From 5d0dbc4a9b2d325458dcbf9a8329bd1d2cc7bd7e Mon Sep 17 00:00:00 2001 From: Gerrit Renker Date: Mon, 27 Nov 2006 20:32:37 -0200 Subject: [PATCH] [DCCP] ccid3: Consolidate handling of t_RTO This patch * removes setting t_RTO in ccid3_hc_tx_init (per [RFC 3448, 4.2], t_RTO is undefined until feedback has been received); * makes some trivial changes (updates of comments); * performs a small optimisation by exploiting that the feedback timeout uses the value of t_ipi. The way it is done is safe, because the timeouts appear after the changes to t_ipi, ensuring that up-to-date values are used; * in ccid3_hc_tx_packet_recv, moves the t_rto statement closer to the calculation of the next_tmout. This makes the code clearer to read and is also safe, since t_rto is not updated until the next call of ccid3_hc_tx_packet_recv, and is not read by the functions called via ccid_wait_for_ccid(); * removes a `max' statement in sk_reset_timer, this is not needed since the timeout value is always greater than 1E6 microseconds. * adds `XXX'es to highlight that currently the nofeedback timer is set in a non-standard way Signed-off-by: Gerrit Renker Acked-by: Ian McDonald Signed-off-by: Arnaldo Carvalho de Melo --- net/dccp/ccids/ccid3.c | 29 ++++++++++++++--------------- 1 file changed, 14 insertions(+), 15 deletions(-) diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c index 4342caf53251..f0ed67c84a55 100644 --- a/net/dccp/ccids/ccid3.c +++ b/net/dccp/ccids/ccid3.c @@ -228,11 +228,10 @@ static void ccid3_hc_tx_no_feedback_timer(unsigned long data) } /* * Schedule no feedback timer to expire in - * max(4 * R, 2 * s / X) + * max(4 * t_RTO, 2 * s/X) = max(4 * t_RTO, 2 * t_ipi) + * XXX This is non-standard, RFC 3448, 4.3 uses 4 * R */ - next_tmout = max_t(u32, hctx->ccid3hctx_t_rto, - 2 * usecs_div(hctx->ccid3hctx_s, - hctx->ccid3hctx_x)); + next_tmout = max(hctx->ccid3hctx_t_rto, 2*hctx->ccid3hctx_t_ipi); break; case TFRC_SSTATE_NO_SENT: DCCP_BUG("Illegal %s state NO_SENT, sk=%p", dccp_role(sk), sk); @@ -460,10 +459,6 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb) "r_sample=%us\n", dccp_role(sk), sk, hctx->ccid3hctx_rtt, r_sample); - /* Update timeout interval */ - hctx->ccid3hctx_t_rto = max_t(u32, 4 * hctx->ccid3hctx_rtt, - USEC_PER_SEC); - /* Update receive rate */ hctx->ccid3hctx_x_recv = x_recv;/* X_recv in bytes per sec */ @@ -491,17 +486,22 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb) &hctx->ccid3hctx_hist, packet); /* * As we have calculated new ipi, delta, t_nom it is possible that - * we now can send a packet, so wake up dccp_wait_for_ccids. + * we now can send a packet, so wake up dccp_wait_for_ccid */ sk->sk_write_space(sk); + + /* Update timeout interval. We use the alternative variant of + * [RFC 3448, 3.1] which sets the upper bound of t_rto to one + * second, as it is suggested for TCP (see RFC 2988, 2.4). */ + hctx->ccid3hctx_t_rto = max_t(u32, 4 * hctx->ccid3hctx_rtt, + USEC_PER_SEC ); /* * Schedule no feedback timer to expire in - * max(4 * R, 2 * s / X) + * max(4 * t_RTO, 2 * s/X) = max(4 * t_RTO, 2 * t_ipi) + * XXX This is non-standard, RFC 3448, 4.3 uses 4 * R */ - next_tmout = max(hctx->ccid3hctx_t_rto, - 2 * usecs_div(hctx->ccid3hctx_s, - hctx->ccid3hctx_x)); + next_tmout = max(hctx->ccid3hctx_t_rto, 2*hctx->ccid3hctx_t_ipi); ccid3_pr_debug("%s, sk=%p, Scheduled no feedback timer to " "expire in %lu jiffies (%luus)\n", @@ -509,7 +509,7 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb) usecs_to_jiffies(next_tmout), next_tmout); sk_reset_timer(sk, &hctx->ccid3hctx_no_feedback_timer, - jiffies + max_t(u32, 1, usecs_to_jiffies(next_tmout))); + jiffies + usecs_to_jiffies(next_tmout)); /* set idle flag */ hctx->ccid3hctx_idle = 1; @@ -607,7 +607,6 @@ static int ccid3_hc_tx_init(struct ccid *ccid, struct sock *sk) /* Set transmission rate to 1 packet per second */ hctx->ccid3hctx_x = hctx->ccid3hctx_s; - hctx->ccid3hctx_t_rto = USEC_PER_SEC; hctx->ccid3hctx_state = TFRC_SSTATE_NO_SENT; INIT_LIST_HEAD(&hctx->ccid3hctx_hist); -- 2.20.1