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authorGerrit Renker <gerrit@erg.abdn.ac.uk>2010-06-22 05:14:35 +0400
committerDavid S. Miller <davem@davemloft.net>2010-06-26 08:33:15 +0400
commit59b80802a8a18b64d38b51aa168253684b2649d5 (patch)
treeb6be92f705d00796733e03e43041605b74d0ce5f /net/dccp/options.c
parenta7d13fbf85375698879d16f118af77fbfcc2de44 (diff)
downloadlinux-59b80802a8a18b64d38b51aa168253684b2649d5.tar.xz
dccp: make implementation of Syn-RTT symmetric
This patch is thanks to Andre Noll who reported the issue and helped testing. The Syn-RTT sampled during the initial handshake currently only works for the client sending the DCCP-Request. TFRC penalizes the absence of an RTT sample with a very slow initial speed (1 packet per second), which delays slow-start significantly, resulting in sluggish performance. This patch mirrors the "Syn RTT" principle by adding a timestamp also onto the DCCP-Response, producing an RTT sample when the (Data)Ack completing the handshake arrives. Also changed the documentation to 'TFRC' since Syn RTTs are also used by CCID-4. Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/dccp/options.c')
-rw-r--r--net/dccp/options.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/net/dccp/options.c b/net/dccp/options.c
index 4973badb5d55..bfda087bd90d 100644
--- a/net/dccp/options.c
+++ b/net/dccp/options.c
@@ -529,7 +529,7 @@ int dccp_insert_options(struct sock *sk, struct sk_buff *skb)
if (DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_REQUEST) {
/*
* Obtain RTT sample from Request/Response exchange.
- * This is currently used in CCID 3 initialisation.
+ * This is currently used for TFRC initialisation.
*/
if (dccp_insert_option_timestamp(skb))
return -1;
@@ -562,6 +562,10 @@ int dccp_insert_options_rsk(struct dccp_request_sock *dreq, struct sk_buff *skb)
if (dccp_feat_insert_opts(NULL, dreq, skb))
return -1;
+ /* Obtain RTT sample from Response/Ack exchange (used by TFRC). */
+ if (dccp_insert_option_timestamp(skb))
+ return -1;
+
if (dreq->dreq_timestamp_echo != 0 &&
dccp_insert_option_timestamp_echo(NULL, dreq, skb))
return -1;