[PATCH mptcp-next v3 0/7] mptcp: add bpf_setsockopt support

[PATCH mptcp-next v3 0/7] mptcp: add bpf_setsockopt support

[Gang Yan]

From: Gang Yan <yangang@kylinos.cn>

Hi, Matt, Geliang, Paolo

Patch 3-4 have been reviewed by Paolo before, and ready for merge
[1][2].

Changelog:
v3:
  - Patch 2 keeps the mptcp_setsockopt_all_sf as Geliang suggested.
v2:
  - Patches 1 and 2 are new in this series; they address TCP_MAXSEG
    handling in the bpf_setsockopt() path.
  - Patch 4 adds an early return to fix msk->sk_rcvlowat being
    unexpectedly modified, an issue seen in v1.
  - Patch 5 makes the hook safe for the non-tcp master socket: it guards
    bpf_sock_ops_cb_flags_set() with sk_is_tcp() to prevent out-of-bounds
    heap reads/writes through tcp_sk(sk)->bpf_sock_ops_cb_flags, and does
    not set is_locked_tcp_sock for the msk (unlike tcp_call_bpf()). That
    flag authorizes the verifier's direct tcp_sock-offset field accesses;
    since the msk is not a tcp_sock, leaving it at the default 0 is safe.

v1:
  Link: https://patchwork.kernel.org/project/mptcp/cover/20260713095735.1222033-1-gang.yan@linux.dev/

[1] https://patchwork.kernel.org/project/mptcp/patch/20260522-sockopt_lock-v5-2-108629a46e98@kylinos.cn/
[2] https://patchwork.kernel.org/project/mptcp/patch/20260522-sockopt_lock-v5-4-108629a46e98@kylinos.cn/

Gang Yan (7):
  mptcp: drop unused @max arg of __mptcp_setsockopt_set_val
  mptcp: take TCP_MAXSEG handling into __mptcp_setsockopt_set_val
  mptcp: use sockopt_lock/release_sock in sockopt
  mptcp: reject sockopt requiring ssks' lock in BPF context
  mptcp: enable bpf_setsockopt on the master socket
  mptcp: add TCP_CONNECT_CB sock_ops hook
  selftests: bpf: verify mptcp bpf_setsockopt from TCP_CONNECT_CB

 include/net/mptcp.h                           |   9 ++
 net/core/filter.c                             |  10 ++
 net/ipv4/tcp.c                                |   1 +
 net/mptcp/protocol.c                          |   6 +
 net/mptcp/protocol.h                          |  29 ++++
 net/mptcp/sockopt.c                           | 127 +++++++++++-------
 .../testing/selftests/bpf/prog_tests/mptcp.c  |  61 +++++++++
 .../selftests/bpf/progs/mptcp_setsockopt.c    |  32 +++++
 8 files changed, 223 insertions(+), 52 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/progs/mptcp_setsockopt.c

-- 
2.43.0

[PATCH mptcp-next v3 1/7] mptcp: drop unused @max arg of __mptcp_setsockopt_set_val

[Gang Yan]

From: Gang Yan <yangang@kylinos.cn>

The @max argument is never read in the function body. Remove it and the
MAX_TCP_KEEP* values passed by the TCP_KEEPIDLE/INTVL/KEEPCNT callers.

Signed-off-by: Gang Yan <yangang@kylinos.cn>
---
 net/mptcp/sockopt.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c
index fcf6feb2a9eb..9c4faa0d82ef 100644
--- a/net/mptcp/sockopt.c
+++ b/net/mptcp/sockopt.c
@@ -632,7 +632,7 @@ static int mptcp_setsockopt_sol_tcp_congestion(struct mptcp_sock *msk, sockptr_t
 	return ret;
 }
 
-static int __mptcp_setsockopt_set_val(struct mptcp_sock *msk, int max,
+static int __mptcp_setsockopt_set_val(struct mptcp_sock *msk,
 				      int (*set_val)(struct sock *, int),
 				      int *msk_val, int val)
 {
@@ -876,18 +876,15 @@ static int mptcp_setsockopt_sol_tcp(struct mptcp_sock *msk, int optname,
 		ret = __mptcp_setsockopt_sol_tcp_nodelay(msk, val);
 		break;
 	case TCP_KEEPIDLE:
-		ret = __mptcp_setsockopt_set_val(msk, MAX_TCP_KEEPIDLE,
-						 &tcp_sock_set_keepidle_locked,
+		ret = __mptcp_setsockopt_set_val(msk, &tcp_sock_set_keepidle_locked,
 						 &msk->keepalive_idle, val);
 		break;
 	case TCP_KEEPINTVL:
-		ret = __mptcp_setsockopt_set_val(msk, MAX_TCP_KEEPINTVL,
-						 &tcp_sock_set_keepintvl,
+		ret = __mptcp_setsockopt_set_val(msk, &tcp_sock_set_keepintvl,
 						 &msk->keepalive_intvl, val);
 		break;
 	case TCP_KEEPCNT:
-		ret = __mptcp_setsockopt_set_val(msk, MAX_TCP_KEEPCNT,
-						 &tcp_sock_set_keepcnt,
+		ret = __mptcp_setsockopt_set_val(msk, &tcp_sock_set_keepcnt,
 						 &msk->keepalive_cnt,
 						 val);
 		break;
-- 
2.43.0

[PATCH mptcp-next v3 2/7] mptcp: take TCP_MAXSEG handling into __mptcp_setsockopt_set_val

[Gang Yan]

From: Gang Yan <yangang@kylinos.cn>

mptcp_setsockopt_all_sf is only used in 'TCP_MAXSEG', and it can be
replaced with __mptcp_setsockopt_set_val.

Signed-off-by: Gang Yan <yangang@kylinos.cn>
---
 net/ipv4/tcp.c      | 1 +
 net/mptcp/sockopt.c | 5 ++---
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index b427f924608c..5915d0e62f43 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3830,6 +3830,7 @@ int tcp_sock_set_maxseg(struct sock *sk, int val)
 	WRITE_ONCE(tcp_sk(sk)->rx_opt.user_mss, val);
 	return 0;
 }
+EXPORT_SYMBOL(tcp_sock_set_maxseg);
 
 /*
  *	Socket option code for TCP.
diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c
index 9c4faa0d82ef..a7d4135757e7 100644
--- a/net/mptcp/sockopt.c
+++ b/net/mptcp/sockopt.c
@@ -889,9 +889,8 @@ static int mptcp_setsockopt_sol_tcp(struct mptcp_sock *msk, int optname,
 						 val);
 		break;
 	case TCP_MAXSEG:
-		msk->maxseg = val;
-		ret = mptcp_setsockopt_all_sf(msk, SOL_TCP, optname, optval,
-					      optlen);
+		ret = __mptcp_setsockopt_set_val(msk, &tcp_sock_set_maxseg,
+						 &msk->maxseg, val);
 		break;
 	default:
 		ret = -ENOPROTOOPT;
-- 
2.43.0

[PATCH mptcp-next v3 3/7] mptcp: use sockopt_lock/release_sock in sockopt

[Gang Yan]

From: Gang Yan <yangang@kylinos.cn>

TCP and the core socket layer use sockopt_lock_sock() /
sockopt_release_sock() in their setsockopt and getsockopt handlers.

