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-rw-r--r--net/ipv4/tcp_input.c80
1 files changed, 62 insertions, 18 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 26713e5d89db..c0e8f2b1fa7e 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -863,6 +863,9 @@ void tcp_enter_cwr(struct sock *sk, const int set_ssthresh)
*/
static void tcp_disable_fack(struct tcp_sock *tp)
{
+ /* RFC3517 uses different metric in lost marker => reset on change */
+ if (tcp_is_fack(tp))
+ tp->lost_skb_hint = NULL;
tp->rx_opt.sack_ok &= ~2;
}
@@ -1470,6 +1473,13 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
tp->sacked_out += tcp_skb_pcount(skb);
fack_count += tcp_skb_pcount(skb);
+
+ /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
+ if (!tcp_is_fack(tp) && (tp->lost_skb_hint != NULL) &&
+ before(TCP_SKB_CB(skb)->seq,
+ TCP_SKB_CB(tp->lost_skb_hint)->seq))
+ tp->lost_cnt_hint += tcp_skb_pcount(skb);
+
if (fack_count > tp->fackets_out)
tp->fackets_out = fack_count;
@@ -1504,7 +1514,7 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
flag &= ~FLAG_ONLY_ORIG_SACKED;
}
- if (tp->retrans_out &&
+ if (tcp_is_fack(tp) && tp->retrans_out &&
after(highest_sack_end_seq, tp->lost_retrans_low) &&
icsk->icsk_ca_state == TCP_CA_Recovery)
flag |= tcp_mark_lost_retrans(sk, highest_sack_end_seq);
@@ -1858,6 +1868,26 @@ static inline int tcp_fackets_out(struct tcp_sock *tp)
return tcp_is_reno(tp) ? tp->sacked_out+1 : tp->fackets_out;
}
+/* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
+ * counter when SACK is enabled (without SACK, sacked_out is used for
+ * that purpose).
+ *
+ * Instead, with FACK TCP uses fackets_out that includes both SACKed
+ * segments up to the highest received SACK block so far and holes in
+ * between them.
+ *
+ * With reordering, holes may still be in flight, so RFC3517 recovery
+ * uses pure sacked_out (total number of SACKed segments) even though
+ * it violates the RFC that uses duplicate ACKs, often these are equal
+ * but when e.g. out-of-window ACKs or packet duplication occurs,
+ * they differ. Since neither occurs due to loss, TCP should really
+ * ignore them.
+ */
+static inline int tcp_dupack_heurestics(struct tcp_sock *tp)
+{
+ return tcp_is_fack(tp) ? tp->fackets_out : tp->sacked_out + 1;
+}
+
static inline int tcp_skb_timedout(struct sock *sk, struct sk_buff *skb)
{
return (tcp_time_stamp - TCP_SKB_CB(skb)->when > inet_csk(sk)->icsk_rto);
@@ -1978,13 +2008,13 @@ static int tcp_time_to_recover(struct sock *sk)
return 1;
/* Not-A-Trick#2 : Classic rule... */
- if (tcp_fackets_out(tp) > tp->reordering)
+ if (tcp_dupack_heurestics(tp) > tp->reordering)
return 1;
/* Trick#3 : when we use RFC2988 timer restart, fast
* retransmit can be triggered by timeout of queue head.
