timeout robustness: Track start time and duration

This allows us to detect if the clock rewinds, and restart our
timeouts from the new time.  Otherwise we might try to wait a very
long time.

The result is that clock instability may now produce spurious failures
of some queries, but it should no longer cause queries to be
indefinitely delayed.

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

diff --git a/src/event.c b/src/event.c
index 845bc690af88a80a3308d2ef3f5c89cb1baa3902..10d64b1da0c356575b7e5a50452e02f845ec1030 100644 (file)
--- a/src/event.c
+++ b/src/event.c
@@ -149,11 +149,6 @@ void adns__tcp_tryconnect(adns_state ads, struct timeval now) {
 
 /* Timeout handling functions. */
 
-void adns__timeout_set(adns_query qu, struct timeval now, int ms) {
-  qu->timeout_expires= now;
-  timevaladd(&qu->timeout_expires,ms);
-}
-
 void adns__must_gettimeofday(adns_state ads, const struct timeval **now_io,
                             struct timeval *tv_buf) {
   const struct timeval *now;
@@ -214,11 +209,16 @@ static void timeouts_queue(adns_state ads, int act,
                           struct timeval **tv_io, struct timeval *tvbuf,
                           struct timeval now, struct query_queue *queue) {
   adns_query qu, nqu;
+  struct timeval expires;
   
   for (qu= queue->head; qu; qu= nqu) {
     nqu= qu->next;
-    if (!timercmp(&now,&qu->timeout_expires,>)) {
-      inter_maxtoabs(tv_io,tvbuf,now,qu->timeout_expires);
+    if (timercmp(&now,&qu->timeout_started,<)) /* clock rewound */
+      qu->timeout_started= now;
+    expires= qu->timeout_started;
+    timevaladd(&expires, qu->timeout_ms);
+    if (!timercmp(&now,&expires,>)) {
+      inter_maxtoabs(tv_io,tvbuf,now,expires);
     } else {
       if (!act) { inter_immed(tv_io,tvbuf); return; }
       LIST_UNLINK(*queue,qu);

diff --git a/src/internal.h b/src/internal.h
index 23c7aa6fddc3dd371173fc889e3c3af7260e2b94..121c6d8fb36afd9f3e12edd1f388384a2266f007 100644 (file)
--- a/src/internal.h
+++ b/src/internal.h
@@ -298,7 +298,8 @@ struct adns__query {
   int id, flags, retries;
   int udpnextserver;
   unsigned long udpsent; /* bitmap indexed by server */
-  struct timeval timeout_expires;
+  int timeout_ms;
+  struct timeval timeout_started;
   time_t expires; /* Earliest expiry time of any record we used. */
 
   qcontext ctx;
@@ -885,9 +886,13 @@ void adns__autosys(adns_state ads, struct timeval now);
  * lest we end up in recursive descent !
  */
 
-void adns__timeout_set(adns_query qu, struct timeval now, int ms);
-static inline void adns__timeout_clear(adns_query qu)
-  { timerclear(&qu->timeout_expires); }
+static inline void
+adns__timeout_set(adns_query qu, struct timeval now, long ms)
+  { qu->timeout_ms= ms; qu->timeout_started= now; }
+
+static inline void
+adns__timeout_clear(adns_query qu)
+  { qu->timeout_ms= 0; timerclear(&qu->timeout_started); }
 
 
 void adns__must_gettimeofday(adns_state ads, const struct timeval **now_io,