[PATCH v3 bpf-next/net 0/5] bpf: Allow decoupling memcg from sk->sk_prot->memory_allocated.

[PATCH v3 bpf-next/net 0/5] bpf: Allow decoupling memcg from sk->sk_prot->memory_allocated.

[Kuniyuki Iwashima]

Some protocols (e.g., TCP, UDP) have their own memory accounting for
socket buffers and charge memory to global per-protocol counters such
as /proc/net/ipv4/tcp_mem.

When running under a non-root cgroup, this memory is also charged to
the memcg as sock in memory.stat.

Sockets of such protocols are still subject to the global limits,
thus affected by a noisy neighbour outside cgroup.

This makes it difficult to accurately estimate and configure appropriate
global limits.

This series allows decoupling memcg from the global memory accounting
if socket is configured as such by BPF prog.

This simplifies the memcg configuration while keeping the global limits
within a reasonable range, which is only 10% of the physical memory by
default.

Overview of the series:

  patch 1 & 2 are prep
  patch 3 intorduces SK_BPF_MEMCG_SOCK_ISOLATED for bpf_setsockopt()
  patch 4 decouples memcg from sk_prot->memory_allocated based on the flag
  patch 5 is selftest


Changes:
  v3:
    * Drop accept() hook and use BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB instead
    * Patch 1
      * Merge if blocks
    * Patch2
      * Drop bpf_func_proto for accept()
    * Patch 3
      * Allow flagging without sk->sk_memcg
      * Inherit SK_BPF_MEMCG_SOCK_ISOLATED in __inet_accept()

  v2: https://lore.kernel.org/bpf/20250825204158.2414402-1-kuniyu@google.com/
    * Patch 2
      * Define BPF_CGROUP_RUN_PROG_INET_SOCK_ACCEPT() when CONFIG_CGROUP_BPF=n
    * Patch 5
      * Make 2 new bpf_func_proto static
    * Patch 6
      * s/mem_cgroup_sk_set_flag/mem_cgroup_sk_set_flags/ when CONFIG_MEMCG=n
      * Use finer CONFIG_CGROUP_BPF instead of CONFIG_BPF_SYSCALL for ifdef

  v1: https://lore.kernel.org/netdev/20250822221846.744252-1-kuniyu@google.com/



Kuniyuki Iwashima (5):
  tcp: Save lock_sock() for memcg in inet_csk_accept().
  bpf: Support bpf_setsockopt() for BPF_CGROUP_INET_SOCK_CREATE.
  bpf: Introduce SK_BPF_MEMCG_FLAGS and SK_BPF_MEMCG_SOCK_ISOLATED.
  net-memcg: Allow decoupling memcg from global protocol memory
    accounting.
  selftest: bpf: Add test for SK_BPF_MEMCG_SOCK_ISOLATED.

 include/net/proto_memory.h                    |  15 +-
 include/net/sock.h                            |  48 ++++
 include/net/tcp.h                             |  10 +-
 include/uapi/linux/bpf.h                      |   6 +
 net/core/filter.c                             |  52 ++++-
 net/core/sock.c                               |  64 +++--
 net/ipv4/af_inet.c                            |  37 +++
 net/ipv4/inet_connection_sock.c               |  26 +--
 net/ipv4/tcp.c                                |   3 +-
 net/ipv4/tcp_output.c                         |  10 +-
 net/mptcp/protocol.c                          |   3 +-
 net/tls/tls_device.c                          |   4 +-
 tools/include/uapi/linux/bpf.h                |   6 +
 .../selftests/bpf/prog_tests/sk_memcg.c       | 218 ++++++++++++++++++
 tools/testing/selftests/bpf/progs/sk_memcg.c  |  30 +++
 15 files changed, 475 insertions(+), 57 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/sk_memcg.c
 create mode 100644 tools/testing/selftests/bpf/progs/sk_memcg.c

-- 
2.51.0.318.gd7df087d1a-goog

[PATCH v3 bpf-next/net 1/5] tcp: Save lock_sock() for memcg in inet_csk_accept().

[Kuniyuki Iwashima]

If memcg is enabled, accept() acquires lock_sock() twice for each new
TCP/MPTCP socket in inet_csk_accept() and __inet_accept().

Let's move memcg operations from inet_csk_accept() to __inet_accept().

Note that SCTP somehow allocates a new socket by sk_alloc() in
sk->sk_prot->accept() and clones fields manually, instead of using
sk_clone_lock().

mem_cgroup_sk_alloc() is called for SCTP before __inet_accept(),
so I added the protocol check in __inet_accept(), but this can be
removed once SCTP uses sk_clone_lock().

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
---
v3: Don't split if blocks
---
 net/ipv4/af_inet.c              | 23 +++++++++++++++++++++++
 net/ipv4/inet_connection_sock.c | 25 -------------------------
 2 files changed, 23 insertions(+), 25 deletions(-)

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 76e38092cd8a..d42757f74c6e 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -753,6 +753,29 @@ EXPORT_SYMBOL(inet_stream_connect);
 
 void __inet_accept(struct socket *sock, struct socket *newsock, struct sock *newsk)
 {
+	/* TODO: use sk_clone_lock() in SCTP and remove protocol checks */
+	if (mem_cgroup_sockets_enabled &&
+	    (!IS_ENABLED(CONFIG_IP_SCTP) ||
+	     sk_is_tcp(newsk) || sk_is_mptcp(newsk))) {
+		gfp_t gfp = GFP_KERNEL | __GFP_NOFAIL;
+
+		mem_cgroup_sk_alloc(newsk);
+
+		if (mem_cgroup_from_sk(newsk)) {
+			int amt;
+
+			/* The socket has not been accepted yet, no need
+			 * to look at newsk->sk_wmem_queued.
+			 */
+			amt = sk_mem_pages(newsk->sk_forward_alloc +
+					   atomic_read(&newsk->sk_rmem_alloc));
+			if (amt)
+				mem_cgroup_sk_charge(newsk, amt, gfp);
+		}
+
+		kmem_cache_charge(newsk, gfp);
+	}
+
 	sock_rps_record_flow(newsk);
 	WARN_ON(!((1 << newsk->sk_state) &
 		  (TCPF_ESTABLISHED | TCPF_SYN_RECV |
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 0ef1eacd539d..ed10b959a906 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -708,31 +708,6 @@ struct sock *inet_csk_accept(struct sock *sk, struct proto_accept_arg *arg)
 
 	release_sock(sk);
 
-	if (mem_cgroup_sockets_enabled) {
-		gfp_t gfp = GFP_KERNEL | __GFP_NOFAIL;
-		int amt = 0;
-
-		/* atomically get the memory usage, set and charge the
-		 * newsk->sk_memcg.
-		 */
-		lock_sock(newsk);
-
-		mem_cgroup_sk_alloc(newsk);
-		if (mem_cgroup_from_sk(newsk)) {
-			/* The socket has not been accepted yet, no need
-			 * to look at newsk->sk_wmem_queued.
-			 */
-			amt = sk_mem_pages(newsk->sk_forward_alloc +
-					   atomic_read(&newsk->sk_rmem_alloc));
-		}
-
-		if (amt)
-			mem_cgroup_sk_charge(newsk, amt, gfp);
-		kmem_cache_charge(newsk, gfp);
-
-		release_sock(newsk);
-	}
-
 	if (req)
 		reqsk_put(req);
 
-- 
2.51.0.318.gd7df087d1a-goog

[PATCH v3 bpf-next/net 2/5] bpf: Support bpf_setsockopt() for BPF_CGROUP_INET_SOCK_CREATE.

[Kuniyuki Iwashima]

We will store a flag in sk->sk_memcg by bpf_setsockopt() during
socket() or before sk->sk_memcg is set in accept().

BPF_CGROUP_INET_SOCK_CREATE is invoked by __cgroup_bpf_run_filter_sk()
that passes a pointer to struct sock to the bpf prog as void *ctx.

But there are no bpf_func_proto for bpf_setsockopt() that receives
the ctx as a pointer to struct sock.

Let's add a new bpf_setsockopt() variant for BPF_CGROUP_INET_SOCK_CREATE.

Note that inet_create() is not under lock_sock().

