selftests/bpf: Add selftest for sockmap/hashmap redirection

Test redirection logic. All supported and unsupported redirect combinations
are tested for success and failure respectively.

BPF_MAP_TYPE_SOCKMAP
BPF_MAP_TYPE_SOCKHASH
x
sk_msg-to-egress
sk_msg-to-ingress
sk_skb-to-egress
sk_skb-to-ingress
x
AF_INET, SOCK_STREAM
AF_INET6, SOCK_STREAM
AF_INET, SOCK_DGRAM
AF_INET6, SOCK_DGRAM
AF_UNIX, SOCK_STREAM
AF_UNIX, SOCK_DGRAM
AF_VSOCK, SOCK_STREAM
AF_VSOCK, SOCK_SEQPACKET

Suggested-by: Jakub Sitnicki <[e-mail]>
Signed-off-by: Michal Luczaj <[e-mail]>
Signed-off-by: Martin KaFai Lau <[e-mail]>
Acked-by: John Fastabend <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

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

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Test for sockmap/sockhash redirection.
+ *
+ * BPF_MAP_TYPE_SOCKMAP
+ * BPF_MAP_TYPE_SOCKHASH
+ *	x
+ * sk_msg-to-egress
+ * sk_msg-to-ingress
+ * sk_skb-to-egress
+ * sk_skb-to-ingress
+ *	x
+ * AF_INET, SOCK_STREAM
+ * AF_INET6, SOCK_STREAM
+ * AF_INET, SOCK_DGRAM
+ * AF_INET6, SOCK_DGRAM
+ * AF_UNIX, SOCK_STREAM
+ * AF_UNIX, SOCK_DGRAM
+ * AF_VSOCK, SOCK_STREAM
+ * AF_VSOCK, SOCK_SEQPACKET
+ */
+
+#include <errno.h>
+#include <error.h>
+#include <sched.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#include <netinet/in.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <sys/un.h>
+#include <linux/string.h>
+#include <linux/vm_sockets.h>
+
+#include <bpf/bpf.h>
+#include <bpf/libbpf.h>
+
+#include "linux/const.h"
+#include "test_progs.h"
+#include "sockmap_helpers.h"
+#include "test_sockmap_redir.skel.h"
+
+/* The meaning of SUPPORTED is "will redirect packet as expected".
+ */
+#define SUPPORTED		_BITUL(0)
+
+/* Note on sk_skb-to-ingress ->af_vsock:
+ *
+ * Peer socket may receive the packet some time after the return from sendmsg().
+ * In a typical usage scenario, recvmsg() will block until the redirected packet
+ * appears in the destination queue, or timeout if the packet was dropped. By
+ * that point, the verdict map has already been updated to reflect what has
+ * happened.
+ *
+ * But sk_skb-to-ingress/af_vsock is an unsupported combination, so no recvmsg()
+ * takes place. Which means we may race the execution of the verdict logic and
+ * read map_verd before it has been updated, i.e. we might observe
+ * map_verd[SK_DROP]=0 instead of map_verd[SK_DROP]=1.
+ *
+ * This confuses the selftest logic: if there was no packet dropped, where's the
+ * packet? So here's a heuristic: on map_verd[SK_DROP]=map_verd[SK_PASS]=0
+ * (which implies the verdict program has not been ran) just re-read the verdict
+ * map again.
