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-rw-r--r--include/net/tcp.h10
-rw-r--r--net/ipv4/tcp_input.c119
-rw-r--r--net/ipv4/tcp_output.c6
3 files changed, 52 insertions, 83 deletions
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 1421b02a7905..a8cb00c0c6d9 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -913,15 +913,21 @@ static inline bool tcp_in_initial_slowstart(const struct tcp_sock *tp)
return tp->snd_ssthresh >= TCP_INFINITE_SSTHRESH;
}
+static inline bool tcp_in_cwnd_reduction(const struct sock *sk)
+{
+ return (TCPF_CA_CWR | TCPF_CA_Recovery) &
+ (1 << inet_csk(sk)->icsk_ca_state);
+}
+
/* If cwnd > ssthresh, we may raise ssthresh to be half-way to cwnd.
- * The exception is rate halving phase, when cwnd is decreasing towards
+ * The exception is cwnd reduction phase, when cwnd is decreasing towards
* ssthresh.
*/
static inline __u32 tcp_current_ssthresh(const struct sock *sk)
{
const struct tcp_sock *tp = tcp_sk(sk);
- if ((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_CWR | TCPF_CA_Recovery))
+ if (tcp_in_cwnd_reduction(sk))
return tp->snd_ssthresh;
else
return max(tp->snd_ssthresh,
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 38589e464e63..e2bec815ff23 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2470,35 +2470,6 @@ static inline void tcp_moderate_cwnd(struct tcp_sock *tp)
tp->snd_cwnd_stamp = tcp_time_stamp;
}
-/* Lower bound on congestion window is slow start threshold
- * unless congestion avoidance choice decides to overide it.
- */
-static inline u32 tcp_cwnd_min(const struct sock *sk)
-{
- const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
-
- return ca_ops->min_cwnd ? ca_ops->min_cwnd(sk) : tcp_sk(sk)->snd_ssthresh;
-}
-
-/* Decrease cwnd each second ack. */
-static void tcp_cwnd_down(struct sock *sk, int flag)
-{
- struct tcp_sock *tp = tcp_sk(sk);
- int decr = tp->snd_cwnd_cnt + 1;
-
- if ((flag & (FLAG_ANY_PROGRESS | FLAG_DSACKING_ACK)) ||
- (tcp_is_reno(tp) && !(flag & FLAG_NOT_DUP))) {
- tp->snd_cwnd_cnt = decr & 1;
- decr >>= 1;
-
- if (decr && tp->snd_cwnd > tcp_cwnd_min(sk))
- tp->snd_cwnd -= decr;
-
- tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp) + 1);
- tp->snd_cwnd_stamp = tcp_time_stamp;
- }
-}
-
/* Nothing was retransmitted or returned timestamp is less
* than timestamp of the first retransmission.
*/
@@ -2700,9 +2671,8 @@ static bool tcp_try_undo_loss(struct sock *sk)
return false;
}
-/* This function implements the PRR algorithm, specifcally the PRR-SSRB
- * (proportional rate reduction with slow start reduction bound) as described in
- * http://www.ietf.org/id/draft-mathis-tcpm-proportional-rate-reduction-01.txt.
+/* The cwnd reduction in CWR and Recovery use the PRR algorithm
+ * https://datatracker.ietf.org/doc/draft-ietf-tcpm-proportional-rate-reduction/
* It computes the number of packets to send (sndcnt) based on packets newly
* delivered:
* 1) If the packets in flight is larger than ssthresh, PRR spreads the
@@ -2711,13 +2681,29 @@ static bool tcp_try_undo_loss(struct sock *sk)
* losses and/or application stalls), do not perform any further cwnd
* reductions, but instead slow start up to ssthresh.
