l2tp: make datapath resilient to packet loss when sequence numbers enabled

[karo-tx-linux.git] / net / l2tp / l2tp_core.c

diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index 735cc06971ef7a911eaa0778531e78db058f70b1..feae495a0a30accd9eb5a88baf1c23095bb38d66 100644 (file)
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -572,12 +572,33 @@ static int l2tp_recv_data_seq(struct l2tp_session *session, struct sk_buff *skb)
                 * reorder queue, in order of ns.
                 */
                l2tp_recv_queue_skb(session, skb);
+               goto out;
+       }
+
+       /* Packet reordering disabled. Discard out-of-sequence packets, while
+        * tracking the number if in-sequence packets after the first OOS packet
+        * is seen. After nr_oos_count_max in-sequence packets, reset the
+        * sequence number to re-enable packet reception.
+        */
+       if (L2TP_SKB_CB(skb)->ns == session->nr) {
+               skb_queue_tail(&session->reorder_q, skb);
        } else {
-               /* Packet reordering disabled. Discard out-of-sequence
-                * packets
-                */
-               if ((L2TP_SKB_CB(skb)->ns != session->nr) &&
-                   (!session->reorder_skip)) {
+               u32 nr_oos = L2TP_SKB_CB(skb)->ns;
+               u32 nr_next = (session->nr_oos + 1) & session->nr_max;
+
+               if (nr_oos == nr_next)
+                       session->nr_oos_count++;
+               else
+                       session->nr_oos_count = 0;
+
+               session->nr_oos = nr_oos;
+               if (session->nr_oos_count > session->nr_oos_count_max) {
+                       session->reorder_skip = 1;
+                       l2tp_dbg(session, L2TP_MSG_SEQ,
+                                "%s: %d oos packets received. Resetting sequence numbers\n",
+                                session->name, session->nr_oos_count);
+               }
+               if (!session->reorder_skip) {
                        atomic_long_inc(&session->stats.rx_seq_discards);
                        l2tp_dbg(session, L2TP_MSG_SEQ,
                                 "%s: oos pkt %u len %d discarded, waiting for %u, reorder_q_len=%d\n",
@@ -589,6 +610,7 @@ static int l2tp_recv_data_seq(struct l2tp_session *session, struct sk_buff *skb)
                skb_queue_tail(&session->reorder_q, skb);
        }
 
+out:
        return 0;
 
 discard:
@@ -1852,6 +1874,10 @@ struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunn
                else
                        session->nr_max = 0xffffff;
                session->nr_window_size = session->nr_max / 2;
+               session->nr_oos_count_max = 4;
+
+               /* Use NR of first received packet */
+               session->reorder_skip = 1;
 
                sprintf(&session->name[0], "sess %u/%u",
                        tunnel->tunnel_id, session->session_id);