This implements TFRC faster restart as per: draft-ietf-dccp-tfrc-faster-restart-03.txt and with changes from: http://www3.ietf.org/proceedings/07jul/slides/dccp-6.pdf Most notably we don't do pings. Signed-off-by: Ian McDonald <ian.mcdonald@xxxxxxxxxxx> --- diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c index 6a6dc63..55f675f 100644 --- a/net/dccp/ccids/ccid3.c +++ b/net/dccp/ccids/ccid3.c @@ -88,9 +88,12 @@ static void ccid3_hc_tx_set_state(struct sock *sk, static inline u64 rfc3390_initial_rate(struct sock *sk) { const struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk); - const __u32 w_init = min_t(__u32, 4 * hctx->ccid3hctx_s, + __u32 w_init = min_t(__u32, 4 * hctx->ccid3hctx_s, max_t(__u32, 2 * hctx->ccid3hctx_s, 4380)); + if (ccid3_hc_tx_faster_restart_on(ccid3_hc_tx_sk(sk))) + w_init *= 2; + return scaled_div(w_init << 6, hctx->ccid3hctx_rtt); } @@ -121,6 +124,29 @@ static u32 ccid3_hc_tx_idle_rtt(struct ccid3_hc_tx_sock *hctx, ktime_t now) } /** + * ccid3_hc_tx_fr_loss - indicate if loss for faster restart + * + * According to draft-ietf-dccp-tfrc-faster-restart-03.txt section 3.2 + * we can say there is a loss if loss rate has increased in last two + * feedback packets + * + */ + +static bool ccid3_hc_tx_fr_loss(const struct ccid3_hc_tx_sock *hctx) +{ + if (hctx->ccid3hctx_p_prev1 > hctx->ccid3hctx_p_prev2) + return true; + + if (hctx->ccid3hctx_p > hctx->ccid3hctx_p_prev2) + return true; + + if (hctx->ccid3hctx_p > hctx->ccid3hctx_p_prev1) + return true; + + return false; +} + +/** * ccid3_hc_tx_update_x - Update allowed sending rate X * @stamp: most recent time if available - can be left NULL. * This function tracks draft rfc3448bis, check there for latest details. @@ -130,13 +156,13 @@ static u32 ccid3_hc_tx_idle_rtt(struct ccid3_hc_tx_sock *hctx, ktime_t now) * throughout the code. Only X_calc is unscaled (in bytes/second). * */ -static void ccid3_hc_tx_update_x(struct sock *sk, ktime_t *stamp) - +static void ccid3_hc_tx_update_x(struct sock *sk, ktime_t *stamp, bool nofeedback) { struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk); __u64 min_rate = 2 * hctx->ccid3hctx_x_recv; const __u64 old_x = hctx->ccid3hctx_x; ktime_t now = stamp? *stamp : ktime_get_real(); + u64 x_fast_max; /* * Handle IDLE periods: do not reduce below RFC3390 initial sending rate @@ -149,14 +175,36 @@ static void ccid3_hc_tx_update_x(struct sock *sk, ktime_t *stamp) min_rate = max(min_rate, 2 * hctx->ccid3hctx_x_recv); } - if (hctx->ccid3hctx_p > 0) { + if (ccid3_hc_tx_faster_restart_on(hctx) && !nofeedback) + if (hctx->ccid3hctx_p > 0) { + x_fast_max = hctx->ccid3hctx_x_active_recv; + /* FIXME We should interpolate here but this is under + * discussion and doesn't affect my research IAM */ + if (!ccid3_hc_tx_fr_loss(hctx) && + (hctx->ccid3hctx_x_recv > x_fast_max)) { + x_fast_max = hctx->ccid3hctx_x_recv; + hctx->ccid3hctx_x_active_recv = x_fast_max; + hctx->ccid3hctx_t_active_recv = now; + } else if (ccid3_hc_tx_fr_loss(hctx) && + (hctx->ccid3hctx_x_recv < x_fast_max)) { + x_fast_max = hctx->ccid3hctx_x_recv / 2; + hctx->ccid3hctx_x_active_recv = x_fast_max; + hctx->ccid3hctx_t_active_recv = now; + } + if (min_rate < x_fast_max) + min_rate = min(2*min_rate, x_fast_max); + /* We double again for faster rate */ + /* FIXME - draft refers to X_recv_set but base + * implementation doesn't use this so we stay + * consistent with this IAM */ + } + if (hctx->ccid3hctx_p > 0) { hctx->ccid3hctx_x = min(((__u64)hctx->ccid3hctx_x_calc) << 6, min_rate); hctx->ccid3hctx_x = max(hctx->ccid3hctx_x, (((__u64)hctx->ccid3hctx_s) << 6) / TFRC_T_MBI); - } else if (ktime_us_delta(now, hctx->ccid3hctx_t_ld) - (s64)hctx->ccid3hctx_rtt >= 0) { @@ -220,6 +268,9 @@ static void ccid3_hc_tx_no_feedback_timer(unsigned long data) struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk); unsigned long t_nfb = USEC_PER_SEC / 5; + /* FIXME Section 4.2 of Faster restart should really + * be implemented in here IAM */ + bh_lock_sock(sk); if (sock_owned_by_user(sk)) { /* Try again later. */ @@ -268,7 +319,7 @@ static void ccid3_hc_tx_no_feedback_timer(unsigned long data) hctx->ccid3hctx_x_recv = hctx->ccid3hctx_x_calc; hctx->ccid3hctx_x_recv <<= 4; } - ccid3_hc_tx_update_x(sk, NULL); + ccid3_hc_tx_update_x(sk, NULL, true); } ccid3_pr_debug("Reduced X to %llu/64 bytes/sec\n", (unsigned long long)hctx->ccid3hctx_x); @@ -324,6 +375,13 @@ static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb) hctx->ccid3hctx_s = skb->len; + hctx->ccid3hctx_p_prev2 = 0; + hctx->ccid3hctx_p_prev1 = 0; + hctx->ccid3hctx_p = 0; + hctx->ccid3hctx_t_active_recv = now; + hctx->ccid3hctx_x_active_recv = 0; + /* we initialise above for faster restart */ + /* * Use initial RTT sample when available: recommended by erratum * to RFC 4342. This implements the initialisation procedure of @@ -423,6 +481,8 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb) /* Update loss event rate (scaled by 1e6), cf. RFC 4342, 8.5 */ pinv = opt_recv->ccid3or_loss_event_rate; + hctx->ccid3hctx_p_prev2 = hctx->ccid3hctx_p_prev1; + hctx->ccid3hctx_p_prev1 = hctx->ccid3hctx_p; hctx->ccid3hctx_p = (pinv == ~0U || pinv == 0)? 0 : scaled_div(1, pinv); /* @@ -462,7 +522,7 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb) hctx->ccid3hctx_x_calc = tfrc_calc_x(hctx->ccid3hctx_s, hctx->ccid3hctx_rtt, hctx->ccid3hctx_p); - ccid3_hc_tx_update_x(sk, &now); + ccid3_hc_tx_update_x(sk, &now, false); done_computing_x: ccid3_pr_debug("%s(%p), RTT=%uus (sample=%uus), s=%u, p=%u, X_calc=%u, " - To unsubscribe from this list: send the line "unsubscribe dccp" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
