selftests/bpf: Check bpf_sk_storage has uncharged sk_omem_alloc

This patch checks the sk_omem_alloc has been uncharged by bpf_sk_storage
during the __sk_destruct.
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20230901231129.578493-4-martin.lau@linux.dev

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

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2023 Facebook */
+#include <test_progs.h>
+#include <bpf/libbpf.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include "sk_storage_omem_uncharge.skel.h"
+
+void test_sk_storage_omem_uncharge(void)
+{
+	struct sk_storage_omem_uncharge *skel;
+	int sk_fd = -1, map_fd, err, value;
+	socklen_t optlen;
+
+	skel = sk_storage_omem_uncharge__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel open_and_load"))
+		return;
+	map_fd = bpf_map__fd(skel->maps.sk_storage);
+
+	/* A standalone socket not binding to addr:port,
+	 * so nentns is not needed.
+	 */
+	sk_fd = socket(AF_INET6, SOCK_STREAM, 0);
+	if (!ASSERT_GE(sk_fd, 0, "socket"))
+		goto done;
+
+	optlen = sizeof(skel->bss->cookie);
+	err = getsockopt(sk_fd, SOL_SOCKET, SO_COOKIE, &skel->bss->cookie, &optlen);
+	if (!ASSERT_OK(err, "getsockopt(SO_COOKIE)"))
+		goto done;
+
+	value = 0;
+	err = bpf_map_update_elem(map_fd, &sk_fd, &value, 0);
+	if (!ASSERT_OK(err, "bpf_map_update_elem(value=0)"))
+		goto done;
+
+	value = 0xdeadbeef;
+	err = bpf_map_update_elem(map_fd, &sk_fd, &value, 0);
+	if (!ASSERT_OK(err, "bpf_map_update_elem(value=0xdeadbeef)"))
+		goto done;
+
+	err = sk_storage_omem_uncharge__attach(skel);
+	if (!ASSERT_OK(err, "attach"))
+		goto done;
+
+	close(sk_fd);
+	sk_fd = -1;
+
+	ASSERT_EQ(skel->bss->cookie_found, 2, "cookie_found");
+	ASSERT_EQ(skel->bss->omem, 0, "omem");
+
+done:
+	sk_storage_omem_uncharge__destroy(skel);
+	if (sk_fd != -1)
+		close(sk_fd);
+}

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

@@ -88,6 +88,7 @@
 #define sk_v6_rcv_saddr		__sk_common.skc_v6_rcv_saddr
 #define sk_flags		__sk_common.skc_flags
 #define sk_reuse		__sk_common.skc_reuse
+#define sk_cookie		__sk_common.skc_cookie
 
 #define s6_addr32		in6_u.u6_addr32
 

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

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2023 Facebook */
+#include "vmlinux.h"
+#include "bpf_tracing_net.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_core_read.h>
+
+void *local_storage_ptr = NULL;
+void *sk_ptr = NULL;
+int cookie_found = 0;
+__u64 cookie = 0;
+__u32 omem = 0;
+
+void *bpf_rdonly_cast(void *, __u32) __ksym;
+
+struct {
+	__uint(type, BPF_MAP_TYPE_SK_STORAGE);
+	__uint(map_flags, BPF_F_NO_PREALLOC);
+	__type(key, int);
+	__type(value, int);
+} sk_storage SEC(".maps");
+
+SEC("fexit/bpf_local_storage_destroy")
+int BPF_PROG(bpf_local_storage_destroy, struct bpf_local_storage *local_storage)
+{
+	struct sock *sk;
+
+	if (local_storage_ptr != local_storage)
+		return 0;
+
+	sk = bpf_rdonly_cast(sk_ptr, bpf_core_type_id_kernel(struct sock));
+	if (sk->sk_cookie.counter != cookie)
+		return 0;
+
+	cookie_found++;
+	omem = sk->sk_omem_alloc.counter;
+	local_storage_ptr = NULL;
+
+	return 0;
+}
+
+SEC("fentry/inet6_sock_destruct")
+int BPF_PROG(inet6_sock_destruct, struct sock *sk)
+{
+	int *value;
+
+	if (!cookie || sk->sk_cookie.counter != cookie)
+		return 0;
+
+	value = bpf_sk_storage_get(&sk_storage, sk, 0, 0);
+	if (value && *value == 0xdeadbeef) {
+		cookie_found++;
+		sk_ptr = sk;
+		local_storage_ptr = sk->sk_bpf_storage;
+	}
+
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";