diff options
author | Gerrit Renker <gerrit@erg.abdn.ac.uk> | 2008-09-04 07:30:19 +0200 |
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committer | Gerrit Renker <gerrit@erg.abdn.ac.uk> | 2008-09-04 07:45:41 +0200 |
commit | 2b81143aa3505e2460b24b357996c2f21840ea58 (patch) | |
tree | 37f752fb85c563f965655cec834bb289fd831137 /net/dccp/ccids/lib | |
parent | dccp ccid-3: Remove duplicate RX states (diff) | |
download | linux-2b81143aa3505e2460b24b357996c2f21840ea58.tar.xz linux-2b81143aa3505e2460b24b357996c2f21840ea58.zip |
dccp ccid-3: Always perform receiver RTT sampling
This updates the CCID-3 receiver in part with regard to errata 610 and 611
(http://www.rfc-editor.org/errata_list.php), which change RFC 4342 to use the
Receive Rate as specified in rfc3448bis, requiring to constantly sample the
RTT (or use a sender RTT).
Doing this requires reusing the RX history structure after dealing with a loss.
The patch does not resolve how to compute X_recv if the interval is less
than 1 RTT. A FIXME has been added (and is resolved in subsequent patch).
Furthermore, since this is all TFRC-based functionality, the RTT estimation
is now also performed by the dccp_tfrc_lib module. This further simplifies
the CCID-3 code.
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Diffstat (limited to 'net/dccp/ccids/lib')
-rw-r--r-- | net/dccp/ccids/lib/packet_history.c | 60 | ||||
-rw-r--r-- | net/dccp/ccids/lib/packet_history.h | 17 |
2 files changed, 59 insertions, 18 deletions
diff --git a/net/dccp/ccids/lib/packet_history.c b/net/dccp/ccids/lib/packet_history.c index ee34b4564242..e2e250aa5c89 100644 --- a/net/dccp/ccids/lib/packet_history.c +++ b/net/dccp/ccids/lib/packet_history.c @@ -151,14 +151,31 @@ int tfrc_rx_hist_duplicate(struct tfrc_rx_hist *h, struct sk_buff *skb) } EXPORT_SYMBOL_GPL(tfrc_rx_hist_duplicate); + +static void __tfrc_rx_hist_swap(struct tfrc_rx_hist *h, const u8 a, const u8 b) +{ + struct tfrc_rx_hist_entry *tmp = h->ring[a]; + + h->ring[a] = h->ring[b]; + h->ring[b] = tmp; +} + static void tfrc_rx_hist_swap(struct tfrc_rx_hist *h, const u8 a, const u8 b) { - const u8 idx_a = tfrc_rx_hist_index(h, a), - idx_b = tfrc_rx_hist_index(h, b); - struct tfrc_rx_hist_entry *tmp = h->ring[idx_a]; + __tfrc_rx_hist_swap(h, tfrc_rx_hist_index(h, a), + tfrc_rx_hist_index(h, b)); +} - h->ring[idx_a] = h->ring[idx_b]; - h->ring[idx_b] = tmp; +/** + * tfrc_rx_hist_resume_rtt_sampling - Prepare RX history for RTT sampling + * This is called after loss detection has finished, when the history entry + * with the index of `loss_count' holds the highest-received sequence number. + * RTT sampling requires this information at ring[0] (tfrc_rx_hist_sample_rtt). + */ +static inline void tfrc_rx_hist_resume_rtt_sampling(struct tfrc_rx_hist *h) +{ + __tfrc_rx_hist_swap(h, 0, tfrc_rx_hist_index(h, h->loss_count)); + h->loss_count = h->loss_start = 0; } /* @@ -200,8 +217,7 @@ static void __one_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n2 if (dccp_loss_free(s2, s1, n1)) { /* hole is filled: S0, S2, and S1 are consecutive */ - h->loss_count = 0; - h->loss_start = tfrc_rx_hist_index(h, 1); + tfrc_rx_hist_resume_rtt_sampling(h); } else /* gap between S2 and S1: just update loss_prev */ tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_loss_prev(h), skb, n2); @@ -254,8 +270,7 @@ static int __two_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n3) if (dccp_loss_free(s1, s2, n2)) { /* entire hole filled by S0, S3, S1, S2 */ - h->loss_start = tfrc_rx_hist_index(h, 2); - h->loss_count = 0; + tfrc_rx_hist_resume_rtt_sampling(h); } else { /* gap remains between S1 and S2 */ h->loss_start = tfrc_rx_hist_index(h, 1); @@ -299,8 +314,7 @@ static void __three_after_loss(struct tfrc_rx_hist *h) if (dccp_loss_free(s2, s3, n3)) { /* no gap between S2 and