[PATCH net-next v2 13/14] selftests/bpf: Test skb_ext read from sk_skb stream verdict hook

[Jakub Sitnicki <jakub@cloudflare.com>]

Test bpf_dynptr_from_skb_ext() from sk_skb context. Write to skb_ext from
TC on loopback; read from skb_ext from the sockmap verdict program.

Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
---
 .../selftests/bpf/prog_tests/socket_helpers.h      |  1 +
 .../bpf/prog_tests/xdp_context_test_run.c          | 80 ++++++++++++++++++++++
 tools/testing/selftests/bpf/progs/test_xdp_meta.c  | 18 +++++
 3 files changed, 99 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/socket_helpers.h b/tools/testing/selftests/bpf/prog_tests/socket_helpers.h
index 0d59503a0c73..eb114a6ea6f9 100644
--- a/tools/testing/selftests/bpf/prog_tests/socket_helpers.h
+++ b/tools/testing/selftests/bpf/prog_tests/socket_helpers.h
@@ -3,6 +3,7 @@
 #ifndef __SOCKET_HELPERS__
 #define __SOCKET_HELPERS__
 
+#include <error.h>
 #include <sys/un.h>
 #include <linux/vm_sockets.h>
 
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 2814bfa0d6b5..01241276c4d3 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
@@ -4,6 +4,7 @@
 #include <linux/ipv6.h>
 #include <linux/netfilter.h>
 #include <arpa/inet.h>
+#include "socket_helpers.h"
 #include "test_xdp_context_test_run.skel.h"
 #include "test_xdp_meta.skel.h"
 
@@ -1678,6 +1679,83 @@ static void test_skb_ext_seg6local(struct test_xdp_meta *skel)
 		unlink(SEG6_PIN_PATH);
 }
 
+/*
+ * Test skb_ext survival across TC ingress -> sk_skb verdict hook.  TC ingress
+ * writes skb_ext on loopback; the verdict program reads it on skb delivery to a
+ * socket in the sockmap.
+ */
+static void test_skb_ext_sk_skb(struct test_xdp_meta *skel)
+{
+	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 *verdict_link = NULL;
+	struct sockaddr_in addr;
+	socklen_t addr_len = sizeof(addr);
+	struct netns_obj *ns = NULL;
+	char buf[TEST_PAYLOAD_LEN];
+	int c1 = -1, p1 = -1;
+	int map = -1, zero = 0;
+	ssize_t n;
+	int ret;
+
+	ns = netns_new("tc_to_sk_skb", true);
+	if (!ASSERT_OK_PTR(ns, "netns_new"))
+		return;
+
+	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;
+
+	map = bpf_map_create(BPF_MAP_TYPE_SOCKMAP, NULL, sizeof(int),
+			     sizeof(int), 1, NULL);
+	if (!ASSERT_GE(map, 0, "bpf_map_create"))
+		goto cleanup;
+
+	verdict_link = bpf_program__attach_sockmap(skel->progs.sk_skb_skb_ext_read,
+						   map);
+	if (!ASSERT_OK_PTR(verdict_link, "attach_sockmap"))
+		goto cleanup;
+
+	if (!ASSERT_OK(create_pair(AF_INET, SOCK_STREAM, &c1, &p1), "create_pair"))
+		goto cleanup;
+
+	if (!ASSERT_OK(bpf_map_update_elem(map, &zero, &c1, BPF_NOEXIST), "map_update"))
+		goto cleanup;
+
+	if (!ASSERT_OK(getsockname(c1, (struct sockaddr *)&addr, &addr_len),
+		       "getsockname"))
+		goto cleanup;
+	skel->bss->target_port = addr.sin_port;
+
+	n = send(p1, test_payload, TEST_PAYLOAD_LEN, 0);
+	if (!ASSERT_EQ(n, TEST_PAYLOAD_LEN, "send"))
+		goto cleanup;
+
+	n = recv_timeout(c1, buf, sizeof(buf), MSG_DONTWAIT, IO_TIMEOUT_SEC);
+	ASSERT_EQ(n, TEST_PAYLOAD_LEN, "recv");
+	ASSERT_TRUE(skel->bss->test_pass, "test_pass");
+
+cleanup:
+	if (c1 >= 0)
+		close(c1);
+	if (p1 >= 0)
+		close(p1);
+	bpf_link__destroy(verdict_link);
+	if (map >= 0)
+		close(map);
+	bpf_tc_hook_destroy(&tc_hook);
+	netns_free(ns);
+}
+
 void test_skb_ext_cross_hook(void)
 {
 	struct test_xdp_meta *skel = NULL;
@@ -1709,6 +1787,8 @@ void test_skb_ext_cross_hook(void)
 				 skel->progs.lwt_xmit_skb_ext_write, "xmit", true);
 	if (test__start_subtest("tc_to_seg6local"))
 		test_skb_ext_seg6local(skel);
+	if (test__start_subtest("tc_to_sk_skb"))
+		test_skb_ext_sk_skb(skel);
 
 	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 00312a549ea9..5b1a5b9b610e 100644
--- a/tools/testing/selftests/bpf/progs/test_xdp_meta.c
+++ b/tools/testing/selftests/bpf/progs/test_xdp_meta.c
@@ -1232,4 +1232,22 @@ int seg6local_skb_ext_read(struct __sk_buff *ctx)
 	return BPF_OK;
 }
 
+/* Read skb_ext from sk_skb stream verdict hook */
+SEC("sk_skb/stream_verdict")
+int sk_skb_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 SK_PASS;
+	if (bpf_dynptr_read(meta_have, META_SIZE, &meta, 0, 0))
+		return SK_PASS;
+	if (!check_metadata(meta_have))
+		return SK_PASS;
+
+	test_pass = true;
+	return SK_PASS;
+}
+
 char _license[] SEC("license") = "GPL";

-- 
2.43.0