Packet Sniffing using Raw Sockets in Linux in C

Question

I need to write a packet sniffer in Linux that detects HTTPS packet that are sent and save the url from the request. I found code for this in security-freak and ran it. This code runs and only sniffs the received packet but I need to get the sent packet in the sniffer. How do I get the sent packet in this code?

I can't use any library like libcap (forbidden). The code is :sniffer.c

Solution 1

You should be using ETH_P_ALL instead of ETH_P_IP as the protocol. ETH_P_IP only listens for incoming IP packets.

Solution 2

Why can't you use any library? Homework?

It's hard to answer without having examples from your code, for example how you set sll_pkttype.

The urlsnarf tool in the dnsiff suite could be worth a look.

Comments

[Sajad Bahmani]

we cant use any library like libcap or dnet

[JXG]

If the goal is to see http packets, why not use ETH_P_IP? You don't need everything.

[JXG]

Are you sure that your system allows detecting outgoing packets? You could use libpcap to determine if it's even possible.

[gte525u]

The goal is to see outgoing http packets. ETH_IP_P only sees incoming packets. See thread: lkml.indiana.edu/hypermail/linux/kernel/9604.1/0603.html

[karimvai]

@bua "I can't use any library like libcap (forbidden)."

[71GA]

Where is the official documentation for these kind of macros? I have been searching all over the POSIX standard but I can't find nothing. Also Linux kernel doesn't say anything!