*/
-static void tcp_update_cwnd_in_recovery(struct sock *sk, int newly_acked_sacked,
- int fast_rexmit, int flag)
+static void tcp_init_cwnd_reduction(struct sock *sk, const bool set_ssthresh)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ tp->high_seq = tp->snd_nxt;
+ tp->bytes_acked = 0;
+ tp->snd_cwnd_cnt = 0;
+ tp->prior_cwnd = tp->snd_cwnd;
+ tp->prr_delivered = 0;
+ tp->prr_out = 0;
+ if (set_ssthresh)
+ tp->snd_ssthresh = inet_csk(sk)->icsk_ca_ops->ssthresh(sk);
+ TCP_ECN_queue_cwr(tp);
+}
+
+static void tcp_cwnd_reduction(struct sock *sk, int newly_acked_sacked,
+ int fast_rexmit)
{
struct tcp_sock *tp = tcp_sk(sk);
int sndcnt = 0;
int delta = tp->snd_ssthresh - tcp_packets_in_flight(tp);
+ tp->prr_delivered += newly_acked_sacked;
if (tcp_packets_in_flight(tp) > tp->snd_ssthresh) {
u64 dividend = (u64)tp->snd_ssthresh * tp->prr_delivered +
tp->prior_cwnd - 1;
@@ -2732,43 +2718,29 @@ static void tcp_update_cwnd_in_recovery(struct sock *sk, int newly_acked_sacked,
tp->snd_cwnd = tcp_packets_in_flight(tp) + sndcnt;
}
-static inline void tcp_complete_cwr(struct sock *sk)
+static inline void tcp_end_cwnd_reduction(struct sock *sk)
{
struct tcp_sock *tp = tcp_sk(sk);
- /* Do not moderate cwnd if it's already undone in cwr or recovery. */
- if (tp->undo_marker) {
- if (inet_csk(sk)->icsk_ca_state == TCP_CA_CWR) {
- tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
- tp->snd_cwnd_stamp = tcp_time_stamp;
- } else if (tp->snd_ssthresh < TCP_INFINITE_SSTHRESH) {
- /* PRR algorithm. */
- tp->snd_cwnd = tp->snd_ssthresh;
- tp->snd_cwnd_stamp = tcp_time_stamp;
- }
+ /* Reset cwnd to ssthresh in CWR or Recovery (unless it's undone) */
+ if (inet_csk(sk)->icsk_ca_state == TCP_CA_CWR ||
+ (tp->undo_marker && tp->snd_ssthresh < TCP_INFINITE_SSTHRESH)) {
+ tp->snd_cwnd = tp->snd_ssthresh;
+ tp->snd_cwnd_stamp = tcp_time_stamp;
}
tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR);
}
-/* Set slow start threshold and cwnd not falling to slow start */
+/* Enter CWR state. Disable cwnd undo since congestion is proven with ECN */
void tcp_enter_cwr(struct sock *sk, const int set_ssthresh)
{
struct tcp_sock *tp = tcp_sk(sk);
- const struct inet_connection_sock *icsk = inet_csk(sk);
tp->prior_ssthresh = 0;
tp->bytes_acked = 0;
- if (icsk->icsk_ca_state < TCP_CA_CWR) {
+ if (inet_csk(sk)->icsk_ca_state < TCP_CA_CWR) {
tp->undo_marker = 0;
- if (set_ssthresh)
- tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
- tp->snd_cwnd = min(tp->snd_cwnd,
- tcp_packets_in_flight(tp) + 1U);
- tp->snd_cwnd_cnt = 0;
- tp->high_seq = tp->snd_nxt;
- tp->snd_cwnd_stamp = tcp_time_stamp;
- TCP_ECN_queue_cwr(tp);
-
+ tcp_init_cwnd_reduction(sk, set_ssthresh);
tcp_set_ca_state(sk, TCP_CA_CWR);
}
}
@@ -2787,7 +2759,7 @@ static void tcp_try_keep_open(struct sock *sk)
}
}
-static void tcp_try_to_open(struct sock *sk, int flag)
+static void tcp_try_to_open(struct sock *sk, int flag, int newly_acked_sacked)
{
struct tcp_sock *tp = tcp_sk(sk);
@@ -2804,7 +2776,7 @@ static void tcp_try_to_open(struct sock *sk, int flag)
if (inet_csk(sk)->icsk_ca_state != TCP_CA_Open)
tcp_moderate_cwnd(tp);
} else {
- tcp_cwnd_down(sk, flag);
+ tcp_cwnd_reduction(sk, newly_acked_sacked, 0);
}
}
@@ -2898,7 +2870,6 @@ static void tcp_enter_recovery(struct sock *sk, bool ece_ack)
NET_INC_STATS_BH(sock_net(sk), mib_idx);
- tp->high_seq = tp->snd_nxt;
tp->prior_ssthresh = 0;
tp->undo_marker = tp->snd_una;
tp->undo_retrans = tp->retrans_out;
@@ -2906,15 +2877,8 @@ static void tcp_enter_recovery(struct sock *sk, bool ece_ack)