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
---
v3: Remove bpf_func_proto for accept()
v2: Make 2 new bpf_func_proto static
---
 net/core/filter.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/net/core/filter.c b/net/core/filter.c
index 63f3baee2daf..443d12b7d3b2 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5743,6 +5743,23 @@ static const struct bpf_func_proto bpf_sock_ops_setsockopt_proto = {
 	.arg5_type	= ARG_CONST_SIZE,
 };
 
+BPF_CALL_5(bpf_unlocked_sock_setsockopt, struct sock *, sk, int, level,
+	   int, optname, char *, optval, int, optlen)
+{
+	return _bpf_setsockopt(sk, level, optname, optval, optlen);
+}
+
+static const struct bpf_func_proto bpf_unlocked_sock_setsockopt_proto = {
+	.func		= bpf_unlocked_sock_setsockopt,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+	.arg2_type	= ARG_ANYTHING,
+	.arg3_type	= ARG_ANYTHING,
+	.arg4_type	= ARG_PTR_TO_MEM | MEM_RDONLY,
+	.arg5_type	= ARG_CONST_SIZE,
+};
+
 static int bpf_sock_ops_get_syn(struct bpf_sock_ops_kern *bpf_sock,
 				int optname, const u8 **start)
 {
@@ -8051,6 +8068,13 @@ sock_filter_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_sk_storage_get_cg_sock_proto;
 	case BPF_FUNC_ktime_get_coarse_ns:
 		return &bpf_ktime_get_coarse_ns_proto;
+	case BPF_FUNC_setsockopt:
+		switch (prog->expected_attach_type) {
+		case BPF_CGROUP_INET_SOCK_CREATE:
+			return &bpf_unlocked_sock_setsockopt_proto;
+		default:
+			return NULL;
+		}
 	default:
 		return bpf_base_func_proto(func_id, prog);
 	}
-- 
2.51.0.318.gd7df087d1a-goog

[PATCH v3 bpf-next/net 3/5] bpf: Introduce SK_BPF_MEMCG_FLAGS and SK_BPF_MEMCG_SOCK_ISOLATED.

[Kuniyuki Iwashima]

We will decouple sockets from the global protocol memory accounting
if sockets have SK_BPF_MEMCG_SOCK_ISOLATED.

This can be flagged, during socket() or before sk->sk_memcg is set
in accept(), via bpf_setsockopt():

  flags = SK_BPF_MEMCG_SOCK_ISOLATED;
  bpf_setsockopt(ctx, SOL_SOCKET, SK_BPF_MEMCG_FLAGS,
                 &flags, sizeof(flags));

Given sk->sk_memcg can be accessed in the fast path, it would
be preferable to place the flag field in the same cache line as
sk->sk_memcg.

However, struct sock does not have such a 1-byte hole.

Let's store the flag in the lowest bit of sk->sk_memcg and add
a helper to check the bit.

In the next patch, if mem_cgroup_sk_isolated() returns true,
the socket will not be charged to sk->sk_prot->memory_allocated.

The main targets are BPF_CGROUP_INET_SOCK_CREATE and
BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB as demonstrated in the selftest.

Note that we do not support modifying the flag once sk->sk_memcg is set
especially because UDP charges memory under sk->sk_receive_queue.lock
instead of lock_sock().

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
---
v3:
  * Allow setting flags without sk->sk_memcg in sk_bpf_set_get_memcg_flags()
  * Inherit flags in __inet_accept()

v2:
  * s/mem_cgroup_sk_set_flag/mem_cgroup_sk_set_flags/ when CONFIG_MEMCG=n
  * Use CONFIG_CGROUP_BPF instead of CONFIG_BPF_SYSCALL for ifdef
---
 include/net/sock.h             | 48 ++++++++++++++++++++++++++++++++++
 include/uapi/linux/bpf.h       |  6 +++++
 net/core/filter.c              | 28 +++++++++++++++++++-
 net/ipv4/af_inet.c             |  4 +++
 tools/include/uapi/linux/bpf.h |  6 +++++
 5 files changed, 91 insertions(+), 1 deletion(-)

diff --git a/include/net/sock.h b/include/net/sock.h
index 63a6a48afb48..d41a2f8f8b30 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -2596,10 +2596,39 @@ static inline gfp_t gfp_memcg_charge(void)
 	return in_softirq() ? GFP_ATOMIC : GFP_KERNEL;
 }
 
+#define SK_BPF_MEMCG_FLAG_MASK	(SK_BPF_MEMCG_FLAG_MAX - 1)
+#define SK_BPF_MEMCG_PTR_MASK	~SK_BPF_MEMCG_FLAG_MASK
+
 #ifdef CONFIG_MEMCG
+static inline void mem_cgroup_sk_set_flags(struct sock *sk, unsigned short flags)
+{
+	unsigned long val = (unsigned long)sk->sk_memcg;
+
+	val |= flags;
+	sk->sk_memcg = (struct mem_cgroup *)val;
+}
+
+static inline unsigned short mem_cgroup_sk_get_flags(const struct sock *sk)
+{
+#ifdef CONFIG_CGROUP_BPF
+	unsigned long val = (unsigned long)sk->sk_memcg;
+
+	return val & SK_BPF_MEMCG_FLAG_MASK;
+#else
+	return 0;
+#endif
+}
+
 static inline struct mem_cgroup *mem_cgroup_from_sk(const struct sock *sk)
 {
+#ifdef CONFIG_CGROUP_BPF
+	unsigned long val = (unsigned long)sk->sk_memcg;
+
+	val &= SK_BPF_MEMCG_PTR_MASK;
+	return (struct mem_cgroup *)val;
+#else
 	return sk->sk_memcg;
+#endif
 }
 
 static inline bool mem_cgroup_sk_enabled(const struct sock *sk)
@@ -2607,6 +2636,11 @@ static inline bool mem_cgroup_sk_enabled(const struct sock *sk)
 	return mem_cgroup_sockets_enabled && mem_cgroup_from_sk(sk);
 }
 
+static inline bool mem_cgroup_sk_isolated(const struct sock *sk)
+{
+	return mem_cgroup_sk_get_flags(sk) & SK_BPF_MEMCG_SOCK_ISOLATED;
+}
+
 static inline bool mem_cgroup_sk_under_memory_pressure(const struct sock *sk)
 {
 	struct mem_cgroup *memcg = mem_cgroup_from_sk(sk);
@@ -2624,6 +2658,15 @@ static inline bool mem_cgroup_sk_under_memory_pressure(const struct sock *sk)
 	return false;
 }
 #else
+static inline void mem_cgroup_sk_set_flags(struct sock *sk, unsigned short flags)
+{
+}
+
+static inline unsigned short mem_cgroup_sk_get_flags(const struct sock *sk)
+{
+	return 0;
+}
+
 static inline struct mem_cgroup *mem_cgroup_from_sk(const struct sock *sk)
 {
 	return NULL;
@@ -2634,6 +2677,11 @@ static inline bool mem_cgroup_sk_enabled(const struct sock *sk)
 	return false;
 }
 
+static inline bool mem_cgroup_sk_isolated(const struct sock *sk)
+{
+	return false;
+}
+
 static inline bool mem_cgroup_sk_under_memory_pressure(const struct sock *sk)
 {
 	return false;
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 233de8677382..52b8c2278589 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -7182,6 +7182,7 @@ 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_MEMCG_FLAGS	= 1010, /* Get or Set flags saved in sk->sk_memcg */
 };
 
 enum {
@@ -7204,6 +7205,11 @@ enum {
 						 */
 };
 
+enum {
+	SK_BPF_MEMCG_SOCK_ISOLATED	= (1UL << 0),
+	SK_BPF_MEMCG_FLAG_MAX		= (1UL << 1),
+};
+
 struct bpf_perf_event_value {
 	__u64 counter;
 	__u64 enabled;
diff --git a/net/core/filter.c b/net/core/filter.c
index 443d12b7d3b2..943ae6d7d637 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5267,6 +5267,27 @@ static int sk_bpf_set_get_cb_flags(struct sock *sk, char *optval, bool getopt)
 	return 0;
 }
 
+static int sk_bpf_set_get_memcg_flags(struct sock *sk, int *optval, bool getopt)
+{
+	if (!sk_has_account(sk))
+		return -EOPNOTSUPP;
+
+	if (getopt) {
+		*optval = mem_cgroup_sk_get_flags(sk);
+		return 0;
+	}
+
+	if (sock_owned_by_user_nocheck(sk) && mem_cgroup_from_sk(sk))
+		return -EBUSY;
+
+	if (*optval <= 0 || *optval >= SK_BPF_MEMCG_FLAG_MAX)
+		return -EINVAL;
+
+	mem_cgroup_sk_set_flags(sk, *optval);
+
+	return 0;
+}
+
 static int sol_socket_sockopt(struct sock *sk, int optname,
 			      char *optval, int *optlen,
 			      bool getopt)
@@ -5284,6 +5305,7 @@ static int sol_socket_sockopt(struct sock *sk, int optname,
 	case SO_BINDTOIFINDEX:
 	case SO_TXREHASH:
 	case SK_BPF_CB_FLAGS:
+	case SK_BPF_MEMCG_FLAGS:
 		if (*optlen != sizeof(int))
 			return -EINVAL;
 		break;
@@ -5293,8 +5315,12 @@ static int sol_socket_sockopt(struct sock *sk, int optname,
 		return -EINVAL;
 	}
 
