[PATCH net-next 11/14] selftests/bpf: Test skb_ext from LWT in, out, and xmit hooks

Add cross-hook tests for bpf_dynptr_from_skb_ext() covering all
generic LWT program types. For lwt_in, a TC ingress program writes
skb_ext on loopback and the LWT program reads it back. For lwt_out
and lwt_xmit, the LWT programs write skb_ext on the output path and a
TC ingress program reads it back after loopback.

Signed-off-by: Jakub Sitnicki <[email protected]>
---
 .../bpf/prog_tests/xdp_context_test_run.c          | 98 ++++++++++++++++++++++
 tools/testing/selftests/bpf/progs/test_xdp_meta.c  | 45 ++++++++++
 2 files changed, 143 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c b/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c
index 82c57ea3957e..7a7537ef80e7 100644
--- a/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c
+++ b/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c
@@ -1303,6 +1303,95 @@ static void test_skb_ext_nf(struct test_xdp_meta *skel, const char *name)
 	netns_free(ns);
 }
 
+#define LWT_EXT_PIN_PATH "/sys/fs/bpf/skb_ext_lwt"
+
+/* Test skb_ext across LWT hooks on loopback.
+ *
+ * @lwt_prog:  BPF program to pin and attach via ip route encap
+ * @encap_dir: "in", "out", or "xmit"
+ * @writer:    true if lwt_prog writes skb_ext (reader on TC ingress),
+ *             false if lwt_prog reads skb_ext (writer on TC ingress)
+ */
+static void test_skb_ext_lwt(struct test_xdp_meta *skel, const char *name,
+			     struct bpf_program *lwt_prog,
+			     const char *encap_dir, bool writer)
+{
+	LIBBPF_OPTS(bpf_tc_hook, tc_hook,
+		    .ifindex = 1 /* IFINDEX_LO */,
+		    .attach_point = BPF_TC_INGRESS);
+	LIBBPF_OPTS(bpf_tc_opts, tc_opts, .handle = 1, .priority = 1);
+	struct sockaddr_in addr = {
+		.sin_family = AF_INET,
+	};
+	struct bpf_program *tc_prog;
+	char buf[TEST_PAYLOAD_LEN];
+	struct netns_obj *ns = NULL;
+	bool pinned = false;
+	int server_fd = -1;
+	int fd = -1;
+	__be16 port;
+	int ret;
+
+	unlink(LWT_EXT_PIN_PATH);
+	ret = bpf_program__pin(lwt_prog, LWT_EXT_PIN_PATH);
+	if (!ASSERT_OK(ret, "pin lwt"))
+		return;
+	pinned = true;
+
+	ns = netns_new(name, true);
+	if (!ASSERT_OK_PTR(ns, "netns_new"))
+		goto cleanup;
+
+	SYS(cleanup, "ip addr add 10.0.0.1/32 dev lo");
+	SYS(cleanup, "ip route replace table local local 10.0.0.1 "
+		     "encap bpf %s pinned " LWT_EXT_PIN_PATH " dev lo",
+		     encap_dir);
+
+	server_fd = start_server(AF_INET, SOCK_DGRAM, "10.0.0.1", 0, 0);
+	if (!ASSERT_GE(server_fd, 0, "start_server"))
+		goto cleanup;
+
+	skel->bss->test_pass = false;
+
+	ret = bpf_tc_hook_create(&tc_hook);
+	if (!ASSERT_OK(ret, "bpf_tc_hook_create"))
+		goto cleanup;
+
+	/* When LWT writes, TC ingress reads; when LWT reads, TC ingress writes */
+	tc_prog = writer ? skel->progs.tc_skb_ext_read
+			 : skel->progs.tc_skb_ext_write;
+	tc_opts.prog_fd = bpf_program__fd(tc_prog);
+	ret = bpf_tc_attach(&tc_hook, &tc_opts);
+	if (!ASSERT_OK(ret, "bpf_tc_attach"))
+		goto cleanup;
+
+	port = get_socket_local_port(server_fd);
+	if (!ASSERT_GE(port, 0, "get_port"))
+		goto cleanup;
+
+	fd = socket(AF_INET, SOCK_DGRAM, 0);
+	if (!ASSERT_GE(fd, 0, "socket"))
+		goto cleanup;
+
+	inet_pton(AF_INET, "10.0.0.1", &addr.sin_addr);
+	addr.sin_port = port;
+	sendto(fd, test_payload, TEST_PAYLOAD_LEN, 0,
+	       (void *)&addr, sizeof(addr));
+	recvfrom(server_fd, buf, sizeof(buf), 0, NULL, NULL);
+
+	ASSERT_TRUE(skel->bss->test_pass, "test_pass");
+
+cleanup:
+	if (fd >= 0)
+		close(fd);
+	bpf_tc_hook_destroy(&tc_hook);
+	if (server_fd >= 0)
+		close(server_fd);
+	netns_free(ns);
+	if (pinned)
+		unlink(LWT_EXT_PIN_PATH);
+}
+
 void test_skb_ext_cross_hook(void)
 {
 	struct test_xdp_meta *skel = NULL;
@@ -1323,6 +1412,15 @@ void test_skb_ext_cross_hook(void)
 		test_cgrp_egress_to_kfree_skb(skel);
 	if (test__start_subtest("tc_to_nf"))
 		test_skb_ext_nf(skel, "tc_to_nf");
+	if (test__start_subtest("tc_to_lwt_in"))
+		test_skb_ext_lwt(skel, "tc_to_lwt_in",
+				 skel->progs.lwt_in_skb_ext_read, "in", false);
+	if (test__start_subtest("lwt_out_to_tc"))
+		test_skb_ext_lwt(skel, "lwt_out_to_tc",
+				 skel->progs.lwt_out_skb_ext_write, "out", true);
+	if (test__start_subtest("lwt_xmit_to_tc"))
+		test_skb_ext_lwt(skel, "lwt_xmit_to_tc",
+				 skel->progs.lwt_xmit_skb_ext_write, "xmit", true);
 
