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authorGerrit Renker <gerrit@erg.abdn.ac.uk>2010-06-22 01:14:35 +0000
committerDavid S. Miller <davem@davemloft.net>2010-06-25 21:33:15 -0700
commit59b80802a8a18b64d38b51aa168253684b2649d5 (patch)
treeb6be92f705d00796733e03e43041605b74d0ce5f /net/dccp
parenta7d13fbf85375698879d16f118af77fbfcc2de44 (diff)
downloadvexpress-lsk-59b80802a8a18b64d38b51aa168253684b2649d5.tar.gz
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')
-rw-r--r--net/dccp/input.c13
-rw-r--r--net/dccp/options.c6
2 files changed, 16 insertions, 3 deletions
diff --git a/net/dccp/input.c b/net/dccp/input.c
index 6beb6a7d6fb..10c957a88f4 100644
--- a/net/dccp/input.c
+++ b/net/dccp/input.c
@@ -430,7 +430,7 @@ static int dccp_rcv_request_sent_state_process(struct sock *sk,
if (dccp_parse_options(sk, NULL, skb))
return 1;
- /* Obtain usec RTT sample from SYN exchange (used by CCID 3) */
+ /* Obtain usec RTT sample from SYN exchange (used by TFRC). */
if (likely(dp->dccps_options_received.dccpor_timestamp_echo))
dp->dccps_syn_rtt = dccp_sample_rtt(sk, 10 * (tstamp -
dp->dccps_options_received.dccpor_timestamp_echo));
@@ -535,6 +535,8 @@ static int dccp_rcv_respond_partopen_state_process(struct sock *sk,
const struct dccp_hdr *dh,
const unsigned len)
{
+ struct dccp_sock *dp = dccp_sk(sk);
+ u32 sample = dp->dccps_options_received.dccpor_timestamp_echo;
int queued = 0;
switch (dh->dccph_type) {
@@ -559,7 +561,14 @@ static int dccp_rcv_respond_partopen_state_process(struct sock *sk,
if (sk->sk_state == DCCP_PARTOPEN)
inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
- dccp_sk(sk)->dccps_osr = DCCP_SKB_CB(skb)->dccpd_seq;
+ /* Obtain usec RTT sample from SYN exchange (used by TFRC). */
+ if (likely(sample)) {
+ long delta = dccp_timestamp() - sample;
+
+ dp->dccps_syn_rtt = dccp_sample_rtt(sk, 10 * delta);
+ }
+
+ dp->dccps_osr = DCCP_SKB_CB(skb)->dccpd_seq;
dccp_set_state(sk, DCCP_OPEN);
if (dh->dccph_type == DCCP_PKT_DATAACK ||
diff --git a/net/dccp/options.c b/net/dccp/options.c
index 4973badb5d5..bfda087bd90 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;