-	if (optname == SK_BPF_CB_FLAGS)
+	switch (optname) {
+	case SK_BPF_CB_FLAGS:
 		return sk_bpf_set_get_cb_flags(sk, optval, getopt);
+	case SK_BPF_MEMCG_FLAGS:
+		return sk_bpf_set_get_memcg_flags(sk, (int *)optval, getopt);
+	}
 
 	if (getopt) {
 		if (optname == SO_BINDTODEVICE)
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index d42757f74c6e..9b62f1ae13ba 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -758,12 +758,16 @@ void __inet_accept(struct socket *sock, struct socket *newsock, struct sock *new
 	    (!IS_ENABLED(CONFIG_IP_SCTP) ||
 	     sk_is_tcp(newsk) || sk_is_mptcp(newsk))) {
 		gfp_t gfp = GFP_KERNEL | __GFP_NOFAIL;
+		unsigned short flags;
 
+		flags = mem_cgroup_sk_get_flags(newsk);
 		mem_cgroup_sk_alloc(newsk);
 
 		if (mem_cgroup_from_sk(newsk)) {
 			int amt;
 
+			mem_cgroup_sk_set_flags(newsk, flags);
+
 			/* The socket has not been accepted yet, no need
 			 * to look at newsk->sk_wmem_queued.
 			 */
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 233de8677382..52b8c2278589 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -7182,6 +7182,7 @@ 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_MEMCG_FLAGS	= 1010, /* Get or Set flags saved in sk->sk_memcg */
 };
 
 enum {
@@ -7204,6 +7205,11 @@ enum {
 						 */
 };
 
+enum {
+	SK_BPF_MEMCG_SOCK_ISOLATED	= (1UL << 0),
+	SK_BPF_MEMCG_FLAG_MAX		= (1UL << 1),
+};
+
 struct bpf_perf_event_value {
 	__u64 counter;
 	__u64 enabled;
-- 
2.51.0.318.gd7df087d1a-goog

[PATCH v3 bpf-next/net 4/5] net-memcg: Allow decoupling memcg from global protocol memory accounting.

[Kuniyuki Iwashima]

Some protocols (e.g., TCP, UDP) implement memory accounting for socket
buffers and charge memory to per-protocol global counters pointed to by
sk->sk_proto->memory_allocated.

When running under a non-root cgroup, this memory is also charged to the
memcg as "sock" in memory.stat.

Even when a memcg controls memory usage, sockets of such protocols are
still subject to global limits (e.g., /proc/sys/net/ipv4/tcp_mem).

This makes it difficult to accurately estimate and configure appropriate
global limits, especially in multi-tenant environments.

If all workloads were guaranteed to be controlled under memcg, the issue
could be worked around by setting tcp_mem[0~2] to UINT_MAX.

In reality, this assumption does not always hold, and processes not
controlled by memcg lose the seatbelt and can consume memory up to
the global limit, becoming noisy neighbour.

Let's decouple sockets in memcg from the global per-protocol memory
accounting if sockets have SK_BPF_MEMCG_SOCK_ISOLATED in sk->sk_memcg.

This simplifies memcg configuration while keeping the global limits
within a reasonable range.

If mem_cgroup_sk_isolated(sk) returns true, the per-protocol memory
accounting is skipped.

In __inet_accept(), we need to reclaim counts that are already charged
for child sockets because we do not allocate sk->sk_memcg until accept().

Note that trace_sock_exceed_buf_limit() will always show 0 as accounted
for the isolated sockets, but this can be obtained via memory.stat.

Tested with a script that creates local socket pairs and send()s a
bunch of data without recv()ing.

Setup:

  # mkdir /sys/fs/cgroup/test
  # echo $$ >> /sys/fs/cgroup/test/cgroup.procs
  # sysctl -q net.ipv4.tcp_mem="1000 1000 1000"

Without bpf prog:

  # prlimit -n=524288:524288 bash -c "python3 pressure.py" &
  # cat /sys/fs/cgroup/test/memory.stat | grep sock
  sock 22642688
  # cat /proc/net/sockstat| grep TCP
  TCP: inuse 2006 orphan 0 tw 0 alloc 2008 mem 5376
  # ss -tn | head -n 5
  State Recv-Q Send-Q Local Address:Port  Peer Address:Port
  ESTAB 2000   0          127.0.0.1:34479    127.0.0.1:53188
  ESTAB 2000   0          127.0.0.1:34479    127.0.0.1:49972
  ESTAB 2000   0          127.0.0.1:34479    127.0.0.1:53868
  ESTAB 2000   0          127.0.0.1:34479    127.0.0.1:53554
  # nstat | grep Pressure || echo no pressure
  TcpExtTCPMemoryPressures        1                  0.0

With bpf prog in the next patch:

  # bpftool prog load sk_memcg.bpf.o /sys/fs/bpf/sk_memcg_create type cgroup/sock_create
  # bpftool prog load sk_memcg.bpf.o /sys/fs/bpf/sk_memcg_estab type sockops
  # bpftool cgroup attach /sys/fs/cgroup/test cgroup_inet_sock_create pinned /sys/fs/bpf/sk_memcg_create
  # bpftool cgroup attach /sys/fs/cgroup/test cgroup_sock_ops pinned /sys/fs/bpf/sk_memcg_estab
  # prlimit -n=524288:524288 bash -c "python3 pressure.py" &
  # cat /sys/fs/cgroup/test/memory.stat | grep sock
  sock 2757468160
  # cat /proc/net/sockstat | grep TCP
  TCP: inuse 2006 orphan 0 tw 0 alloc 2008 mem 0
  # ss -tn | head -n 5
  State Recv-Q Send-Q  Local Address:Port  Peer Address:Port
  ESTAB 111000 0           127.0.0.1:36019    127.0.0.1:49026
  ESTAB 110000 0           127.0.0.1:36019    127.0.0.1:45630
  ESTAB 110000 0           127.0.0.1:36019    127.0.0.1:44870
  ESTAB 111000 0           127.0.0.1:36019    127.0.0.1:45274
  # nstat | grep Pressure || echo no pressure
  no pressure

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
---
 include/net/proto_memory.h      | 15 ++++++--
 include/net/tcp.h               | 10 ++++--
 net/core/sock.c                 | 64 ++++++++++++++++++++++-----------
 net/ipv4/af_inet.c              | 12 ++++++-
 net/ipv4/inet_connection_sock.c |  1 +
 net/ipv4/tcp.c                  |  3 +-
 net/ipv4/tcp_output.c           | 10 ++++--
 net/mptcp/protocol.c            |  3 +-
 net/tls/tls_device.c            |  4 ++-
 9 files changed, 90 insertions(+), 32 deletions(-)

diff --git a/include/net/proto_memory.h b/include/net/proto_memory.h
index 8e91a8fa31b5..8e8432b13515 100644
--- a/include/net/proto_memory.h
+++ b/include/net/proto_memory.h
@@ -31,13 +31,22 @@ static inline bool sk_under_memory_pressure(const struct sock *sk)
 	if (!sk->sk_prot->memory_pressure)
 		return false;
 
-	if (mem_cgroup_sk_enabled(sk) &&
-	    mem_cgroup_sk_under_memory_pressure(sk))
-		return true;
+	if (mem_cgroup_sk_enabled(sk)) {
+		if (mem_cgroup_sk_under_memory_pressure(sk))
+			return true;
+
+		if (mem_cgroup_sk_isolated(sk))
+			return false;
+	}
 
 	return !!READ_ONCE(*sk->sk_prot->memory_pressure);
 }
 
+static inline bool sk_should_enter_memory_pressure(struct sock *sk)
+{
+	return !mem_cgroup_sk_enabled(sk) || !mem_cgroup_sk_isolated(sk);
+}
+
 static inline long
 proto_memory_allocated(const struct proto *prot)
 {
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 2936b8175950..0191a4585bba 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -275,9 +275,13 @@ extern unsigned long tcp_memory_pressure;
 /* optimized version of sk_under_memory_pressure() for TCP sockets */
 static inline bool tcp_under_memory_pressure(const struct sock *sk)
 {
-	if (mem_cgroup_sk_enabled(sk) &&
-	    mem_cgroup_sk_under_memory_pressure(sk))
-		return true;
+	if (mem_cgroup_sk_enabled(sk)) {
+		if (mem_cgroup_sk_under_memory_pressure(sk))
+			return true;
+
+		if (mem_cgroup_sk_isolated(sk))
+			return false;
+	}
 
 	return READ_ONCE(tcp_memory_pressure);
 }
diff --git a/net/core/sock.c b/net/core/sock.c
index 8002ac6293dc..be5574f9a025 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1046,17 +1046,21 @@ static int sock_reserve_memory(struct sock *sk, int bytes)
 	if (!charged)
 		return -ENOMEM;
 
