selftests: bpf: Test iterating a sockmap

Add a test that exercises a basic sockmap / sockhash iteration. For
now we simply count the number of elements seen. Once sockmap update
from iterators works we can extend this to perform a full copy.
Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200909162712.221874-4-lmb@cloudflare.com

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

@@ -6,6 +6,9 @@
 #include "test_skmsg_load_helpers.skel.h"
 #include "test_sockmap_update.skel.h"
 #include "test_sockmap_invalid_update.skel.h"
+#include "bpf_iter_sockmap.skel.h"
+
+#include "progs/bpf_iter_sockmap.h"
 
 #define TCP_REPAIR		19	/* TCP sock is under repair right now */
 
@@ -171,6 +174,88 @@ static void test_sockmap_invalid_update(void)
 		test_sockmap_invalid_update__destroy(skel);
 }
 
+static void test_sockmap_iter(enum bpf_map_type map_type)
+{
+	DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
+	int err, len, src_fd, iter_fd, duration = 0;
+	union bpf_iter_link_info linfo = {0};
+	__s64 sock_fd[SOCKMAP_MAX_ENTRIES];
+	__u32 i, num_sockets, max_elems;
+	struct bpf_iter_sockmap *skel;
+	struct bpf_link *link;
+	struct bpf_map *src;
+	char buf[64];
+
+	skel = bpf_iter_sockmap__open_and_load();
+	if (CHECK(!skel, "bpf_iter_sockmap__open_and_load", "skeleton open_and_load failed\n"))
+		return;
+
+	for (i = 0; i < ARRAY_SIZE(sock_fd); i++)
+		sock_fd[i] = -1;
+
+	/* Make sure we have at least one "empty" entry to test iteration of
+	 * an empty slot.
+	 */
+	num_sockets = ARRAY_SIZE(sock_fd) - 1;
+
+	if (map_type == BPF_MAP_TYPE_SOCKMAP) {
+		src = skel->maps.sockmap;
+		max_elems = bpf_map__max_entries(src);
+	} else {
+		src = skel->maps.sockhash;
+		max_elems = num_sockets;
+	}
+
+	src_fd = bpf_map__fd(src);
+
+	for (i = 0; i < num_sockets; i++) {
+		sock_fd[i] = connected_socket_v4();
+		if (CHECK(sock_fd[i] == -1, "connected_socket_v4", "cannot connect\n"))
+			goto out;
+
+		err = bpf_map_update_elem(src_fd, &i, &sock_fd[i], BPF_NOEXIST);
+		if (CHECK(err, "map_update", "failed: %s\n", strerror(errno)))
+			goto out;
+	}
+
+	linfo.map.map_fd = src_fd;
+	opts.link_info = &linfo;
+	opts.link_info_len = sizeof(linfo);
+	link = bpf_program__attach_iter(skel->progs.count_elems, &opts);
+	if (CHECK(IS_ERR(link), "attach_iter", "attach_iter failed\n"))
+		goto out;
+
+	iter_fd = bpf_iter_create(bpf_link__fd(link));
+	if (CHECK(iter_fd < 0, "create_iter", "create_iter failed\n"))
+		goto free_link;
+
+	/* do some tests */
+	while ((len = read(iter_fd, buf, sizeof(buf))) > 0)
+		;
+	if (CHECK(len < 0, "read", "failed: %s\n", strerror(errno)))
+		goto close_iter;
+
+	/* test results */
+	if (CHECK(skel->bss->elems != max_elems, "elems", "got %u expected %u\n",
+		  skel->bss->elems, max_elems))
+		goto close_iter;
+
+	if (CHECK(skel->bss->socks != num_sockets, "socks", "got %u expected %u\n",
+		  skel->bss->socks, num_sockets))
+		goto close_iter;
+
+close_iter:
+	close(iter_fd);
+free_link:
+	bpf_link__destroy(link);
+out:
+	for (i = 0; i < num_sockets; i++) {
+		if (sock_fd[i] >= 0)
+			close(sock_fd[i]);
+	}
+	bpf_iter_sockmap__destroy(skel);
+}
+
 void test_sockmap_basic(void)
 {
 	if (test__start_subtest("sockmap create_update_free"))
@@ -187,4 +272,8 @@ void test_sockmap_basic(void)
 		test_sockmap_update(BPF_MAP_TYPE_SOCKHASH);
 	if (test__start_subtest("sockmap update in unsafe context"))
 		test_sockmap_invalid_update();
+	if (test__start_subtest("sockmap iter"))
+		test_sockmap_iter(BPF_MAP_TYPE_SOCKMAP);
+	if (test__start_subtest("sockhash iter"))
+		test_sockmap_iter(BPF_MAP_TYPE_SOCKHASH);
 }

tools/testing/selftests/bpf/progs/bpf_iter.h

@@ -13,6 +13,7 @@
 #define udp6_sock udp6_sock___not_used
 #define bpf_iter__bpf_map_elem bpf_iter__bpf_map_elem___not_used
 #define bpf_iter__bpf_sk_storage_map bpf_iter__bpf_sk_storage_map___not_used
+#define bpf_iter__sockmap bpf_iter__sockmap___not_used
 #include "vmlinux.h"
 #undef bpf_iter_meta
 #undef bpf_iter__bpf_map
@@ -26,6 +27,7 @@
 #undef udp6_sock
 #undef bpf_iter__bpf_map_elem
 #undef bpf_iter__bpf_sk_storage_map
+#undef bpf_iter__sockmap
 
 struct bpf_iter_meta {
 	struct seq_file *seq;
@@ -96,3 +98,10 @@ struct bpf_iter__bpf_sk_storage_map {
 	struct sock *sk;
 	void *value;
 };
+
+struct bpf_iter__sockmap {
+	struct bpf_iter_meta *meta;
+	struct bpf_map *map;
+	void *key;
+	struct sock *sk;
+};

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

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Cloudflare */
+#include "bpf_iter.h"
+#include "bpf_tracing_net.h"
+#include "bpf_iter_sockmap.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <errno.h>
+
+char _license[] SEC("license") = "GPL";
+
+struct {
+	__uint(type, BPF_MAP_TYPE_SOCKMAP);
+	__uint(max_entries, SOCKMAP_MAX_ENTRIES);
+	__type(key, __u32);
+	__type(value, __u64);
+} sockmap SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_SOCKHASH);
+	__uint(max_entries, SOCKMAP_MAX_ENTRIES);
+	__type(key, __u32);
+	__type(value, __u64);
+} sockhash SEC(".maps");
+
+__u32 elems = 0;
+__u32 socks = 0;
+
+SEC("iter/sockmap")
+int count_elems(struct bpf_iter__sockmap *ctx)
+{
+	struct sock *sk = ctx->sk;
+	__u32 tmp, *key = ctx->key;
+	int ret;
+
+	if (key)
+		elems++;
+
+	if (sk)
+		socks++;
+
+	return 0;
+}

tools/testing/selftests/bpf/progs/bpf_iter_sockmap.h

+/* SPDX-License-Identifier: GPL-2.0 */
+
+#define SOCKMAP_MAX_ENTRIES (64)