Switch the MPTCP socket (msk) level lock_sock()/release_sock()
calls to use the BPF-aware wrappers, making the MPTCP sockopt
codepaths consistent with the rest of the networking stack.

Signed-off-by: Gang Yan <yangang@kylinos.cn>
---
 net/mptcp/sockopt.c | 84 ++++++++++++++++++++++-----------------------
 1 file changed, 42 insertions(+), 42 deletions(-)

diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c
index a7d4135757e7..f00d85809c52 100644
--- a/net/mptcp/sockopt.c
+++ b/net/mptcp/sockopt.c
@@ -78,7 +78,7 @@ static void mptcp_sol_socket_sync_intval(struct mptcp_sock *msk, int optname, in
 	struct mptcp_subflow_context *subflow;
 	struct sock *sk = (struct sock *)msk;
 
-	lock_sock(sk);
+	sockopt_lock_sock(sk);
 	sockopt_seq_inc(msk);
 
 	mptcp_for_each_subflow(msk, subflow) {
@@ -123,7 +123,7 @@ static void mptcp_sol_socket_sync_intval(struct mptcp_sock *msk, int optname, in
 		unlock_sock_fast(ssk, slow);
 	}
 
-	release_sock(sk);
+	sockopt_release_sock(sk);
 }
 
 static int mptcp_sol_socket_intval(struct mptcp_sock *msk, int optname, int val)
@@ -162,7 +162,7 @@ static int mptcp_setsockopt_sol_socket_tstamp(struct mptcp_sock *msk, int optnam
 	if (ret)
 		return ret;
 
-	lock_sock(sk);
+	sockopt_lock_sock(sk);
 	mptcp_for_each_subflow(msk, subflow) {
 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
 
@@ -171,7 +171,7 @@ static int mptcp_setsockopt_sol_socket_tstamp(struct mptcp_sock *msk, int optnam
 		release_sock(ssk);
 	}
 
-	release_sock(sk);
+	sockopt_release_sock(sk);
 	return 0;
 }
 
@@ -237,7 +237,7 @@ static int mptcp_setsockopt_sol_socket_timestamping(struct mptcp_sock *msk,
 	if (ret)
 		return ret;
 
-	lock_sock(sk);
+	sockopt_lock_sock(sk);
 
 	mptcp_for_each_subflow(msk, subflow) {
 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
@@ -251,7 +251,7 @@ static int mptcp_setsockopt_sol_socket_timestamping(struct mptcp_sock *msk,
 			ret = err;
 	}
 
-	release_sock(sk);
+	sockopt_release_sock(sk);
 
 	return ret;
 }
@@ -276,7 +276,7 @@ static int mptcp_setsockopt_sol_socket_linger(struct mptcp_sock *msk, sockptr_t
 	if (ret)
 		return ret;
 
-	lock_sock(sk);
+	sockopt_lock_sock(sk);
 	sockopt_seq_inc(msk);
 	mptcp_for_each_subflow(msk, subflow) {
 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
@@ -293,7 +293,7 @@ static int mptcp_setsockopt_sol_socket_linger(struct mptcp_sock *msk, sockptr_t
 		unlock_sock_fast(ssk, slow);
 	}
 
-	release_sock(sk);
+	sockopt_release_sock(sk);
 	return 0;
 }
 
@@ -309,10 +309,10 @@ static int mptcp_setsockopt_sol_socket(struct mptcp_sock *msk, int optname,
 	case SO_REUSEADDR:
 	case SO_BINDTODEVICE:
 	case SO_BINDTOIFINDEX:
-		lock_sock(sk);
+		sockopt_lock_sock(sk);
 		ssk = __mptcp_nmpc_sk(msk);
 		if (IS_ERR(ssk)) {
-			release_sock(sk);
+			sockopt_release_sock(sk);
 			return PTR_ERR(ssk);
 		}
 
@@ -327,7 +327,7 @@ static int mptcp_setsockopt_sol_socket(struct mptcp_sock *msk, int optname,
 			else if (optname == SO_BINDTOIFINDEX)
 				sk->sk_bound_dev_if = ssk->sk_bound_dev_if;
 		}
-		release_sock(sk);
+		sockopt_release_sock(sk);
 		return ret;
 	case SO_KEEPALIVE:
 	case SO_PRIORITY:
@@ -405,16 +405,16 @@ static int mptcp_setsockopt_v6(struct mptcp_sock *msk, int optname,
 	case IPV6_V6ONLY:
 	case IPV6_TRANSPARENT:
 	case IPV6_FREEBIND:
-		lock_sock(sk);
+		sockopt_lock_sock(sk);
 		ssk = __mptcp_nmpc_sk(msk);
 		if (IS_ERR(ssk)) {
-			release_sock(sk);
+			sockopt_release_sock(sk);
 			return PTR_ERR(ssk);
 		}
 
 		ret = tcp_setsockopt(ssk, SOL_IPV6, optname, optval, optlen);
 		if (ret != 0) {
-			release_sock(sk);
+			sockopt_release_sock(sk);
 			return ret;
 		}
 
@@ -434,7 +434,7 @@ static int mptcp_setsockopt_v6(struct mptcp_sock *msk, int optname,
 			break;
 		}
 
-		release_sock(sk);
+		sockopt_release_sock(sk);
 		break;
 	}
 
@@ -611,7 +611,7 @@ static int mptcp_setsockopt_sol_tcp_congestion(struct mptcp_sock *msk, sockptr_t
 	cap_net_admin = ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN);
 
 	ret = 0;
-	lock_sock(sk);
+	sockopt_lock_sock(sk);
 	sockopt_seq_inc(msk);
 	mptcp_for_each_subflow(msk, subflow) {
 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
@@ -628,7 +628,7 @@ static int mptcp_setsockopt_sol_tcp_congestion(struct mptcp_sock *msk, sockptr_t
 	if (ret == 0)
 		strscpy(msk->ca_name, name, sizeof(msk->ca_name));
 
