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dccp: make implementation of Syn-RTT symmetric

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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>
This commit is contained in:
Gerrit Renker 2010-06-22 01:14:35 +00:00 • committed by David S. Miller
parent a7d13fbf85
commit 59b80802a8
2 changed files with 16 additions and 3 deletions
Download patch file Download diff file Expand all files Collapse all files

6
net/dccp/options.c
View file

@ -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;