#define FLAG_DATA_SACKED 0x20 /* New SACK. */
#define FLAG_ECE 0x40 /* ECE in this ACK */
#define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
+#define FLAG_ORIG_SACK_ACKED 0x200 /* Never retransmitted data are (s)acked */
#define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
#define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */
#define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */
tcp_highest_sack_seq(tp)))
state->reord = min(fack_count,
state->reord);
+ if (!after(end_seq, tp->high_seq))
+ state->flag |= FLAG_ORIG_SACK_ACKED;
}
if (sacked & TCPCB_LOST) {
const struct inet_connection_sock *icsk = inet_csk(sk);
struct tcp_sock *tp = tcp_sk(sk);
struct sk_buff *skb;
+ bool new_recovery = false;
/* Reduce ssthresh if it has not yet been made inside this window. */
- if (icsk->icsk_ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq ||
+ if (icsk->icsk_ca_state <= TCP_CA_Disorder ||
+ !after(tp->high_seq, tp->snd_una) ||
(icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) {
+ new_recovery = true;
tp->prior_ssthresh = tcp_current_ssthresh(sk);
tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
tcp_ca_event(sk, CA_EVENT_LOSS);
tcp_set_ca_state(sk, TCP_CA_Loss);
tp->high_seq = tp->snd_nxt;
TCP_ECN_queue_cwr(tp);
+
+ /* F-RTO RFC5682 sec 3.1 step 1: retransmit SND.UNA if no previous
+ * loss recovery is underway except recurring timeout(s) on
+ * the same SND.UNA (sec 3.2). Disable F-RTO on path MTU probing
+ */
+ tp->frto = sysctl_tcp_frto &&
+ (new_recovery || icsk->icsk_retransmits) &&
+ !inet_csk(sk)->icsk_mtup.probe_size;
}
/* If ACK arrived pointing to a remembered SACK, it means that our
return failed;
}
-/* Undo during loss recovery after partial ACK. */
-static bool tcp_try_undo_loss(struct sock *sk)
+/* Undo during loss recovery after partial ACK or using F-RTO. */
+static bool tcp_try_undo_loss(struct sock *sk, bool frto_undo)
{
struct tcp_sock *tp = tcp_sk(sk);
- if (tcp_may_undo(tp)) {
+ if (frto_undo || tcp_may_undo(tp)) {
struct sk_buff *skb;
tcp_for_write_queue(skb, sk) {
if (skb == tcp_send_head(sk))
tp->lost_out = 0;
tcp_undo_cwr(sk, true);
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSSUNDO);
+ if (frto_undo)
+ NET_INC_STATS_BH(sock_net(sk),
+ LINUX_MIB_TCPSPURIOUSRTOS);
inet_csk(sk)->icsk_retransmits = 0;
tp->undo_marker = 0;
- if (tcp_is_sack(tp))
+ if (frto_undo || tcp_is_sack(tp))
tcp_set_ca_state(sk, TCP_CA_Open);
return true;
}
/* 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)
+static void tcp_process_loss(struct sock *sk, int flag, bool is_dupack)
{
struct inet_connection_sock *icsk = inet_csk(sk);
struct tcp_sock *tp = tcp_sk(sk);
+ bool recovered = !before(tp->snd_una, tp->high_seq);
- if (!before(tp->snd_una, tp->high_seq)) {
+ if (tp->frto) { /* F-RTO RFC5682 sec 3.1 (sack enhanced version). */
+ if (flag & FLAG_ORIG_SACK_ACKED) {
+ /* Step 3.b. A timeout is spurious if not all data are
+ * lost, i.e., never-retransmitted data are (s)acked.
+ */
+ tcp_try_undo_loss(sk, true);
+ return;
+ }
+ if (after(tp->snd_nxt, tp->high_seq) &&
+ (flag & FLAG_DATA_SACKED || is_dupack)) {
+ tp->frto = 0; /* Loss was real: 2nd part of step 3.a */
+ } else if (flag & FLAG_SND_UNA_ADVANCED && !recovered) {
+ tp->high_seq = tp->snd_nxt;
+ __tcp_push_pending_frames(sk, tcp_current_mss(sk),
+ TCP_NAGLE_OFF);
+ if (after(tp->snd_nxt, tp->high_seq))
+ return; /* Step 2.b */
+ tp->frto = 0;
+ }
+ }
+
+ if (recovered) {
+ /* F-RTO RFC5682 sec 3.1 step 2.a and 1st part of step 3.a */
icsk->icsk_retransmits = 0;
tcp_try_undo_recovery(sk);
return;
}
-
if (flag & FLAG_DATA_ACKED)
icsk->icsk_retransmits = 0;
- if (tcp_is_reno(tp) && flag & FLAG_SND_UNA_ADVANCED)
- tcp_reset_reno_sack(tp);
- if (tcp_try_undo_loss(sk))
+ if (tcp_is_reno(tp)) {
+ /* 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);
+ else if (flag & FLAG_SND_UNA_ADVANCED)
+ tcp_reset_reno_sack(tp);
+ }
+ if (tcp_try_undo_loss(sk, false))
return;
- tcp_moderate_cwnd(tp);
tcp_xmit_retransmit_queue(sk);
}
newly_acked_sacked = pkts_acked + tp->sacked_out - prior_sacked;
break;
case TCP_CA_Loss:
- tcp_process_loss(sk, flag);
+ tcp_process_loss(sk, flag, is_dupack);
if (icsk->icsk_ca_state != TCP_CA_Open)
return;
/* Fall through to processing in Open state. */
}
if (!(sacked & TCPCB_SACKED_ACKED))
reord = min(pkts_acked, reord);
+ if (!after(scb->end_seq, tp->high_seq))
+ flag |= FLAG_ORIG_SACK_ACKED;
}
if (sacked & TCPCB_SACKED_ACKED)
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