time handling: Support use of CLOCK_MONOTONIC

This involves a new initflag.  And introducing a wrapper for
gettimeofday().

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

squash! time handling: Support use of CLOCK_MONOTONIC

squash! time handling: Support use of CLOCK_MONOTONIC

5 files changed, 63 insertions, 14 deletions

diff --git a/src/adns.h b/src/adns.h
index 3bb63e0..899a731 100644
--- a/src/adns.h
+++ b/src/adns.h
@@ -100,6 +100,7 @@ typedef enum { /* In general, or together the desired flags: */
  adns_if_noautosys=   0x0010,/* do not make syscalls at every opportunity */
  adns_if_eintr=       0x0020,/* allow _wait and _synchronous to return EINTR */
  adns_if_nosigpipe=   0x0040,/* applic has SIGPIPE ignored, do not protect */
+ adns_if_monotonic=   0x0080,/* enable if you can; see adns_processtimeouts  */
  adns_if_checkc_entex=0x0100,/* consistency checks on entry/exit to adns fns */
  adns_if_checkc_freq= 0x0300,/* consistency checks very frequently (slow!) */
 
@@ -485,6 +486,21 @@ typedef struct {
  *   these approaches has optimal performance.
  */
 
+/*
+ * Use of time:
+ *
+ * adns needs to manipulate timeouts.  For API compatibility reasons
+ * (adns predates clock_gettime) the default is to use wall clock time
+ * from gettimeofday.  This will malfunction if the system clock is
+ * not suitably stable.  To avoid this, you should set
+ *   adns_if_monotonic
+ *
+ * If you specify adns_if_monotonic then all `now' values passed to
+ * adns must be from clock_gettime(CLOCK_MONOTONIC).  clock_gettime
+ * returns a struct timespec; you must convert it to a struct timeval
+ * by dividing the nsec by 1000 to make usec, rounding down.
+ */
+
 int adns_init(adns_state *newstate_r, adns_initflags flags,
 	      FILE *diagfile /*0=>stderr*/);
 
@@ -819,6 +835,8 @@ int adns_processexceptional(adns_state ads, int fd, const struct timeval *now);
  * use that fd and only in the manner specified, regardless of whether
  * adns_if_noautosys was specified.
  *
+ * now is as for adns_processtimeouts.
+ *
  * adns_processexceptional should be called when select(2) reports an
  * exceptional condition, or poll(2) reports POLLPRI.
  *
@@ -834,15 +852,19 @@ void adns_processtimeouts(adns_state ads, const struct timeval *now);
 /* Gives adns flow-of-control so that it can process any timeouts
  * which might have happened.  Very like _processreadable/writeable.
  *
- * now may be 0; if it isn't, *now must be the current time, recently
- * obtained from gettimeofday.
+ * now may be 0; if it isn't, *now must be the current time from
+ * gettimeofday, or iff adns_if_monotonic it must be converted
+ * from the results of clock_gettime(CLOCK_MONOTONIC) (with the
+ * timespec.tv_nsec rounded down to make timeval.tv_usec).
  */
 
 void adns_firsttimeout(adns_state ads,
 		       struct timeval **tv_mod, struct timeval *tv_buf,
 		       struct timeval now);
 /* Asks adns when it would first like the opportunity to time
- * something out.  now must be the current time, from gettimeofday.
+ * something out.
+ *
+ * now must be the current time, as for adns_processtimeouts.
  * 
  * If tv_mod points to 0 then tv_buf must be non-null, and
  * _firsttimeout will fill in *tv_buf with the time until the first
@@ -866,8 +888,9 @@ void adns_globalsystemfailure(adns_state ads);
  * adns_s_systemfail, and adns will close any stream sockets it has
  * open.
  *
- * This is used by adns, for example, if gettimeofday() fails.
- * Without this the program's event loop might start to spin !
+ * This is used by adns, for example, if gettimeofday() or
+ * clock_gettime fails.  Without this the program's event loop might
+ * start to spin !
  *
  * This call will never block.
  */
@@ -883,9 +906,11 @@ void adns_beforeselect(adns_state ads, int *maxfd, fd_set *readfds,
 /* Find out file descriptors adns is interested in, and when it would
  * like the opportunity to time something out.  If you do not plan to
  * block then tv_mod may be 0.  Otherwise, tv_mod and tv_buf are as
- * for adns_firsttimeout.  readfds, writefds, exceptfds and maxfd_io may
+ * for adns_processtimeouts.  readfds, writefds, exceptfds and maxfd_io may
  * not be 0.
  *
+ * now is as for adns_processtimeouts.
+ *
  * If tv_mod is 0 on entry then this will never actually do any I/O,
  * or change the fds that adns is using or the timeouts it wants.  In
  * any case it won't block, and it will set the timeout to zero if a
@@ -899,6 +924,8 @@ void adns_afterselect(adns_state ads, int maxfd, const fd_set *readfds,
  * select.  This is just a fancy way of calling adns_processreadable/
  * writeable/timeouts as appropriate, as if select had returned the
  * data being passed.  Always succeeds.
+ *
+ * now is as for adns_processtimeouts.
  */
 
