QUIC: separated path validation retransmit backoff.

Path validation packets containing PATH_CHALLENGE frames are sent separately
from regular frame queue, because of the need to use a decicated path and pad
the packets.  The packets are sent periodically, separately from the regular
probe/lost detection mechanism.  A path validation packet is resent up to 3
times, each time after PTO expiration, with increasing per-path PTO backoff.

2 files changed, 10 insertions, 7 deletions

diff --git a/src/event/quic/ngx_event_quic_ack.c b/src/event/quic/ngx_event_quic_ack.c
index 2458c9aea..062b065f9 100644
--- a/src/event/quic/ngx_event_quic_ack.c
+++ b/src/event/quic/ngx_event_quic_ack.c
@@ -736,7 +736,8 @@ ngx_quic_set_lost_timer(ngx_connection_t *c)
 
         q = ngx_queue_last(&ctx->sent);
         f = ngx_queue_data(q, ngx_quic_frame_t, queue);
-        w = (ngx_msec_int_t) (f->last + ngx_quic_pto(c, ctx) - now);
+        w = (ngx_msec_int_t) (f->last + (ngx_quic_pto(c, ctx) << qc->pto_count)
+                              - now);
 
         if (w < 0) {
             w = 0;
@@ -785,10 +786,9 @@ ngx_quic_pto(ngx_connection_t *c, ngx_quic_send_ctx_t *ctx)
 
     duration = qc->avg_rtt;
     duration += ngx_max(4 * qc->rttvar, NGX_QUIC_TIME_GRANULARITY);
-    duration <<= qc->pto_count;
 
     if (ctx->level == ssl_encryption_application && c->ssl->handshaked) {
-        duration += qc->ctp.max_ack_delay << qc->pto_count;
+        duration += qc->ctp.max_ack_delay;
     }
 
     return duration;
@@ -846,7 +846,9 @@ ngx_quic_pto_handler(ngx_event_t *ev)
             continue;
         }
 
-        if ((ngx_msec_int_t) (f->last + ngx_quic_pto(c, ctx) - now) > 0) {
+        if ((ngx_msec_int_t) (f->last + (ngx_quic_pto(c, ctx) << qc->pto_count)
+                              - now) > 0)
+        {
             continue;
         }
 
diff --git a/src/event/quic/ngx_event_quic_migration.c b/src/event/quic/ngx_event_quic_migration.c
index 37c7b8675..4b337ee6c 100644
--- a/src/event/quic/ngx_event_quic_migration.c
+++ b/src/event/quic/ngx_event_quic_migration.c
@@ -496,6 +496,7 @@ ngx_quic_validate_path(ngx_connection_t *c, ngx_quic_path_t *path)
                    "quic initiated validation of path seq:%uL", path->seqnum);
 
     path->validating = 1;
+    path->tries = 0;
 
     if (RAND_bytes(path->challenge1, 8) != 1) {
         return NGX_ERROR;
@@ -513,7 +514,6 @@ ngx_quic_validate_path(ngx_connection_t *c, ngx_quic_path_t *path)
     pto = ngx_quic_pto(c, ctx);
 
     path->expires = ngx_current_msec + pto;
-    path->tries = NGX_QUIC_PATH_RETRIES;
 
     if (!qc->path_validation.timer_set) {
         ngx_add_timer(&qc->path_validation, pto);
@@ -578,7 +578,6 @@ ngx_quic_path_validation_handler(ngx_event_t *ev)
     qc = ngx_quic_get_connection(c);
 
     ctx = ngx_quic_get_send_ctx(qc, ssl_encryption_application);
-    pto = ngx_quic_pto(c, ctx);
 
     next = -1;
     now = ngx_current_msec;
@@ -605,7 +604,9 @@ ngx_quic_path_validation_handler(ngx_event_t *ev)
             continue;
         }
 
-        if (--path->tries) {
+        if (++path->tries < NGX_QUIC_PATH_RETRIES) {
+            pto = ngx_quic_pto(c, ctx) << path->tries;
+
             path->expires = ngx_current_msec + pto;
 
             if (next == -1 || pto < next) {