S3: entire hole is filled */ - h->loss_start = tfrc_rx_hist_index(h, 3); - h->loss_count = 0; + tfrc_rx_hist_resume_rtt_sampling(h); } else { /* gap between S2 and S3 */ h->loss_start = tfrc_rx_hist_index(h, 2); @@ -340,6 +354,7 @@ int tfrc_rx_handle_loss(struct tfrc_rx_hist *h, if (h->loss_count == 0) { __do_track_loss(h, skb, ndp); + tfrc_rx_hist_sample_rtt(h, skb); } else if (h->loss_count == 1) { __one_after_loss(h, skb, ndp); } else if (h->loss_count != 2) { @@ -435,11 +450,24 @@ static inline struct tfrc_rx_hist_entry * * Based on ideas presented in RFC 4342, 8.1. Returns 0 if it was not able * to compute a sample with given data - calling function should check this. */ -u32 tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h, const struct sk_buff *skb) +void tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h, const struct sk_buff *skb) { - u32 sample = 0, - delta_v = SUB16(dccp_hdr(skb)->dccph_ccval, - tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval); + u32 sample = 0, delta_v; + + /* + * When not to sample: + * - on non-data packets + * (RFC 4342, 8.1: CCVal only fully defined for data packets); + * - when no data packets have been received yet + * (FIXME: using sampled packet size as indicator here); + * - as long as there are gaps in the sequence space (pending loss). + */ + if (!dccp_data_packet(skb) || h->packet_size == 0 || + tfrc_rx_hist_loss_pending(h)) + return; + + delta_v = SUB16(dccp_hdr(skb)->dccph_ccval, + tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval); if (delta_v < 1 || delta_v > 4) { /* unsuitable CCVal delta */ if (h->rtt_sample_prev == 2) { /* previous candidate stored */ @@ -479,6 +507,6 @@ u32 tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h, const struct sk_buff *skb) h->rtt_sample_prev = 0; /* use current entry as next reference */ keep_ref_for_next_time: - return sample; + h->rtt_estimate = tfrc_ewma(h->rtt_estimate, sample, 9); } EXPORT_SYMBOL_GPL(tfrc_rx_hist_sample_rtt); diff --git a/net/dccp/ccids/lib/packet_history.h b/net/dccp/ccids/lib/packet_history.h index b7c87a1a2720..ba5832bbc348 100644 --- a/net/dccp/ccids/lib/packet_history.h +++ b/net/dccp/ccids/lib/packet_history.h @@ -91,6 +91,7 @@ struct tfrc_rx_hist_entry { * @loss_count: Number of entries in circular history * @loss_start: Movable index (for loss detection) * @rtt_sample_prev: Used during RTT sampling, points to candidate entry + * @rtt_estimate: Receiver RTT estimate * @packet_size: Packet size in bytes (as per RFC 3448, 3.1) * @bytes_recvd: Number of bytes received since last sending feedback */ @@ -98,7 +99,10 @@ struct tfrc_rx_hist { struct tfrc_rx_hist_entry *ring[TFRC_NDUPACK + 1]; u8 loss_count:2, loss_start:2; + /* Receiver RTT sampling */ #define rtt_sample_prev loss_start + u32 rtt_estimate; + /* Receiver sampling of application payload lengths */ u32 packet_size, bytes_recvd; }; @@ -154,6 +158,15 @@ static inline u32 tfrc_rx_hist_packet_size(const struct tfrc_rx_hist *h) return TCP_MIN_RCVMSS; } return h->packet_size; + +} +static inline u32 tfrc_rx_hist_rtt(const struct tfrc_rx_hist *h) +{ + if (h->rtt_estimate == 0) { + DCCP_WARN("No RTT estimate available, using fallback RTT\n"); + return DCCP_FALLBACK_RTT; + } + return h->rtt_estimate; } extern void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h, @@ -167,8 +180,8 @@ extern int tfrc_rx_handle_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, const u64 ndp, u32 (*first_li)(struct sock *sk), struct sock *sk); -extern u32 tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h, - const struct sk_buff *skb); +extern void tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h, + const struct sk_buff *skb); extern int tfrc_rx_hist_init(struct tfrc_rx_hist *h, struct sock *sk); extern void tfrc_rx_hist_purge(struct tfrc_rx_hist *h); |