-	/* pre-charge to forward_alloc */
-	sk_memory_allocated_add(sk, pages);
-	allocated = sk_memory_allocated(sk);
-	/* If the system goes into memory pressure with this
-	 * precharge, give up and return error.
-	 */
-	if (allocated > sk_prot_mem_limits(sk, 1)) {
-		sk_memory_allocated_sub(sk, pages);
-		mem_cgroup_sk_uncharge(sk, pages);
-		return -ENOMEM;
+	if (!mem_cgroup_sk_isolated(sk)) {
+		/* pre-charge to forward_alloc */
+		sk_memory_allocated_add(sk, pages);
+		allocated = sk_memory_allocated(sk);
+
+		/* If the system goes into memory pressure with this
+		 * precharge, give up and return error.
+		 */
+		if (allocated > sk_prot_mem_limits(sk, 1)) {
+			sk_memory_allocated_sub(sk, pages);
+			mem_cgroup_sk_uncharge(sk, pages);
+			return -ENOMEM;
+		}
 	}
+
 	sk_forward_alloc_add(sk, pages << PAGE_SHIFT);
 
 	WRITE_ONCE(sk->sk_reserved_mem,
@@ -3153,8 +3157,11 @@ bool sk_page_frag_refill(struct sock *sk, struct page_frag *pfrag)
 	if (likely(skb_page_frag_refill(32U, pfrag, sk->sk_allocation)))
 		return true;
 
-	sk_enter_memory_pressure(sk);
+	if (sk_should_enter_memory_pressure(sk))
+		sk_enter_memory_pressure(sk);
+
 	sk_stream_moderate_sndbuf(sk);
+
 	return false;
 }
 EXPORT_SYMBOL(sk_page_frag_refill);
@@ -3267,18 +3274,30 @@ int __sk_mem_raise_allocated(struct sock *sk, int size, int amt, int kind)
 {
 	bool memcg_enabled = false, charged = false;
 	struct proto *prot = sk->sk_prot;
-	long allocated;
-
-	sk_memory_allocated_add(sk, amt);
-	allocated = sk_memory_allocated(sk);
+	long allocated = 0;
 
 	if (mem_cgroup_sk_enabled(sk)) {
+		bool isolated = mem_cgroup_sk_isolated(sk);
+
 		memcg_enabled = true;
 		charged = mem_cgroup_sk_charge(sk, amt, gfp_memcg_charge());
-		if (!charged)
+
+		if (isolated && charged)
+			return 1;
+
+		if (!charged) {
+			if (!isolated) {
+				sk_memory_allocated_add(sk, amt);
+				allocated = sk_memory_allocated(sk);
+			}
+
 			goto suppress_allocation;
+		}
 	}
 
+	sk_memory_allocated_add(sk, amt);
+	allocated = sk_memory_allocated(sk);
+
 	/* Under limit. */
 	if (allocated <= sk_prot_mem_limits(sk, 0)) {
 		sk_leave_memory_pressure(sk);
@@ -3357,7 +3376,8 @@ int __sk_mem_raise_allocated(struct sock *sk, int size, int amt, int kind)
 
 	trace_sock_exceed_buf_limit(sk, prot, allocated, kind);
 
-	sk_memory_allocated_sub(sk, amt);
+	if (allocated)
+		sk_memory_allocated_sub(sk, amt);
 
 	if (charged)
 		mem_cgroup_sk_uncharge(sk, amt);
@@ -3396,11 +3416,15 @@ EXPORT_SYMBOL(__sk_mem_schedule);
  */
 void __sk_mem_reduce_allocated(struct sock *sk, int amount)
 {
-	sk_memory_allocated_sub(sk, amount);
-
-	if (mem_cgroup_sk_enabled(sk))
+	if (mem_cgroup_sk_enabled(sk)) {
 		mem_cgroup_sk_uncharge(sk, amount);
 
+		if (mem_cgroup_sk_isolated(sk))
+			return;
+	}
+
+	sk_memory_allocated_sub(sk, amount);
+
 	if (sk_under_global_memory_pressure(sk) &&
 	    (sk_memory_allocated(sk) < sk_prot_mem_limits(sk, 0)))
 		sk_leave_memory_pressure(sk);
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 9b62f1ae13ba..adbc8bcb760b 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -95,6 +95,7 @@
 #include <net/checksum.h>
 #include <net/ip.h>
 #include <net/protocol.h>
+#include <net/proto_memory.h>
 #include <net/arp.h>
 #include <net/route.h>
 #include <net/ip_fib.h>
@@ -773,8 +774,17 @@ void __inet_accept(struct socket *sock, struct socket *newsock, struct sock *new
 			 */
 			amt = sk_mem_pages(newsk->sk_forward_alloc +
 					   atomic_read(&newsk->sk_rmem_alloc));
-			if (amt)
+			if (amt) {
+				/* This amt is already charged globally to
+				 * sk_prot->memory_allocated due to lack of
+				 * sk_memcg until accept(), thus we need to
+				 * reclaim it here if newsk is isolated.
+				 */
+				if (mem_cgroup_sk_isolated(newsk))
+					sk_memory_allocated_sub(newsk, amt);
+
 				mem_cgroup_sk_charge(newsk, amt, gfp);
+			}
 		}
 
 		kmem_cache_charge(newsk, gfp);
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index ed10b959a906..f8dd53d40dcf 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -22,6 +22,7 @@
 #include <net/tcp.h>
 #include <net/sock_reuseport.h>
 #include <net/addrconf.h>
+#include <net/proto_memory.h>
 
 #if IS_ENABLED(CONFIG_IPV6)
 /* match_sk*_wildcard == true:  IPV6_ADDR_ANY equals to any IPv6 addresses
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 71a956fbfc55..dcbd49e2f8af 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -908,7 +908,8 @@ struct sk_buff *tcp_stream_alloc_skb(struct sock *sk, gfp_t gfp,
 		}
 		__kfree_skb(skb);
 	} else {
-		sk->sk_prot->enter_memory_pressure(sk);
+		if (sk_should_enter_memory_pressure(sk))
+			tcp_enter_memory_pressure(sk);
 		sk_stream_moderate_sndbuf(sk);
 	}
 	return NULL;
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index dfbac0876d96..f7aa86661219 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3574,12 +3574,18 @@ void sk_forced_mem_schedule(struct sock *sk, int size)
 	delta = size - sk->sk_forward_alloc;
 	if (delta <= 0)
 		return;
+
 	amt = sk_mem_pages(delta);
 	sk_forward_alloc_add(sk, amt << PAGE_SHIFT);
-	sk_memory_allocated_add(sk, amt);
 
-	if (mem_cgroup_sk_enabled(sk))
+	if (mem_cgroup_sk_enabled(sk)) {
 		mem_cgroup_sk_charge(sk, amt, gfp_memcg_charge() | __GFP_NOFAIL);
+
+		if (mem_cgroup_sk_isolated(sk))
+			return;
+	}
+
+	sk_memory_allocated_add(sk, amt);
 }
 
 /* Send a FIN. The caller locks the socket for us.
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 9a287b75c1b3..f7487e22a3f8 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -16,6 +16,7 @@
 #include <net/inet_common.h>
 #include <net/inet_hashtables.h>
 #include <net/protocol.h>
+#include <net/proto_memory.h>
 #include <net/tcp_states.h>
 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 #include <net/transp_v6.h>
@@ -1016,7 +1017,7 @@ static void mptcp_enter_memory_pressure(struct sock *sk)
 	mptcp_for_each_subflow(msk, subflow) {
 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
 
-		if (first)
+		if (first && sk_should_enter_memory_pressure(ssk))
 			tcp_enter_memory_pressure(ssk);
 		sk_stream_moderate_sndbuf(ssk);
 
diff --git a/net/tls/tls_device.c b/net/tls/tls_device.c
index f672a62a9a52..6696ef837116 100644
--- a/net/tls/tls_device.c
+++ b/net/tls/tls_device.c
@@ -35,6 +35,7 @@
 #include <linux/netdevice.h>
 #include <net/dst.h>
 #include <net/inet_connection_sock.h>
+#include <net/proto_memory.h>
 #include <net/tcp.h>
 #include <net/tls.h>
 #include <linux/skbuff_ref.h>
@@ -371,7 +372,8 @@ static int tls_do_allocation(struct sock *sk,
 	if (!offload_ctx->open_record) {
 		if (unlikely(!skb_page_frag_refill(prepend_size, pfrag,
 						   sk->sk_allocation))) {
-			READ_ONCE(sk->sk_prot)->enter_memory_pressure(sk);
+			if (sk_should_enter_memory_pressure(sk))
+				READ_ONCE(sk->sk_prot)->enter_memory_pressure(sk);
 			sk_stream_moderate_sndbuf(sk);
 			return -ENOMEM;
 		}
-- 
2.51.0.318.gd7df087d1a-goog

[PATCH v3 bpf-next/net 5/5] selftest: bpf: Add test for SK_BPF_MEMCG_SOCK_ISOLATED.

