From patchwork Tue Jun 22 11:14:35 2010 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Gerrit Renker X-Patchwork-Id: 56460 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 95A98B6F0C for ; Tue, 22 Jun 2010 21:27:40 +1000 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753707Ab0FVL1g (ORCPT ); Tue, 22 Jun 2010 07:27:36 -0400 Received: from dee.erg.abdn.ac.uk ([139.133.204.82]:64371 "EHLO erg.abdn.ac.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753419Ab0FVL1f (ORCPT ); Tue, 22 Jun 2010 07:27:35 -0400 Received: from laptev.erg.abdn.ac.uk (Debian-exim@ra-gerrit.erg.abdn.ac.uk [139.133.204.38]) by erg.abdn.ac.uk (8.13.4/8.13.4) with ESMTP id o5MBEZ9M009404 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=NOT); Tue, 22 Jun 2010 12:14:35 +0100 (BST) Received: from root by laptev.erg.abdn.ac.uk with local (Exim 4.69) (envelope-from ) id 1OR1R5-0001X4-8C; Tue, 22 Jun 2010 13:14:35 +0200 From: Gerrit Renker To: davem@davemloft.net Cc: dccp@vger.kernel.org, netdev@vger.kernel.org, Gerrit Renker Subject: [PATCH 2/2] dccp: make implementation of Syn-RTT symmetric Date: Tue, 22 Jun 2010 13:14:35 +0200 Message-Id: <1277205275-5862-3-git-send-email-gerrit@erg.abdn.ac.uk> X-Mailer: git-send-email 1.6.0.rc2 In-Reply-To: <1277205275-5862-2-git-send-email-gerrit@erg.abdn.ac.uk> References: <1277205275-5862-1-git-send-email-gerrit@erg.abdn.ac.uk> <1277205275-5862-2-git-send-email-gerrit@erg.abdn.ac.uk> X-ERG-MailScanner: Found to be clean X-ERG-MailScanner-From: root@erg.abdn.ac.uk X-Spam-Status: No Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 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 --- net/dccp/input.c | 13 +++++++++++-- net/dccp/options.c | 6 +++++- 2 files changed, 16 insertions(+), 3 deletions(-) --- 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 || --- 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;