From 59b80802a8a18b64d38b51aa168253684b2649d5 Mon Sep 17 00:00:00 2001 From: Gerrit Renker Date: Tue, 22 Jun 2010 01:14:35 +0000 Subject: 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 Signed-off-by: David S. Miller --- net/dccp/options.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'net/dccp/options.c') 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; -- cgit v1.2.2