[Kuniyuki Iwashima]

The test does the following for IPv4/IPv6 x TCP/UDP sockets
with/without BPF prog.

  1. Create socket pairs
  2. Send a bunch of data that require more than 1000 pages
  3. Read memory_allocated from the 3rd column in /proc/net/protocols
  4. Check if unread data is charged to memory_allocated

If BPF prog is attached, memory_allocated should not be changed,
but we allow a small error (up to 10 pages) in case the test is ran
concurrently with other tests using TCP/UDP sockets.

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
---
 .../selftests/bpf/prog_tests/sk_memcg.c       | 218 ++++++++++++++++++
 tools/testing/selftests/bpf/progs/sk_memcg.c  |  30 +++
 2 files changed, 248 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/sk_memcg.c
 create mode 100644 tools/testing/selftests/bpf/progs/sk_memcg.c

diff --git a/tools/testing/selftests/bpf/prog_tests/sk_memcg.c b/tools/testing/selftests/bpf/prog_tests/sk_memcg.c
new file mode 100644
index 000000000000..a45dc30c5ab4
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/sk_memcg.c
@@ -0,0 +1,218 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright 2025 Google LLC */
+
+#include <test_progs.h>
+#include "sk_memcg.skel.h"
+#include "network_helpers.h"
+
+#define NR_SOCKETS	128
+#define NR_SEND		128
+#define BUF_SINGLE	1024
+#define BUF_TOTAL	(BUF_SINGLE * NR_SEND)
+
+struct test_case {
+	char name[10]; /* protocols (%-9s) in /proc/net/protocols, see proto_seq_printf(). */
+	int family;
+	int type;
+	int (*create_sockets)(struct test_case *test_case, int sk[], int len);
+};
+
+static int tcp_create_sockets(struct test_case *test_case, int sk[], int len)
+{
+	int server, i;
+
+	server = start_server(test_case->family, test_case->type, NULL, 0, 0);
+	ASSERT_GE(server, 0, "start_server_str");
+
+	for (i = 0; i < len / 2; i++) {
+		sk[i * 2] = connect_to_fd(server, 0);
+		if (!ASSERT_GE(sk[i * 2], 0, "connect_to_fd"))
+			return sk[i * 2];
+
+		sk[i * 2 + 1] = accept(server, NULL, NULL);
+		if (!ASSERT_GE(sk[i * 2 + 1], 0, "accept"))
+			return sk[i * 2 + 1];
+	}
+
+	close(server);
+
+	return 0;
+}
+
+static int udp_create_sockets(struct test_case *test_case, int sk[], int len)
+{
+	int i, err, rcvbuf = BUF_TOTAL;
+
+	for (i = 0; i < len / 2; i++) {
+		sk[i * 2] = start_server(test_case->family, test_case->type, NULL, 0, 0);
+		if (!ASSERT_GE(sk[i * 2], 0, "start_server"))
+			return sk[i * 2];
+
+		sk[i * 2 + 1] = connect_to_fd(sk[i * 2], 0);
+		if (!ASSERT_GE(sk[i * 2 + 1], 0, "connect_to_fd"))
+			return sk[i * 2 + 1];
+
+		err = connect_fd_to_fd(sk[i * 2], sk[i * 2 + 1], 0);
+		if (!ASSERT_EQ(err, 0, "connect_fd_to_fd"))
+			return err;
+
+		err = setsockopt(sk[i * 2], SOL_SOCKET, SO_RCVBUF, &rcvbuf, sizeof(int));
+		if (!ASSERT_EQ(err, 0, "setsockopt(SO_RCVBUF)"))
+			return err;
+
+		err = setsockopt(sk[i * 2 + 1], SOL_SOCKET, SO_RCVBUF, &rcvbuf, sizeof(int));
+		if (!ASSERT_EQ(err, 0, "setsockopt(SO_RCVBUF)"))
+			return err;
+	}
+
+	return 0;
+}
+
+static int get_memory_allocated(struct test_case *test_case)
+{
+	long memory_allocated = -1;
+	char *line = NULL;
+	size_t unused;
+	FILE *f;
+
+	f = fopen("/proc/net/protocols", "r");
+	if (!ASSERT_OK_PTR(f, "fopen"))
+		goto out;
+
+	while (getline(&line, &unused, f) != -1) {
+		unsigned int unused_0;
+		int unused_1;
+		int ret;
+
+		if (strncmp(line, test_case->name, sizeof(test_case->name)))
+			continue;
+
+		ret = sscanf(line + sizeof(test_case->name), "%4u %6d  %6ld",
+			     &unused_0, &unused_1, &memory_allocated);
+		ASSERT_EQ(ret, 3, "sscanf");
+		break;
+	}
+
+	ASSERT_NEQ(memory_allocated, -1, "get_memory_allocated");
+
+	free(line);
+	fclose(f);
+out:
+	return memory_allocated;
+}
+
+static int check_isolated(struct test_case *test_case, bool isolated)
+{
+	char buf[BUF_SINGLE] = {};
+	long memory_allocated[2];
+	int sk[NR_SOCKETS] = {};
+	int err = -1, i, j;
+
+	memory_allocated[0] = get_memory_allocated(test_case);
+	if (!ASSERT_GE(memory_allocated[0], 0, "memory_allocated[0]"))
+		goto out;
+
+	err = test_case->create_sockets(test_case, sk, ARRAY_SIZE(sk));
+	if (err)
+		goto close;
+
+	/* Must allocate pages >= net.core.mem_pcpu_rsv */
+	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");
+		}
+	}
+
+	memory_allocated[1] = get_memory_allocated(test_case);
+	if (!ASSERT_GE(memory_allocated[1], 0, "memory_allocated[1]"))
+		goto close;
+
+	if (isolated)
+		ASSERT_LE(memory_allocated[1], memory_allocated[0] + 10, "isolated");
+	else
+		ASSERT_GT(memory_allocated[1], memory_allocated[0] + 1000, "not isolated");
+
+close:
+	for (i = 0; i < ARRAY_SIZE(sk); i++)
+		close(sk[i]);
+
+	/* Let RCU destruct sockets */
+	sleep(1);
+out:
+	return err;
+}
+
+void run_test(struct test_case *test_case)
+{
+	struct sk_memcg *skel;
+	int cgroup, err;
+
+	skel = sk_memcg__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "open_and_load"))
+		return;
+
+	cgroup = test__join_cgroup("/sk_memcg");
+	if (!ASSERT_GE(cgroup, 0, "join_cgroup"))
+		goto destroy_skel;
+
+	err = check_isolated(test_case, false);
+	if (!ASSERT_EQ(err, 0, "test_isolated(false)"))
+		goto close_cgroup;
+
+	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_cgroup;
+
+	skel->links.skops_setsockopt = bpf_program__attach_cgroup(skel->progs.skops_setsockopt, cgroup);
+	if (!ASSERT_OK_PTR(skel->links.skops_setsockopt, "attach_cgroup(skops_setsockopt)"))
+		goto close_cgroup;
+
+	err = check_isolated(test_case, true);
+	ASSERT_EQ(err, 0, "test_isolated(false)");
+
+close_cgroup:
+	close(cgroup);
+destroy_skel:
+	sk_memcg__destroy(skel);
+}
+
+struct test_case test_cases[] = {
+	{
+		.name = "TCP       ",
+		.family = AF_INET,
+		.type = SOCK_STREAM,
+		.create_sockets = tcp_create_sockets,
+	},
+	{
+		.name = "UDP       ",
+		.family = AF_INET,
+		.type = SOCK_DGRAM,
+		.create_sockets = udp_create_sockets,
+	},
+	{
+		.name = "TCPv6     ",
+		.family = AF_INET6,
+		.type = SOCK_STREAM,
+		.create_sockets = tcp_create_sockets,
+	},
+	{
+		.name = "UDPv6     ",
+		.family = AF_INET6,
+		.type = SOCK_DGRAM,
+		.create_sockets = udp_create_sockets,
+	},
+};
+
+void test_sk_memcg(void)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(test_cases); i++) {
+		test__start_subtest(test_cases[i].name);
+		run_test(&test_cases[i]);
+	}
+}
diff --git a/tools/testing/selftests/bpf/progs/sk_memcg.c b/tools/testing/selftests/bpf/progs/sk_memcg.c
new file mode 100644
index 000000000000..1b0ea991099d
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/sk_memcg.c
@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright 2025 Google LLC */
+
+#include "bpf_tracing_net.h"
+#include <bpf/bpf_helpers.h>
+
+void isolate_memcg(void *ctx)
+{
+	int flags = SK_BPF_MEMCG_SOCK_ISOLATED;
+
+	bpf_setsockopt(ctx, SOL_SOCKET, SK_BPF_MEMCG_FLAGS,
+		       &flags, sizeof(flags));
+}
+
+SEC("cgroup/sock_create")
+int sock_create(struct bpf_sock *ctx)
+{
+	isolate_memcg(ctx);
+	return 1;
+}
+
+SEC("sockops")
+int skops_setsockopt(struct bpf_sock_ops *skops)
+{
+	if (skops->op == BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB)
+		isolate_memcg(skops);
+	return 1;
+}
+
+char LICENSE[] SEC("license") = "GPL";
-- 
2.51.0.318.gd7df087d1a-goog

Re: [PATCH v3 bpf-next/net 2/5] bpf: Support bpf_setsockopt() for BPF_CGROUP_INET_SOCK_CREATE.

