[PATCH net-next 08/14] selftests/bpf: Test skb_ext read from sock_ops and LSM hooks

Extend skb_ext test coverage to hook on TCP ingress path: attach a TC
ingress program on loopback that writes the metadata to packets, and read
it back from a sock_ops program (BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB,
reaching the skb via bpf_sock_ops_kern->skb) and from the LSM
inet_conn_established hook.

Signed-off-by: Jakub Sitnicki <[email protected]>
---
 .../bpf/prog_tests/xdp_context_test_run.c          | 92 ++++++++++++++++++++++
 tools/testing/selftests/bpf/progs/test_xdp_meta.c  | 75 ++++++++++++++++++
 2 files changed, 167 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 808eb158fe0f..e0ab0fccf9d7 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
@@ -1098,6 +1098,94 @@ static void test_skb_ext_udp(struct test_xdp_meta *skel, const char *name,
 	netns_free(ns);
 }
 
+enum tcp_reader_type {
+	READER_SKOPS,
+	READER_LSM,
+};
+
+/* Test skb_ext survival across TC ingress -> TCP reader hook */
+static void test_skb_ext_tcp(struct test_xdp_meta *skel, const char *name,
+			     enum tcp_reader_type reader)
+{
+	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 bpf_link *reader_link = NULL;
+	struct netns_obj *ns = NULL;
+	int server_fd = -1;
+	int cgroup_fd = -1;
+	int client_fd = -1;
+	int conn_fd = -1;
+	__be16 port;
+	int ret;
+
+	ns = netns_new(name, true);
+	if (!ASSERT_OK_PTR(ns, "netns_new"))
+		return;
+
+	cgroup_fd = test__join_cgroup(name);
+	if (!ASSERT_GE(cgroup_fd, 0, "join_cgroup"))
+		goto cleanup;
+
+	server_fd = start_server(AF_INET, SOCK_STREAM, "127.0.0.1", 0, 0);
+	if (!ASSERT_GE(server_fd, 0, "start_server"))
+		goto cleanup;
+
+	port = get_socket_local_port(server_fd);
+	if (!ASSERT_GE(port, 0, "get_port"))
+		goto cleanup;
+
+	skel->bss->target_port = port;
+	skel->bss->test_pass = false;
+
+	ret = bpf_tc_hook_create(&tc_hook);
+	if (!ASSERT_OK(ret, "bpf_tc_hook_create"))
+		goto cleanup;
+
+	tc_opts.prog_fd = bpf_program__fd(skel->progs.tc_skb_ext_write_port);
+	ret = bpf_tc_attach(&tc_hook, &tc_opts);
+	if (!ASSERT_OK(ret, "bpf_tc_attach"))
+		goto cleanup;
+
+	switch (reader) {
+	case READER_SKOPS:
+		reader_link = bpf_program__attach_cgroup(skel->progs.skops_skb_ext_read,
+							 cgroup_fd);
+		if (!ASSERT_OK_PTR(reader_link, "attach_skops"))
+			goto cleanup;
+		break;
+	case READER_LSM:
+		reader_link = bpf_program__attach_lsm(skel->progs.lsm_skb_ext_read);
+		if (!ASSERT_OK_PTR(reader_link, "attach_lsm"))
+			goto cleanup;
+		break;
+	}
+
+	client_fd = connect_to_fd(server_fd, 0);
+	if (!ASSERT_GE(client_fd, 0, "connect"))
+		goto cleanup;
+
+	conn_fd = accept(server_fd, NULL, NULL);
+	if (!ASSERT_GE(conn_fd, 0, "accept"))
+		goto cleanup;
+
+	ASSERT_TRUE(skel->bss->test_pass, "test_pass");
+
+cleanup:
+	if (conn_fd >= 0)
+		close(conn_fd);
+	if (client_fd >= 0)
+		close(client_fd);
+	bpf_link__destroy(reader_link);
+	bpf_tc_hook_destroy(&tc_hook);
+	if (server_fd >= 0)
+		close(server_fd);
+	if (cgroup_fd >= 0)
+		close(cgroup_fd);
+	netns_free(ns);
+}
+
 void test_skb_ext_cross_hook(void)
 {
 	struct test_xdp_meta *skel = NULL;
@@ -1110,6 +1198,10 @@ void test_skb_ext_cross_hook(void)
 		test_skb_ext_udp(skel, "tc_to_cgrp_ingress", READER_CGRP_SKB);
 	if (test__start_subtest("tc_to_sk_filter"))
 		test_skb_ext_udp(skel, "tc_to_sk_filter", READER_SK_FILTER);
+	if (test__start_subtest("tc_to_lsm"))
+		test_skb_ext_tcp(skel, "tc_to_lsm", READER_LSM);
+	if (test__start_subtest("tc_to_skops"))
+		test_skb_ext_tcp(skel, "tc_to_skops", READER_SKOPS);
 
