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[TCP]: Reduce sacked_out with reno when purging write_queue 

Previously TCP had a transitional state during which reno
counted segments that are already below the current window into
sacked_out, which is now prevented. In addition, re-try now
the unconditional S+L skb catching.

This approach conservatively calls just remove_sack and leaves
reset_sack() calls alone. The best solution to the whole problem
would be to first calculate the new sacked_out fully (this patch
does not move reno_sack_reset calls from original sites and thus
does not implement this). However, that would require very
invasive change to fastretrans_alert (perhaps even slicing it to
two halves). Alternatively, all callers of tcp_packets_in_flight
(i.e., users that depend on sacked_out) should be postponed
until the new sacked_out has been calculated but it isn't any
simpler alternative.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Ilpo Järvinen 2007-08-09 14:53:36 +03:00 committed by David S. Miller
parent d02596e329
commit 1b6d427bb7
2 changed files with 8 additions and 10 deletions
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3
include/net/tcp.h
View File

@ -759,8 +759,7 @@ static inline __u32 tcp_current_ssthresh(const struct sock *sk)
}
/* Use define here intentionally to get BUG_ON location shown at the caller */
#define tcp_verify_left_out(tp) \
BUG_ON(tp->rx_opt.sack_ok && (tcp_left_out(tp) > tp->packets_out))
#define tcp_verify_left_out(tp) BUG_ON(tcp_left_out(tp) > tp->packets_out)
extern void tcp_enter_cwr(struct sock *sk, const int set_ssthresh);
extern __u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst);

15
net/ipv4/tcp_input.c
View File

@ -2187,7 +2187,7 @@ static void tcp_mtup_probe_success(struct sock *sk, struct sk_buff *skb)
* tcp_xmit_retransmit_queue().
*/
static void
tcp_fastretrans_alert(struct sock *sk, int prior_packets, int flag)
tcp_fastretrans_alert(struct sock *sk, int pkts_acked, int flag)
{
struct inet_connection_sock *icsk = inet_csk(sk);
struct tcp_sock *tp = tcp_sk(sk);
@ -2273,12 +2273,8 @@ tcp_fastretrans_alert(struct sock *sk, int prior_packets, int flag)
if (!(flag & FLAG_SND_UNA_ADVANCED)) {
if (IsReno(tp) && is_dupack)
tcp_add_reno_sack(sk);
} else {
int acked = prior_packets - tp->packets_out;
if (IsReno(tp))
tcp_remove_reno_sacks(sk, acked);
do_lost = tcp_try_undo_partial(sk, acked);
}
} else
do_lost = tcp_try_undo_partial(sk, pkts_acked);
break;
case TCP_CA_Loss:
if (flag&FLAG_DATA_ACKED)
@ -2577,6 +2573,9 @@ static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p)
tcp_ack_update_rtt(sk, acked, seq_rtt);
tcp_ack_packets_out(sk);
if (IsReno(tp))
tcp_remove_reno_sacks(sk, pkts_acked);
if (ca_ops->pkts_acked) {
s32 rtt_us = -1;
@ -2927,7 +2926,7 @@ static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
if ((flag & FLAG_DATA_ACKED) && !frto_cwnd &&
tcp_may_raise_cwnd(sk, flag))
tcp_cong_avoid(sk, ack, prior_in_flight, 0);
tcp_fastretrans_alert(sk, prior_packets, flag);
tcp_fastretrans_alert(sk, prior_packets - tp->packets_out, flag);
} else {
if ((flag & FLAG_DATA_ACKED) && !frto_cwnd)
tcp_cong_avoid(sk, ack, prior_in_flight, 1);