diff options
| -rw-r--r-- | src/lib/frct.c | 30 |
1 files changed, 22 insertions, 8 deletions
diff --git a/src/lib/frct.c b/src/lib/frct.c index 40f2e9f9..27c333c6 100644 --- a/src/lib/frct.c +++ b/src/lib/frct.c @@ -26,6 +26,7 @@ #define MAX_RDV (1 * BILLION) /* ns */ #define MAX_RTO_MUL 8 /* caps the RTO backoff shift */ +#define MAX_TLP_PER_EP 2 /* RFC 8985 §7.3: up to 2 TLPs */ #define INITIAL_RTO (1 * BILLION) /* RFC 6298 §2.1: 1 s default */ #define RTT_BOOT_NS (10 * MILLION) /* rtt_hint floor + initial mdev */ #define SRTT_FLOOR_NS 1000L /* 1 us; smoothed RTT floor */ @@ -366,12 +367,13 @@ struct frcti { bool dsack_valid; /* RFC 8985 §7.2 RACK reorder-window scaling. */ - uint8_t reo_wnd_mult; /* 1..REO_WND_MULT_MAX */ + uint8_t reo_wnd_mult; /* REO_WND_MULT_MAX */ uint32_t dsack_lwe_snap; /* lwe @ last DSACK */ - uint64_t t_last_reo_widen; /* once-per-RTT gate */ + uint64_t t_last_reo_widen; /* once-per-RTT */ uint32_t dup_thresh; /* RFC 8985 */ uint32_t tlp_high_seq; /* §7.3: 0 = none */ + uint8_t tlp_count; /* §7.3 per-episode */ uint64_t t_nack; bool open; /* FC window state */ bool in_recovery; @@ -1226,8 +1228,9 @@ static void rxm_snd(struct frcti * frcti, slot->time = TS_TO_UINT64(now); /* RTO supersedes any pending TLP/fast-rxm on this slot. */ slot->flags = (slot->flags & ~(SND_FAST_RXM | SND_TLP)) | SND_RTX; - /* §7.3: RTO supersedes any outstanding TLP. */ + /* §7.3: RTO supersedes TLP probes and ends the probe episode. */ frcti->tlp_high_seq = 0; + frcti->tlp_count = 0; frcti->rtt_lwe = seqno + 1; @@ -2928,12 +2931,17 @@ static void tlp_due(void * arg) if (frcti->snd_cr.seqno == frcti->snd_cr.lwe) goto unlock; + if (!before(frcti->snd_cr.seqno, frcti->snd_cr.rwe)) goto unlock; /* FC-blocked: RDV handles it. */ - /* RFC 8985 §7.3: at most one outstanding TLP per episode. */ + + /* RFC 8985 §7.3: one outstanding probe, MAX_TLP_PER_EP per ep. */ if (frcti->tlp_high_seq != 0) goto unlock; + if (frcti->tlp_count >= MAX_TLP_PER_EP) + goto unlock; + pto = tlp_pto(frcti); /* §7.2: anchor PTO on most recent send; defer if still active. */ @@ -2949,9 +2957,8 @@ static void tlp_due(void * arg) goto unlock; /* Cap: if HoL RTO is due, let rxm_due fire instead. */ - rto_at = rxm->t0 - + ((uint64_t) frcti->rto - << LOAD_RELAXED(&frcti->rto_mul)); + rto_at = rxm->t0 + ((uint64_t) frcti->rto + << LOAD_RELAXED(&frcti->rto_mul)); if (rto_at <= now_ns) goto unlock; @@ -2964,6 +2971,7 @@ static void tlp_due(void * arg) frcti->rtt_lwe = frcti->snd_cr.lwe + 1; /* §7.3 outstanding-probe marker; ack_rcv/rxm_snd clear. */ frcti->tlp_high_seq = frcti->snd_cr.seqno; + frcti->tlp_count++; STAT_BUMP(frcti, tlp_snd); } @@ -2989,9 +2997,11 @@ static int tlp_arm(struct frcti * frcti) uint64_t pto; uint64_t deadline; - /* §7.3: at most one outstanding TLP per recovery episode. */ + /* §7.3: one outstanding probe, MAX_TLP_PER_EP per recovery ep. */ if (LOAD_RELAXED(&frcti->tlp_high_seq) != 0) return 0; + if (LOAD_RELAXED(&frcti->tlp_count) >= MAX_TLP_PER_EP) + return 0; if (__atomic_test_and_set(&frcti->tlp_pending, __ATOMIC_RELAXED)) return 0; @@ -3177,6 +3187,10 @@ static void frcti_ack_rcv(struct frcti * frcti, && !before(ackno, frcti->tlp_high_seq)) frcti->tlp_high_seq = 0; + /* §7.3: end the probe episode once inflight drains. */ + if (ackno == frcti->snd_cr.seqno) + frcti->tlp_count = 0; + /* RFC 8985 §7.2: halve mult per REO_DECAY_PKTS fresh-ACK'd seqnos. */ fresh = ackno - frcti->dsack_lwe_snap; if (frcti->reo_wnd_mult > 1 && fresh >= REO_DECAY_PKTS) { |