Merge branch 'bpf-allow-opt-out-from-sk-sk_prot-memory_allocated'

Kuniyuki Iwashima says:

====================
bpf: Allow opt-out from sk->sk_prot->memory_allocated.

This series allows opting out of the global per-protocol memory
accounting if socket is configured as such by sysctl or BPF prog.

This series is the successor of the series below [0], but the changes
now fall in net and bpf subsystems only.

I discussed with Roman Gushchin offlist, and he suggested not mixing
two independent subsystems and it would be cleaner not to depend on
memcg.

So, sk->sk_memcg and memcg code are no longer touched, and instead we
use another hole near sk->sk_prot to store a flag for the pure net
opt-out feature.

Overview of the series:

  patch 1 is misc cleanup
  patch 2 allows opt-out from sk->sk_prot->memory_allocated
  patch 3 introduces net.core.bypass_prot_mem
  patch 4 & 5 supports flagging sk->sk_bypass_prot_mem via bpf_setsockopt()
  patch 6 is selftest

Thank you very much for all your help, Shakeel, Roman, Martin, and Eric!

[0]: https://lore.kernel.org/bpf/20250920000751.2091731-1-kuniyu@google.com/

Changes:
  v2:
    * Patch 2:
      * Fill kdoc for skc_bypass_prot_mem
    * Patch 6
      * Fix server fd leak in tcp_create_sockets()
      * Avoid close(0) in check_bypass()

  v1: https://lore.kernel.org/bpf/20251007001120.2661442-1-kuniyu@google.com/
====================

Link: https://patch.msgid.link/20251014235604.3057003-1-kuniyu@google.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

3 files changed, 397 insertions, 0 deletions

diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 6829936d33f5..9b17d937edf7 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -7200,6 +7200,7 @@ enum {
 	TCP_BPF_SYN_MAC         = 1007, /* Copy the MAC, IP[46], and TCP header */
 	TCP_BPF_SOCK_OPS_CB_FLAGS = 1008, /* Get or Set TCP sock ops flags */
 	SK_BPF_CB_FLAGS		= 1009, /* Get or set sock ops flags in socket */
+	SK_BPF_BYPASS_PROT_MEM	= 1010, /* Get or Set sk->sk_bypass_prot_mem */
 };
 