+ */
+#define UNSUPPORTED_RACY_VERD	_BITUL(1)
+
+enum prog_type {
+	SK_MSG_EGRESS,
+	SK_MSG_INGRESS,
+	SK_SKB_EGRESS,
+	SK_SKB_INGRESS,
+};
+
+enum {
+	SEND_INNER = 0,
+	SEND_OUTER,
+};
+
+enum {
+	RECV_INNER = 0,
+	RECV_OUTER,
+};
+
+struct maps {
+	int in;
+	int out;
+	int verd;
+};
+
+struct combo_spec {
+	enum prog_type prog_type;
+	const char *in, *out;
+};
+
+struct redir_spec {
+	const char *name;
+	int idx_send;
+	int idx_recv;
+	enum prog_type prog_type;
+};
+
+struct socket_spec {
+	int family;
+	int sotype;
+	int send_flags;
+	int in[2];
+	int out[2];
+};
+
+static int socket_spec_pairs(struct socket_spec *s)
+{
+	return create_socket_pairs(s->family, s->sotype,
+				   &s->in[0], &s->out[0],
+				   &s->in[1], &s->out[1]);
+}
+
+static void socket_spec_close(struct socket_spec *s)
+{
+	xclose(s->in[0]);
+	xclose(s->in[1]);
+	xclose(s->out[0]);
+	xclose(s->out[1]);
+}
+
+static void get_redir_params(struct redir_spec *redir,
+			     struct test_sockmap_redir *skel, int *prog_fd,
+			     enum bpf_attach_type *attach_type,
+			     int *redirect_flags)
+{
+	enum prog_type type = redir->prog_type;
+	struct bpf_program *prog;
+	bool sk_msg;
+
+	sk_msg = type == SK_MSG_INGRESS || type == SK_MSG_EGRESS;
+	prog = sk_msg ? skel->progs.prog_msg_verdict : skel->progs.prog_skb_verdict;
+
+	*prog_fd = bpf_program__fd(prog);
+	*attach_type = sk_msg ? BPF_SK_MSG_VERDICT : BPF_SK_SKB_VERDICT;
+
+	if (type == SK_MSG_INGRESS || type == SK_SKB_INGRESS)
+		*redirect_flags = BPF_F_INGRESS;
+	else
+		*redirect_flags = 0;
+}
+
+static void try_recv(const char *prefix, int fd, int flags, bool expect_success)
+{
+	ssize_t n;
+	char buf;
+
+	errno = 0;
+	n = recv(fd, &buf, 1, flags);
+	if (n < 0 && expect_success)
+		FAIL_ERRNO("%s: unexpected failure: retval=%zd", prefix, n);
+	if (!n && !expect_success)
+		FAIL("%s: expected failure: retval=%zd", prefix, n);
+}
+
+static void handle_unsupported(int sd_send, int sd_peer, int sd_in, int sd_out,
+			       int sd_recv, int map_verd, int status)
+{
+	unsigned int drop, pass;
+	char recv_buf;
+	ssize_t n;
+
+get_verdict:
+	if (xbpf_map_lookup_elem(map_verd, &u32(SK_DROP), &drop) ||
+	    xbpf_map_lookup_elem(map_verd, &u32(SK_PASS), &pass))
+		return;
+
+	if (pass == 0 && drop == 0 && (status & UNSUPPORTED_RACY_VERD)) {
+		sched_yield();
+		goto get_verdict;
+	}
+
+	if (pass != 0) {
+		FAIL("unsupported: wanted verdict pass 0, have %u", pass);
+		return;
+	}
+
+	/* If nothing was dropped, packet should have reached the peer */
+	if (drop == 0) {
+		errno = 0;
+		n = recv_timeout(sd_peer, &recv_buf, 1, 0, IO_TIMEOUT_SEC);
+		if (n != 1)
+			FAIL_ERRNO("unsupported: packet missing, retval=%zd", n);
+	}
+
+	/* Ensure queues are empty */
+	try_recv("bpf.recv(sd_send)", sd_send, MSG_DONTWAIT, false);
+	if (sd_in != sd_send)
+		try_recv("bpf.recv(sd_in)", sd_in, MSG_DONTWAIT, false);
+
+	try_recv("bpf.recv(sd_out)", sd_out, MSG_DONTWAIT, false);
+	if (sd_recv != sd_out)
+		try_recv("bpf.recv(sd_recv)", sd_recv, MSG_DONTWAIT, false);
+}
+
+static void test_send_redir_recv(int sd_send, int send_flags, int sd_peer,
+				 int sd_in, int sd_out, int sd_recv,
+				 struct maps *maps, int status)
+{
+	unsigned int drop, pass;
+	char *send_buf = "ab";
+	char recv_buf = '\0';
+	ssize_t n, len = 1;
+
+	/* Zero out the verdict map */
+	if (xbpf_map_update_elem(maps->verd, &u32(SK_DROP), &u32(0), BPF_ANY) ||
+	    xbpf_map_update_elem(maps->verd, &u32(SK_PASS), &u32(0), BPF_ANY))
+		return;
+
+	if (xbpf_map_update_elem(maps->in, &u32(0), &u64(sd_in), BPF_NOEXIST))
