selftests: bpf: Extend sk_assign tests for UDP

Add support for testing UDP sk_assign to the existing tests.

Signed-off-by: Joe Stringer <joe@wand.net.nz>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Lorenz Bauer <lmb@cloudflare.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200329225342.16317-6-joe@wand.net.nz

tools/testing/selftests/bpf/prog_tests/sk_assign.c

@@ -69,7 +69,7 @@ start_server(const struct sockaddr *addr, socklen_t len, int type)
 		goto close_out;
 	if (CHECK_FAIL(bind(fd, addr, len) == -1))
 		goto close_out;
-	if (CHECK_FAIL(listen(fd, 128) == -1))
+	if (type == SOCK_STREAM && CHECK_FAIL(listen(fd, 128) == -1))
 		goto close_out;
 
 	goto out;
@@ -125,6 +125,20 @@ get_port(int fd)
 	return port;
 }
 
+static ssize_t
+rcv_msg(int srv_client, int type)
+{
+	struct sockaddr_storage ss;
+	char buf[BUFSIZ];
+	socklen_t slen;
+
+	if (type == SOCK_STREAM)
+		return read(srv_client, &buf, sizeof(buf));
+	else
+		return recvfrom(srv_client, &buf, sizeof(buf), 0,
+				(struct sockaddr *)&ss, &slen);
+}
+
 static int
 run_test(int server_fd, const struct sockaddr *addr, socklen_t len, int type)
 {
@@ -139,26 +153,41 @@ run_test(int server_fd, const struct sockaddr *addr, socklen_t len, int type)
 		goto out;
 	}
 
-	srv_client = accept(server_fd, NULL, NULL);
-	if (CHECK_FAIL(srv_client == -1)) {
-		perror("Can't accept connection");
-		goto out;
+	if (type == SOCK_STREAM) {
+		srv_client = accept(server_fd, NULL, NULL);
+		if (CHECK_FAIL(srv_client == -1)) {
+			perror("Can't accept connection");
+			goto out;
+		}
+	} else {
+		srv_client = server_fd;
 	}
 	if (CHECK_FAIL(write(client, buf, sizeof(buf)) != sizeof(buf))) {
 		perror("Can't write on client");
 		goto out;
 	}
-	if (CHECK_FAIL(read(srv_client, &buf, sizeof(buf)) != sizeof(buf))) {
+	if (CHECK_FAIL(rcv_msg(srv_client, type) != sizeof(buf))) {
 		perror("Can't read on server");
 		goto out;
 	}
 
 	port = get_port(srv_client);
 	if (CHECK_FAIL(!port))
 		goto out;
-	if (CHECK(port != htons(CONNECT_PORT), "Expected", "port %u but got %u",
+	/* SOCK_STREAM is connected via accept(), so the server's local address
+	 * will be the CONNECT_PORT rather than the BIND port that corresponds
+	 * to the listen socket. SOCK_DGRAM on the other hand is connectionless
+	 * so we can't really do the same check there; the server doesn't ever
+	 * create a socket with CONNECT_PORT.
+	 */
+	if (type == SOCK_STREAM &&
+	    CHECK(port != htons(CONNECT_PORT), "Expected", "port %u but got %u",
 		  CONNECT_PORT, ntohs(port)))
 		goto out;
+	else if (type == SOCK_DGRAM &&
+		 CHECK(port != htons(BIND_PORT), "Expected",
+		       "port %u but got %u", BIND_PORT, ntohs(port)))
+		goto out;
 
 	ret = 0;
 out:
@@ -230,6 +259,10 @@ void test_sk_assign(void)
 		TEST("ipv4 tcp addr redir", AF_INET, SOCK_STREAM, true),
 		TEST("ipv6 tcp port redir", AF_INET6, SOCK_STREAM, false),
 		TEST("ipv6 tcp addr redir", AF_INET6, SOCK_STREAM, true),
+		TEST("ipv4 udp port redir", AF_INET, SOCK_DGRAM, false),
+		TEST("ipv4 udp addr redir", AF_INET, SOCK_DGRAM, true),
+		TEST("ipv6 udp port redir", AF_INET6, SOCK_DGRAM, false),
+		TEST("ipv6 udp addr redir", AF_INET6, SOCK_DGRAM, true),
 	};
 	int server = -1;
 	int self_net;

