[RFC PATCH] Bluetooth: l2cap: honor local LE connection interval range

[Kyle Pepper <cochcoder@proton.me>]

Intersect a valid peer request with the locally configured interval
range. Reject disjoint ranges and preserve validation of the original
request before applying local policy.

Assisted-by: OpenCode:gpt-6.1-sol
Signed-off-by: Kyle Pepper <cochcoder@proton.me>
---
Submission review notes (not part of the commit message):
October 12 no-intersection trial accepts [16,24] and completes 30 ms
with STATUS 03 02 18 and normal host TX; the user hears silence. Volume
and multi-day acoustic comparison controls are incomplete. The working
intersection yields 20 ms. Maximum-only rejection failed in kernel 5
and is not this proposal. Generic minimum/range policy and LL-path
consistency remain RFC questions, not established by one renderer.

 net/bluetooth/l2cap_core.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 49a998804..49e201d3e 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -4968,6 +4968,13 @@ static inline int l2cap_conn_param_update_req(struct l2cap_conn *conn,
 	memset(&rsp, 0, sizeof(rsp));
 
 	err = hci_check_conn_params(min, max, latency, to_multiplier);
+	if (!err) {
+		/* Apply local policy only after validating the peer's request. */
+		min = max_t(u16, min, hcon->le_conn_min_interval);
+		max = min_t(u16, max, hcon->le_conn_max_interval);
+		err = hci_check_conn_params(min, max, latency, to_multiplier);
+	}
+
 	if (err)
 		rsp.result = cpu_to_le16(L2CAP_CONN_PARAM_REJECTED);
 	else

base-commit: 964430c038967fd06643e866f68115664e1a1bd1