-	release_sock(sk);
+	sockopt_release_sock(sk);
 	return ret;
 }
 
@@ -707,11 +707,11 @@ static int mptcp_setsockopt_sol_ip_set(struct mptcp_sock *msk, int optname,
 	if (err != 0)
 		return err;
 
-	lock_sock(sk);
+	sockopt_lock_sock(sk);
 
 	ssk = __mptcp_nmpc_sk(msk);
 	if (IS_ERR(ssk)) {
-		release_sock(sk);
+		sockopt_release_sock(sk);
 		return PTR_ERR(ssk);
 	}
 
@@ -732,13 +732,13 @@ static int mptcp_setsockopt_sol_ip_set(struct mptcp_sock *msk, int optname,
 			   READ_ONCE(inet_sk(sk)->local_port_range));
 		break;
 	default:
-		release_sock(sk);
+		sockopt_release_sock(sk);
 		WARN_ON_ONCE(1);
 		return -EOPNOTSUPP;
 	}
 
 	sockopt_seq_inc(msk);
-	release_sock(sk);
+	sockopt_release_sock(sk);
 	return 0;
 }
 
@@ -754,7 +754,7 @@ static int mptcp_setsockopt_v4_set_tos(struct mptcp_sock *msk, int optname,
 	if (err != 0)
 		return err;
 
-	lock_sock(sk);
+	sockopt_lock_sock(sk);
 	sockopt_seq_inc(msk);
 	val = READ_ONCE(inet_sk(sk)->tos);
 	mptcp_for_each_subflow(msk, subflow) {
@@ -765,7 +765,7 @@ static int mptcp_setsockopt_v4_set_tos(struct mptcp_sock *msk, int optname,
 		__ip_sock_set_tos(ssk, val);
 		unlock_sock_fast(ssk, slow);
 	}
-	release_sock(sk);
+	sockopt_release_sock(sk);
 
 	return 0;
 }
@@ -794,7 +794,7 @@ static int mptcp_setsockopt_first_sf_only(struct mptcp_sock *msk, int level, int
 	int ret;
 
 	/* Limit to first subflow, before the connection establishment */
-	lock_sock(sk);
+	sockopt_lock_sock(sk);
 	ssk = __mptcp_nmpc_sk(msk);
 	if (IS_ERR(ssk)) {
 		ret = PTR_ERR(ssk);
@@ -804,7 +804,7 @@ static int mptcp_setsockopt_first_sf_only(struct mptcp_sock *msk, int level, int
 	ret = tcp_setsockopt(ssk, level, optname, optval, optlen);
 
 unlock:
-	release_sock(sk);
+	sockopt_release_sock(sk);
 	return ret;
 }
 
@@ -857,7 +857,7 @@ static int mptcp_setsockopt_sol_tcp(struct mptcp_sock *msk, int optname,
 	if (ret)
 		return ret;
 
-	lock_sock(sk);
+	sockopt_lock_sock(sk);
 	switch (optname) {
 	case TCP_INQ:
 		if (val < 0 || val > 1)
@@ -896,7 +896,7 @@ static int mptcp_setsockopt_sol_tcp(struct mptcp_sock *msk, int optname,
 		ret = -ENOPROTOOPT;
 	}
 
-	release_sock(sk);
+	sockopt_release_sock(sk);
 	return ret;
 }
 
@@ -920,9 +920,9 @@ int mptcp_setsockopt(struct sock *sk, int level, int optname,
 	 * is in TCP fallback, when TCP socket options are passed through
 	 * to the one remaining subflow.
 	 */
-	lock_sock(sk);
+	sockopt_lock_sock(sk);
 	ssk = __mptcp_tcp_fallback(msk);
-	release_sock(sk);
+	sockopt_release_sock(sk);
 	if (ssk)
 		return tcp_setsockopt(ssk, level, optname, optval, optlen);
 
@@ -945,7 +945,7 @@ static int mptcp_getsockopt_first_sf_only(struct mptcp_sock *msk, int level, int
 	struct sock *ssk;
 	int ret;
 
-	lock_sock(sk);
+	sockopt_lock_sock(sk);
 	ssk = msk->first;
 	if (ssk)
 		goto get;
@@ -960,7 +960,7 @@ static int mptcp_getsockopt_first_sf_only(struct mptcp_sock *msk, int level, int
 	ret = tcp_getsockopt(ssk, level, optname, optval, optlen);
 
 out:
-	release_sock(sk);
+	sockopt_release_sock(sk);
 	return ret;
 }
 
@@ -1131,7 +1131,7 @@ static int mptcp_getsockopt_tcpinfo(struct mptcp_sock *msk, char __user *optval,
 
 	infoptr = optval + sfd.size_subflow_data;
 
-	lock_sock(sk);
+	sockopt_lock_sock(sk);
 
 	mptcp_for_each_subflow(msk, subflow) {
 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
@@ -1144,7 +1144,7 @@ static int mptcp_getsockopt_tcpinfo(struct mptcp_sock *msk, char __user *optval,
 			tcp_get_info(ssk, &info);
 
 			if (copy_to_user(infoptr, &info, sfd.size_user)) {
-				release_sock(sk);
+				sockopt_release_sock(sk);
 				return -EFAULT;
 			}
 
@@ -1154,7 +1154,7 @@ static int mptcp_getsockopt_tcpinfo(struct mptcp_sock *msk, char __user *optval,
 		}
 	}
 
-	release_sock(sk);
+	sockopt_release_sock(sk);
 
 	sfd.num_subflows = sfcount;
 
@@ -1223,7 +1223,7 @@ static int mptcp_getsockopt_subflow_addrs(struct mptcp_sock *msk, char __user *o
 
 	addrptr = optval + sfd.size_subflow_data;
 
-	lock_sock(sk);
+	sockopt_lock_sock(sk);
 
 	mptcp_for_each_subflow(msk, subflow) {
 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
@@ -1236,7 +1236,7 @@ static int mptcp_getsockopt_subflow_addrs(struct mptcp_sock *msk, char __user *o
 			mptcp_get_sub_addrs(ssk, &a);
 
 			if (copy_to_user(addrptr, &a, sfd.size_user)) {
-				release_sock(sk);
+				sockopt_release_sock(sk);
 				return -EFAULT;
 			}
 
@@ -1246,7 +1246,7 @@ static int mptcp_getsockopt_subflow_addrs(struct mptcp_sock *msk, char __user *o
 		}
 	}
 
-	release_sock(sk);
+	sockopt_release_sock(sk);
 
 	sfd.num_subflows = sfcount;
 
@@ -1332,7 +1332,7 @@ static int mptcp_getsockopt_full_info(struct mptcp_sock *msk, char __user *optva
 				     sizeof(struct mptcp_subflow_info));
 	tcpinfoptr = u64_to_user_ptr(mfi.tcp_info);
 
