has only the tcp/udp layer of things, anything else, your program would have to make up.

joblack · 07-19-2008, 11:48 AM

Quote:

Originally Posted by resetreset

i maybe completely wrong about all this, but from what i remember from a long time ago, you'd have to do that in userspace. icmp uses udp. linux itself has only the tcp/udp layer of things, anything else, your program would have to make up.

ICMP is a L4 layer protocol. It uses IP in the network layer (UDP is also a L4 layer protocol so you can't use it). In fact the kernel reacts to icmp requests and you can create icmp error messages as well.

joblack · 07-19-2008, 03:08 PM

Quote:

Originally Posted by storkus

Wow, you're talking kernel programming, which is known to be something of a black art!

Instead of Linux Questions, you should probably try places like:

www.kerneltrap.org Kernel news
www.osdever.net General kernel development
www.kernelnewbies.org Maybe t00 n00bish for you
www.linuxfoundation.org The authoritative source, but maybe not technical enough for you--I just skimmed it
www.linuxchix.org What it says. You might find something useful there...

There are undoubtedly more. In addition, talking to the people who develop the code you're trying to hook into is probably a really good idea as well.

Mike

Thanks for the links.

There is no function for that. I have to adjust the icmp_send function for it.

Well as far as I see it kernel development is not a black art. It depends on your frustration threshold. The source code is fine but there is not enough documentation / comments included. The result is that you have to crawl through the code to get what they are doing.

I would need a black arts teacher .. if you know any?

storkus · 07-24-2008, 08:18 AM

LOL, no I don't! I may be looking for one myself next year as I intend to go back to school. I'm not sure yet exactly what I'll be doing (net admin maybe?) but I'd love to be able to learn kernel hacking.

BTW, I just looked at the comments between your reply and mine: I thought ICMP was its own Layer 4 protocol alongside UDP and TCP and above IP? (At least for IPv4--I haven't remotely begun to study IPv6 yet!)

Mike

joblack · 07-25-2008, 05:37 AM

Quote:

Originally Posted by storkus

LOL, no I don't! I may be looking for one myself next year as I intend to go back to school. I'm not sure yet exactly what I'll be doing (net admin maybe?) but I'd love to be able to learn kernel hacking.

BTW, I just looked at the comments between your reply and mine: I thought ICMP was its own Layer 4 protocol alongside UDP and TCP and above IP? (At least for IPv4--I haven't remotely begun to study IPv6 yet!)

Mike

Yes, it´s an own L4 protocol, but still depends on IPv4. I think it works the same way with IPv6, but I haven´t checked that out yet.

If you´re intested in networking read the books from O´Reilly 'Internet Core Protocols' and every book about the kernel code you can get. After a while it´s fun to see how the system really works.