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authorJames Chapman <jchapman@katalix.com>2013-07-02 20:28:59 +0100
committerDavid S. Miller <davem@davemloft.net>2013-07-02 16:33:24 -0700
commit8a1631d588a39e826f4248e60310498d5266c6fa (patch)
treed4bc90f912c4f54a3becf34c2d8a7f35d2c605c6 /net
parentb6dc01a43aaca24e6e6928e24d9b37ba599f1e3c (diff)
l2tp: make datapath sequence number support RFC-compliant
The L2TP datapath is not currently RFC-compliant when sequence numbers are used in L2TP data packets. According to the L2TP RFC, any received sequence number NR greater than or equal to the next expected NR is acceptable, where the "greater than or equal to" test is determined by the NR wrap point. This differs for L2TPv2 and L2TPv3, so add state in the session context to hold the max NR value and the NR window size in order to do the acceptable sequence number value check. These might be configurable later, but for now we derive it from the tunnel L2TP version, which determines the sequence number field size. Signed-off-by: James Chapman <jchapman@katalix.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/l2tp/l2tp_core.c36
-rw-r--r--net/l2tp/l2tp_core.h2
2 files changed, 33 insertions, 5 deletions
diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index 5ca29659171d..735cc06971ef 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -414,10 +414,7 @@ static void l2tp_recv_dequeue_skb(struct l2tp_session *session, struct sk_buff *
if (L2TP_SKB_CB(skb)->has_seq) {
/* Bump our Nr */
session->nr++;
- if (tunnel->version == L2TP_HDR_VER_2)
- session->nr &= 0xffff;
- else
- session->nr &= 0xffffff;
+ session->nr &= session->nr_max;
l2tp_dbg(session, L2TP_MSG_SEQ, "%s: updated nr to %hu\n",
session->name, session->nr);
@@ -542,11 +539,34 @@ static inline int l2tp_verify_udp_checksum(struct sock *sk,
return __skb_checksum_complete(skb);
}
+static int l2tp_seq_check_rx_window(struct l2tp_session *session, u32 nr)
+{
+ u32 nws;
+
+ if (nr >= session->nr)
+ nws = nr - session->nr;
+ else
+ nws = (session->nr_max + 1) - (session->nr - nr);
+
+ return nws < session->nr_window_size;
+}
+
/* If packet has sequence numbers, queue it if acceptable. Returns 0 if
* acceptable, else non-zero.
*/
static int l2tp_recv_data_seq(struct l2tp_session *session, struct sk_buff *skb)
{
+ if (!l2tp_seq_check_rx_window(session, L2TP_SKB_CB(skb)->ns)) {
+ /* Packet sequence number is outside allowed window.
+ * Discard it.
+ */
+ l2tp_dbg(session, L2TP_MSG_SEQ,
+ "%s: pkt %u len %d discarded, outside window, nr=%u\n",
+ session->name, L2TP_SKB_CB(skb)->ns,
+ L2TP_SKB_CB(skb)->length, session->nr);
+ goto discard;
+ }
+
if (session->reorder_timeout != 0) {
/* Packet reordering enabled. Add skb to session's
* reorder queue, in order of ns.
@@ -556,7 +576,8 @@ static int l2tp_recv_data_seq(struct l2tp_session *session, struct sk_buff *skb)
/* Packet reordering disabled. Discard out-of-sequence
* packets
*/
- if (L2TP_SKB_CB(skb)->ns != session->nr) {
+ if ((L2TP_SKB_CB(skb)->ns != session->nr) &&
+ (!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",
@@ -1826,6 +1847,11 @@ struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunn
session->session_id = session_id;
session->peer_session_id = peer_session_id;
session->nr = 0;
+ if (tunnel->version == L2TP_HDR_VER_2)
+ session->nr_max = 0xffff;
+ else
+ session->nr_max = 0xffffff;
+ session->nr_window_size = session->nr_max / 2;
sprintf(&session->name[0], "sess %u/%u",
tunnel->tunnel_id, session->session_id);
diff --git a/net/l2tp/l2tp_core.h b/net/l2tp/l2tp_core.h
index 485a490fd990..4b9a3b724423 100644
--- a/net/l2tp/l2tp_core.h
+++ b/net/l2tp/l2tp_core.h
@@ -102,6 +102,8 @@ struct l2tp_session {
u32 nr; /* session NR state (receive) */
u32 ns; /* session NR state (send) */
struct sk_buff_head reorder_q; /* receive reorder queue */
+ u32 nr_max; /* max NR. Depends on tunnel */
+ u32 nr_window_size; /* NR window size */
struct hlist_node hlist; /* Hash list node */
atomic_t ref_count;