-	lock_sock(sk);
+	sockopt_lock_sock(sk);
 	mptcp_for_each_subflow(msk, subflow) {
 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
 		struct mptcp_subflow_info sfinfo;
@@ -1362,7 +1362,7 @@ static int mptcp_getsockopt_full_info(struct mptcp_sock *msk, char __user *optva
 		tcpinfoptr += mfi.size_tcpinfo_user;
 		sfinfoptr += mfi.size_sfinfo_user;
 	}
-	release_sock(sk);
+	sockopt_release_sock(sk);
 
 	mfi.num_subflows = sfcount;
 	if (mptcp_put_full_info(&mfi, optval, copylen, optlen))
@@ -1371,7 +1371,7 @@ static int mptcp_getsockopt_full_info(struct mptcp_sock *msk, char __user *optva
 	return 0;
 
 fail_release:
-	release_sock(sk);
+	sockopt_release_sock(sk);
 	return -EFAULT;
 }
 
@@ -1526,9 +1526,9 @@ int mptcp_getsockopt(struct sock *sk, int level, int optname,
 	 * is in TCP fallback, when socket options are passed through
 	 * to the one remaining subflow.
 	 */
-	lock_sock(sk);
+	sockopt_lock_sock(sk);
 	ssk = __mptcp_tcp_fallback(msk);
-	release_sock(sk);
+	sockopt_release_sock(sk);
 	if (ssk)
 		return tcp_getsockopt(ssk, level, optname, optval, option);
 
-- 
2.43.0

[PATCH mptcp-next v3 4/7] mptcp: reject sockopt requiring ssks' lock in BPF context

[Gang Yan]

From: Gang Yan <yangang@kylinos.cn>

Several MPTCP setsockopt handlers need to acquire the subflow lock
via lock_sock(ssk) to propagate settings to each subflow.  This lock
can sleep and is therefore not usable in BPF context where sleeping
is forbidden.

The short-term solution is to make any sockopt operation that requires
subflow-level lock fail with -EOPNOTSUPP when called from BPF context.

Signed-off-by: Gang Yan <yangang@kylinos.cn>
---
 net/mptcp/sockopt.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c
index f00d85809c52..a26758a82150 100644
--- a/net/mptcp/sockopt.c
+++ b/net/mptcp/sockopt.c
@@ -185,6 +185,9 @@ static int mptcp_setsockopt_sol_socket_int(struct mptcp_sock *msk, int optname,
 	if (ret)
 		return ret;
 
+	if (has_current_bpf_ctx())
+		return -EOPNOTSUPP;
+
 	switch (optname) {
 	case SO_KEEPALIVE:
 	case SO_DEBUG:
@@ -218,6 +221,9 @@ static int mptcp_setsockopt_sol_socket_timestamping(struct mptcp_sock *msk,
 	struct so_timestamping timestamping;
 	int ret;
 
+	if (has_current_bpf_ctx())
+		return -EOPNOTSUPP;
+
 	if (optlen == sizeof(timestamping)) {
 		if (copy_from_sockptr(&timestamping, optval,
 				      sizeof(timestamping)))
@@ -265,6 +271,9 @@ static int mptcp_setsockopt_sol_socket_linger(struct mptcp_sock *msk, sockptr_t
 	sockptr_t kopt;
 	int ret;
 
+	if (has_current_bpf_ctx())
+		return -EOPNOTSUPP;
+
 	if (optlen < sizeof(ling))
 		return -EINVAL;
 
@@ -598,6 +607,9 @@ static int mptcp_setsockopt_sol_tcp_congestion(struct mptcp_sock *msk, sockptr_t
 	bool cap_net_admin;
 	int ret;
 
+	if (has_current_bpf_ctx())
+		return -EOPNOTSUPP;
+
 	if (optlen < 1)
 		return -EINVAL;
 
@@ -639,6 +651,9 @@ static int __mptcp_setsockopt_set_val(struct mptcp_sock *msk,
 	struct mptcp_subflow_context *subflow;
 	int err = 0;
 
+	if (has_current_bpf_ctx())
+		return -EOPNOTSUPP;
+
 	mptcp_for_each_subflow(msk, subflow) {
 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
 		int ret;
@@ -662,6 +677,9 @@ static int __mptcp_setsockopt_sol_tcp_cork(struct mptcp_sock *msk, int val)
 	struct mptcp_subflow_context *subflow;
 	struct sock *sk = (struct sock *)msk;
 
+	if (has_current_bpf_ctx())
+		return -EOPNOTSUPP;
+
 	sockopt_seq_inc(msk);
 	msk->cork = !!val;
 	mptcp_for_each_subflow(msk, subflow) {
@@ -682,6 +700,9 @@ static int __mptcp_setsockopt_sol_tcp_nodelay(struct mptcp_sock *msk, int val)
 	struct mptcp_subflow_context *subflow;
 	struct sock *sk = (struct sock *)msk;
 
+	if (has_current_bpf_ctx())
+		return -EOPNOTSUPP;
+
 	sockopt_seq_inc(msk);
 	msk->nodelay = !!val;
 	mptcp_for_each_subflow(msk, subflow) {
@@ -749,6 +770,9 @@ static int mptcp_setsockopt_v4_set_tos(struct mptcp_sock *msk, int optname,
 	struct sock *sk = (struct sock *)msk;
 	int err, val;
 
+	if (has_current_bpf_ctx())
+		return -EOPNOTSUPP;
+
 	err = ip_setsockopt(sk, SOL_IP, optname, optval, optlen);
 
 	if (err != 0)
@@ -1632,6 +1656,9 @@ int mptcp_set_rcvlowat(struct sock *sk, int val)
 	if (sk->sk_protocol == IPPROTO_TCP)
 		return -EINVAL;
 
+	if (has_current_bpf_ctx())
+		return -EOPNOTSUPP;
+
 	if (sk->sk_userlocks & SOCK_RCVBUF_LOCK)
 		cap = sk->sk_rcvbuf >> 1;
 	else
-- 
2.43.0

[PATCH mptcp-next v3 5/7] mptcp: enable bpf_setsockopt on the master socket

[Gang Yan]

From: Gang Yan <yangang@kylinos.cn>

bpf_setsockopt() currently cannot be used on mptcp master sockets:
__bpf_setsockopt() dispatches by level to the protocol-agnostic
sol_*_sockopt() helpers, which either reject the msk
(sk_protocol == IPPROTO_MPTCP) and the ssk (sk_is_tcp() is false)
or bypass mptcp's own dispatch (e.g. SOL_IP going straight to
do_ip_setsockopt()).