+		return;
+
+	if (xbpf_map_update_elem(maps->out, &u32(0), &u64(sd_out), BPF_NOEXIST))
+		goto del_in;
+
+	/* Last byte is OOB data when send_flags has MSG_OOB bit set */
+	if (send_flags & MSG_OOB)
+		len++;
+	n = send(sd_send, send_buf, len, send_flags);
+	if (n >= 0 && n < len)
+		FAIL("incomplete send");
+	if (n < 0) {
+		/* sk_msg redirect combo not supported? */
+		if (status & SUPPORTED || errno != EACCES)
+			FAIL_ERRNO("send");
+		goto out;
+	}
+
+	if (!(status & SUPPORTED)) {
+		handle_unsupported(sd_send, sd_peer, sd_in, sd_out, sd_recv,
+				   maps->verd, status);
+		goto out;
+	}
+
+	errno = 0;
+	n = recv_timeout(sd_recv, &recv_buf, 1, 0, IO_TIMEOUT_SEC);
+	if (n != 1) {
+		FAIL_ERRNO("recv_timeout()");
+		goto out;
+	}
+
+	/* Check verdict _after_ recv(); af_vsock may need time to catch up */
+	if (xbpf_map_lookup_elem(maps->verd, &u32(SK_DROP), &drop) ||
+	    xbpf_map_lookup_elem(maps->verd, &u32(SK_PASS), &pass))
+		goto out;
+
+	if (drop != 0 || pass != 1)
+		FAIL("unexpected verdict drop/pass: wanted 0/1, have %u/%u",
+		     drop, pass);
+
+	if (recv_buf != send_buf[0])
+		FAIL("recv(): payload check, %02x != %02x", recv_buf, send_buf[0]);
+
+	if (send_flags & MSG_OOB) {
+		/* Fail reading OOB while in sockmap */
+		try_recv("bpf.recv(sd_out, MSG_OOB)", sd_out,
+			 MSG_OOB | MSG_DONTWAIT, false);
+
+		/* Remove sd_out from sockmap */
+		xbpf_map_delete_elem(maps->out, &u32(0));
+
+		/* Check that OOB was dropped on redirect */
+		try_recv("recv(sd_out, MSG_OOB)", sd_out,
+			 MSG_OOB | MSG_DONTWAIT, false);
+
+		goto del_in;
+	}
+out:
+	xbpf_map_delete_elem(maps->out, &u32(0));
+del_in:
+	xbpf_map_delete_elem(maps->in, &u32(0));
+}
+
+static int is_redir_supported(enum prog_type type, const char *in,
+			      const char *out)
+{
+	/* Matching based on strings returned by socket_kind_to_str():
+	 * tcp4, udp4, tcp6, udp6, u_str, u_dgr, v_str, v_seq
+	 * Plus a wildcard: any
+	 * Not in use: u_seq, v_dgr
+	 */
+	struct combo_spec *c, combos[] = {
+		/* Send to local: TCP -> any, but vsock */
+		{ SK_MSG_INGRESS,	"tcp",	"tcp"	},
+		{ SK_MSG_INGRESS,	"tcp",	"udp"	},
+		{ SK_MSG_INGRESS,	"tcp",	"u_str"	},
+		{ SK_MSG_INGRESS,	"tcp",	"u_dgr"	},
+
+		/* Send to egress: TCP -> TCP */
+		{ SK_MSG_EGRESS,	"tcp",	"tcp"	},
+
+		/* Ingress to egress: any -> any */
+		{ SK_SKB_EGRESS,	"any",	"any"	},
+
+		/* Ingress to local: any -> any, but vsock */
+		{ SK_SKB_INGRESS,	"any",	"tcp"	},
+		{ SK_SKB_INGRESS,	"any",	"udp"	},
+		{ SK_SKB_INGRESS,	"any",	"u_str"	},
+		{ SK_SKB_INGRESS,	"any",	"u_dgr"	},
+	};
+
+	for (c = combos; c < combos + ARRAY_SIZE(combos); c++) {
+		if (c->prog_type == type &&
+		    (!strcmp(c->in, "any") || strstarts(in, c->in)) &&
+		    (!strcmp(c->out, "any") || strstarts(out, c->out)))
+			return SUPPORTED;
+	}
+
+	return 0;
+}
+
+static int get_support_status(enum prog_type type, const char *in,
+			      const char *out)
+{
+	int status = is_redir_supported(type, in, out);
+
+	if (type == SK_SKB_INGRESS && strstarts(out, "v_"))
+		status |= UNSUPPORTED_RACY_VERD;
+
+	return status;
+}
+
+static void test_socket(enum bpf_map_type type, struct redir_spec *redir,
+			struct maps *maps, struct socket_spec *s_in,
+			struct socket_spec *s_out)
+{
+	int fd_in, fd_out, fd_send, fd_peer, fd_recv, flags, status;
+	const char *in_str, *out_str;
+	char s[MAX_TEST_NAME];
+
+	fd_in = s_in->in[0];
+	fd_out = s_out->out[0];
+	fd_send = s_in->in[redir->idx_send];
+	fd_peer = s_in->in[redir->idx_send ^ 1];