 	test_xdp_meta__destroy(skel);
 }
diff --git a/tools/testing/selftests/bpf/progs/test_xdp_meta.c b/tools/testing/selftests/bpf/progs/test_xdp_meta.c
index 0688120f3d40..97c1760fbd6d 100644
--- a/tools/testing/selftests/bpf/progs/test_xdp_meta.c
+++ b/tools/testing/selftests/bpf/progs/test_xdp_meta.c
@@ -1089,4 +1089,49 @@ int nf_skb_ext_read(struct bpf_nf_ctx *ctx)
 	return NF_ACCEPT;
 }
 
+SEC("lwt_in")
+int lwt_in_skb_ext_read(struct __sk_buff *ctx)
+{
+	__u8 meta_have[META_SIZE];
+	struct bpf_dynptr meta;
+
+	if (bpf_dynptr_from_skb_ext(ctx, 0, 0, &meta))
+		return BPF_OK;
+	if (bpf_dynptr_read(meta_have, META_SIZE, &meta, 0, 0))
+		return BPF_OK;
+	if (!check_metadata(meta_have))
+		return BPF_OK;
+
+	test_pass = true;
+	return BPF_OK;
+}
+
+SEC("lwt_out")
+int lwt_out_skb_ext_write(struct __sk_buff *ctx)
+{
+	struct bpf_dynptr meta;
+
+	if (!is_test_packet_tc(ctx))
+		return BPF_OK;
+	if (bpf_dynptr_from_skb_ext(ctx, 0, BPF_SKB_EXT_F_CREATE, &meta))
+		return BPF_OK;
+	bpf_dynptr_write(&meta, 0, (void *)meta_want, ARRAY_SIZE(meta_want), 0);
+
+	return BPF_OK;
+}
+
+SEC("lwt_xmit")
+int lwt_xmit_skb_ext_write(struct __sk_buff *ctx)
+{
+	struct bpf_dynptr meta;
+
+	if (!is_test_packet_tc(ctx))
+		return BPF_OK;
+	if (bpf_dynptr_from_skb_ext(ctx, 0, BPF_SKB_EXT_F_CREATE, &meta))
+		return BPF_OK;
+	bpf_dynptr_write(&meta, 0, (void *)meta_want, ARRAY_SIZE(meta_want), 0);
+
+	return BPF_OK;
+}
+
 char _license[] SEC("license") = "GPL";

-- 
2.43.0