Linux API to determine sockets owned by a process

Question

Is there a Linux library that will enable me to tell what IP sockets are owned by what processes? I guess I\'m looking for the programmatic equivalent of lsof -i

Answer 1

/proc//net is equivalent to /proc/net for all processes in the same network namespace as you – in other words, it's "global" information.

You can do what lsof and fuser do, which is to iterate through both /proc//fd/* and /proc/net/* looking for matching inodes. Quick demonstration:

#!/bin/sh
pgrep "$@" | while read pid; do
    for fd in /proc/$pid/fd/*; do
        name=$(readlink $fd)
        case $name in
            socket:\[*\])
                ino=${name#*:}
                for proto in tcp:10 tcp6:10 udp:10 udp6:10 unix:7; do
                    [[ ! -e /proc/net/${proto%:*} ]] ||
                    awk "
                        \$${proto##*:} == ${ino:1:${#ino}-2} {
                            print \"${proto%:*}:\", \$0
                            exit 1
                        }
                    " /proc/net/${proto%:*} || break
                done
                ;;
        esac
    done
done

You can extend this to other protocols (I see ax25, ipx, packet, raw, raw6, udplite, udp6lite in /proc/net/ too) or rewrite in a language of your choosing.