samples/bpf: add userspace example for prohibiting sockets

Add examples preventing a process in a cgroup from opening a socket
based family, protocol and type.

Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

samples/bpf/test_cgrp2_sock2.sh

@@ -0,0 +1,81 @@
+#!/bin/bash
+
+function config_device {
+	ip netns add at_ns0
+	ip link add veth0 type veth peer name veth0b
+	ip link set veth0b up
+	ip link set veth0 netns at_ns0
+	ip netns exec at_ns0 ip addr add 172.16.1.100/24 dev veth0
+	ip netns exec at_ns0 ip addr add 2401:db00::1/64 dev veth0 nodad
+	ip netns exec at_ns0 ip link set dev veth0 up
+	ip addr add 172.16.1.101/24 dev veth0b
+	ip addr add 2401:db00::2/64 dev veth0b nodad
+}
+
+function config_cgroup {
+	rm -rf /tmp/cgroupv2
+	mkdir -p /tmp/cgroupv2
+	mount -t cgroup2 none /tmp/cgroupv2
+	mkdir -p /tmp/cgroupv2/foo
+	echo $$ >> /tmp/cgroupv2/foo/cgroup.procs
+}
+
+
+function attach_bpf {
+	test_cgrp2_sock2 /tmp/cgroupv2/foo sock_flags_kern.o $1
+	[ $? -ne 0 ] && exit 1
+}
+
+function cleanup {
+	ip link del veth0b
+	ip netns delete at_ns0
+	umount /tmp/cgroupv2
+	rm -rf /tmp/cgroupv2
+}
+
+cleanup 2>/dev/null
+
+set -e
+config_device
+config_cgroup
+set +e
+
+#
+# Test 1 - fail ping6
+#
+attach_bpf 0
+ping -c1 -w1 172.16.1.100
+if [ $? -ne 0 ]; then
+	echo "ping failed when it should succeed"
+	cleanup
+	exit 1
+fi
+
+ping6 -c1 -w1 2401:db00::1
+if [ $? -eq 0 ]; then
+	echo "ping6 succeeded when it should not"
+	cleanup
+	exit 1
+fi
+
+#
+# Test 2 - fail ping
+#
+attach_bpf 1
+ping6 -c1 -w1 2401:db00::1
+if [ $? -ne 0 ]; then
+	echo "ping6 failed when it should succeed"
+	cleanup
+	exit 1
+fi
+
+ping -c1 -w1 172.16.1.100
+if [ $? -eq 0 ]; then
+	echo "ping succeeded when it should not"
+	cleanup
+	exit 1
+fi
+
+cleanup
+echo
+echo "*** PASS ***"