bpf, selftests: Add redirect_peer selftest

Extend the test_tc_redirect test and add a small test that exercises the new
redirect_peer() helper for the IPv4 and IPv6 case.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201010234006.7075-7-daniel@iogearbox.net

tools/testing/selftests/bpf/progs/test_tc_peer.c

@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <stdint.h>
+#include <stdbool.h>
+
+#include <linux/bpf.h>
+#include <linux/stddef.h>
+#include <linux/pkt_cls.h>
+
+#include <bpf/bpf_helpers.h>
+
+enum {
+	dev_src,
+	dev_dst,
+};
+
+struct bpf_map_def SEC("maps") ifindex_map = {
+	.type		= BPF_MAP_TYPE_ARRAY,
+	.key_size	= sizeof(int),
+	.value_size	= sizeof(int),
+	.max_entries	= 2,
+};
+
+static __always_inline int get_dev_ifindex(int which)
+{
+	int *ifindex = bpf_map_lookup_elem(&ifindex_map, &which);
+
+	return ifindex ? *ifindex : 0;
+}
+
+SEC("chk_egress") int tc_chk(struct __sk_buff *skb)
+{
+	return TC_ACT_SHOT;
+}
+
+SEC("dst_ingress") int tc_dst(struct __sk_buff *skb)
+{
+	return bpf_redirect_peer(get_dev_ifindex(dev_src), 0);
+}
+
+SEC("src_ingress") int tc_src(struct __sk_buff *skb)
+{
+	return bpf_redirect_peer(get_dev_ifindex(dev_dst), 0);
+}
+
+char __license[] SEC("license") = "GPL";

tools/testing/selftests/bpf/test_tc_redirect.sh

@@ -4,9 +4,10 @@
 # This test sets up 3 netns (src <-> fwd <-> dst). There is no direct veth link
 # between src and dst. The netns fwd has veth links to each src and dst. The
 # client is in src and server in dst. The test installs a TC BPF program to each
-# host facing veth in fwd which calls into bpf_redirect_peer() to perform the
-# neigh addr population and redirect; it also installs a dropper prog on the
-# egress side to drop skbs if neigh addrs were not populated.
+# host facing veth in fwd which calls into i) bpf_redirect_neigh() to perform the
+# neigh addr population and redirect or ii) bpf_redirect_peer() for namespace
+# switch from ingress side; it also installs a checker prog on the egress side
+# to drop unexpected traffic.
 
 if [[ $EUID -ne 0 ]]; then
 	echo "This script must be run as root"
@@ -166,15 +167,17 @@ hex_mem_str()
 	perl -e 'print join(" ", unpack("(H2)8", pack("L", @ARGV)))' $1
 }
 
-netns_setup_neigh()
+netns_setup_bpf()
 {
+	local obj=$1
+
 	ip netns exec ${NS_FWD} tc qdisc add dev veth_src_fwd clsact
-	ip netns exec ${NS_FWD} tc filter add dev veth_src_fwd ingress bpf da obj test_tc_neigh.o sec src_ingress
-	ip netns exec ${NS_FWD} tc filter add dev veth_src_fwd egress  bpf da obj test_tc_neigh.o sec chk_egress
+	ip netns exec ${NS_FWD} tc filter add dev veth_src_fwd ingress bpf da obj $obj sec src_ingress
+	ip netns exec ${NS_FWD} tc filter add dev veth_src_fwd egress  bpf da obj $obj sec chk_egress
 
 	ip netns exec ${NS_FWD} tc qdisc add dev veth_dst_fwd clsact
-	ip netns exec ${NS_FWD} tc filter add dev veth_dst_fwd ingress bpf da obj test_tc_neigh.o sec dst_ingress
-	ip netns exec ${NS_FWD} tc filter add dev veth_dst_fwd egress  bpf da obj test_tc_neigh.o sec chk_egress
+	ip netns exec ${NS_FWD} tc filter add dev veth_dst_fwd ingress bpf da obj $obj sec dst_ingress
+	ip netns exec ${NS_FWD} tc filter add dev veth_dst_fwd egress  bpf da obj $obj sec chk_egress
 
 	veth_src=$(ip netns exec ${NS_FWD} cat /sys/class/net/veth_src_fwd/ifindex)
 	veth_dst=$(ip netns exec ${NS_FWD} cat /sys/class/net/veth_dst_fwd/ifindex)
@@ -193,5 +196,9 @@ trap netns_cleanup EXIT
 set -e
 
 netns_setup
-netns_setup_neigh
+netns_setup_bpf test_tc_neigh.o
+netns_test_connectivity
+netns_cleanup
+netns_setup
+netns_setup_bpf test_tc_peer.o
 netns_test_connectivity