CODEWITHSUNDEEP
c++linuxqtnetfilter
ali ghalambaz
ali ghalambaz

Reputation: 11

How to alter an Ethernet Packet (a packet that comes from the NIC)? Can I Use Netfilter Hooks?

I want to catch a packet before that packet come up tcp/ip layers and give it to user space with C++ and a UI.

How can I do this? Is Qt & Netfilter something that can do this?

Upvotes: 0

Views: 2841

Answers (3)

Arnav K
Arnav K

Reputation: 1

You can also use something called a Packet Socket. They are used to send or receive raw packets at Layer 2. So basically the packet will come directly to your program and you can implement your own layer 3 and 4 protocols over it. Check this official man page for packet socket.

http://man7.org/linux/man-pages/man7/packet.7.html

Upvotes: 0

user3370720
user3370720

Reputation: 11

You may use NFQUEUE and libnetfilter_queue.

iptables -t raw -I PREROUTING -p tcp -j NFQUEUE --queue-num 1

You can see an example in this site:

libnetfilter_queue_samplecode

Iptables flow

Upvotes: 0

BatchyX
BatchyX

Reputation: 5114

Qt is helpless there. What you need is to write an netlink NFQueue handler. When your packets are matched by a rule that says -j NFQUEUE, your userspace program will receive those packets, allowing you to accept, drop, or mangle (modify) the packet (only in the mangle table). If you can use GPLv2 libraries, you should use libnetfilter_queue to help you.

Note however, that the mac layer is not complete. This because the networking code need to support various device types, and some non-Ethernet devices do not have MAc addresses. On an Ethernet device, what you get is generally only the MAC address of the sender.

Upvotes: 3

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