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Date: Tue, 27 Nov 2018 14:42:01 -0800
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>,
Jean-Louis Dupond <jean-louis@...ond.be>,
Neal Cardwell <ncardwell@...gle.com>,
Yuchung Cheng <ycheng@...gle.com>,
Eric Dumazet <edumazet@...gle.com>,
Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH v3 net-next 2/4] tcp: take care of compressed acks in tcp_add_reno_sack()
Neal pointed out that non sack flows might suffer from ACK compression
added in the following patch ("tcp: implement coalescing on backlog queue")
Instead of tweaking tcp_add_backlog() we can take into
account how many ACK were coalesced, this information
will be available in skb_shinfo(skb)->gso_segs
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
net/ipv4/tcp_input.c | 58 +++++++++++++++++++++++++-------------------
1 file changed, 33 insertions(+), 25 deletions(-)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index f32397890b6dcbc34976954c4be142108efa04d8..e5f3819ad859f6e6ca28e09c0f2dbdb7052708ee 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1863,16 +1863,20 @@ static void tcp_check_reno_reordering(struct sock *sk, const int addend)
/* Emulate SACKs for SACKless connection: account for a new dupack. */
-static void tcp_add_reno_sack(struct sock *sk)
+static void tcp_add_reno_sack(struct sock *sk, int num_dupack)
{
- struct tcp_sock *tp = tcp_sk(sk);
- u32 prior_sacked = tp->sacked_out;
+ if (num_dupack) {
+ struct tcp_sock *tp = tcp_sk(sk);
+ u32 prior_sacked = tp->sacked_out;
+ s32 delivered;
- tp->sacked_out++;
- tcp_check_reno_reordering(sk, 0);
- if (tp->sacked_out > prior_sacked)
- tp->delivered++; /* Some out-of-order packet is delivered */
- tcp_verify_left_out(tp);
+ tp->sacked_out += num_dupack;
+ tcp_check_reno_reordering(sk, 0);
+ delivered = tp->sacked_out - prior_sacked;
+ if (delivered > 0)
+ tp->delivered += delivered;
+ tcp_verify_left_out(tp);
+ }
}
/* Account for ACK, ACKing some data in Reno Recovery phase. */
@@ -2634,7 +2638,7 @@ void tcp_enter_recovery(struct sock *sk, bool ece_ack)
/* Process an ACK in CA_Loss state. Move to CA_Open if lost data are
* recovered or spurious. Otherwise retransmits more on partial ACKs.
*/
-static void tcp_process_loss(struct sock *sk, int flag, bool is_dupack,
+static void tcp_process_loss(struct sock *sk, int flag, int num_dupack,
int *rexmit)
{
struct tcp_sock *tp = tcp_sk(sk);
@@ -2653,7 +2657,7 @@ static void tcp_process_loss(struct sock *sk, int flag, bool is_dupack,
return;
if (after(tp->snd_nxt, tp->high_seq)) {
- if (flag & FLAG_DATA_SACKED || is_dupack)
+ if (flag & FLAG_DATA_SACKED || num_dupack)
tp->frto = 0; /* Step 3.a. loss was real */
} else if (flag & FLAG_SND_UNA_ADVANCED && !recovered) {
tp->high_seq = tp->snd_nxt;
@@ -2679,8 +2683,8 @@ static void tcp_process_loss(struct sock *sk, int flag, bool is_dupack,
/* A Reno DUPACK means new data in F-RTO step 2.b above are
* delivered. Lower inflight to clock out (re)tranmissions.
*/
- if (after(tp->snd_nxt, tp->high_seq) && is_dupack)
- tcp_add_reno_sack(sk);
+ if (after(tp->snd_nxt, tp->high_seq) && num_dupack)
+ tcp_add_reno_sack(sk, num_dupack);
else if (flag & FLAG_SND_UNA_ADVANCED)
tcp_reset_reno_sack(tp);
}
@@ -2757,13 +2761,13 @@ static bool tcp_force_fast_retransmit(struct sock *sk)
* tcp_xmit_retransmit_queue().
