Bluetooth: Send SREJ frames when packets go missing

The ERTM specification lays out three scenarios for sending SREJ
frames to request retransmission of specific frames.  l2cap_send_srej
requests all frames up to a given txseq that are not already queued
for reassembly.  l2cap_send_srej_tail only requests the most recent
missing frame.  l2cap_send_srej_list resends SREJ frames for data that
was requested for resend but never received.

Signed-off-by: Mat Martineau <mathewm@codeaurora.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>

1 files changed, 53 insertions, 3 deletions

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 26963a5e3f5..5823697cf9d 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -2239,17 +2239,67 @@ int l2cap_chan_send(struct l2cap_chan *chan, struct msghdr *msg, size_t len,
 
 static void l2cap_send_srej(struct l2cap_chan *chan, u16 txseq)
 {
-        /* Placeholder */
+        struct l2cap_ctrl control;
+        u16 seq;
+
+        BT_DBG("chan %p, txseq %d", chan, txseq);
+
+        memset(&control, 0, sizeof(control));
+        control.sframe = 1;
+        control.super = L2CAP_SUPER_SREJ;
+
+        for (seq = chan->expected_tx_seq; seq != txseq;
+             seq = __next_seq(chan, seq)) {
+                if (!l2cap_ertm_seq_in_queue(&chan->srej_q, seq)) {
+                        control.reqseq = seq;
+                        l2cap_send_sframe(chan, &control);
+                        l2cap_seq_list_append(&chan->srej_list, seq);
+                }
+        }
+
+        chan->expected_tx_seq = __next_seq(chan, txseq);
 }
 
 static void l2cap_send_srej_tail(struct l2cap_chan *chan)
 {
-        /* Placeholder */
+        struct l2cap_ctrl control;
+
+        BT_DBG("chan %p", chan);
+
+        if (chan->srej_list.tail == L2CAP_SEQ_LIST_CLEAR)
+                return;
+
+        memset(&control, 0, sizeof(control));
+        control.sframe = 1;
+        control.super = L2CAP_SUPER_SREJ;
+        control.reqseq = chan->srej_list.tail;
+        l2cap_send_sframe(chan, &control);
 }
 
 static void l2cap_send_srej_list(struct l2cap_chan *chan, u16 txseq)
 {
-        /* Placeholder */
+        struct l2cap_ctrl control;
+        u16 initial_head;
+        u16 seq;
+
+        BT_DBG("chan %p, txseq %d", chan, txseq);
+
+        memset(&control, 0, sizeof(control));
+        control.sframe = 1;
+        control.super = L2CAP_SUPER_SREJ;
+
+        /* Capture initial list head to allow only one pass through the list. */
+        initial_head = chan->srej_list.head;
+
+        do {
+                seq = l2cap_seq_list_pop(&chan->srej_list);
+                if (seq == txseq || seq == L2CAP_SEQ_LIST_CLEAR)
+                        break;
+
+                control.reqseq = seq;
+                l2cap_send_sframe(chan, &control);
+                l2cap_seq_list_append(&chan->srej_list, seq);
+        } while (chan->srej_list.head != initial_head);
 }
 
 static void l2cap_process_reqseq(struct l2cap_chan *chan, u16 reqseq)