[DCCP]: Fix CCID3

This fixes CCID3 to give much closer performance to RFC4342.

CCID3 is meant to alter sending rate based on RTT and loss.

The performance was verified against:
http://wand.net.nz/~perry/max_download.php

For example I tested with netem and had the following parameters:
Delayed Acks 1, MSS 256 bytes, RTT 105 ms, packet loss 5%.

This gives a theoretical speed of 71.9 Kbits/s. I measured across three
runs with this patch set and got 70.1 Kbits/s. Without this patchset the
average was 232 Kbits/s which means Linux can't be used for CCID3 research
properly.

I also tested with netem turned off so box just acting as router with 1.2
msec RTT. The performance with this is the same with or without the patch
at around 30 Mbit/s.

Signed off by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 131 deletions

diff --git a/net/dccp/ccids/lib/packet_history.c b/net/dccp/ccids/lib/packet_history.c
index 420c60f8604d..b876c9c81c65 100644
--- a/net/dccp/ccids/lib/packet_history.c
+++ b/net/dccp/ccids/lib/packet_history.c
@@ -112,64 +112,27 @@ struct dccp_rx_hist_entry *
 
 EXPORT_SYMBOL_GPL(dccp_rx_hist_find_data_packet);
 
-int dccp_rx_hist_add_packet(struct dccp_rx_hist *hist,
+void dccp_rx_hist_add_packet(struct dccp_rx_hist *hist,
 			    struct list_head *rx_list,
 			    struct list_head *li_list,
-			    struct dccp_rx_hist_entry *packet)
+			    struct dccp_rx_hist_entry *packet,
+			    u64 nonloss_seqno)
 {
-	struct dccp_rx_hist_entry *entry, *next, *iter;
+	struct dccp_rx_hist_entry *entry, *next;
 	u8 num_later = 0;
 
-	iter = dccp_rx_hist_head(rx_list);
-	if (iter == NULL)
-		dccp_rx_hist_add_entry(rx_list, packet);
-	else {
-		const u64 seqno = packet->dccphrx_seqno;
-
-		if (after48(seqno, iter->dccphrx_seqno))
-			dccp_rx_hist_add_entry(rx_list, packet);
-		else {
-			if (dccp_rx_hist_entry_data_packet(iter))
-				num_later = 1;
-
-			list_for_each_entry_continue(iter, rx_list,
-						     dccphrx_node) {
-				if (after48(seqno, iter->dccphrx_seqno)) {
-					dccp_rx_hist_add_entry(&iter->dccphrx_node,
-							       packet);
-					goto trim_history;
-				}
-
-				if (dccp_rx_hist_entry_data_packet(iter))
-					num_later++;
-
-				if (num_later == TFRC_RECV_NUM_LATE_LOSS) {
-					dccp_rx_hist_entry_delete(hist, packet);
-					return 1;
-				}
-			}
-
-			if (num_later < TFRC_RECV_NUM_LATE_LOSS)
-				dccp_rx_hist_add_entry(rx_list, packet);
-			/*
-			 * FIXME: else what? should we destroy the packet
-			 * like above?
-			 */
-		}
-	}
+	list_add(&packet->dccphrx_node, rx_list);
 
-trim_history:
-	/*
-	 * Trim history (remove all packets after the NUM_LATE_LOSS + 1
-	 * data packets)
-	 */
 	num_later = TFRC_RECV_NUM_LATE_LOSS + 1;
 
 	if (!list_empty(li_list)) {
 		list_for_each_entry_safe(entry, next, rx_list, dccphrx_node) {
 			if (num_later == 0) {
-				list_del_init(&entry->dccphrx_node);
-				dccp_rx_hist_entry_delete(hist, entry);
+				if (after48(nonloss_seqno,
+				   entry->dccphrx_seqno)) {
+					list_del_init(&entry->dccphrx_node);
+					dccp_rx_hist_entry_delete(hist, entry);
+				}
 			} else if (dccp_rx_hist_entry_data_packet(entry))
 				--num_later;
 		}
@@ -217,94 +180,10 @@ trim_history:
 				--num_later;
 		}
 	}
-
-	return 0;
 }
 
 EXPORT_SYMBOL_GPL(dccp_rx_hist_add_packet);
 
-u64 dccp_rx_hist_detect_loss(struct list_head *rx_list,
-			     struct list_head *li_list, u8 *win_loss)
-{
-	struct dccp_rx_hist_entry *entry, *next, *packet;
-	struct dccp_rx_hist_entry *a_loss = NULL;
-	struct dccp_rx_hist_entry *b_loss = NULL;
-	u64 seq_loss = DCCP_MAX_SEQNO + 1;
-	u8 num_later = TFRC_RECV_NUM_LATE_LOSS;
-
-	list_for_each_entry_safe(entry, next, rx_list, dccphrx_node) {
-		if (num_later == 0) {
-			b_loss = entry;
-			break;
-		} else if (dccp_rx_hist_entry_data_packet(entry))
-			--num_later;
-	}
-
-	if (b_loss == NULL)
-		goto out;
-
-	num_later = 1;
-	list_for_each_entry_safe_continue(entry, next, rx_list, dccphrx_node) {
-		if (num_later == 0) {
-			a_loss = entry;
-			break;
-		} else if (dccp_rx_hist_entry_data_packet(entry))
-			--num_later;
-	}
-
-	if (a_loss == NULL) {
-		if (list_empty(li_list)) {
-			/* no loss event have occured yet */
-			LIMIT_NETDEBUG("%s: TODO: find a lost data packet by "
-				       "comparing to initial seqno\n",
-				       __FUNCTION__);
-			goto out;
-		} else {
-			LIMIT_NETDEBUG("%s: Less than 4 data pkts in history!",
-				       __FUNCTION__);
-			goto out;
-		}
-	}
-
-	/* Locate a lost data packet */
-	entry = packet = b_loss;
-	list_for_each_entry_safe_continue(entry, next, rx_list, dccphrx_node) {
-		u64 delta = dccp_delta_seqno(entry->dccphrx_seqno,
-					     packet->dccphrx_seqno);
-
-		if (delta != 0) {
-			if (dccp_rx_hist_entry_data_packet(packet))
-				--delta;
-			/*
-			 * FIXME: check this, probably this % usage is because
-			 * in earlier drafts the ndp count was just 8 bits
-			 * long, but now it cam be up to 24 bits long.
-			 */
-#if 0
-			if (delta % DCCP_NDP_LIMIT !=
-			    (packet->dccphrx_ndp -
-			     entry->dccphrx_ndp) % DCCP_NDP_LIMIT)
-#endif
-			if (delta != packet->dccphrx_ndp - entry->dccphrx_ndp) {
-				seq_loss = entry->dccphrx_seqno;
-				dccp_inc_seqno(&seq_loss);
-			}
-		}
-		packet = entry;
-		if (packet == a_loss)
-			break;
-	}
-out:
-	if (seq_loss != DCCP_MAX_SEQNO + 1)
-		*win_loss = a_loss->dccphrx_ccval;
-	else
-		*win_loss = 0; /* Paranoia */
-
-	return seq_loss;
-}
-
-EXPORT_SYMBOL_GPL(dccp_rx_hist_detect_loss);
-
 struct dccp_tx_hist *dccp_tx_hist_new(const char *name)
 {
 	struct dccp_tx_hist *hist = kmalloc(sizeof(*hist), GFP_ATOMIC);