[Stanislav Fomichev]

On 08/26, Kuniyuki Iwashima wrote:
> We will store a flag in sk->sk_memcg by bpf_setsockopt() during
> socket() or before sk->sk_memcg is set in accept().
> 
> BPF_CGROUP_INET_SOCK_CREATE is invoked by __cgroup_bpf_run_filter_sk()
> that passes a pointer to struct sock to the bpf prog as void *ctx.
> 
> But there are no bpf_func_proto for bpf_setsockopt() that receives
> the ctx as a pointer to struct sock.
> 
> Let's add a new bpf_setsockopt() variant for BPF_CGROUP_INET_SOCK_CREATE.

[..]

> Note that inet_create() is not under lock_sock().

Does anything prevent us from grabbing the lock before running
SOCK_CREATE progs? This is not the fast path, so should be ok?
Will make it easier to reason about socket options (where all paths
are locked). We do similar things for sock_addr progs in
BPF_CGROUP_RUN_SA_PROG_LOCK.

Re: [PATCH v3 bpf-next/net 2/5] bpf: Support bpf_setsockopt() for BPF_CGROUP_INET_SOCK_CREATE.

[Kuniyuki Iwashima]

On Tue, Aug 26, 2025 at 2:02 PM Stanislav Fomichev <stfomichev@gmail.com> wrote:
>
> On 08/26, Kuniyuki Iwashima wrote:
> > We will store a flag in sk->sk_memcg by bpf_setsockopt() during
> > socket() or before sk->sk_memcg is set in accept().
> >
> > BPF_CGROUP_INET_SOCK_CREATE is invoked by __cgroup_bpf_run_filter_sk()
> > that passes a pointer to struct sock to the bpf prog as void *ctx.
> >
> > But there are no bpf_func_proto for bpf_setsockopt() that receives
> > the ctx as a pointer to struct sock.
> >
> > Let's add a new bpf_setsockopt() variant for BPF_CGROUP_INET_SOCK_CREATE.
>
> [..]
>
> > Note that inet_create() is not under lock_sock().
>
> Does anything prevent us from grabbing the lock before running
> SOCK_CREATE progs? This is not the fast path, so should be ok?
> Will make it easier to reason about socket options (where all paths
> are locked). We do similar things for sock_addr progs in
> BPF_CGROUP_RUN_SA_PROG_LOCK.

We can do that, but the reasoning here is exactly same with
how we allow unlocked setsockopt() for LSM hooks.  Also, SA_
prog actually needs lock_sock() to prevent sk->{addr fields} from
being changed concurrently.

---8<---
/* List of LSM hooks that trigger while the socket is _not_ locked,
 * but it's ok to call bpf_{g,s}etsockopt because the socket is still
 * in the early init phase.
 */
BTF_SET_START(bpf_lsm_unlocked_sockopt_hooks)
#ifdef CONFIG_SECURITY_NETWORK
BTF_ID(func, bpf_lsm_socket_post_create)
BTF_ID(func, bpf_lsm_socket_socketpair)
#endif
BTF_SET_END(bpf_lsm_unlocked_sockopt_hooks)
---8<---

Re: [PATCH v3 bpf-next/net 2/5] bpf: Support bpf_setsockopt() for BPF_CGROUP_INET_SOCK_CREATE.

[Stanislav Fomichev]

On 08/26, Kuniyuki Iwashima wrote:
> On Tue, Aug 26, 2025 at 2:02 PM Stanislav Fomichev <stfomichev@gmail.com> wrote:
> >
> > On 08/26, Kuniyuki Iwashima wrote:
> > > We will store a flag in sk->sk_memcg by bpf_setsockopt() during
> > > socket() or before sk->sk_memcg is set in accept().
> > >
> > > BPF_CGROUP_INET_SOCK_CREATE is invoked by __cgroup_bpf_run_filter_sk()
> > > that passes a pointer to struct sock to the bpf prog as void *ctx.
> > >
> > > But there are no bpf_func_proto for bpf_setsockopt() that receives
> > > the ctx as a pointer to struct sock.
> > >
> > > Let's add a new bpf_setsockopt() variant for BPF_CGROUP_INET_SOCK_CREATE.
> >
> > [..]
> >
> > > Note that inet_create() is not under lock_sock().
> >
> > Does anything prevent us from grabbing the lock before running
> > SOCK_CREATE progs? This is not the fast path, so should be ok?
> > Will make it easier to reason about socket options (where all paths
> > are locked). We do similar things for sock_addr progs in
> > BPF_CGROUP_RUN_SA_PROG_LOCK.
> 
> We can do that, but the reasoning here is exactly same with
> how we allow unlocked setsockopt() for LSM hooks.  Also, SA_
> prog actually needs lock_sock() to prevent sk->{addr fields} from
> being changed concurrently.
> 
> ---8<---
> /* List of LSM hooks that trigger while the socket is _not_ locked,
>  * but it's ok to call bpf_{g,s}etsockopt because the socket is still
>  * in the early init phase.
>  */
> BTF_SET_START(bpf_lsm_unlocked_sockopt_hooks)
> #ifdef CONFIG_SECURITY_NETWORK
> BTF_ID(func, bpf_lsm_socket_post_create)
> BTF_ID(func, bpf_lsm_socket_socketpair)
> #endif
> BTF_SET_END(bpf_lsm_unlocked_sockopt_hooks)
> ---8<---

Good point, I forgot about these :-(

Re: [PATCH v3 bpf-next/net 2/5] bpf: Support bpf_setsockopt() for BPF_CGROUP_INET_SOCK_CREATE.

[Martin KaFai Lau]

On 8/26/25 11:38 AM, Kuniyuki Iwashima wrote:
> We will store a flag in sk->sk_memcg by bpf_setsockopt() during
> socket() or before sk->sk_memcg is set in accept().
> 
> BPF_CGROUP_INET_SOCK_CREATE is invoked by __cgroup_bpf_run_filter_sk()
> that passes a pointer to struct sock to the bpf prog as void *ctx.
> 
> But there are no bpf_func_proto for bpf_setsockopt() that receives
> the ctx as a pointer to struct sock.
> 
> Let's add a new bpf_setsockopt() variant for BPF_CGROUP_INET_SOCK_CREATE.
> 
> Note that inet_create() is not under lock_sock().
> 
> Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
> ---
> v3: Remove bpf_func_proto for accept()
> v2: Make 2 new bpf_func_proto static
> ---
>   net/core/filter.c | 24 ++++++++++++++++++++++++
>   1 file changed, 24 insertions(+)
> 
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 63f3baee2daf..443d12b7d3b2 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -5743,6 +5743,23 @@ static const struct bpf_func_proto bpf_sock_ops_setsockopt_proto = {
>   	.arg5_type	= ARG_CONST_SIZE,
>   };
>   
> +BPF_CALL_5(bpf_unlocked_sock_setsockopt, struct sock *, sk, int, level,
> +	   int, optname, char *, optval, int, optlen)
> +{
> +	return _bpf_setsockopt(sk, level, optname, optval, optlen);

The sock_owned_by_me() will warn.

 From CI:
WARNING: CPU: 0 PID: 102 at include/net/sock.h:1756 bpf_unlocked_sock_setsockopt+0xc7/0x110

> +}
> +
> +static const struct bpf_func_proto bpf_unlocked_sock_setsockopt_proto = {
> +	.func		= bpf_unlocked_sock_setsockopt,
> +	.gpl_only	= false,
> +	.ret_type	= RET_INTEGER,
> +	.arg1_type	= ARG_PTR_TO_CTX,
> +	.arg2_type	= ARG_ANYTHING,
> +	.arg3_type	= ARG_ANYTHING,
> +	.arg4_type	= ARG_PTR_TO_MEM | MEM_RDONLY,
> +	.arg5_type	= ARG_CONST_SIZE,
> +};
> +
>   static int bpf_sock_ops_get_syn(struct bpf_sock_ops_kern *bpf_sock,
>   				int optname, const u8 **start)
>   {
> @@ -8051,6 +8068,13 @@ sock_filter_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
>   		return &bpf_sk_storage_get_cg_sock_proto;
>   	case BPF_FUNC_ktime_get_coarse_ns:
>   		return &bpf_ktime_get_coarse_ns_proto;
> +	case BPF_FUNC_setsockopt:
> +		switch (prog->expected_attach_type) {
> +		case BPF_CGROUP_INET_SOCK_CREATE:
> +			return &bpf_unlocked_sock_setsockopt_proto;
> +		default:
> +			return NULL;
> +		}
>   	default:
>   		return bpf_base_func_proto(func_id, prog);
>   	}

Re: [PATCH v3 bpf-next/net 2/5] bpf: Support bpf_setsockopt() for BPF_CGROUP_INET_SOCK_CREATE.