 	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 0a3afb5c3461..8f0a0fea5d84 100644
--- a/tools/testing/selftests/bpf/progs/test_xdp_meta.c
+++ b/tools/testing/selftests/bpf/progs/test_xdp_meta.c
@@ -938,6 +938,81 @@ int cgrp_skb_ext_read(struct __sk_buff *ctx)
 	return 1;
 }
 
+volatile __be16 target_port;
+
+#define TCPV4_HDR_OFF	(sizeof(struct ethhdr) + sizeof(struct iphdr))
+#define TCPV4_SPORT_OFF	(TCPV4_HDR_OFF + offsetof(struct tcphdr, source))
+#define TCPV4_DPORT_OFF	(TCPV4_HDR_OFF + offsetof(struct tcphdr, dest))
+
+/* Write skb_ext on TCP packets to/from target_port */
+SEC("tc")
+int tc_skb_ext_write_port(struct __sk_buff *ctx)
+{
+	struct bpf_dynptr meta;
+	__be16 sport, dport;
+
+	if (ctx->protocol != __bpf_constant_htons(ETH_P_IP))
+		return TC_ACT_UNSPEC;
+	if (bpf_skb_load_bytes(ctx, TCPV4_SPORT_OFF, &sport, sizeof(sport)))
+		return TC_ACT_UNSPEC;
+	if (bpf_skb_load_bytes(ctx, TCPV4_DPORT_OFF, &dport, sizeof(dport)))
+		return TC_ACT_UNSPEC;
+	if (sport != target_port && dport != target_port)
+		return TC_ACT_UNSPEC;
+
+	if (bpf_dynptr_from_skb_ext(ctx, 0, BPF_SKB_EXT_F_CREATE, &meta))
+		return TC_ACT_UNSPEC;
+	bpf_dynptr_write(&meta, 0, (void *)meta_want, META_SIZE, 0);
+
+	return TC_ACT_UNSPEC;
+}
+
+/* Read skb_ext from sock_ops passive established -- tests TC -> sock_ops path */
+SEC("sockops")
+int skops_skb_ext_read(struct bpf_sock_ops *ctx)
+{
+	struct bpf_sock_ops_kern *kctx;
+	__u8 meta_have[META_SIZE];
+	struct bpf_dynptr meta;
+	struct sk_buff *skb;
+
+	if (ctx->op != BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB)
+		return 1;
+
+	kctx = bpf_cast_to_kern_ctx(ctx);
+	skb = kctx->skb;
+	if (!skb)
+		return 1;
+
+	if (bpf_dynptr_from_skb_ext((struct __sk_buff *)skb, 0, 0, &meta))
+		return 1;
+	if (bpf_dynptr_read(meta_have, META_SIZE, &meta, 0, 0))
+		return 1;
+	if (!check_metadata(meta_have))
+		return 1;
+
+	test_pass = true;
+	return 1;
+}
+
+/* Read skb_ext from LSM inet_conn_established -- tests TC -> LSM path */
+SEC("lsm/inet_conn_established")
+int BPF_PROG(lsm_skb_ext_read, struct sock *sk, struct sk_buff *skb)
+{
+	__u8 meta_have[META_SIZE];
+	struct bpf_dynptr meta;
+
+	if (bpf_dynptr_from_skb_ext((struct __sk_buff *)skb, 0, 0, &meta))
+		return 0;
+	if (bpf_dynptr_read(meta_have, META_SIZE, &meta, 0, 0))
+		return 0;
+	if (!check_metadata(meta_have))
+		return 0;
+
+	test_pass = true;
+	return 0;
+}
+
 /* Read skb_ext from socket filter -- tests TC -> sk_filter path */
 SEC("socket")
 int sk_filter_skb_ext_read(struct __sk_buff *ctx)

-- 
2.43.0