+	fd_recv = s_out->out[redir->idx_recv];
+	flags = s_in->send_flags;
+
+	in_str = socket_kind_to_str(fd_in);
+	out_str = socket_kind_to_str(fd_out);
+	status = get_support_status(redir->prog_type, in_str, out_str);
+
+	snprintf(s, sizeof(s),
+		 "%-4s %-17s %-5s %s %-5s%6s",
+		 /* hash sk_skb-to-ingress u_str → v_str (OOB) */
+		 type == BPF_MAP_TYPE_SOCKMAP ? "map" : "hash",
+		 redir->name,
+		 in_str,
+		 status & SUPPORTED ? "→" : " ",
+		 out_str,
+		 (flags & MSG_OOB) ? "(OOB)" : "");
+
+	if (!test__start_subtest(s))
+		return;
+
+	test_send_redir_recv(fd_send, flags, fd_peer, fd_in, fd_out, fd_recv,
+			     maps, status);
+}
+
+static void test_redir(enum bpf_map_type type, struct redir_spec *redir,
+		       struct maps *maps)
+{
+	struct socket_spec *s, sockets[] = {
+		{ AF_INET, SOCK_STREAM },
+		// { AF_INET, SOCK_STREAM, MSG_OOB }, /* Known to be broken */
+		{ AF_INET6, SOCK_STREAM },
+		{ AF_INET, SOCK_DGRAM },
+		{ AF_INET6, SOCK_DGRAM },
+		{ AF_UNIX, SOCK_STREAM },
+		{ AF_UNIX, SOCK_STREAM, MSG_OOB },
+		{ AF_UNIX, SOCK_DGRAM },
+		// { AF_UNIX, SOCK_SEQPACKET},	/* Unsupported BPF_MAP_UPDATE_ELEM */
+		{ AF_VSOCK, SOCK_STREAM },
+		// { AF_VSOCK, SOCK_DGRAM },	/* Unsupported socket() */
+		{ AF_VSOCK, SOCK_SEQPACKET },
+	};
+
+	for (s = sockets; s < sockets + ARRAY_SIZE(sockets); s++)
+		if (socket_spec_pairs(s))
+			goto out;
+
+	/* Intra-proto */
+	for (s = sockets; s < sockets + ARRAY_SIZE(sockets); s++)
+		test_socket(type, redir, maps, s, s);
+
+	/* Cross-proto */
+	for (int i = 0; i < ARRAY_SIZE(sockets); i++) {
+		for (int j = 0; j < ARRAY_SIZE(sockets); j++) {
+			struct socket_spec *out = &sockets[j];
+			struct socket_spec *in = &sockets[i];
+
+			/* Skip intra-proto and between variants */
+			if (out->send_flags ||
+			    (in->family == out->family &&
+			     in->sotype == out->sotype))
+				continue;
+
+			test_socket(type, redir, maps, in, out);
+		}
+	}
+out:
+	while (--s >= sockets)
+		socket_spec_close(s);
+}
+
+static void test_map(enum bpf_map_type type)
+{
+	struct redir_spec *r, redirs[] = {
+		{ "sk_msg-to-ingress", SEND_INNER, RECV_INNER, SK_MSG_INGRESS },
+		{ "sk_msg-to-egress", SEND_INNER, RECV_OUTER, SK_MSG_EGRESS },
+		{ "sk_skb-to-egress", SEND_OUTER, RECV_OUTER, SK_SKB_EGRESS },
+		{ "sk_skb-to-ingress", SEND_OUTER, RECV_INNER, SK_SKB_INGRESS },
+	};
+
+	for (r = redirs; r < redirs + ARRAY_SIZE(redirs); r++) {
+		enum bpf_attach_type attach_type;
+		struct test_sockmap_redir *skel;
+		struct maps maps;
+		int prog_fd;
+
+		skel = test_sockmap_redir__open_and_load();
+		if (!skel) {
+			FAIL("open_and_load");
+			return;
+		}
+
+		switch (type) {
+		case BPF_MAP_TYPE_SOCKMAP:
+			maps.in = bpf_map__fd(skel->maps.nop_map);
+			maps.out = bpf_map__fd(skel->maps.sock_map);
+			break;
+		case BPF_MAP_TYPE_SOCKHASH:
+			maps.in = bpf_map__fd(skel->maps.nop_hash);
+			maps.out = bpf_map__fd(skel->maps.sock_hash);
+			break;
+		default:
+			FAIL("Unsupported bpf_map_type");
+			return;
+		}
+
+		skel->bss->redirect_type = type;
+		maps.verd = bpf_map__fd(skel->maps.verdict_map);
+		get_redir_params(r, skel, &prog_fd, &attach_type,
+				 &skel->bss->redirect_flags);
+
+		if (xbpf_prog_attach(prog_fd, maps.in, attach_type, 0))
+			return;
+
+		test_redir(type, r, &maps);
+
+		if (xbpf_prog_detach2(prog_fd, maps.in, attach_type))
+			return;
+
+		test_sockmap_redir__destroy(skel);
+	}
+}
+
+void serial_test_sockmap_redir(void)
+{
+	test_map(BPF_MAP_TYPE_SOCKMAP);
+	test_map(BPF_MAP_TYPE_SOCKHASH);
+}