[Kuniyuki Iwashima]

On Wed, Aug 27, 2025 at 3:23 PM Martin KaFai Lau <martin.lau@linux.dev> wrote:
>
> On 8/26/25 11:38 AM, Kuniyuki Iwashima wrote:
> > We will store a flag in sk->sk_memcg by bpf_setsockopt() during
> > socket() or before sk->sk_memcg is set in accept().
> >
> > BPF_CGROUP_INET_SOCK_CREATE is invoked by __cgroup_bpf_run_filter_sk()
> > that passes a pointer to struct sock to the bpf prog as void *ctx.
> >
> > But there are no bpf_func_proto for bpf_setsockopt() that receives
> > the ctx as a pointer to struct sock.
> >
> > Let's add a new bpf_setsockopt() variant for BPF_CGROUP_INET_SOCK_CREATE.
> >
> > Note that inet_create() is not under lock_sock().
> >
> > Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
> > ---
> > v3: Remove bpf_func_proto for accept()
> > v2: Make 2 new bpf_func_proto static
> > ---
> >   net/core/filter.c | 24 ++++++++++++++++++++++++
> >   1 file changed, 24 insertions(+)
> >
> > diff --git a/net/core/filter.c b/net/core/filter.c
> > index 63f3baee2daf..443d12b7d3b2 100644
> > --- a/net/core/filter.c
> > +++ b/net/core/filter.c
> > @@ -5743,6 +5743,23 @@ static const struct bpf_func_proto bpf_sock_ops_setsockopt_proto = {
> >       .arg5_type      = ARG_CONST_SIZE,
> >   };
> >
> > +BPF_CALL_5(bpf_unlocked_sock_setsockopt, struct sock *, sk, int, level,
> > +        int, optname, char *, optval, int, optlen)
> > +{
> > +     return _bpf_setsockopt(sk, level, optname, optval, optlen);
>
> The sock_owned_by_me() will warn.
>
>  From CI:
> WARNING: CPU: 0 PID: 102 at include/net/sock.h:1756 bpf_unlocked_sock_setsockopt+0xc7/0x110

Oh sorry, I copied from a wrong place.. will fix it.

BTW, I'm thinking I should inherit flags from the listener
in sk_clone_lock() and disallow other bpf hooks.

Given the listener's flag and bpf hooks come from the
same cgroup, there is no point having other hooks.


>
> > +}
> > +
> > +static const struct bpf_func_proto bpf_unlocked_sock_setsockopt_proto = {
> > +     .func           = bpf_unlocked_sock_setsockopt,
> > +     .gpl_only       = false,
> > +     .ret_type       = RET_INTEGER,
> > +     .arg1_type      = ARG_PTR_TO_CTX,
> > +     .arg2_type      = ARG_ANYTHING,
> > +     .arg3_type      = ARG_ANYTHING,
> > +     .arg4_type      = ARG_PTR_TO_MEM | MEM_RDONLY,
> > +     .arg5_type      = ARG_CONST_SIZE,
> > +};
> > +
> >   static int bpf_sock_ops_get_syn(struct bpf_sock_ops_kern *bpf_sock,
> >                               int optname, const u8 **start)
> >   {
> > @@ -8051,6 +8068,13 @@ sock_filter_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
> >               return &bpf_sk_storage_get_cg_sock_proto;
> >       case BPF_FUNC_ktime_get_coarse_ns:
> >               return &bpf_ktime_get_coarse_ns_proto;
> > +     case BPF_FUNC_setsockopt:
> > +             switch (prog->expected_attach_type) {
> > +             case BPF_CGROUP_INET_SOCK_CREATE:
> > +                     return &bpf_unlocked_sock_setsockopt_proto;
> > +             default:
> > +                     return NULL;
> > +             }
> >       default:
> >               return bpf_base_func_proto(func_id, prog);
> >       }
>

Re: [PATCH v3 bpf-next/net 1/5] tcp: Save lock_sock() for memcg in inet_csk_accept().

[Shakeel Butt]

On Tue, Aug 26, 2025 at 06:38:07PM +0000, Kuniyuki Iwashima wrote:
> If memcg is enabled, accept() acquires lock_sock() twice for each new
> TCP/MPTCP socket in inet_csk_accept() and __inet_accept().
> 
> Let's move memcg operations from inet_csk_accept() to __inet_accept().
> 
> Note that SCTP somehow allocates a new socket by sk_alloc() in
> sk->sk_prot->accept() and clones fields manually, instead of using
> sk_clone_lock().
> 
> mem_cgroup_sk_alloc() is called for SCTP before __inet_accept(),
> so I added the protocol check in __inet_accept(), but this can be
> removed once SCTP uses sk_clone_lock().
> 
> Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>

Reviewed-by: Shakeel Butt <shakeel.butt@linux.dev>

Re: [PATCH v3 bpf-next/net 3/5] bpf: Introduce SK_BPF_MEMCG_FLAGS and SK_BPF_MEMCG_SOCK_ISOLATED.

[Martin KaFai Lau]

On 8/26/25 11:38 AM, Kuniyuki Iwashima wrote:
> The main targets are BPF_CGROUP_INET_SOCK_CREATE and
> BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB as demonstrated in the selftest.
> 
> Note that we do not support modifying the flag once sk->sk_memcg is set
> especially because UDP charges memory under sk->sk_receive_queue.lock
> instead of lock_sock().
> 

[ ... ]

> diff --git a/include/net/sock.h b/include/net/sock.h
> index 63a6a48afb48..d41a2f8f8b30 100644
> --- a/include/net/sock.h
> +++ b/include/net/sock.h
> @@ -2596,10 +2596,39 @@ static inline gfp_t gfp_memcg_charge(void)
>   	return in_softirq() ? GFP_ATOMIC : GFP_KERNEL;
>   }
>   
> +#define SK_BPF_MEMCG_FLAG_MASK	(SK_BPF_MEMCG_FLAG_MAX - 1)
> +#define SK_BPF_MEMCG_PTR_MASK	~SK_BPF_MEMCG_FLAG_MASK
> +
>   #ifdef CONFIG_MEMCG
> +static inline void mem_cgroup_sk_set_flags(struct sock *sk, unsigned short flags)
> +{
> +	unsigned long val = (unsigned long)sk->sk_memcg;
> +
> +	val |= flags;
> +	sk->sk_memcg = (struct mem_cgroup *)val;
> +}
> +

[ ... ]

> +static int sk_bpf_set_get_memcg_flags(struct sock *sk, int *optval, bool getopt)
> +{
> +	if (!sk_has_account(sk))
> +		return -EOPNOTSUPP;
> +
> +	if (getopt) {
> +		*optval = mem_cgroup_sk_get_flags(sk);
> +		return 0;
> +	}
> +
> +	if (sock_owned_by_user_nocheck(sk) && mem_cgroup_from_sk(sk))

I still don't see how this can stop some of the bh bpf prog to set/clear the bit 
after mem_cgroup_sk_alloc() is done. For example, in BPF_SOCK_OPS_RETRANS_CB, 
bh_lock_sock() is held but not owned by user, so the bpf prog can continue to 
change the SK_BPF_MEMCG_FLAGS. What am I missing?

Passing some more args to __bpf_setsockopt() for caller context purpose is quite 
ugly which I think you also mentioned/tried earlier. May be it can check "if 
(in_softirq() && mem_cgroup_from_sk(sk)) return -EBUSY" but looks quite tricky 
together with the sock_owned_by_user_nocheck().

It seems this sk_memcg bit change is only needed for sock_ops hook and create 
hook? sock_ops already has its only func_proto bpf_sock_ops_setsockopt(). 
bpf_sock_ops_setsockopt can directly call sk_bpf_set_get_memcg_flags() but limit 
it to the BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB. Is it also safe to allow it for 
BPF_SOCK_OPS_TCP_LISTEN_CB? For the create hook, create a new func proto which 
can directly call sk_bpf_set_get_memcg_flags(). wdyt?

> +		return -EBUSY;
> +
> +	if (*optval <= 0 || *optval >= SK_BPF_MEMCG_FLAG_MAX)

It seems the bit cannot be cleared (the *optval <= 0 check). There could be 
multiple bpf progs running in a cgroup which want to clear this bit. e.g. the 
parent cgroup's prog may want to ensure this bit is not set.