This patch routes any level to mptcp_setsockopt(), which already
handles all levels.

Signed-off-by: Gang Yan <yangang@kylinos.cn>
---
 include/net/mptcp.h | 9 +++++++++
 net/core/filter.c   | 7 +++++++
 2 files changed, 16 insertions(+)

diff --git a/include/net/mptcp.h b/include/net/mptcp.h
index 333bde2a0b76..fcce2b7e9ef9 100644
--- a/include/net/mptcp.h
+++ b/include/net/mptcp.h
@@ -237,6 +237,9 @@ static inline __be32 mptcp_reset_option(const struct sk_buff *skb)
 }
 
 void mptcp_active_detect_blackhole(struct sock *sk, bool expired);
+
+int mptcp_setsockopt(struct sock *sk, int level, int optname,
+		     sockptr_t optval, unsigned int optlen);
 #else
 
 static inline void mptcp_init(void)
@@ -314,6 +317,12 @@ static inline struct request_sock *mptcp_subflow_reqsk_alloc(const struct reques
 static inline __be32 mptcp_reset_option(const struct sk_buff *skb)  { return htonl(0u); }
 
 static inline void mptcp_active_detect_blackhole(struct sock *sk, bool expired) { }
+
+static inline int mptcp_setsockopt(struct sock *sk, int level, int optname,
+				   sockptr_t optval, unsigned int optlen)
+{
+	return -EINVAL;
+}
 #endif /* CONFIG_MPTCP */
 
 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
diff --git a/net/core/filter.c b/net/core/filter.c
index b446aa8be5c3..18e650bf7393 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5683,6 +5683,13 @@ static int __bpf_setsockopt(struct sock *sk, int level, int optname,
 	if (!sk_fullsock(sk))
 		return -EINVAL;
 
+	/* Route any bpf_setsockopt on the mptcp socket to mptcp_setsockopt,
+	 * which handles all levels.
+	 */
+	if (IS_ENABLED(CONFIG_MPTCP) && sk->sk_protocol == IPPROTO_MPTCP)
+		return mptcp_setsockopt(sk, level, optname,
+					KERNEL_SOCKPTR(optval), optlen);
+
 	if (level == SOL_SOCKET)
 		return sol_socket_sockopt(sk, optname, optval, &optlen, false);
 	else if (IS_ENABLED(CONFIG_INET) && level == SOL_IP)
-- 
2.43.0

[PATCH mptcp-next v3 6/7] mptcp: add TCP_CONNECT_CB sock_ops hook

[Gang Yan]

From: Gang Yan <yangang@kylinos.cn>

This patch adds a helper named 'mptcp_call_bpf' like tcp_call_bpf.
Invoke the new helper from mptcp_connect() with
BPF_SOCK_OPS_TCP_CONNECT_CB, placed after the subflow lock is acquired
and before tcp_connect(). At this point the msk lock is held by
__inet_stream_connect(), mirroring the placement of TCP_CONNECT_CB in
tcp_v4_connect()/tcp_v6_connect().

'bpf_sock_ops_cb_flags_set' can be called via msk, so using sk_is_tcp()
to avoid this issue.

Signed-off-by: Gang Yan <yangang@kylinos.cn>
---
 net/core/filter.c    |  3 +++
 net/mptcp/protocol.c |  6 ++++++
 net/mptcp/protocol.h | 29 +++++++++++++++++++++++++++++
 3 files changed, 38 insertions(+)

diff --git a/net/core/filter.c b/net/core/filter.c
index 18e650bf7393..2f9778181279 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -6097,6 +6097,9 @@ BPF_CALL_2(bpf_sock_ops_cb_flags_set, struct bpf_sock_ops_kern *, bpf_sock,
 	if (!IS_ENABLED(CONFIG_INET) || !sk_fullsock(sk))
 		return -EINVAL;
 
+	if (!sk_is_tcp(sk))
+		return -EOPNOTSUPP;
+
 	tcp_sk(sk)->bpf_sock_ops_cb_flags = val;
 
 	return argval & (~BPF_SOCK_OPS_ALL_CB_FLAGS);
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index ffcf5a1788f6..837bb76e5c2d 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -4149,6 +4149,12 @@ static int mptcp_connect(struct sock *sk, struct sockaddr_unsized *uaddr,
 	if (!msk->fastopening)
 		lock_sock(ssk);
 
+	/* Notify cgroup BPF on the msk before initiating the subflow connect.
+	 * Mirrors BPF_SOCK_OPS_TCP_CONNECT_CB; msk lock is held by the
+	 * caller (__inet_stream_connect) and ssk is held before.
+	 */
+	mptcp_call_bpf(sk, BPF_SOCK_OPS_TCP_CONNECT_CB, 0, NULL);
+
 	/* the following mirrors closely a very small chunk of code from
 	 * __inet_stream_connect()
 	 */
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index da40c6f3705f..e862310b2f81 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -1374,4 +1374,33 @@ mptcp_token_join_cookie_init_state(struct mptcp_subflow_request_sock *subflow_re
 static inline void mptcp_join_cookie_init(void) {}
 #endif
 
+#ifdef CONFIG_BPF_JIT
+static inline int mptcp_call_bpf(struct sock *sk, int op, u32 nargs, u32 *args)
+{
+	struct bpf_sock_ops_kern sock_ops;
+	int ret;
+
+	memset(&sock_ops, 0, offsetof(struct bpf_sock_ops_kern, temp));
+
+	if (sk_fullsock(sk)) {
+		sock_ops.is_fullsock = 1;
+		sock_owned_by_me(sk);
+	}
+
+	sock_ops.sk = sk;
+	sock_ops.op = op;
+
+	if (nargs > 0)
+		memcpy(sock_ops.args, args, nargs * sizeof(*args));
+
+	ret = BPF_CGROUP_RUN_PROG_SOCK_OPS(&sock_ops);
+	return ret == 0 ? sock_ops.reply : -1;
+}
+#else
+static inline int mptcp_call_bpf(struct sock *sk, int op, u32 nargs, u32 *args)
+{
+	return -1;
+}
+#endif
+
 #endif /* __MPTCP_PROTOCOL_H */
-- 
2.43.0

[PATCH mptcp-next v3 7/7] selftests: bpf: verify mptcp bpf_setsockopt from TCP_CONNECT_CB

[Gang Yan]

From: Gang Yan <yangang@kylinos.cn>

Add a BPF sockops program attached to BPF_CGROUP_SOCK_OPS that fires
on BPF_SOCK_OPS_TCP_CONNECT_CB and exercises bpf_setsockopt() on the
mptcp master socket (msk).

