lib: Fix buffer allocation when retransmitting0.19.0

The timerwheel was retransmitting packets and the error check for
negative values of the rbuff allocation was instead checking for
non-zero values, causing a buffer allocation to succeed but the
program to continue down the unhappy path leaving that packet stuck in
the buffer unattended.

Also fixes wrongly scheduled retransmissions that cause packet storms.
FRCP is much more stable now. Still needs some work for high
bandwidth-delay products (fast-retransmit).

Signed-off-by: Dimitri Staessens <dimitri@ouroboros.rocks>
Signed-off-by: Sander Vrijders <sander@ouroboros.rocks>

1 files changed, 29 insertions, 9 deletions

diff --git a/src/lib/timerwheel.c b/src/lib/timerwheel.c
index 5c0fbfa0..0a6e48e1 100644
--- a/src/lib/timerwheel.c
+++ b/src/lib/timerwheel.c
@@ -174,6 +174,7 @@ static void timerwheel_move(void)
                                 uint32_t             snd_lwe;
                                 uint32_t             rcv_lwe;
                                 time_t               rto;
+                                size_t               new_i;
 
                                 r = list_entry(p, struct rxm, next);
 
@@ -205,26 +206,36 @@ static void timerwheel_move(void)
                                 if (ts_to_ns(now) - r->t0 > r->frcti->r)
                                         goto flow_down;
 
+                                pthread_rwlock_wrlock(&r->frcti->lock);
+
                                 if (r->frcti->probe
-                                    && (r->frcti->rttseq + 1) == r->seqno)
+                                    && (r->frcti->rttseq == r->seqno)) {
                                         r->frcti->probe = false;
+                                        r->frcti->rto += (rto >> 3);
+                                }
+
+                                r->frcti->n_rtx++;
+
+                                pthread_rwlock_unlock(&r->frcti->lock);
 #ifdef RXM_BLOCKING
   #ifdef RXM_BUFFER_ON_HEAP
-                                if (ipcp_sdb_reserve(&sdb, r->pkt_len))
+                                if (ipcp_sdb_reserve(&sdb, r->pkt_len) < 0)
   #else
-                                if (ipcp_sdb_reserve(&sdb, r->tail - r->head))
+                                if (ipcp_sdb_reserve(&sdb,
+                                                     r->tail - r->head) < 0)
   #endif
 #else
   #ifdef RXM_BUFFER_ON_HEAP
                                 if (shm_rdrbuff_alloc(ai.rdrb, r->pkt_len, NULL,
-                                                      &sdb))
+                                                      &sdb) < 0)
   #else
                                 if (shm_rdrbuff_alloc(ai.rdrb,
                                                       r->tail - r->head, NULL,
-                                                      &sdb))
+                                                      &sdb) < 0)
   #endif
 #endif
                                         goto reschedule; /* rbuff full */
+
                                 idx = shm_du_buff_get_idx(sdb);
 
                                 head = shm_du_buff_head(sdb);
@@ -248,15 +259,24 @@ static void timerwheel_move(void)
 #endif
                                         shm_flow_set_notify(f->set, f->flow_id,
                                                             FLOW_PKT);
+
                         reschedule:
-                                r->mul++;
+                                rslot = (rto << r->mul++) >> (RXMQ_RES * i);
+
+                                new_i = i;
+                                while (rslot >= RXMQ_SLOTS) {
+                                        ++ new_i;
+                                        rslot >>= RXMQ_BUMP;
+                                }
+
+                                if (new_i >= RXMQ_LVLS) /* Can't reschedule */
+                                        continue;
 
                                 /* Schedule at least in the next time slot. */
-                                rslot = (rxm_slot
-                                         + MAX(((rto * r->mul) >> RXMQ_RES), 1))
+                                rslot = ((rxm_slot >> (RXMQ_BUMP * (new_i - 1))) + MAX(rslot, 1))
                                         & (RXMQ_SLOTS - 1);
 
-                                list_add_tail(&r->next, &rw.rxms[i][rslot]);
+                                list_add_tail(&r->next, &rw.rxms[new_i][rslot]);
 
                                 continue;