aboutsummaryrefslogtreecommitdiffstats
path: root/net/tipc
diff options
context:
space:
mode:
authorJon Paul Maloy <jon.maloy@ericsson.com>2015-03-25 12:07:26 -0400
committerDavid S. Miller <davem@davemloft.net>2015-03-25 14:05:56 -0400
commit8b4ed8634f8b3f9aacfc42b4a872d30c36b9e255 (patch)
treea53fedc6a39f617600e4aebf4957d67195d7a37a /net/tipc
parent3127a0200d4a46cf279bb388cc0f71827cd60699 (diff)
tipc: eliminate race condition at dual link establishment
Despite recent improvements, the establishment of dual parallel links still has a small glitch where messages can bypass each other. When the second link in a dual-link configuration is established, part of the first link's traffic will be steered over to the new link. Although we do have a mechanism to ensure that packets sent before and after the establishment of the new link arrive in sequence to the destination node, this is not enough. The arriving messages will still be delivered upwards in different threads, something entailing a risk of message disordering during the transition phase. To fix this, we introduce a synchronization mechanism between the two parallel links, so that traffic arriving on the new link cannot be added to its input queue until we are guaranteed that all pre-establishment messages have been delivered on the old, parallel link. This problem seems to always have been around, but its occurrence is so rare that it has not been noticed until recent intensive testing. Reviewed-by: Ying Xue <ying.xue@windriver.com> Reviewed-by: Erik Hugne <erik.hugne@ericsson.com> Signed-off-by: Jon Maloy <jon.maloy@ericsson.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/tipc')
-rw-r--r--net/tipc/link.c45
-rw-r--r--net/tipc/link.h2
-rw-r--r--net/tipc/msg.h8
3 files changed, 55 insertions, 0 deletions
diff --git a/net/tipc/link.c b/net/tipc/link.c
index 58e2460682da..1287161e9424 100644
--- a/net/tipc/link.c
+++ b/net/tipc/link.c
@@ -139,6 +139,13 @@ static void tipc_link_put(struct tipc_link *l_ptr)
kref_put(&l_ptr->ref, tipc_link_release);
}
+static struct tipc_link *tipc_parallel_link(struct tipc_link *l)
+{
+ if (l->owner->active_links[0] != l)
+ return l->owner->active_links[0];
+ return l->owner->active_links[1];
+}
+
static void link_init_max_pkt(struct tipc_link *l_ptr)
{
struct tipc_node *node = l_ptr->owner;
@@ -1026,6 +1033,32 @@ void tipc_link_retransmit(struct tipc_link *l_ptr, struct sk_buff *skb,
}
}
+/* link_synch(): check if all packets arrived before the synch
+ * point have been consumed
+ * Returns true if the parallel links are synched, otherwise false
+ */
+static bool link_synch(struct tipc_link *l)
+{
+ unsigned int post_synch;
+ struct tipc_link *pl;
+
+ pl = tipc_parallel_link(l);
+ if (pl == l)
+ goto synched;
+
+ /* Was last pre-synch packet added to input queue ? */
+ if (less_eq(pl->next_in_no, l->synch_point))
+ return false;
+
+ /* Is it still in the input queue ? */
+ post_synch = mod(pl->next_in_no - l->synch_point) - 1;
+ if (skb_queue_len(&pl->inputq) > post_synch)
+ return false;
+synched:
+ l->flags &= ~LINK_SYNCHING;
+ return true;
+}
+
static void link_retrieve_defq(struct tipc_link *link,
struct sk_buff_head *list)
{
@@ -1156,6 +1189,14 @@ void tipc_rcv(struct net *net, struct sk_buff *skb, struct tipc_bearer *b_ptr)
skb = NULL;
goto unlock;
}
+ /* Synchronize with parallel link if applicable */
+ if (unlikely((l_ptr->flags & LINK_SYNCHING) && !msg_dup(msg))) {
+ link_handle_out_of_seq_msg(l_ptr, skb);
+ if (link_synch(l_ptr))
+ link_retrieve_defq(l_ptr, &head);
+ skb = NULL;
+ goto unlock;
+ }
l_ptr->next_in_no++;
if (unlikely(!skb_queue_empty(&l_ptr->deferdq)))
link_retrieve_defq(l_ptr, &head);
@@ -1231,6 +1272,10 @@ static void tipc_link_input(struct tipc_link *link, struct sk_buff *skb)
switch (msg_user(msg)) {
case CHANGEOVER_PROTOCOL:
+ if (msg_dup(msg)) {
+ link->flags |= LINK_SYNCHING;
+ link->synch_point = msg_seqno(msg_get_wrapped(msg));
+ }
if (!tipc_link_tunnel_rcv(node, &skb))
break;
if (msg_user(buf_msg(skb)) != MSG_BUNDLER) {
diff --git a/net/tipc/link.h b/net/tipc/link.h
index 99543a46095a..d2b5663643da 100644
--- a/net/tipc/link.h
+++ b/net/tipc/link.h
@@ -60,6 +60,7 @@
*/
#define LINK_STARTED 0x0001
#define LINK_STOPPED 0x0002
+#define LINK_SYNCHING 0x0004
/* Starting value for maximum packet size negotiation on unicast links
* (unless bearer MTU is less)
@@ -170,6 +171,7 @@ struct tipc_link {
/* Changeover */
u32 exp_msg_count;
u32 reset_checkpoint;
+ u32 synch_point;
/* Max packet negotiation */
u32 max_pkt;
diff --git a/net/tipc/msg.h b/net/tipc/msg.h
index 6445db09c0c4..d273207ede28 100644
--- a/net/tipc/msg.h
+++ b/net/tipc/msg.h
@@ -554,6 +554,14 @@ static inline void msg_set_node_capabilities(struct tipc_msg *m, u32 n)
msg_set_bits(m, 1, 15, 0x1fff, n);
}
+static inline bool msg_dup(struct tipc_msg *m)
+{
+ if (likely(msg_user(m) != CHANGEOVER_PROTOCOL))
+ return false;
+ if (msg_type(m) != DUPLICATE_MSG)
+ return false;
+ return true;
+}
/*
* Word 2

Privacy Policy