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tcp: fix cwnd reduction for non-sack recovery 

The cwnd reduction in fast recovery is based on the number of packets
newly delivered per ACK. For non-sack connections every DUPACK
signifies a packet has been delivered, but the sender mistakenly
skips counting them for cwnd reduction.

The fix is to compute newly_acked_sacked after DUPACKs are accounted
in sacked_out for non-sack connections.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Nandita Dukkipati <nanditad@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Yuchung Cheng 2012-08-23 07:05:17 +00:00 committed by David S. Miller
parent 20e1db19db
commit 7c4a56fec3
1 changed files with 7 additions and 8 deletions
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15
net/ipv4/tcp_input.c
View File

@ -2926,13 +2926,14 @@ static void tcp_enter_recovery(struct sock *sk, bool ece_ack)
* tcp_xmit_retransmit_queue(). * tcp_xmit_retransmit_queue().
*/ */
static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked, static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked,
int newly_acked_sacked, bool is_dupack, int prior_sacked, bool is_dupack,
int flag) int flag)
{ {
struct inet_connection_sock *icsk = inet_csk(sk); struct inet_connection_sock *icsk = inet_csk(sk);
struct tcp_sock *tp = tcp_sk(sk); struct tcp_sock *tp = tcp_sk(sk);
int do_lost = is_dupack || ((flag & FLAG_DATA_SACKED) && int do_lost = is_dupack || ((flag & FLAG_DATA_SACKED) &&
(tcp_fackets_out(tp) > tp->reordering)); (tcp_fackets_out(tp) > tp->reordering));
int newly_acked_sacked = 0;
int fast_rexmit = 0; int fast_rexmit = 0;
if (WARN_ON(!tp->packets_out && tp->sacked_out)) if (WARN_ON(!tp->packets_out && tp->sacked_out))
@ -2992,6 +2993,7 @@ static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked,
tcp_add_reno_sack(sk); tcp_add_reno_sack(sk);
} else } else
do_lost = tcp_try_undo_partial(sk, pkts_acked); do_lost = tcp_try_undo_partial(sk, pkts_acked);
newly_acked_sacked = pkts_acked + tp->sacked_out - prior_sacked;
break; break;
case TCP_CA_Loss: case TCP_CA_Loss:
if (flag & FLAG_DATA_ACKED) if (flag & FLAG_DATA_ACKED)
@ -3013,6 +3015,7 @@ static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked,
if (is_dupack) if (is_dupack)
tcp_add_reno_sack(sk); tcp_add_reno_sack(sk);
} }
newly_acked_sacked = pkts_acked + tp->sacked_out - prior_sacked;
if (icsk->icsk_ca_state <= TCP_CA_Disorder) if (icsk->icsk_ca_state <= TCP_CA_Disorder)
tcp_try_undo_dsack(sk); tcp_try_undo_dsack(sk);
@ -3590,7 +3593,6 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
int prior_packets; int prior_packets;
int prior_sacked = tp->sacked_out; int prior_sacked = tp->sacked_out;
int pkts_acked = 0; int pkts_acked = 0;
int newly_acked_sacked = 0;
bool frto_cwnd = false; bool frto_cwnd = false;
/* If the ack is older than previous acks /* If the ack is older than previous acks
@ -3666,8 +3668,6 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
flag |= tcp_clean_rtx_queue(sk, prior_fackets, prior_snd_una); flag |= tcp_clean_rtx_queue(sk, prior_fackets, prior_snd_una);
pkts_acked = prior_packets - tp->packets_out; pkts_acked = prior_packets - tp->packets_out;
newly_acked_sacked = (prior_packets - prior_sacked) -
(tp->packets_out - tp->sacked_out);
if (tp->frto_counter) if (tp->frto_counter)
frto_cwnd = tcp_process_frto(sk, flag); frto_cwnd = tcp_process_frto(sk, flag);
@ -3681,7 +3681,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
tcp_may_raise_cwnd(sk, flag)) tcp_may_raise_cwnd(sk, flag))
tcp_cong_avoid(sk, ack, prior_in_flight); tcp_cong_avoid(sk, ack, prior_in_flight);
is_dupack = !(flag & (FLAG_SND_UNA_ADVANCED | FLAG_NOT_DUP)); is_dupack = !(flag & (FLAG_SND_UNA_ADVANCED | FLAG_NOT_DUP));
tcp_fastretrans_alert(sk, pkts_acked, newly_acked_sacked, tcp_fastretrans_alert(sk, pkts_acked, prior_sacked,
is_dupack, flag); is_dupack, flag);
} else { } else {
if ((flag & FLAG_DATA_ACKED) && !frto_cwnd) if ((flag & FLAG_DATA_ACKED) && !frto_cwnd)
@ -3698,7 +3698,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
no_queue: no_queue:
/* If data was DSACKed, see if we can undo a cwnd reduction. */ /* If data was DSACKed, see if we can undo a cwnd reduction. */
if (flag & FLAG_DSACKING_ACK) if (flag & FLAG_DSACKING_ACK)
tcp_fastretrans_alert(sk, pkts_acked, newly_acked_sacked, tcp_fastretrans_alert(sk, pkts_acked, prior_sacked,
is_dupack, flag); is_dupack, flag);
/* If this ack opens up a zero window, clear backoff. It was /* If this ack opens up a zero window, clear backoff. It was
* being used to time the probes, and is probably far higher than * being used to time the probes, and is probably far higher than
@ -3718,8 +3718,7 @@ old_ack:
*/ */
if (TCP_SKB_CB(skb)->sacked) { if (TCP_SKB_CB(skb)->sacked) {
flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una); flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una);
newly_acked_sacked = tp->sacked_out - prior_sacked; tcp_fastretrans_alert(sk, pkts_acked, prior_sacked,
tcp_fastretrans_alert(sk, pkts_acked, newly_acked_sacked,
is_dupack, flag); is_dupack, flag);
} }