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authorJames Chapman <jchapman@katalix.com>2013-07-02 20:29:00 +0100
committerDavid S. Miller <davem@davemloft.net>2013-07-02 16:33:25 -0700
commita0dbd822273ce7660bf35525d61d7a8ac5e679a3 (patch)
tree3f5187519c078bfa265654239854ab0a41597719 /net/l2tp/l2tp_core.c
parent8a1631d588a39e826f4248e60310498d5266c6fa (diff)
downloadlinux-a0dbd822273ce7660bf35525d61d7a8ac5e679a3.tar.bz2
l2tp: make datapath resilient to packet loss when sequence numbers enabled
If L2TP data sequence numbers are enabled and reordering is not enabled, data reception stops if a packet is lost since the kernel waits for a sequence number that is never resent. (When reordering is enabled, data reception restarts when the reorder timeout expires.) If no reorder timeout is set, we should count the number of in-sequence packets after the out-of-sequence (OOS) condition is detected, and reset sequence number state after a number of such packets are received. For now, the number of in-sequence packets while in OOS state which cause the sequence number state to be reset is hard-coded to 5. This could be configurable later. Signed-off-by: James Chapman <jchapman@katalix.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/l2tp/l2tp_core.c')
-rw-r--r--net/l2tp/l2tp_core.c36
1 files changed, 31 insertions, 5 deletions
diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index 735cc06971ef..feae495a0a30 100644
--- 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);