Re: [PATCH v3 bpf-next/net 2/5] bpf: Support bpf_setsockopt() for BPF_CGROUP_INET_SOCK_CREATE.

[Martin KaFai Lau]

On 8/27/25 3:49 PM, Kuniyuki Iwashima wrote:
> BTW, I'm thinking I should inherit flags from the listener
> in sk_clone_lock() and disallow other bpf hooks.

Agree and I think in general this flag should be inherited to the child. It is 
less surprising to the user.

> 
> Given the listener's flag and bpf hooks come from the
> same cgroup, there is no point having other hooks.
iiuc, this will narrow down the use case to the create hook only? Sure, it can 
start with the create hook if there is no use case for sock_ops. sock_ops can do 
setsockopt differently based on the ip/port but I don't have a use case for now.

Re: [PATCH v3 bpf-next/net 5/5] selftest: bpf: Add test for SK_BPF_MEMCG_SOCK_ISOLATED.

[Martin KaFai Lau]

On 8/26/25 11:38 AM, Kuniyuki Iwashima wrote:
> The test does the following for IPv4/IPv6 x TCP/UDP sockets
> with/without BPF prog.
> 
>    1. Create socket pairs
>    2. Send a bunch of data that require more than 1000 pages
>    3. Read memory_allocated from the 3rd column in /proc/net/protocols
>    4. Check if unread data is charged to memory_allocated
> 
> If BPF prog is attached, memory_allocated should not be changed,
> but we allow a small error (up to 10 pages) in case the test is ran
> concurrently with other tests using TCP/UDP sockets.

hmm... there is a "./test_progs -j" that multiple tests can run in parallel. 
Will it be reliable enough or it needs the "serial_" prefix in the test 
function? Beside, the test took ~20s in my qemu. Is it feasible to shorten the test?

Re: [PATCH v3 bpf-next/net 3/5] bpf: Introduce SK_BPF_MEMCG_FLAGS and SK_BPF_MEMCG_SOCK_ISOLATED.

[Kuniyuki Iwashima]

On Wed, Aug 27, 2025 at 4:48 PM Martin KaFai Lau <martin.lau@linux.dev> wrote:
>
> On 8/26/25 11:38 AM, Kuniyuki Iwashima wrote:
> > The main targets are BPF_CGROUP_INET_SOCK_CREATE and
> > BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB as demonstrated in the selftest.
> >
> > Note that we do not support modifying the flag once sk->sk_memcg is set
> > especially because UDP charges memory under sk->sk_receive_queue.lock
> > instead of lock_sock().
> >
>
> [ ... ]
>
> > diff --git a/include/net/sock.h b/include/net/sock.h
> > index 63a6a48afb48..d41a2f8f8b30 100644
> > --- a/include/net/sock.h
> > +++ b/include/net/sock.h
> > @@ -2596,10 +2596,39 @@ static inline gfp_t gfp_memcg_charge(void)
> >       return in_softirq() ? GFP_ATOMIC : GFP_KERNEL;
> >   }
> >
> > +#define SK_BPF_MEMCG_FLAG_MASK       (SK_BPF_MEMCG_FLAG_MAX - 1)
> > +#define SK_BPF_MEMCG_PTR_MASK        ~SK_BPF_MEMCG_FLAG_MASK
> > +
> >   #ifdef CONFIG_MEMCG
> > +static inline void mem_cgroup_sk_set_flags(struct sock *sk, unsigned short flags)
> > +{
> > +     unsigned long val = (unsigned long)sk->sk_memcg;
> > +
> > +     val |= flags;
> > +     sk->sk_memcg = (struct mem_cgroup *)val;
> > +}
> > +
>
> [ ... ]
>
> > +static int sk_bpf_set_get_memcg_flags(struct sock *sk, int *optval, bool getopt)
> > +{
> > +     if (!sk_has_account(sk))
> > +             return -EOPNOTSUPP;
> > +
> > +     if (getopt) {
> > +             *optval = mem_cgroup_sk_get_flags(sk);
> > +             return 0;
> > +     }
> > +
> > +     if (sock_owned_by_user_nocheck(sk) && mem_cgroup_from_sk(sk))
>
> I still don't see how this can stop some of the bh bpf prog to set/clear the bit
> after mem_cgroup_sk_alloc() is done. For example, in BPF_SOCK_OPS_RETRANS_CB,
> bh_lock_sock() is held but not owned by user, so the bpf prog can continue to
> change the SK_BPF_MEMCG_FLAGS. What am I missing?

You are totally right.  I think I was just confused.

>
> Passing some more args to __bpf_setsockopt() for caller context purpose is quite
> ugly which I think you also mentioned/tried earlier.

Another option I was thinking (but didn't try) was extending void *ctx
from struct sock * to like below and silently cast ctx back to the original
one in the dedicated setsockopt proto.

struct {
    struct sock * sk;
    /* caller info here */
}

>  May be it can check "if
> (in_softirq() && mem_cgroup_from_sk(sk)) return -EBUSY" but looks quite tricky
> together with the sock_owned_by_user_nocheck().
>
> It seems this sk_memcg bit change is only needed for sock_ops hook and create
> hook? sock_ops already has its only func_proto bpf_sock_ops_setsockopt().
> bpf_sock_ops_setsockopt can directly call sk_bpf_set_get_memcg_flags() but limit
> it to the BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB. Is it also safe to allow it for
> BPF_SOCK_OPS_TCP_LISTEN_CB? For the create hook, create a new func proto which
> can directly call sk_bpf_set_get_memcg_flags(). wdyt?

I prefer the new proto instead of a hacky/complicated approach.


>
> > +             return -EBUSY;
> > +
> > +     if (*optval <= 0 || *optval >= SK_BPF_MEMCG_FLAG_MAX)
>
> It seems the bit cannot be cleared (the *optval <= 0 check). There could be
> multiple bpf progs running in a cgroup which want to clear this bit. e.g. the
> parent cgroup's prog may want to ensure this bit is not set.

I didn't think about the situation, so the set helper will need to
reset all flags (in case there could be multiple bit flags in the future)

static inline void mem_cgroup_sk_set_flags(struct sock *sk, unsigned short flags
{
    unsigned long val = (unsigned long)sk->sk_memcg;

    val &= SK_BPF_MEMCG_PTR_MASK;
    val |= flags;

    sk->sk_memcg = (struct mem_cgroup *)val;
}

Re: [PATCH v3 bpf-next/net 2/5] bpf: Support bpf_setsockopt() for BPF_CGROUP_INET_SOCK_CREATE.

[Kuniyuki Iwashima]

On Wed, Aug 27, 2025 at 5:06 PM Martin KaFai Lau <martin.lau@linux.dev> wrote:
>
> On 8/27/25 3:49 PM, Kuniyuki Iwashima wrote:
> > BTW, I'm thinking I should inherit flags from the listener
> > in sk_clone_lock() and disallow other bpf hooks.
>
> Agree and I think in general this flag should be inherited to the child. It is
> less surprising to the user.
>
> >
> > Given the listener's flag and bpf hooks come from the
> > same cgroup, there is no point having other hooks.
> iiuc, this will narrow down the use case to the create hook only? Sure, it can
> start with the create hook if there is no use case for sock_ops. sock_ops can do
> setsockopt differently based on the ip/port but I don't have a use case for now.

Yes, we can support another hook later when needed.

Re: [PATCH v3 bpf-next/net 5/5] selftest: bpf: Add test for SK_BPF_MEMCG_SOCK_ISOLATED.

[Kuniyuki Iwashima]

On Wed, Aug 27, 2025 at 5:14 PM Martin KaFai Lau <martin.lau@linux.dev> wrote:
>
> On 8/26/25 11:38 AM, Kuniyuki Iwashima wrote:
> > The test does the following for IPv4/IPv6 x TCP/UDP sockets
> > with/without BPF prog.
> >
> >    1. Create socket pairs
> >    2. Send a bunch of data that require more than 1000 pages
> >    3. Read memory_allocated from the 3rd column in /proc/net/protocols
> >    4. Check if unread data is charged to memory_allocated
> >
> > If BPF prog is attached, memory_allocated should not be changed,
> > but we allow a small error (up to 10 pages) in case the test is ran
> > concurrently with other tests using TCP/UDP sockets.
>
> hmm... there is a "./test_progs -j" that multiple tests can run in parallel.
> Will it be reliable enough or it needs the "serial_" prefix in the test
> function?

Didn't know the prefix, sounds useful :)


> Beside, the test took ~20s in my qemu. Is it feasible to shorten the test?

Same on my qemu setup, and I think it's feasible with serial_.

Currently, the test consumes 2000> pages for each TCP/UDP
case, but this was just to make it more reliable on uncertain env.