*/
static void tcp_fastretrans_alert(struct sock *sk, const u32 prior_snd_una,
- bool is_dupack, int *ack_flag, int *rexmit)
+ int num_dupack, int *ack_flag, int *rexmit)
{
struct inet_connection_sock *icsk = inet_csk(sk);
struct tcp_sock *tp = tcp_sk(sk);
int fast_rexmit = 0, flag = *ack_flag;
- bool do_lost = is_dupack || ((flag & FLAG_DATA_SACKED) &&
- tcp_force_fast_retransmit(sk));
+ bool do_lost = num_dupack || ((flag & FLAG_DATA_SACKED) &&
+ tcp_force_fast_retransmit(sk));
if (!tp->packets_out && tp->sacked_out)
tp->sacked_out = 0;
@@ -2810,8 +2814,8 @@ static void tcp_fastretrans_alert(struct sock *sk, const u32 prior_snd_una,
switch (icsk->icsk_ca_state) {
case TCP_CA_Recovery:
if (!(flag & FLAG_SND_UNA_ADVANCED)) {
- if (tcp_is_reno(tp) && is_dupack)
- tcp_add_reno_sack(sk);
+ if (tcp_is_reno(tp))
+ tcp_add_reno_sack(sk, num_dupack);
} else {
if (tcp_try_undo_partial(sk, prior_snd_una))
return;
@@ -2826,7 +2830,7 @@ static void tcp_fastretrans_alert(struct sock *sk, const u32 prior_snd_una,
tcp_identify_packet_loss(sk, ack_flag);
break;
case TCP_CA_Loss:
- tcp_process_loss(sk, flag, is_dupack, rexmit);
+ tcp_process_loss(sk, flag, num_dupack, rexmit);
tcp_identify_packet_loss(sk, ack_flag);
if (!(icsk->icsk_ca_state == TCP_CA_Open ||
(*ack_flag & FLAG_LOST_RETRANS)))
@@ -2837,8 +2841,7 @@ static void tcp_fastretrans_alert(struct sock *sk, const u32 prior_snd_una,
if (tcp_is_reno(tp)) {
if (flag & FLAG_SND_UNA_ADVANCED)
tcp_reset_reno_sack(tp);
- if (is_dupack)
- tcp_add_reno_sack(sk);
+ tcp_add_reno_sack(sk, num_dupack);
}
if (icsk->icsk_ca_state <= TCP_CA_Disorder)
@@ -3558,7 +3561,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
bool is_sack_reneg = tp->is_sack_reneg;
u32 ack_seq = TCP_SKB_CB(skb)->seq;
u32 ack = TCP_SKB_CB(skb)->ack_seq;
- bool is_dupack = false;
+ int num_dupack = 0;
int prior_packets = tp->packets_out;
u32 delivered = tp->delivered;
u32 lost = tp->lost;
@@ -3669,8 +3672,13 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
tcp_set_xmit_timer(sk);
if (tcp_ack_is_dubious(sk, flag)) {
- is_dupack = !(flag & (FLAG_SND_UNA_ADVANCED | FLAG_NOT_DUP));
- tcp_fastretrans_alert(sk, prior_snd_una, is_dupack, &flag,
+ if (!(flag & (FLAG_SND_UNA_ADVANCED | FLAG_NOT_DUP))) {
+ num_dupack = 1;
+ /* Consider if pure acks were aggregated in tcp_add_backlog() */
+ if (!(flag & FLAG_DATA))
+ num_dupack = max_t(u16, 1, skb_shinfo(skb)->gso_segs);
+ }
+ tcp_fastretrans_alert(sk, prior_snd_una, num_dupack, &flag,
&rexmit);
}
@@ -3688,7 +3696,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
no_queue:
/* If data was DSACKed, see if we can undo a cwnd reduction. */
if (flag & FLAG_DSACKING_ACK) {
- tcp_fastretrans_alert(sk, prior_snd_una, is_dupack, &flag,
+ tcp_fastretrans_alert(sk, prior_snd_una, num_dupack, &flag,
&rexmit);
tcp_newly_delivered(sk, delivered, flag);
}
@@ -3713,7 +3721,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
if (TCP_SKB_CB(skb)->sacked) {
flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una,
&sack_state);
- tcp_fastretrans_alert(sk, prior_snd_una, is_dupack, &flag,
+ tcp_fastretrans_alert(sk, prior_snd_una, num_dupack, &flag,
&rexmit);
tcp_newly_delivered(sk, delivered, flag);
tcp_xmit_recovery(sk, rexmit);
--
2.20.0.rc0.387.gc7a69e6b6c-goog
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