* patch to implement RFC3517 in linux 2.4.22
@ 2003-10-09 7:27 Douglas Leith
2003-10-10 8:27 ` David S. Miller
0 siblings, 1 reply; 4+ messages in thread
From: Douglas Leith @ 2003-10-09 7:27 UTC (permalink / raw)
To: linux-net; +Cc: davem, linux-kernel, kuznet, jmorris, yoshfuji
[-- Attachment #1: Type: text/plain, Size: 4064 bytes --]
Attached is a short patch against version 2.4.22 to implement the recent
rfc3517 for SACK in TCP (see ftp://ftp.rfc-editor.org/in-notes/rfc3517.txt).
This modifies how packets which fail to be sacked are marked as lost. At
present, any packets falling into sack holes are marked lost after the first
successful retransmit. The new code marks packets in sack holes as lost as
soon as tp->reordering or more packets with higher sequence number are
sacked. This is consistent with how reordering is handled elsewhere and
should lead to faster retransmission and recovery when multiple drops occur.
Comments appreciated.
Regards,
Doug Leith
www.hamilton.ie
diff -u -wbrP --exclude=config.save linux-2.4.22/net/ipv4/tcp_input.c linux-
2.4.22-retrans/net/ipv4/tcp_input.c
--- linux-2.4.22/net/ipv4/tcp_input.c 2003-06-13 15:51:39.000000000 +0100
+++ linux-2.4.22-retrans/net/ipv4/tcp_input.c 2003-10-09 07:59:48.000000000
+0100
@@ -61,6 +61,7 @@
* Panu Kuhlberg: Experimental audit of TCP (re)
transmission
* engine. Lots of bugs are found.
* Pasi Sarolahti: F-RTO for dealing with spurious RTOs
+ * Doug Leith: Early retransmission of packets
falling into sack holes.
*/
#include <linux/config.h>
@@ -757,6 +758,10 @@
* for retransmitted and already SACKed segment -> reordering..
* Both of these heuristics are not used in Loss state, when we cannot
* account for retransmits accurately.
+ *
+ * Retransmission of packets
+ * -------------------------
+ * Extension of Hoe's retransmit to allow early retransmission of packets
which fall into sack holes
*/
static int
tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32
prior_snd_una)
@@ -770,6 +775,7 @@
u32 lost_retrans = 0;
int flag = 0;
int i;
+ u32 prior_sacked_out=tp->sacked_out;
if (!tp->sacked_out)
tp->fackets_out = 0;
@@ -781,6 +787,7 @@
__u32 end_seq = ntohl(sp->end_seq);
int fack_count = 0;
int dup_sack = 0;
+ u32 sack_count=0;
/* Check for D-SACK. */
if (i == 0) {
@@ -828,6 +835,8 @@
break;
fack_count++;
+ if (sacked&TCPCB_RETRANS)
+ sack_count++;
in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
!before(end_seq, TCP_SKB_CB(skb)->end_seq);
@@ -860,8 +869,14 @@
(!lost_retrans || after(end_seq, lost_retrans)))
lost_retrans = end_seq;
- if (!in_sack)
+ if (!in_sack) {
+ /* force early retransmit ? */
+ if (!(sacked&TCPCB_TAGBITS) && (prior_sacked_out
> sack_count + tp->reordering)) {
+ TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
+ tp->lost_out++;
+ }
continue;
+ }
if (!(sacked&TCPCB_SACKED_ACKED)) {
if (sacked & TCPCB_SACKED_RETRANS) {
@@ -1599,7 +1614,7 @@
if ((flag&FLAG_DATA_LOST) &&
before(tp->snd_una, tp->high_seq) &&
tp->ca_state != TCP_CA_Open &&
- tp->fackets_out > tp->reordering) {
+ tp->fackets_out > tp->reordering && IsReno(tp) ) {
tcp_mark_head_lost(sk, tp, tp->fackets_out-tp->reordering, tp-
>high_seq);
NET_INC_STATS_BH(TCPLoss);
}
@@ -1714,7 +1729,7 @@
tp->ca_state = TCP_CA_Recovery;
}
- if (is_dupack || tcp_head_timedout(sk, tp))
+ if ( (is_dupack || tcp_head_timedout(sk, tp)) && IsReno(tp) )
tcp_update_scoreboard(sk, tp);
tcp_cwnd_down(tp);
tcp_xmit_retransmit_queue(sk);
[-- Attachment #2: rfc3517.patch --]
[-- Type: text/plain, Size: 2765 bytes --]
diff -u -wbrP --exclude=config.save linux-2.4.22/net/ipv4/tcp_input.c linux-2.4.22-retrans/net/ipv4/tcp_input.c
--- linux-2.4.22/net/ipv4/tcp_input.c 2003-06-13 15:51:39.000000000 +0100
+++ linux-2.4.22-retrans/net/ipv4/tcp_input.c 2003-10-09 07:59:48.000000000 +0100
@@ -61,6 +61,7 @@
* Panu Kuhlberg: Experimental audit of TCP (re)transmission
* engine. Lots of bugs are found.