*/
- if (tcp_head_timedout(sk))
+ if (tcp_is_fack(tp) && tcp_head_timedout(sk))
return 1;
/* Trick#4: It is still not OK... But will it be useful to delay
@@ -2017,8 +2047,10 @@ static void tcp_verify_retransmit_hint(struct tcp_sock *tp,
tp->retransmit_skb_hint = NULL;
}
-/* Mark head of queue up as lost. */
-static void tcp_mark_head_lost(struct sock *sk, int packets)
+/* Mark head of queue up as lost. With RFC3517 SACK, the packets is
+ * is against sacked "cnt", otherwise it's against facked "cnt"
+ */
+static void tcp_mark_head_lost(struct sock *sk, int packets, int fast_rexmit)
{
struct tcp_sock *tp = tcp_sk(sk);
struct sk_buff *skb;
@@ -2040,8 +2072,13 @@ static void tcp_mark_head_lost(struct sock *sk, int packets)
/* this is not the most efficient way to do this... */
tp->lost_skb_hint = skb;
tp->lost_cnt_hint = cnt;
- cnt += tcp_skb_pcount(skb);
- if (cnt > packets || after(TCP_SKB_CB(skb)->end_seq, tp->high_seq))
+
+ if (tcp_is_fack(tp) ||
+ (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
+ cnt += tcp_skb_pcount(skb);
+
+ if (((!fast_rexmit || (tp->lost_out > 0)) && (cnt > packets)) ||
+ after(TCP_SKB_CB(skb)->end_seq, tp->high_seq))
break;
if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_SACKED_ACKED|TCPCB_LOST))) {
TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
@@ -2054,17 +2091,22 @@ static void tcp_mark_head_lost(struct sock *sk, int packets)
/* Account newly detected lost packet(s) */
-static void tcp_update_scoreboard(struct sock *sk)
+static void tcp_update_scoreboard(struct sock *sk, int fast_rexmit)
{
struct tcp_sock *tp = tcp_sk(sk);
- if (tcp_is_fack(tp)) {
+ if (tcp_is_reno(tp)) {
+ tcp_mark_head_lost(sk, 1, fast_rexmit);
+ } else if (tcp_is_fack(tp)) {
int lost = tp->fackets_out - tp->reordering;
if (lost <= 0)
lost = 1;
- tcp_mark_head_lost(sk, lost);
+ tcp_mark_head_lost(sk, lost, fast_rexmit);
} else {
- tcp_mark_head_lost(sk, 1);
+ int sacked_upto = tp->sacked_out - tp->reordering;
+ if (sacked_upto < 0)
+ sacked_upto = 0;
+ tcp_mark_head_lost(sk, sacked_upto, fast_rexmit);
}
/* New heuristics: it is possible only after we switched
@@ -2072,7 +2114,7 @@ static void tcp_update_scoreboard(struct sock *sk)
* Hence, we can detect timed out packets during fast
* retransmit without falling to slow start.
*/
- if (!tcp_is_reno(tp) && tcp_head_timedout(sk)) {
+ if (tcp_is_fack(tp) && tcp_head_timedout(sk)) {
struct sk_buff *skb;
skb = tp->scoreboard_skb_hint ? tp->scoreboard_skb_hint
@@ -2245,7 +2287,7 @@ static int tcp_try_undo_partial(struct sock *sk, int acked)
{
struct tcp_sock *tp = tcp_sk(sk);
/* Partial ACK arrived. Force Hoe's retransmit. */
- int failed = tcp_is_reno(tp) || tp->fackets_out>tp->reordering;
+ int failed = tcp_is_reno(tp) || (tcp_fackets_out(tp) > tp->reordering);
if (tcp_may_undo(tp)) {
/* Plain luck! Hole if filled with delayed
@@ -2379,7 +2421,8 @@ tcp_fastretrans_alert(struct sock *sk, int pkts_acked, int flag)
struct tcp_sock *tp = tcp_sk(sk);
int is_dupack = !(flag&(FLAG_SND_UNA_ADVANCED|FLAG_NOT_DUP));
int do_lost = is_dupack || ((flag&FLAG_DATA_SACKED) &&
- (tp->fackets_out > tp->reordering));
+ (tcp_fackets_out(tp) > tp->reordering));
+ int fast_rexmit = 0;
/* Some technical things:
* 1. Reno does not count dupacks (sacked_out) automatically. */
@@ -2399,11 +2442,11 @@ tcp_fastretrans_alert(struct sock *sk, int pkts_acked, int flag)
return;
/* C. Process data loss notification, provided it is valid. */
- if ((flag&FLAG_DATA_LOST) &&
+ if (tcp_is_fack(tp) && (flag & FLAG_DATA_LOST) &&
before(tp->snd_una, tp->high_seq) &&
icsk->icsk_ca_state != TCP_CA_Open &&
tp->fackets_out > tp->reordering) {
- tcp_mark_head_lost(sk, tp->fackets_out - tp->reordering);
+ tcp_mark_head_lost(sk, tp->fackets_out-tp->reordering, 0);
NET_INC_STATS_BH(LINUX_MIB_TCPLOSS);
}
@@ -2522,10 +2565,11 @@ tcp_fastretrans_alert(struct sock *sk, int pkts_acked, int flag)
tp->bytes_acked = 0;
tp->snd_cwnd_cnt = 0;
tcp_set_ca_state(sk, TCP_CA_Recovery);
+ fast_rexmit = 1;
}
- if (do_lost || tcp_head_timedout(sk))
- tcp_update_scoreboard(sk);
+ if (do_lost || (tcp_is_fack(tp) && tcp_head_timedout(sk)))
+ tcp_update_scoreboard(sk, fast_rexmit);
tcp_cwnd_down(sk, flag);
tcp_xmit_retransmit_queue(sk);
}
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-29 09:20:39 +0100