netdevsim: add selftest for forwarding skb between connected ports

Connect two netdevsim ports in different namespaces together, then send
packets between them using socat.

Signed-off-by: David Wei <dw@davidwei.uk>
Signed-off-by: NipaLocal <nipa@local>

tools/testing/selftests/drivers/net/netdevsim/peer.sh

@@ -0,0 +1,111 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0-only
+
+NSIM_DEV_SYS=/sys/bus/netdevsim
+NSIM_DEV_DFS=/sys/kernel/debug/netdevsim/netdevsim
+
+socat_check()
+{
+	if [ ! -x "$(command -v socat)" ]; then
+		echo "socat command not found. Skipping test"
+		return 1
+	fi
+
+	return 0
+}
+
+setup_ns()
+{
+	set -e
+	ip netns add nssv
+	ip netns add nscl
+
+	ip link set eni1np1 netns nssv
+	ip link set eni2np1 netns nscl
+
+	ip netns exec nssv ip addr add '192.168.1.1/24' dev eni1np1
+	ip netns exec nscl ip addr add '192.168.1.2/24' dev eni2np1
+
+	ip netns exec nssv ip link set dev eni1np1 up
+	ip netns exec nscl ip link set dev eni2np1 up
+	set +e
+}
+
+cleanup_ns()
+{
+	ip netns del nscl
+	ip netns del nssv
+}
+
+###
+### Code start
+###
+
+modprobe netdevsim
+
+# linking
+
+echo 1 > ${NSIM_DEV_SYS}/new_device
+
+echo "2 0" > ${NSIM_DEV_DFS}1/ports/0/peer 2>/dev/null
+if [ $? -eq 0 ]; then
+	echo "linking with non-existent netdevsim should fail"
+	exit 1
+fi
+
+echo 2 > /sys/bus/netdevsim/new_device
+
+echo "2 0" > ${NSIM_DEV_DFS}1/ports/0/peer
+if [ $? -ne 0 ]; then
+	echo "linking netdevsim1 port0 with netdevsim2 port0 should succeed"
+	exit 1
+fi
+
+# argument error checking
+
+echo "2 1" > ${NSIM_DEV_DFS}1/ports/0/peer 2>/dev/null
+if [ $? -eq 0 ]; then
+	echo "linking with non-existent port in a netdevsim should fail"
+	exit 1
+fi
+
+echo "1 0" > ${NSIM_DEV_DFS}1/ports/0/peer 2>/dev/null
+if [ $? -eq 0 ]; then
+	echo "linking with self should fail"
+	exit 1
+fi
+
+echo "2 a" > ${NSIM_DEV_DFS}1/ports/0/peer 2>/dev/null
+if [ $? -eq 0 ]; then
+	echo "invalid arg should fail"
+	exit 1
+fi
+
+# send/recv packets
+
+socat_check || exit 1
+
+setup_ns
+
+tmp_file=$(mktemp)
+ip netns exec nssv socat TCP-LISTEN:1234,fork $tmp_file &
+pid=$!
+
+echo "HI" | ip netns exec nscl socat STDIN TCP:192.168.1.1:1234
+
+count=$(cat $tmp_file | wc -c)
+if [[ $count -ne 3 ]]; then
+	echo "expected 3 bytes, got $count"
+	exit 1
+fi
+
+echo 2 > ${NSIM_DEV_SYS}/del_device
+
+kill $pid
+echo 1 > ${NSIM_DEV_SYS}/del_device
+
+cleanup_ns
+
+modprobe -r netdevsim
+
+exit 0