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

1 files changed, 48 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/test_sockmap_update.c b/tools/testing/selftests/bpf/progs/test_sockmap_update.c
new file mode 100644
index 000000000000..9d0c9f28cab2
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_sockmap_update.c
@@ -0,0 +1,48 @@
+// 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";