How Do I Use Raw Socket in Python?

Question

I am writing an application to test a network driver for handling corrupted data. And I thought of sending this data using raw socket, so it will not be corrected by the sending machine's TCP-IP stack.

I am writing this application solely on Linux. I have code examples of using raw sockets in system-calls, but I would really like to keep my test as dynamic as possible, and write most if not all of it in Python.

I have googled the web a bit for explanations and examples of the usage of raw sockets in python, but haven't found anything really enlightening. Just a a very old code example that demonstrates the idea, but in no means work.

From what I gathered, Raw Socket usage in Python is nearly identical in semantics to UNIX's raw socket, but without the structs that define the packets structure.

I was wondering if it would even be better not to write the raw socket part of the test in Python, but in C with system-calls, and call it from the main Python code?

Answer 1

The socket class should help. If not you'll need to either write a Python module in C or just use C. See http://mail.python.org/pipermail/python-list/2001-April/077454.html.

Basic Googling found that.

Answer 2

Is this the old code you mentioned finding? It looks sensible to me, but I haven't tested it myself (or used raw sockets much). This example from the documentation shows how to use raw sockets to sniff packets, and it looks similar enough.

Answer 3

Sockets system calls (or Winsocks, on Windows), are already wrapped in the standard module socket: intro, reference.

I've never used raw sockets but it looks like they can be used with this module:

The last example shows how to write a very simple network sniffer with raw sockets on Windows. The example requires administrator privileges to modify the interface:

import socket

# the public network interface
HOST = socket.gethostbyname(socket.gethostname())

# create a raw socket and bind it to the public interface
s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_IP)
s.bind((HOST, 0))

# Include IP headers
s.setsockopt(socket.IPPROTO_IP, socket.IP_HDRINCL, 1)

# receive all packages
s.ioctl(socket.SIO_RCVALL, socket.RCVALL_ON)

# receive a package
print s.recvfrom(65565)

# disabled promiscuous mode
s.ioctl(socket.SIO_RCVALL, socket.RCVALL_OFF)

Answer 4

i've a similar problem trying to send out raw ip packets. in fact the kernel must be responsible to lookup MAC addresses (ethernet). otherwise it won't know where to send the packets. if i figure out how it works, i'll report back. OR: If someone has a solution, please report it. I've tried with this code so far, but w/o luck:

self.rawserver = socket.socket(socket.AF_INET, socket.SOCK_RAW, self.proto) self.rawserver.bind((self.interface, self.proto))

Answer 5

Eventually the best solution for this case was to write the entire thing in C, because it's not a big application, so it would've incurred greater penalty to write such a small thing in more than 1 language.

After much toying with both the C and python RAW sockets, I eventually preferred the C RAW sockets. RAW sockets require bit-level modifications of less than 8 bit groups for writing the packet headers. Sometimes writing only 4 bits or less. python defines no assistance to this, whereas Linux C has a full API for this.

But I definitely believe that if only this little bit of header initialization was handled conveniently in python, I would've never used C here.