 enum {
diff --git a/tools/testing/selftests/bpf/prog_tests/sk_bypass_prot_mem.c b/tools/testing/selftests/bpf/prog_tests/sk_bypass_prot_mem.c
new file mode 100644
index 000000000000..e4940583924b
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/sk_bypass_prot_mem.c
@@ -0,0 +1,292 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright 2025 Google LLC */
+
+#include <test_progs.h>
+#include "sk_bypass_prot_mem.skel.h"
+#include "network_helpers.h"
+
+#define NR_PAGES	32
+#define NR_SOCKETS	2
+#define BUF_TOTAL	(NR_PAGES * 4096 / NR_SOCKETS)
+#define BUF_SINGLE	1024
+#define NR_SEND		(BUF_TOTAL / BUF_SINGLE)
+
+struct test_case {
+	char name[8];
+	int family;
+	int type;
+	int (*create_sockets)(struct test_case *test_case, int sk[], int len);
+	long (*get_memory_allocated)(struct test_case *test_case, struct sk_bypass_prot_mem *skel);
+};
+
+static int tcp_create_sockets(struct test_case *test_case, int sk[], int len)
+{
+	int server, i, err = 0;
+
+	server = start_server(test_case->family, test_case->type, NULL, 0, 0);
+	if (!ASSERT_GE(server, 0, "start_server_str"))
+		return server;
+
+	/* Keep for-loop so we can change NR_SOCKETS easily. */
+	for (i = 0; i < len; i += 2) {
+		sk[i] = connect_to_fd(server, 0);
+		if (sk[i] < 0) {
+			ASSERT_GE(sk[i], 0, "connect_to_fd");
+			err = sk[i];
+			break;
+		}
+
+		sk[i + 1] = accept(server, NULL, NULL);
+		if (sk[i + 1] < 0) {
+			ASSERT_GE(sk[i + 1], 0, "accept");
+			err = sk[i + 1];
+			break;
+		}
+	}
+
+	close(server);
+
+	return err;
+}
+
+static int udp_create_sockets(struct test_case *test_case, int sk[], int len)
+{
+	int i, j, err, rcvbuf = BUF_TOTAL;
+
+	/* Keep for-loop so we can change NR_SOCKETS easily. */
+	for (i = 0; i < len; i += 2) {
+		sk[i] = start_server(test_case->family, test_case->type, NULL, 0, 0);
+		if (sk[i] < 0) {
+			ASSERT_GE(sk[i], 0, "start_server");
+			return sk[i];
+		}
+
+		sk[i + 1] = connect_to_fd(sk[i], 0);
+		if (sk[i + 1] < 0) {
+			ASSERT_GE(sk[i + 1], 0, "connect_to_fd");
+			return sk[i + 1];
+		}
+
+		err = connect_fd_to_fd(sk[i], sk[i + 1], 0);
+		if (err) {
+			ASSERT_EQ(err, 0, "connect_fd_to_fd");
+			return err;
+		}
+
+		for (j = 0; j < 2; j++) {
+			err = setsockopt(sk[i + j], SOL_SOCKET, SO_RCVBUF, &rcvbuf, sizeof(int));
+			if (err) {
+				ASSERT_EQ(err, 0, "setsockopt(SO_RCVBUF)");
+				return err;
+			}
+		}
+	}
+
+	return 0;
+}
+
+static long get_memory_allocated(struct test_case *test_case,
+				 bool *activated, long *memory_allocated)
+{
+	int sk;
+
+	*activated = true;
+
+	/* AF_INET and AF_INET6 share the same memory_allocated.
+	 * tcp_init_sock() is called by AF_INET and AF_INET6,
+	 * but udp_lib_init_sock() is inline.
+	 */
+	sk = socket(AF_INET, test_case->type, 0);
+	if (!ASSERT_GE(sk, 0, "get_memory_allocated"))
+		return -1;
+
+	close(sk);
+
+	return *memory_allocated;
+}
+
+static long tcp_get_memory_allocated(struct test_case *test_case, struct sk_bypass_prot_mem *skel)
+{
+	return get_memory_allocated(test_case,
+				    &skel->bss->tcp_activated,
+				    &skel->bss->tcp_memory_allocated);
+}
+
+static long udp_get_memory_allocated(struct test_case *test_case, struct sk_bypass_prot_mem *skel)
+{
+	return get_memory_allocated(test_case,
+				    &skel->bss->udp_activated,
+				    &skel->bss->udp_memory_allocated);
+}
+
+static int check_bypass(struct test_case *test_case,
+			struct sk_bypass_prot_mem *skel, bool bypass)
+{
+	char buf[BUF_SINGLE] = {};
+	long memory_allocated[2];
