udpfwd

Forward UDP packets captured by libpcap.

This command-line tool leverages the functionality of libpcap to facilitate the forwarding of filtered UDP packets without affecting the original UDP data flow.

The third-party source code argparse.hpp is involved for the advantage of parsing arguments.

For performance, a simple pre-allocated ring-buffer is used in the program to avoid continually malloc and free memory.

Build

make

Then udpfwd is built. See Makefile for details.

Usage

See the help message with the -h option:

$ ./udpfwd -h

Test

Terminal-1:

# Send UDP packets from 9000 to 9001.
$ ./test/test.py

Terminal-2:

# Forward UDP packets (filtered by dst port 9001) to 9002.
$ ./test/udpfwd.sh

Terminal-3:

# Listen to UDP port 9002 and print the content onto stdout.
$ ./test/nc.sh

Terminal-4 (optional):

# Use tcpdump to capture the UDP packets going to port 9002.
$ ./test/tcpdump.sh

Dependencies

libpcap

# On Ubuntu
sudo apt install libpcap-dev

# On macOS
brew install libpcap

clang++

• clang++ is the default C++ compiler on macOS.
• On Ubuntu, install clang++ with the following cmdline.

sudo apt install llvm clang

argparse.hpp

The argparse.hpp file under the top directory is simply copied from p-ranav/argparse, which is a good C++ argument parser.