malloc and free WSL interop sockets

malloc_wsl_socket.sh

#!/usr/bin/env bash

# malloc_wsl_interop_socket synopsis
# stdout: absolute path to valid interop socket
function malloc_wsl_interop_socket {
	local INTEROP_PARENT_PID=0
	local INTEROP_SOCKET_PID=0
	local INTEROP_BAIT_PROCESS='sleep infinity'
	pushd / >/dev/null
	(/mnt/c/Windows/system32/wsl.exe ${INTEROP_BAIT_PROCESS[@]} >/dev/null) &
	INTEROP_PARENT_PID=${!}
	popd >/dev/null
# Give time for wsl.exe to fork our process
	sleep 1
	local CHECKSUM=$(printf "${INTEROP_BAIT_PROCESS}" | sed 's/\ *$/\ /' | tr ' ' '\0' | sha256sum - | awk '{ print $1 }')
	local CHILD_PID_OF_WSL_SOCKET=$(ps -o uid,pid= -p $(find /proc -mindepth 2 -maxdepth 2 -type f -name cmdline -exec sha256sum {} \; | awk '{ if ( $1 == "'${CHECKSUM}'" ) { print $2 } }' | awk -F '/' '{ print $3 }' | sed 1d | awk '{ if ( $1 != 0 ) { print $2 } }')
	if [ "x${CHILD_PID_OF_WSL_SOCKET}" = "x" ]; then
		echo "No process found" >&2
		return -1
	fi
	local VALID_INTEROP_SOCKET="/run/WSL/$(ps -o ppid= -p ${CHILD_PID_OF_WSL_SOCKET} | grep -Eo [0-9]+)_interop"
	kill -15 ${INTEROP_PARENT_PID}
	echo ${VALID_INTEROP_SOCKET}
}

# free_wsl_interop_socket synopsis
# return value: same as kill's
# stdout: none hopefully
function free_wsl_interop_socket {
	local CHILD_PID_OF_WSL_SOCKET=${1}
	kill -15 ${CHILD_PID_OF_WSL_SOCKET}
	local retval=${?}
# Allow the socket to actually close
	sleep 1
	return ${retval}
}

# Example usage
socket_path=$(malloc_wsl_interop_socket)
socket_pid=$(echo ${socket_path} | sed 's_^.*/__;s/_interop$//')
pointer=$(awk '{ print $1 }' /proc/${socket_pid}/task/${socket_pid}/children | head -n1)

# There exists a socket
ls -l /run/WSL
echo "Pointer is: ${pointer}"
echo "Socket is:  ${socket_path}"
echo "Socket PID: ${socket_pid}"

# Let's free what we malloc'd
free_wsl_interop_socket ${pointer}

# Let's check if it's gone :)
ls -l /run/WSL