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authorTuong Lien <tuong.t.lien@dektech.com.au>2019-04-04 11:09:52 +0700
committerDavid S. Miller <davem@davemloft.net>2019-04-04 18:29:25 -0700
commit382f598fb66b14a8451f2794abf70ea7b5826c96 (patch)
tree5d25199c0053b40e74a797c16c2d17dfe29d4479 /net/tipc/msg.h
parent9195948fbf3406f75b1f133ddb57304169c44341 (diff)
tipc: reduce duplicate packets for unicast traffic
For unicast transmission, the current NACK sending althorithm is over- active that forces the sending side to retransmit a packet that is not really lost but just arrived at the receiving side with some delay, or even retransmit same packets that have already been retransmitted before. As a result, many duplicates are observed also under normal condition, ie. without packet loss. One example case is: node1 transmits 1 2 3 4 10 5 6 7 8 9, when node2 receives packet #10, it puts into the deferdq. When the packet #5 comes it sends NACK with gap [6 - 9]. However, shortly after that, when packet #6 arrives, it pulls out packet #10 from the deferfq, but it is still out of order, so it makes another NACK with gap [7 - 9] and so on ... Finally, node1 has to retransmit the packets 5 6 7 8 9 a number of times, but in fact all the packets are not lost at all, so duplicates! This commit reduces duplicates by changing the condition to send NACK, also restricting the retransmissions on individual packets via a timer of about 1ms. However, it also needs to say that too tricky condition for NACKs or too long timeout value for retransmissions will result in performance reducing! The criterias in this commit are found to be effective for both the requirements to reduce duplicates but not affect performance. The tipc_link_rcv() is also improved to only dequeue skb from the link deferdq if it is expected (ie. its seqno <= rcv_nxt). Acked-by: Ying Xue <ying.xue@windriver.com> Acked-by: Jon Maloy <jon.maloy@ericsson.com> Signed-off-by: Tuong Lien <tuong.t.lien@dektech.com.au> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/tipc/msg.h')
-rw-r--r--net/tipc/msg.h21
1 files changed, 21 insertions, 0 deletions
diff --git a/net/tipc/msg.h b/net/tipc/msg.h
index ec5c511a9c9c..8de02ad6e352 100644
--- a/net/tipc/msg.h
+++ b/net/tipc/msg.h
@@ -1151,4 +1151,25 @@ static inline void tipc_skb_queue_splice_tail_init(struct sk_buff_head *list,
tipc_skb_queue_splice_tail(&tmp, head);
}
+/* __tipc_skb_dequeue() - dequeue the head skb according to expected seqno
+ * @list: list to be dequeued from
+ * @seqno: seqno of the expected msg
+ *
+ * returns skb dequeued from the list if its seqno is less than or equal to
+ * the expected one, otherwise the skb is still hold
+ *
+ * Note: must be used with appropriate locks held only
+ */
+static inline struct sk_buff *__tipc_skb_dequeue(struct sk_buff_head *list,
+ u16 seqno)
+{
+ struct sk_buff *skb = skb_peek(list);
+
+ if (skb && less_eq(buf_seqno(skb), seqno)) {
+ __skb_unlink(skb, list);
+ return skb;
+ }
+ return NULL;
+}
+
#endif