Two scenarios are covered by the new "setsockopt" subtest:
 - TCP_INQ must succeed and the value (1) must be observable from
   userspace via getsockopt() on the mptcp socket.
 - TCP_CONGESTION needs the subflow lock and is therefore rejected
   in bpf context with -EOPNOTSUPP.

Signed-off-by: Gang Yan <yangang@kylinos.cn>
---
 .../testing/selftests/bpf/prog_tests/mptcp.c  | 61 +++++++++++++++++++
 .../selftests/bpf/progs/mptcp_setsockopt.c    | 32 ++++++++++
 2 files changed, 93 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/mptcp_setsockopt.c

diff --git a/tools/testing/selftests/bpf/prog_tests/mptcp.c b/tools/testing/selftests/bpf/prog_tests/mptcp.c
index 7f48fd9e94e1..ad59f8fcbb68 100644
--- a/tools/testing/selftests/bpf/prog_tests/mptcp.c
+++ b/tools/testing/selftests/bpf/prog_tests/mptcp.c
@@ -18,6 +18,7 @@
 #include "mptcp_bpf_rr.skel.h"
 #include "mptcp_bpf_red.skel.h"
 #include "mptcp_bpf_burst.skel.h"
+#include "mptcp_setsockopt.skel.h"
 
 #define NS_TEST "mptcp_ns"
 #define ADDR_1	"10.0.1.1"
@@ -813,6 +814,64 @@ static void test_burst(void)
 	mptcp_bpf_burst__destroy(skel);
 }
 
+static void test_setsockopt(void)
+{
+	struct mptcp_setsockopt *skel;
+	struct netns_obj *netns;
+	int cgroup_fd, server_fd, client_fd;
+	int err;
+	int inq;
+	socklen_t len;
+
+	cgroup_fd = test__join_cgroup("/mptcp_setsockopt");
+	if (!ASSERT_OK_FD(cgroup_fd, "join_cgroup"))
+		return;
+
+	skel = mptcp_setsockopt__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_open_load"))
+		goto close_cgroup;
+
+	skel->links.mptcp_connect_cb =
+		bpf_program__attach_cgroup(skel->progs.mptcp_connect_cb,
+					   cgroup_fd);
+	if (!ASSERT_OK_PTR(skel->links.mptcp_connect_cb, "attach connect_cb"))
+		goto skel_destroy;
+
+	netns = netns_new(NS_TEST, true);
+	if (!ASSERT_OK_PTR(netns, "netns_new"))
+		goto skel_destroy;
+
+	server_fd = start_mptcp_server(AF_INET, NULL, 0, 0);
+	if (!ASSERT_OK_FD(server_fd, "start_mptcp_server"))
+		goto close_netns;
+
+	client_fd = connect_to_fd(server_fd, 0);
+	if (!ASSERT_OK_FD(client_fd, "connect_to_fd"))
+		goto close_server;
+
+	/* TCP_INQ should be set successfullly */
+	ASSERT_EQ(skel->bss->connect_cb_inq_ret, 0, "connect_cb TCP_INQ ret");
+
+	len = sizeof(inq);
+	err = getsockopt(client_fd, SOL_TCP, TCP_INQ, &inq, &len);
+	if (ASSERT_OK(err, "getsockopt TCP_INQ"))
+		ASSERT_EQ(inq, 1, "TCP_INQ value");
+
+	/* TCP_CONGESTION should be -EOPNOTSUPP */
+	ASSERT_EQ(skel->bss->connect_cb_cc_ret, -EOPNOTSUPP,
+		  "connect_cb TCP_CONGESTION ret");
+
+	close(client_fd);
+close_server:
+	close(server_fd);
+close_netns:
+	netns_free(netns);
+skel_destroy:
+	mptcp_setsockopt__destroy(skel);
+close_cgroup:
+	close(cgroup_fd);
+}
+
 void test_mptcp(void)
 {
 	if (test__start_subtest("base"))
@@ -835,4 +894,6 @@ void test_mptcp(void)
 		test_red();
 	if (test__start_subtest("burst"))
 		test_burst();
+	if (test__start_subtest("setsockopt"))
+		test_setsockopt();
 }
diff --git a/tools/testing/selftests/bpf/progs/mptcp_setsockopt.c b/tools/testing/selftests/bpf/progs/mptcp_setsockopt.c
new file mode 100644
index 000000000000..f54b77ea6c5f
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/mptcp_setsockopt.c
@@ -0,0 +1,32 @@
+#include "bpf_tracing_net.h"
+#include "mptcp_bpf.h"
+
+#ifndef TCP_INQ
+#define TCP_INQ 36
+#endif
+
+int connect_cb_inq_ret;
+int connect_cb_cc_ret;
+
+char cc_reno[TCP_CA_NAME_MAX] = "reno";
+
+SEC("sockops")
+int mptcp_connect_cb(struct bpf_sock_ops *skops)
+{
+	struct bpf_sock *sk = skops->sk;
+	int one = 1;
+
+	if (skops->op != BPF_SOCK_OPS_TCP_CONNECT_CB)
+		return 1;
+
+	if (!sk || sk->protocol != IPPROTO_MPTCP)
+		return 1;
+
+	connect_cb_inq_ret =
+		bpf_setsockopt(skops, SOL_TCP, TCP_INQ, &one, sizeof(one));
+	connect_cb_cc_ret =
+		bpf_setsockopt(skops, SOL_TCP, TCP_CONGESTION,
+			       cc_reno, sizeof(cc_reno));
+
+	return 1;
+}
-- 
2.43.0

Re: [PATCH mptcp-next v3 0/7] mptcp: add bpf_setsockopt support

[MPTCP CI]

Hi Gang,

Thank you for your modifications, that's great!

