selftests: bpf: Test sockmap update from BPF

Add a test which copies a socket from a sockmap into another sockmap
or sockhash. This excercises bpf_map_update_elem support from BPF
context. Compare the socket cookies from source and destination to
ensure that the copy succeeded.

Also check that the verifier rejects map_update from unsafe contexts.
Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200821102948.21918-7-lmb@cloudflare.com

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

@@ -4,6 +4,8 @@
 
 #include "test_progs.h"
 #include "test_skmsg_load_helpers.skel.h"
+#include "test_sockmap_update.skel.h"
+#include "test_sockmap_invalid_update.skel.h"
 
 #define TCP_REPAIR		19	/* TCP sock is under repair right now */
 
@@ -101,6 +103,76 @@ static void test_skmsg_helpers(enum bpf_map_type map_type)
 	test_skmsg_load_helpers__destroy(skel);
 }
 
+static void test_sockmap_update(enum bpf_map_type map_type)
+{
+	struct bpf_prog_test_run_attr tattr;
+	int err, prog, src, dst, duration = 0;
+	struct test_sockmap_update *skel;
+	__u64 src_cookie, dst_cookie;
+	const __u32 zero = 0;
+	char dummy[14] = {0};
+	__s64 sk;
+
+	sk = connected_socket_v4();
+	if (CHECK(sk == -1, "connected_socket_v4", "cannot connect\n"))
+		return;
+
+	skel = test_sockmap_update__open_and_load();
+	if (CHECK(!skel, "open_and_load", "cannot load skeleton\n")) {
+		close(sk);
+		return;
+	}
+
+	prog = bpf_program__fd(skel->progs.copy_sock_map);
+	src = bpf_map__fd(skel->maps.src);
+	if (map_type == BPF_MAP_TYPE_SOCKMAP)
+		dst = bpf_map__fd(skel->maps.dst_sock_map);
+	else
+		dst = bpf_map__fd(skel->maps.dst_sock_hash);
+
+	err = bpf_map_update_elem(src, &zero, &sk, BPF_NOEXIST);
+	if (CHECK(err, "update_elem(src)", "errno=%u\n", errno))
+		goto out;
+
+	err = bpf_map_lookup_elem(src, &zero, &src_cookie);
+	if (CHECK(err, "lookup_elem(src, cookie)", "errno=%u\n", errno))
+		goto out;
+
+	tattr = (struct bpf_prog_test_run_attr){
+		.prog_fd = prog,
+		.repeat = 1,
+		.data_in = dummy,
+		.data_size_in = sizeof(dummy),
+	};
+
+	err = bpf_prog_test_run_xattr(&tattr);
+	if (CHECK_ATTR(err || !tattr.retval, "bpf_prog_test_run",
+		       "errno=%u retval=%u\n", errno, tattr.retval))
+		goto out;
+
+	err = bpf_map_lookup_elem(dst, &zero, &dst_cookie);
+	if (CHECK(err, "lookup_elem(dst, cookie)", "errno=%u\n", errno))
+		goto out;
+
+	CHECK(dst_cookie != src_cookie, "cookie mismatch", "%llu != %llu\n",
+	      dst_cookie, src_cookie);
+
+out:
+	close(sk);
+	test_sockmap_update__destroy(skel);
+}
+
+static void test_sockmap_invalid_update(void)
+{
+	struct test_sockmap_invalid_update *skel;
+	int duration = 0;
+
+	skel = test_sockmap_invalid_update__open_and_load();
+	CHECK(skel, "open_and_load", "verifier accepted map_update\n");
+	if (skel)
+		test_sockmap_invalid_update__destroy(skel);
+}
+
 void test_sockmap_basic(void)
 {
 	if (test__start_subtest("sockmap create_update_free"))
@@ -111,4 +183,10 @@ void test_sockmap_basic(void)
 		test_skmsg_helpers(BPF_MAP_TYPE_SOCKMAP);
 	if (test__start_subtest("sockhash sk_msg load helpers"))
 		test_skmsg_helpers(BPF_MAP_TYPE_SOCKHASH);
+	if (test__start_subtest("sockmap update"))
+		test_sockmap_update(BPF_MAP_TYPE_SOCKMAP);
+	if (test__start_subtest("sockhash update"))
+		test_sockmap_update(BPF_MAP_TYPE_SOCKHASH);
+	if (test__start_subtest("sockmap update in unsafe context"))
+		test_sockmap_invalid_update();
 }

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

+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2020 Cloudflare
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+
+struct {
+	__uint(type, BPF_MAP_TYPE_SOCKMAP);
+	__uint(max_entries, 1);
+	__type(key, __u32);
+	__type(value, __u64);
+} map SEC(".maps");
+
+SEC("sockops")
+int bpf_sockmap(struct bpf_sock_ops *skops)
+{
+	__u32 key = 0;
+
+	if (skops->sk)
+		bpf_map_update_elem(&map, &key, skops->sk, 0);
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";

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

+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2020 Cloudflare
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+
+struct {
+	__uint(type, BPF_MAP_TYPE_SOCKMAP);
+	__uint(max_entries, 1);
+	__type(key, __u32);
+	__type(value, __u64);
+} src SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_SOCKMAP);
+	__uint(max_entries, 1);
+	__type(key, __u32);
+	__type(value, __u64);
+} dst_sock_map SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_SOCKHASH);
+	__uint(max_entries, 1);
+	__type(key, __u32);
+	__type(value, __u64);
+} dst_sock_hash SEC(".maps");
+
+SEC("classifier/copy_sock_map")
+int copy_sock_map(void *ctx)
+{
+	struct bpf_sock *sk;
+	bool failed = false;
+	__u32 key = 0;
+
+	sk = bpf_map_lookup_elem(&src, &key);
+	if (!sk)
+		return SK_DROP;
+
+	if (bpf_map_update_elem(&dst_sock_map, &key, sk, 0))
+		failed = true;
+
+	if (bpf_map_update_elem(&dst_sock_hash, &key, sk, 0))
+		failed = true;
+
+	bpf_sk_release(sk);
+	return failed ? SK_DROP : SK_PASS;
+}
+
+char _license[] SEC("license") = "GPL";