Get local network interface addresses using only proc?

by

/proc/net/fib_trie holds the network topography

To simply print the addresses of all adapters:

$ awk '/32 host/ { print f } {f=$2}' <<< "$(</proc/net/fib_trie)"
127.0.0.1
192.168.0.5
192.168.1.14

To determine the adapter of those addresses (a) consult the adapters’ destination networks from /proc/net/route, (b) match those networks with the ones of /proc/net/fib_trie and (c) print the corresponding /32 host addresses listed under those networks.

Again no python unfortunately, but a quite awky bash approach:

#!/bin/bash

ft_local=$(awk '$1=="Local:" {flag=1} flag' <<< "$(</proc/net/fib_trie)")

for IF in $(ls /sys/class/net/); do
    networks=$(awk '$1=="'$IF'" && $3=="00000000" && $8!="FFFFFFFF" {printf $2 $8 "\n"}' <<< "$(</proc/net/route)" )
    for net_hex in $networks; do
            net_dec=$(awk '{gsub(/../, "0x& "); printf "%d.%d.%d.%d\n", $4, $3, $2, $1}' <<< $net_hex)
            mask_dec=$(awk '{gsub(/../, "0x& "); printf "%d.%d.%d.%d\n", $8, $7, $6, $5}' <<< $net_hex)
            awk "https://stackoverflow.com/"$net_dec'/{flag=1} /32 host/{flag=0} flag {a=$2} END {print "'$IF':\t" a "\n\t'$mask_dec'\n"}' <<< "$ft_local"
    done
done

exit 0

output:

eth0:     192.168.0.5
          255.255.255.0

lo:       127.0.0.1
          255.0.0.0

wlan0:    192.168.1.14
          255.255.255.0

Known limitation:

This approach does not work reliably for host addresses that share the network with other host addresses. This loss of network uniqueness makes it impossible to determine the correct host address from fib_trie as the order of those addresses does not necessarily match the order of networks of route.

Having said that, I’m not sure why you would want multiple host addresses belonging to the same network in first place. So in most use cases this approach should work just fine.

More Related Contents:

  1. Getting MAC Address
  2. How to close a socket left open by a killed program?
  3. ImageMagick not authorized to convert PDF to an image
  4. Pycharm and sys.argv arguments
  5. Install tkinter for Python
  6. Pass input/variables to command/script over SSH using Python Paramiko
  7. os.makedirs doesn’t understand “~” in my path
  8. What is the simplest way to SSH using Python?
  9. Python subprocess.Popen “OSError: [Errno 12] Cannot allocate memory”
  10. How to activate virtualenv in Linux?
  11. standard_init_linux.go:178: exec user process caused “exec format error”
  12. Cross-platform subprocess with hidden window
  13. Python virtualenv questions
  14. How do I get monotonic time durations in python?
  15. Get total physical memory in Python
  16. ‘yes’ reporting error with subprocess communicate()
  17. Unable to install pyodbc on Linux
  18. How to do sed like text replace with python?
  19. Sending a reset in TCP/IP Socket connection
  20. After Anaconda installation, conda command fails with “ImportError: no module named conda.cli”
  21. How to use “/” (directory separator) in both Linux and Windows in Python?
  22. os.walk without hidden folders
  23. Run interactive Bash with popen and a dedicated TTY Python
  24. How can I activate a virtualenv in Linux?
  25. How to select a specific input device with PyAudio
  26. Change working directory in shell with a python script
  27. Could not find or load the Qt platform plugin “xcb”
  28. Python multiprocessing memory usage
  29. How to move .conda from one folder to another at the moment of creating the environment
  30. Python – Trap all signals

Leave a Comment