+	int sk[NR_SOCKETS];
+	int err, i, j;
+
+	for (i = 0; i < ARRAY_SIZE(sk); i++)
+		sk[i] = -1;
+
+	err = test_case->create_sockets(test_case, sk, ARRAY_SIZE(sk));
+	if (err)
+		goto close;
+
+	memory_allocated[0] = test_case->get_memory_allocated(test_case, skel);
+
+	/* allocate pages >= NR_PAGES */
+	for (i = 0; i < ARRAY_SIZE(sk); i++) {
+		for (j = 0; j < NR_SEND; j++) {
+			int bytes = send(sk[i], buf, sizeof(buf), 0);
+
+			/* Avoid too noisy logs when something failed. */
+			if (bytes != sizeof(buf)) {
+				ASSERT_EQ(bytes, sizeof(buf), "send");
+				if (bytes < 0) {
+					err = bytes;
+					goto drain;
+				}
+			}
+		}
+	}
+
+	memory_allocated[1] = test_case->get_memory_allocated(test_case, skel);
+
+	if (bypass)
+		ASSERT_LE(memory_allocated[1], memory_allocated[0] + 10, "bypass");
+	else
+		ASSERT_GT(memory_allocated[1], memory_allocated[0] + NR_PAGES, "no bypass");
+
+drain:
+	if (test_case->type == SOCK_DGRAM) {
+		/* UDP starts purging sk->sk_receive_queue after one RCU
+		 * grace period, then udp_memory_allocated goes down,
+		 * so drain the queue before close().
+		 */
+		for (i = 0; i < ARRAY_SIZE(sk); i++) {
+			for (j = 0; j < NR_SEND; j++) {
+				int bytes = recv(sk[i], buf, 1, MSG_DONTWAIT | MSG_TRUNC);
+
+				if (bytes == sizeof(buf))
+					continue;
+				if (bytes != -1 || errno != EAGAIN)
+					PRINT_FAIL("bytes: %d, errno: %s\n", bytes, strerror(errno));
+				break;
+			}
+		}
+	}
+
+close:
+	for (i = 0; i < ARRAY_SIZE(sk); i++) {
+		if (sk[i] < 0)
+			break;
+
+		close(sk[i]);
+	}
+
+	return err;
+}
+
+static void run_test(struct test_case *test_case)
+{
+	struct sk_bypass_prot_mem *skel;
+	struct nstoken *nstoken;
+	int cgroup, err;
+
+	skel = sk_bypass_prot_mem__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "open_and_load"))
+		return;
+
+	skel->bss->nr_cpus = libbpf_num_possible_cpus();
+
+	err = sk_bypass_prot_mem__attach(skel);
+	if (!ASSERT_OK(err, "attach"))
+		goto destroy_skel;
+
+	cgroup = test__join_cgroup("/sk_bypass_prot_mem");
+	if (!ASSERT_GE(cgroup, 0, "join_cgroup"))
+		goto destroy_skel;
+
+	err = make_netns("sk_bypass_prot_mem");
+	if (!ASSERT_EQ(err, 0, "make_netns"))
+		goto close_cgroup;
+
+	nstoken = open_netns("sk_bypass_prot_mem");
+	if (!ASSERT_OK_PTR(nstoken, "open_netns"))
+		goto remove_netns;
+
+	err = check_bypass(test_case, skel, false);
+	if (!ASSERT_EQ(err, 0, "test_bypass(false)"))
+		goto close_netns;
+
+	err = write_sysctl("/proc/sys/net/core/bypass_prot_mem", "1");
+	if (!ASSERT_EQ(err, 0, "write_sysctl(1)"))
+		goto close_netns;
+
+	err = check_bypass(test_case, skel, true);
+	if (!ASSERT_EQ(err, 0, "test_bypass(true by sysctl)"))
+		goto close_netns;
+
+	err = write_sysctl("/proc/sys/net/core/bypass_prot_mem", "0");
+	if (!ASSERT_EQ(err, 0, "write_sysctl(0)"))
+		goto close_netns;
+
+	skel->links.sock_create = bpf_program__attach_cgroup(skel->progs.sock_create, cgroup);
+	if (!ASSERT_OK_PTR(skel->links.sock_create, "attach_cgroup(sock_create)"))
+		goto close_netns;
+
+	err = check_bypass(test_case, skel, true);
+	ASSERT_EQ(err, 0, "test_bypass(true by bpf)");
+
+close_netns:
+	close_netns(nstoken);
+remove_netns:
+	remove_netns("sk_bypass_prot_mem");
+close_cgroup:
+	close(cgroup);
+destroy_skel:
+	sk_bypass_prot_mem__destroy(skel);
+}
+
+static struct test_case test_cases[] = {
+	{
+		.name = "TCP  ",
+		.family = AF_INET,
+		.type = SOCK_STREAM,
+		.create_sockets = tcp_create_sockets,
+		.get_memory_allocated = tcp_get_memory_allocated,
+	},