Our CI did some validations and here is its report:

- KVM Validation: normal (except selftest_mptcp_join): Script error! ❓
- KVM Validation: normal (only selftest_mptcp_join): Script error! ❓
- KVM Validation: debug (except selftest_mptcp_join): Script error! ❓
- KVM Validation: debug (only selftest_mptcp_join): Script error! ❓
- KVM Validation: btf-normal (only bpftest_all): Script error! ❓
- KVM Validation: btf-debug (only bpftest_all): Script error! ❓
- Task: https://github.com/multipath-tcp/mptcp_net-next/actions/runs/30233020793

Initiator: Patchew Applier
Commits: https://github.com/multipath-tcp/mptcp_net-next/commits/acb09ec8b8b1
Patchwork: https://patchwork.kernel.org/project/mptcp/list/?series=1134827


If there are some issues, you can reproduce them using the same environment as
the one used by the CI thanks to a docker image, e.g.:

    $ cd [kernel source code]
    $ docker run -v "${PWD}:${PWD}:rw" -w "${PWD}" --privileged --rm -it \
        --pull always mptcp/mptcp-upstream-virtme-docker:latest \
        auto-normal

For more details:

    https://github.com/multipath-tcp/mptcp-upstream-virtme-docker


Please note that despite all the efforts that have been already done to have a
stable tests suite when executed on a public CI like here, it is possible some
reported issues are not due to your modifications. Still, do not hesitate to
help us improve that ;-)

Cheers,
MPTCP GH Action bot
Bot operated by Matthieu Baerts (NGI0 Core)

Re: [PATCH mptcp-next v3 0/7] mptcp: add bpf_setsockopt support

[Geliang Tang]

Hi Gang,

On Mon, 2026-07-27 at 10:28 +0800, Gang Yan wrote:
> From: Gang Yan <yangang@kylinos.cn>
> 
> Hi, Matt, Geliang, Paolo
> 
> Patch 3-4 have been reviewed by Paolo before, and ready for merge
> [1][2].

Do not put unrelated code into a single series. This series is for
adding bpf_setsockopt support; other patches do not belong here.

> 
> Changelog:
> v3:
>   - Patch 2 keeps the mptcp_setsockopt_all_sf as Geliang suggested.

I recommend that you hold off on sending this patch for now: "Let's
wait until IPV6_TCLASS is merged before posting this patch." Rather
than keeping an unused mptcp_setsockopt_all_sf.

Do not send code that has not passed compilation to the mailing list.

> v2:
>   - Patches 1 and 2 are new in this series; they address TCP_MAXSEG
>     handling in the bpf_setsockopt() path.
>   - Patch 4 adds an early return to fix msk->sk_rcvlowat being
>     unexpectedly modified, an issue seen in v1.
>   - Patch 5 makes the hook safe for the non-tcp master socket: it
> guards
>     bpf_sock_ops_cb_flags_set() with sk_is_tcp() to prevent out-of-
> bounds
>     heap reads/writes through tcp_sk(sk)->bpf_sock_ops_cb_flags, and
> does
>     not set is_locked_tcp_sock for the msk (unlike tcp_call_bpf()).
> That
>     flag authorizes the verifier's direct tcp_sock-offset field
> accesses;
>     since the msk is not a tcp_sock, leaving it at the default 0 is
> safe.
> 
> v1:
>   Link:
> https://patchwork.kernel.org/project/mptcp/cover/20260713095735.1222033-1-gang.yan@linux.dev/
> 
> [1]
> https://patchwork.kernel.org/project/mptcp/patch/20260522-sockopt_lock-v5-2-108629a46e98@kylinos.cn/
> [2]
> https://patchwork.kernel.org/project/mptcp/patch/20260522-sockopt_lock-v5-4-108629a46e98@kylinos.cn/
> 
> Gang Yan (7):
>   mptcp: drop unused @max arg of __mptcp_setsockopt_set_val
>   mptcp: take TCP_MAXSEG handling into __mptcp_setsockopt_set_val
>   mptcp: use sockopt_lock/release_sock in sockopt
>   mptcp: reject sockopt requiring ssks' lock in BPF context
>   mptcp: enable bpf_setsockopt on the master socket
>   mptcp: add TCP_CONNECT_CB sock_ops hook
>   selftests: bpf: verify mptcp bpf_setsockopt from TCP_CONNECT_CB
> 
>  include/net/mptcp.h                           |   9 ++
>  net/core/filter.c                             |  10 ++
>  net/ipv4/tcp.c                                |   1 +
>  net/mptcp/protocol.c                          |   6 +
>  net/mptcp/protocol.h                          |  29 ++++
>  net/mptcp/sockopt.c                           | 127 +++++++++++-----
> --
>  .../testing/selftests/bpf/prog_tests/mptcp.c  |  61 +++++++++
>  .../selftests/bpf/progs/mptcp_setsockopt.c    |  32 +++++
>  8 files changed, 223 insertions(+), 52 deletions(-)
>  create mode 100644
> tools/testing/selftests/bpf/progs/mptcp_setsockopt.c

Re: [PATCH mptcp-next v3 0/7] mptcp: add bpf_setsockopt support

[gang.yan]

July 27, 2026 at 2:04 PM, "Geliang Tang" <geliang@kernel.org mailto:geliang@kernel.org?to=%22Geliang%20Tang%22%20%3Cgeliang%40kernel.org%3E > wrote:


> 
> Hi Gang,
> 
> On Mon, 2026-07-27 at 10:28 +0800, Gang Yan wrote:
> 
> > 
> > From: Gang Yan <yangang@kylinos.cn>
> >  
> >  Hi, Matt, Geliang, Paolo
> >  
> >  Patch 3-4 have been reviewed by Paolo before, and ready for merge
> >  [1][2].
> > 
> Do not put unrelated code into a single series. This series is for
> adding bpf_setsockopt support; other patches do not belong here.
> 
> > 
> > Changelog:
> >  v3:
> >    - Patch 2 keeps the mptcp_setsockopt_all_sf as Geliang suggested.
> > 
> I recommend that you hold off on sending this patch for now: "Let's
> wait until IPV6_TCLASS is merged before posting this patch." Rather
> than keeping an unused mptcp_setsockopt_all_sf.
> 
> Do not send code that has not passed compilation to the mailing list.
>

Hi Geliang
 
I sincerely apologize for the noise. I'll drop this patch and wait for the IPV6_TCLASS merge.