* Pasi Sarolahti: F-RTO for dealing with spurious RTOs
+ * Doug Leith: Early retransmission of packets falling into sack holes.
*/
#include <linux/config.h>
@@ -757,6 +758,10 @@
* for retransmitted and already SACKed segment -> reordering..
* Both of these heuristics are not used in Loss state, when we cannot
* account for retransmits accurately.
+ *
+ * Retransmission of packets
+ * -------------------------
+ * Extension of Hoe's retransmit to allow early retransmission of packets which fall into sack holes
*/
static int
tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_una)
@@ -770,6 +775,7 @@
u32 lost_retrans = 0;
int flag = 0;
int i;
+ u32 prior_sacked_out=tp->sacked_out;
if (!tp->sacked_out)
tp->fackets_out = 0;
@@ -781,6 +787,7 @@
__u32 end_seq = ntohl(sp->end_seq);
int fack_count = 0;
int dup_sack = 0;
+ u32 sack_count=0;
/* Check for D-SACK. */
if (i == 0) {
@@ -828,6 +835,8 @@
break;
fack_count++;
+ if (sacked&TCPCB_RETRANS)
+ sack_count++;
in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
!before(end_seq, TCP_SKB_CB(skb)->end_seq);
@@ -860,8 +869,14 @@
(!lost_retrans || after(end_seq, lost_retrans)))
lost_retrans = end_seq;
- if (!in_sack)
+ if (!in_sack) {
+ /* force early retransmit ? */
+ if (!(sacked&TCPCB_TAGBITS) && (prior_sacked_out > sack_count + tp->reordering)) {
+ TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
+ tp->lost_out++;
+ }
continue;
+ }
if (!(sacked&TCPCB_SACKED_ACKED)) {
if (sacked & TCPCB_SACKED_RETRANS) {
@@ -1599,7 +1614,7 @@
if ((flag&FLAG_DATA_LOST) &&
before(tp->snd_una, tp->high_seq) &&
tp->ca_state != TCP_CA_Open &&
- tp->fackets_out > tp->reordering) {
+ tp->fackets_out > tp->reordering && IsReno(tp) ) {
tcp_mark_head_lost(sk, tp, tp->fackets_out-tp->reordering, tp->high_seq);
NET_INC_STATS_BH(TCPLoss);
}
@@ -1714,7 +1729,7 @@
tp->ca_state = TCP_CA_Recovery;
}
- if (is_dupack || tcp_head_timedout(sk, tp))
+ if ( (is_dupack || tcp_head_timedout(sk, tp)) && IsReno(tp) )
tcp_update_scoreboard(sk, tp);
tcp_cwnd_down(tp);
tcp_xmit_retransmit_queue(sk);
^ permalink raw reply [flat|nested] 4+ messages in thread[parent not found: <006c01c38f50$7bc26940$0603dc0a@hamilton.local>]
* Re: patch to implement RFC3517 in linux 2.4.22
[not found] <006c01c38f50$7bc26940$0603dc0a@hamilton.local>
@ 2003-10-10 17:35 ` kuznet
0 siblings, 0 replies; 4+ messages in thread
From: kuznet @ 2003-10-10 17:35 UTC (permalink / raw)
To: doug.leith; +Cc: davem, linux-net, linux-kernel, kuznet, jmorris, yoshfuji
Hello!
> The new code marks packets in sack holes as lost as soon as three or more packets with higher sequence numbers are sacked and these will then be immediately retransmitted - this should mean that retransmission of lost packets generally happens earlier and recovery is faster.
What those chunks of code which you killed with IsReno() do to your
opinion?
Alexey
PS Please, try to format mails more sanely. This one is close to unreadable.
Alexey
^ permalink raw reply [flat|nested] 4+ messages in thread
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2003-10-09 7:27 patch to implement RFC3517 in linux 2.4.22 Douglas Leith
2003-10-10 8:27 ` David S. Miller
2003-10-10 13:29 ` kuznet
[not found] <006c01c38f50$7bc26940$0603dc0a@hamilton.local>
2003-10-10 17:35 ` kuznet
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