diff mbox series

[net-next,v2,3/8] mptcp: sockopt: info: stop early if no buffer

Message ID 20240514011335.176158-4-martineau@kernel.org (mailing list archive)
State Accepted
Commit ce5f6f71b029f6a96267a7d876da4a055d7d1611
Delegated to: Netdev Maintainers
Headers show
Series mptcp: small improvements, fix and clean-ups | expand

Checks

Context Check Description
netdev/tree_selection success Clearly marked for net-next
netdev/apply success Patch already applied to net-next-0

Commit Message

Mat Martineau May 14, 2024, 1:13 a.m. UTC 
From: "Matthieu Baerts (NGI0)" <matttbe@kernel.org>

Up to recently, it has been recommended to use getsockopt(MPTCP_INFO) to
check if a fallback to TCP happened, or if the client requested to use
MPTCP.

In this case, the userspace app is only interested by the returned value
of the getsocktop() call, and can then give 0 for the option length, and
NULL for the buffer address. An easy optimisation is then to stop early,
and avoid filling a local buffer -- which now requires two different
locks -- if it is not needed.

Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Mat Martineau <martineau@kernel.org>
---
 net/mptcp/sockopt.c | 4 ++++
 1 file changed, 4 insertions(+)
diff mbox series

Patch

diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c
index fcca9433c858..a77b33488176 100644
--- a/net/mptcp/sockopt.c
+++ b/net/mptcp/sockopt.c
@@ -999,6 +999,10 @@  static int mptcp_getsockopt_info(struct mptcp_sock *msk, char __user *optval, in
 	if (get_user(len, optlen))
 		return -EFAULT;
 
+	/* When used only to check if a fallback to TCP happened. */
+	if (len == 0)
+		return 0;
+
 	len = min_t(unsigned int, len, sizeof(struct mptcp_info));
 
 	mptcp_diag_fill_info(msk, &m_info);