Thanks
Gang
> > 
> > v2:
> >    - Patches 1 and 2 are new in this series; they address TCP_MAXSEG
> >      handling in the bpf_setsockopt() path.
> >    - Patch 4 adds an early return to fix msk->sk_rcvlowat being
> >      unexpectedly modified, an issue seen in v1.
> >    - Patch 5 makes the hook safe for the non-tcp master socket: it
> >  guards
> >      bpf_sock_ops_cb_flags_set() with sk_is_tcp() to prevent out-of-
> >  bounds
> >      heap reads/writes through tcp_sk(sk)->bpf_sock_ops_cb_flags, and
> >  does
> >      not set is_locked_tcp_sock for the msk (unlike tcp_call_bpf()).
> >  That
> >      flag authorizes the verifier's direct tcp_sock-offset field
> >  accesses;
> >      since the msk is not a tcp_sock, leaving it at the default 0 is
> >  safe.
> >  
> >  v1:
> >    Link:
> >  https://patchwork.kernel.org/project/mptcp/cover/20260713095735.1222033-1-gang.yan@linux.dev/
> >  
> >  [1]
> >  https://patchwork.kernel.org/project/mptcp/patch/20260522-sockopt_lock-v5-2-108629a46e98@kylinos.cn/
> >  [2]
> >  https://patchwork.kernel.org/project/mptcp/patch/20260522-sockopt_lock-v5-4-108629a46e98@kylinos.cn/
> >  
> >  Gang Yan (7):
> >    mptcp: drop unused @max arg of __mptcp_setsockopt_set_val
> >    mptcp: take TCP_MAXSEG handling into __mptcp_setsockopt_set_val
> >    mptcp: use sockopt_lock/release_sock in sockopt
> >    mptcp: reject sockopt requiring ssks' lock in BPF context
> >    mptcp: enable bpf_setsockopt on the master socket
> >    mptcp: add TCP_CONNECT_CB sock_ops hook
> >    selftests: bpf: verify mptcp bpf_setsockopt from TCP_CONNECT_CB
> >  
> >   include/net/mptcp.h                           |   9 ++
> >   net/core/filter.c                             |  10 ++
> >   net/ipv4/tcp.c                                |   1 +
> >   net/mptcp/protocol.c                          |   6 +
> >   net/mptcp/protocol.h                          |  29 ++++
> >   net/mptcp/sockopt.c                           | 127 +++++++++++-----
> >  --
> >   .../testing/selftests/bpf/prog_tests/mptcp.c  |  61 +++++++++
> >   .../selftests/bpf/progs/mptcp_setsockopt.c    |  32 +++++
> >   8 files changed, 223 insertions(+), 52 deletions(-)
> >   create mode 100644
> >  tools/testing/selftests/bpf/progs/mptcp_setsockopt.c
> >
>

Re: [PATCH mptcp-next v3 1/7] mptcp: drop unused @max arg of __mptcp_setsockopt_set_val

[Geliang Tang]

On Mon, 2026-07-27 at 10:28 +0800, Gang Yan wrote:
> From: Gang Yan <yangang@kylinos.cn>
> 
> The @max argument is never read in the function body. Remove it and
> the
> MAX_TCP_KEEP* values passed by the TCP_KEEPIDLE/INTVL/KEEPCNT
> callers.

No, we shouldn't drop this "max" argument. Instead, we need to add some
code to check the "val" argument against the "max" argument in
__mptcp_setsockopt_set_val(), something like:

        if (val < 1 || val > max) 
                return -EINVAL;

> 
> Signed-off-by: Gang Yan <yangang@kylinos.cn>
> ---
>  net/mptcp/sockopt.c | 11 ++++-------
>  1 file changed, 4 insertions(+), 7 deletions(-)
> 
> diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c
> index fcf6feb2a9eb..9c4faa0d82ef 100644
> --- a/net/mptcp/sockopt.c
> +++ b/net/mptcp/sockopt.c
> @@ -632,7 +632,7 @@ static int
> mptcp_setsockopt_sol_tcp_congestion(struct mptcp_sock *msk, sockptr_t
>  	return ret;
>  }
>  
> -static int __mptcp_setsockopt_set_val(struct mptcp_sock *msk, int
> max,
> +static int __mptcp_setsockopt_set_val(struct mptcp_sock *msk,
>  				      int (*set_val)(struct sock *,
> int),
>  				      int *msk_val, int val)
>  {
> @@ -876,18 +876,15 @@ static int mptcp_setsockopt_sol_tcp(struct
> mptcp_sock *msk, int optname,
>  		ret = __mptcp_setsockopt_sol_tcp_nodelay(msk, val);
>  		break;
>  	case TCP_KEEPIDLE:
> -		ret = __mptcp_setsockopt_set_val(msk,
> MAX_TCP_KEEPIDLE,
> -						
> &tcp_sock_set_keepidle_locked,
> +		ret = __mptcp_setsockopt_set_val(msk,
> &tcp_sock_set_keepidle_locked,
>  						 &msk-
> >keepalive_idle, val);
>  		break;
>  	case TCP_KEEPINTVL:
> -		ret = __mptcp_setsockopt_set_val(msk,
> MAX_TCP_KEEPINTVL,
> -						
> &tcp_sock_set_keepintvl,
> +		ret = __mptcp_setsockopt_set_val(msk,
> &tcp_sock_set_keepintvl,
>  						 &msk-
> >keepalive_intvl, val);
>  		break;
>  	case TCP_KEEPCNT:
> -		ret = __mptcp_setsockopt_set_val(msk,
> MAX_TCP_KEEPCNT,
> -						
> &tcp_sock_set_keepcnt,
> +		ret = __mptcp_setsockopt_set_val(msk,
> &tcp_sock_set_keepcnt,
>  						 &msk-
> >keepalive_cnt,
>  						 val);
>  		break;

Re: [PATCH mptcp-next v3 2/7] mptcp: take TCP_MAXSEG handling into __mptcp_setsockopt_set_val

[Geliang Tang]

On Mon, 2026-07-27 at 10:28 +0800, Gang Yan wrote:
> From: Gang Yan <yangang@kylinos.cn>
> 
> mptcp_setsockopt_all_sf is only used in 'TCP_MAXSEG', and it can be
> replaced with __mptcp_setsockopt_set_val.
> 
> Signed-off-by: Gang Yan <yangang@kylinos.cn>
> ---
>  net/ipv4/tcp.c      | 1 +
>  net/mptcp/sockopt.c | 5 ++---
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index b427f924608c..5915d0e62f43 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -3830,6 +3830,7 @@ int tcp_sock_set_maxseg(struct sock *sk, int
> val)
>  	WRITE_ONCE(tcp_sk(sk)->rx_opt.user_mss, val);
>  	return 0;
>  }
> +EXPORT_SYMBOL(tcp_sock_set_maxseg);
>  
>  /*
>   *	Socket option code for TCP.
> diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c
> index 9c4faa0d82ef..a7d4135757e7 100644
> --- a/net/mptcp/sockopt.c
> +++ b/net/mptcp/sockopt.c
> @@ -889,9 +889,8 @@ static int mptcp_setsockopt_sol_tcp(struct
> mptcp_sock *msk, int optname,
>  						 val);
>  		break;
>  	case TCP_MAXSEG:
> -		msk->maxseg = val;
> -		ret = mptcp_setsockopt_all_sf(msk, SOL_TCP, optname,
> optval,
> -					      optlen);
> +		ret = __mptcp_setsockopt_set_val(msk,
> &tcp_sock_set_maxseg,
> +						 &msk->maxseg, val);

So, here you do need to pass in MAX_TCP_MAXSEG, and you need to
consider what would be a reasonable value to define it as.

>  		break;
>  	default:
>  		ret = -ENOPROTOOPT;