if (inet_csk(sk)->icsk_ca_state < TCP_CA_CWR) {
if (!ece_ack)
tp->prior_ssthresh = tcp_current_ssthresh(sk);
- tp->snd_ssthresh = inet_csk(sk)->icsk_ca_ops->ssthresh(sk);
- TCP_ECN_queue_cwr(tp);
+ tcp_init_cwnd_reduction(sk, true);
}
-
- tp->bytes_acked = 0;
- tp->snd_cwnd_cnt = 0;
- tp->prior_cwnd = tp->snd_cwnd;
- tp->prr_delivered = 0;
- tp->prr_out = 0;
tcp_set_ca_state(sk, TCP_CA_Recovery);
}
@@ -2974,7 +2938,7 @@ static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked,
/* CWR is to be held something *above* high_seq
* is ACKed for CWR bit to reach receiver. */
if (tp->snd_una != tp->high_seq) {
- tcp_complete_cwr(sk);
+ tcp_end_cwnd_reduction(sk);
tcp_set_ca_state(sk, TCP_CA_Open);
}
break;
@@ -2984,7 +2948,7 @@ static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked,
tcp_reset_reno_sack(tp);
if (tcp_try_undo_recovery(sk))
return;
- tcp_complete_cwr(sk);
+ tcp_end_cwnd_reduction(sk);
break;
}
}
@@ -3025,7 +2989,7 @@ static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked,
tcp_try_undo_dsack(sk);
if (!tcp_time_to_recover(sk, flag)) {
- tcp_try_to_open(sk, flag);
+ tcp_try_to_open(sk, flag, newly_acked_sacked);
return;
}
@@ -3047,8 +3011,7 @@ static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked,
if (do_lost || (tcp_is_fack(tp) && tcp_head_timedout(sk)))
tcp_update_scoreboard(sk, fast_rexmit);
- tp->prr_delivered += newly_acked_sacked;
- tcp_update_cwnd_in_recovery(sk, newly_acked_sacked, fast_rexmit, flag);
+ tcp_cwnd_reduction(sk, newly_acked_sacked, fast_rexmit);
tcp_xmit_retransmit_queue(sk);
}
@@ -3394,7 +3357,7 @@ static inline bool tcp_may_raise_cwnd(const struct sock *sk, const int flag)
{
const struct tcp_sock *tp = tcp_sk(sk);
return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) &&
- !((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_Recovery | TCPF_CA_CWR));
+ !tcp_in_cwnd_reduction(sk);
}
/* Check that window update is acceptable.
@@ -3462,9 +3425,9 @@ static void tcp_conservative_spur_to_response(struct tcp_sock *tp)
}
/* A conservative spurious RTO response algorithm: reduce cwnd using
- * rate halving and continue in congestion avoidance.
+ * PRR and continue in congestion avoidance.
*/
-static void tcp_ratehalving_spur_to_response(struct sock *sk)
+static void tcp_cwr_spur_to_response(struct sock *sk)
{
tcp_enter_cwr(sk, 0);
}
@@ -3472,7 +3435,7 @@ static void tcp_ratehalving_spur_to_response(struct sock *sk)
static void tcp_undo_spur_to_response(struct sock *sk, int flag)
{
if (flag & FLAG_ECE)
- tcp_ratehalving_spur_to_response(sk);
+ tcp_cwr_spur_to_response(sk);
else
tcp_undo_cwr(sk, true);
}
@@ -3579,7 +3542,7 @@ static bool tcp_process_frto(struct sock *sk, int flag)
tcp_conservative_spur_to_response(tp);
break;
default:
- tcp_ratehalving_spur_to_response(sk);
+ tcp_cwr_spur_to_response(sk);
break;
}
tp->frto_counter = 0;
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 9383b51f3efc..cfe6ffe1c177 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2037,10 +2037,10 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
if (push_one)
break;
}
- if (inet_csk(sk)->icsk_ca_state == TCP_CA_Recovery)
- tp->prr_out += sent_pkts;
if (likely(sent_pkts)) {
+ if (tcp_in_cwnd_reduction(sk))
+ tp->prr_out += sent_pkts;
tcp_cwnd_validate(sk);
return false;
}
@@ -2542,7 +2542,7 @@ begin_fwd:
}
NET_INC_STATS_BH(sock_net(sk), mib_idx);
- if (inet_csk(sk)->icsk_ca_state == TCP_CA_Recovery)
+ if (tcp_in_cwnd_reduction(sk))
tp->prr_out += tcp_skb_pcount(skb);
if (skb == tcp_write_queue_head(sk))
generated by cgit v1.2.3-55-g7522 (git 2.39.0) at 2024-06-20 04:15:59 +0200