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[TCP]: Prevent unrelated cwnd adjustment while using FRTO 

FRTO controls cwnd when it still processes the ACK input or it
has just reverted back to conventional RTO recovery; the normal
rules apply when FRTO has reverted to standard congestion
control.

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 2007-02-21 23:08:34 -08:00 committed by David S. Miller
parent 94d0ea7786
commit 7c9a4a5b67
1 changed files with 11 additions and 7 deletions
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18
net/ipv4/tcp_input.c
View File

@ -2522,7 +2522,7 @@ static void tcp_conservative_spur_to_response(struct tcp_sock *tp)
* to prove that the RTO is indeed spurious. It transfers the control * to prove that the RTO is indeed spurious. It transfers the control
* from F-RTO to the conventional RTO recovery * from F-RTO to the conventional RTO recovery
*/ */
static void tcp_process_frto(struct sock *sk, u32 prior_snd_una, int flag) static int tcp_process_frto(struct sock *sk, u32 prior_snd_una, int flag)
{ {
struct tcp_sock *tp = tcp_sk(sk); struct tcp_sock *tp = tcp_sk(sk);
@ -2534,7 +2534,7 @@ static void tcp_process_frto(struct sock *sk, u32 prior_snd_una, int flag)
if (!before(tp->snd_una, tp->frto_highmark)) { if (!before(tp->snd_una, tp->frto_highmark)) {
tcp_enter_frto_loss(sk, tp->frto_counter + 1); tcp_enter_frto_loss(sk, tp->frto_counter + 1);
return; return 1;
} }
/* RFC4138 shortcoming in step 2; should also have case c): ACK isn't /* RFC4138 shortcoming in step 2; should also have case c): ACK isn't
@ -2542,20 +2542,22 @@ static void tcp_process_frto(struct sock *sk, u32 prior_snd_una, int flag)
*/ */
if ((tp->snd_una == prior_snd_una) && (flag&FLAG_NOT_DUP) && if ((tp->snd_una == prior_snd_una) && (flag&FLAG_NOT_DUP) &&
!(flag&FLAG_FORWARD_PROGRESS)) !(flag&FLAG_FORWARD_PROGRESS))
return; return 1;
if (!(flag&FLAG_DATA_ACKED)) { if (!(flag&FLAG_DATA_ACKED)) {
tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 0 : 3)); tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 0 : 3));
return; return 1;
} }
if (tp->frto_counter == 1) { if (tp->frto_counter == 1) {
tp->snd_cwnd = tcp_packets_in_flight(tp) + 2; tp->snd_cwnd = tcp_packets_in_flight(tp) + 2;
tp->frto_counter = 2; tp->frto_counter = 2;
return 1;
} else /* frto_counter == 2 */ { } else /* frto_counter == 2 */ {
tcp_conservative_spur_to_response(tp); tcp_conservative_spur_to_response(tp);
tp->frto_counter = 0; tp->frto_counter = 0;
} }
return 0;
} }
/* This routine deals with incoming acks, but not outgoing ones. */ /* This routine deals with incoming acks, but not outgoing ones. */
@ -2569,6 +2571,7 @@ static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
u32 prior_in_flight; u32 prior_in_flight;
s32 seq_rtt; s32 seq_rtt;
int prior_packets; int prior_packets;
int frto_cwnd = 0;
/* If the ack is newer than sent or older than previous acks /* If the ack is newer than sent or older than previous acks
* then we can probably ignore it. * then we can probably ignore it.
@ -2631,15 +2634,16 @@ static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
flag |= tcp_clean_rtx_queue(sk, &seq_rtt); flag |= tcp_clean_rtx_queue(sk, &seq_rtt);
if (tp->frto_counter) if (tp->frto_counter)
tcp_process_frto(sk, prior_snd_una, flag); frto_cwnd = tcp_process_frto(sk, prior_snd_una, flag);
if (tcp_ack_is_dubious(sk, flag)) { if (tcp_ack_is_dubious(sk, flag)) {
/* Advance CWND, if state allows this. */ /* Advance CWND, if state allows this. */
if ((flag & FLAG_DATA_ACKED) && tcp_may_raise_cwnd(sk, flag)) if ((flag & FLAG_DATA_ACKED) && !frto_cwnd &&
tcp_may_raise_cwnd(sk, flag))
tcp_cong_avoid(sk, ack, seq_rtt, prior_in_flight, 0); tcp_cong_avoid(sk, ack, seq_rtt, prior_in_flight, 0);
tcp_fastretrans_alert(sk, prior_snd_una, prior_packets, flag); tcp_fastretrans_alert(sk, prior_snd_una, prior_packets, flag);
} else { } else {
if ((flag & FLAG_DATA_ACKED)) if ((flag & FLAG_DATA_ACKED) && !frto_cwnd)
tcp_cong_avoid(sk, ack, seq_rtt, prior_in_flight, 1); tcp_cong_avoid(sk, ack, seq_rtt, prior_in_flight, 1);
} }