From f8ecb1142c7bfe06c09809b017c6c9d145930404 Mon Sep 17 00:00:00 2001
From: Matthias Ringwald <matthias@ringwald.ch>
Date: Mon, 30 Sep 2019 14:38:37 +0200
Subject: [PATCH] l2cap-ertm: on information response verify ertm requirements
 for outgoing connection only

---
 src/l2cap.c | 46 +++++++++++++++++++++++++++-------------------
 1 file changed, 27 insertions(+), 19 deletions(-)

diff --git a/src/l2cap.c b/src/l2cap.c
index afc4d1b64..96080fdba 100644
--- a/src/l2cap.c
+++ b/src/l2cap.c
@@ -2865,31 +2865,39 @@ static void l2cap_signaling_handler_dispatch(hci_con_handle_t handle, uint8_t *
                 l2cap_channel_t * channel = (l2cap_channel_t *) btstack_linked_list_iterator_next(&it);
                 if (!l2cap_is_dynamic_channel_type(channel->channel_type)) continue;
                 if (channel->con_handle != handle) continue;
-                // bail if ERTM was requested but is not supported
-                if ((channel->mode == L2CAP_CHANNEL_MODE_ENHANCED_RETRANSMISSION) && ((connection->l2cap_state.extended_feature_mask & 0x08) == 0)){
-                    if (channel->ertm_mandatory){
-                        // channel closed
-                        channel->state = L2CAP_STATE_CLOSED;
-                        // map l2cap connection response result to BTstack status enumeration
-                        l2cap_handle_channel_open_failed(channel, L2CAP_CONNECTION_RESPONSE_RESULT_ERTM_NOT_SUPPORTED);
-                        // discard channel
-                        btstack_linked_list_remove(&l2cap_channels, (btstack_linked_item_t *) channel);
-                        l2cap_free_channel_entry(channel);
-                        continue;
+
+                // incoming connection: ask user for channel configuration, esp. if ertm will be mandatory
+                if (channel->state == L2CAP_STATE_WAIT_INCOMING_EXTENDED_FEATURES){
+                    channel->state = L2CAP_STATE_WAIT_CLIENT_ACCEPT_OR_REJECT;
+                    l2cap_emit_incoming_connection(channel);
+                    continue;
+                }
+
+                // outgoing connection
+                if (channel->state == L2CAP_STATE_WAIT_OUTGOING_EXTENDED_FEATURES){
+
+                    // verify ERTM requirements
+                    if ((channel->mode == L2CAP_CHANNEL_MODE_ENHANCED_RETRANSMISSION) && ((connection->l2cap_state.extended_feature_mask & 0x08) == 0)){
+                        // bail if ERTM was requested but is not supported
+                        if (channel->ertm_mandatory){
+                            // channel closed
+                            channel->state = L2CAP_STATE_CLOSED;
+                            // map l2cap connection response result to BTstack status enumeration
+                            l2cap_handle_channel_open_failed(channel, L2CAP_CONNECTION_RESPONSE_RESULT_ERTM_NOT_SUPPORTED);
+                            // discard channel
+                            btstack_linked_list_remove(&l2cap_channels, (btstack_linked_item_t *) channel);
+                            l2cap_free_channel_entry(channel);
+                            continue;
+                        }
                     } else {
                         // fallback to Basic mode
                         l2cap_emit_simple_event_with_cid(channel, L2CAP_EVENT_ERTM_BUFFER_RELEASED);
                         channel->mode = L2CAP_CHANNEL_MODE_BASIC;
                     }
-                }
-                // start connecting
-                if (channel->state == L2CAP_STATE_WAIT_OUTGOING_EXTENDED_FEATURES){
+
+                    // respond to connection request
                     channel->state = L2CAP_STATE_WILL_SEND_CONNECTION_REQUEST;
-                }
-                // respond to connection request
-                if (channel->state == L2CAP_STATE_WAIT_INCOMING_EXTENDED_FEATURES){
-                    channel->state = L2CAP_STATE_WAIT_CLIENT_ACCEPT_OR_REJECT;
-                    l2cap_emit_incoming_connection(channel);
+                    continue;
                 }
             }
             return;