+	{
+		.name = "UDP  ",
+		.family = AF_INET,
+		.type = SOCK_DGRAM,
+		.create_sockets = udp_create_sockets,
+		.get_memory_allocated = udp_get_memory_allocated,
+	},
+	{
+		.name = "TCPv6",
+		.family = AF_INET6,
+		.type = SOCK_STREAM,
+		.create_sockets = tcp_create_sockets,
+		.get_memory_allocated = tcp_get_memory_allocated,
+	},
+	{
+		.name = "UDPv6",
+		.family = AF_INET6,
+		.type = SOCK_DGRAM,
+		.create_sockets = udp_create_sockets,
+		.get_memory_allocated = udp_get_memory_allocated,
+	},
+};
+
+void serial_test_sk_bypass_prot_mem(void)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(test_cases); i++) {
+		if (test__start_subtest(test_cases[i].name))
+			run_test(&test_cases[i]);
+	}
+}
diff --git a/tools/testing/selftests/bpf/progs/sk_bypass_prot_mem.c b/tools/testing/selftests/bpf/progs/sk_bypass_prot_mem.c
new file mode 100644
index 000000000000..09a00d11ffcc
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/sk_bypass_prot_mem.c
@@ -0,0 +1,104 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright 2025 Google LLC */
+
+#include "bpf_tracing_net.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <errno.h>
+
+extern int tcp_memory_per_cpu_fw_alloc __ksym;
+extern int udp_memory_per_cpu_fw_alloc __ksym;
+
+int nr_cpus;
+bool tcp_activated, udp_activated;
+long tcp_memory_allocated, udp_memory_allocated;
+
+struct sk_prot {
+	long *memory_allocated;
+	int *memory_per_cpu_fw_alloc;
+};
+
+static int drain_memory_per_cpu_fw_alloc(__u32 i, struct sk_prot *sk_prot_ctx)
+{
+	int *memory_per_cpu_fw_alloc;
+
+	memory_per_cpu_fw_alloc = bpf_per_cpu_ptr(sk_prot_ctx->memory_per_cpu_fw_alloc, i);
+	if (memory_per_cpu_fw_alloc)
+		*sk_prot_ctx->memory_allocated += *memory_per_cpu_fw_alloc;
+
+	return 0;
+}
+
+static long get_memory_allocated(struct sock *_sk, int *memory_per_cpu_fw_alloc)
+{
+	struct sock *sk = bpf_core_cast(_sk, struct sock);
+	struct sk_prot sk_prot_ctx;
+	long memory_allocated;
+
+	/* net_aligned_data.{tcp,udp}_memory_allocated was not available. */
+	memory_allocated = sk->__sk_common.skc_prot->memory_allocated->counter;
+
+	sk_prot_ctx.memory_allocated = &memory_allocated;
+	sk_prot_ctx.memory_per_cpu_fw_alloc = memory_per_cpu_fw_alloc;
+
+	bpf_loop(nr_cpus, drain_memory_per_cpu_fw_alloc, &sk_prot_ctx, 0);
+
+	return memory_allocated;
+}
+
+static void fentry_init_sock(struct sock *sk, bool *activated,
+			     long *memory_allocated, int *memory_per_cpu_fw_alloc)
+{
+	if (!*activated)
+		return;
+
+	*memory_allocated = get_memory_allocated(sk, memory_per_cpu_fw_alloc);
+	*activated = false;
+}
+
+SEC("fentry/tcp_init_sock")
+int BPF_PROG(fentry_tcp_init_sock, struct sock *sk)
+{
+	fentry_init_sock(sk, &tcp_activated,
+			 &tcp_memory_allocated, &tcp_memory_per_cpu_fw_alloc);
+	return 0;
+}
+
+SEC("fentry/udp_init_sock")
+int BPF_PROG(fentry_udp_init_sock, struct sock *sk)
+{
+	fentry_init_sock(sk, &udp_activated,
+			 &udp_memory_allocated, &udp_memory_per_cpu_fw_alloc);
+	return 0;
+}
+
+SEC("cgroup/sock_create")
+int sock_create(struct bpf_sock *ctx)
+{
+	int err, val = 1;
+
+	err = bpf_setsockopt(ctx, SOL_SOCKET, SK_BPF_BYPASS_PROT_MEM,
+			     &val, sizeof(val));
+	if (err)
+		goto err;
+
+	val = 0;
+
+	err = bpf_getsockopt(ctx, SOL_SOCKET, SK_BPF_BYPASS_PROT_MEM,
+			     &val, sizeof(val));
+	if (err)
+		goto err;
+
+	if (val != 1) {
+		err = -EINVAL;
+		goto err;
+	}
+
+	return 1;
+
+err:
+	bpf_set_retval(err);
+	return 0;
+}
+
+char LICENSE[] SEC("license") = "GPL";