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

@@ -21,7 +21,7 @@ char _license[] SEC("license") = "GPL";
 
 /* Fill 'tuple' with L3 info, and attempt to find L4. On fail, return NULL. */
 static inline struct bpf_sock_tuple *
-get_tuple(struct __sk_buff *skb, bool *ipv4)
+get_tuple(struct __sk_buff *skb, bool *ipv4, bool *tcp)
 {
 	void *data_end = (void *)(long)skb->data_end;
 	void *data = (void *)(long)skb->data;
@@ -60,12 +60,64 @@ get_tuple(struct __sk_buff *skb, bool *ipv4)
 		return (struct bpf_sock_tuple *)data;
 	}
 
-	if (result + 1 > data_end || proto != IPPROTO_TCP)
+	if (proto != IPPROTO_TCP && proto != IPPROTO_UDP)
 		return NULL;
 
+	*tcp = (proto == IPPROTO_TCP);
 	return result;
 }
 
+static inline int
+handle_udp(struct __sk_buff *skb, struct bpf_sock_tuple *tuple, bool ipv4)
+{
+	struct bpf_sock_tuple ln = {0};
+	struct bpf_sock *sk;
+	size_t tuple_len;
+	int ret;
+
+	tuple_len = ipv4 ? sizeof(tuple->ipv4) : sizeof(tuple->ipv6);
+	if ((void *)tuple + tuple_len > (void *)(long)skb->data_end)
+		return TC_ACT_SHOT;
+
+	sk = bpf_sk_lookup_udp(skb, tuple, tuple_len, BPF_F_CURRENT_NETNS, 0);
+	if (sk)
+		goto assign;
+
+	if (ipv4) {
+		if (tuple->ipv4.dport != bpf_htons(4321))
+			return TC_ACT_OK;
+
+		ln.ipv4.daddr = bpf_htonl(0x7f000001);
+		ln.ipv4.dport = bpf_htons(1234);
+
+		sk = bpf_sk_lookup_udp(skb, &ln, sizeof(ln.ipv4),
+					BPF_F_CURRENT_NETNS, 0);
+	} else {
+		if (tuple->ipv6.dport != bpf_htons(4321))
+			return TC_ACT_OK;
+
+		/* Upper parts of daddr are already zero. */
+		ln.ipv6.daddr[3] = bpf_htonl(0x1);
+		ln.ipv6.dport = bpf_htons(1234);
+
+		sk = bpf_sk_lookup_udp(skb, &ln, sizeof(ln.ipv6),
+					BPF_F_CURRENT_NETNS, 0);
+	}
+
+	/* workaround: We can't do a single socket lookup here, because then
+	 * the compiler will likely spill tuple_len to the stack. This makes it
+	 * lose all bounds information in the verifier, which then rejects the
+	 * call as unsafe.
+	 */
+	if (!sk)
+		return TC_ACT_SHOT;
+
+assign:
+	ret = bpf_sk_assign(skb, sk, 0);
+	bpf_sk_release(sk);
+	return ret;
+}
+
 static inline int
 handle_tcp(struct __sk_buff *skb, struct bpf_sock_tuple *tuple, bool ipv4)
 {
@@ -130,14 +182,23 @@ int bpf_sk_assign_test(struct __sk_buff *skb)
 {
 	struct bpf_sock_tuple *tuple, ln = {0};
 	bool ipv4 = false;
+	bool tcp = false;
 	int tuple_len;
 	int ret = 0;
 
-	tuple = get_tuple(skb, &ipv4);
+	tuple = get_tuple(skb, &ipv4, &tcp);
 	if (!tuple)
 		return TC_ACT_SHOT;
 
-	ret = handle_tcp(skb, tuple, ipv4);
+	/* Note that the verifier socket return type for bpf_skc_lookup_tcp()
+	 * differs from bpf_sk_lookup_udp(), so even though the C-level type is
+	 * the same here, if we try to share the implementations they will
+	 * fail to verify because we're crossing pointer types.
+	 */
+	if (tcp)
+		ret = handle_tcp(skb, tuple, ipv4);
+	else
+		ret = handle_udp(skb, tuple, ipv4);
 
 	return ret == 0 ? TC_ACT_OK : TC_ACT_SHOT;
 }