 /*
@@ -962,6 +989,8 @@ int adns_beforepoll(adns_state ads, struct pollfd *fds,
  * descriptors, and use _firsttimeout is used to find out when adns
  * might want to time something out.)
  *
+ * now is as for adns_processtimeouts.
+ *
  * adns_beforepoll will return 0 on success, and will not fail for any
  * reason other than the fds buffer being too small (ERANGE).
  *
@@ -984,6 +1013,8 @@ void adns_afterpoll(adns_state ads, const struct pollfd *fds, int nfds,
 /* Gives adns flow-of-control for a bit; intended for use after
  * poll(2).  fds and nfds should be the results from poll().  pollfd
  * structs mentioning fds not belonging to adns will be ignored.
+ *
+ * now is as for adns_processtimeouts.
  */
 
 
diff --git a/src/event.c b/src/event.c
index 10d64b1..c326c28 100644
--- a/src/event.c
+++ b/src/event.c
@@ -36,6 +36,7 @@
 #include <sys/socket.h>
 #include <netinet/in.h>
 #include <arpa/inet.h>
+#include <time.h>
 
 #include "internal.h"
 #include "tvarith.h"
@@ -149,6 +150,19 @@ void adns__tcp_tryconnect(adns_state ads, struct timeval now) {
 
 /* Timeout handling functions. */
 
+int adns__gettimeofday(adns_state ads, struct timeval *tv) {
+  if (!(ads->iflags & adns_if_monotonic))
+    return gettimeofday(tv,0);
+
+  struct timespec ts;
+  int r = clock_gettime(CLOCK_MONOTONIC,&ts);
+  if (r) return r;
+
+  tv->tv_sec =  ts.tv_sec;
+  tv->tv_usec = ts.tv_nsec / 1000;
+  return 0;
+}
+
 void adns__must_gettimeofday(adns_state ads, const struct timeval **now_io,
 			     struct timeval *tv_buf) {
   const struct timeval *now;
@@ -156,8 +170,9 @@ void adns__must_gettimeofday(adns_state ads, const struct timeval **now_io,
 
   now= *now_io;
   if (now) return;
-  r= gettimeofday(tv_buf,0); if (!r) { *now_io= tv_buf; return; }
-  adns__diag(ads,-1,0,"gettimeofday failed: %s",strerror(errno));
+  r= adns__gettimeofday(ads,tv_buf); if (!r) { *now_io= tv_buf; return; }
+  adns__diag(ads,-1,0,"gettimeofday/clock_gettime failed: %s",
+	     strerror(errno));
   adns_globalsystemfailure(ads);
   return;
 }
@@ -670,7 +685,7 @@ int adns_processany(adns_state ads) {
 
   adns__consistency(ads,0,cc_enter);
 
-  r= gettimeofday(&now,0);
+  r= adns__gettimeofday(ads,&now);
   if (!r) adns_processtimeouts(ads,&now);
 
   /* We just use adns__fdevents to loop over the fd's trying them.
@@ -760,7 +775,7 @@ int adns_check(adns_state ads,
   int r;
   
   adns__consistency(ads,*query_io,cc_enter);
-  r= gettimeofday(&now,0);
+  r= adns__gettimeofday(ads,&now);
   if (!r) adns__autosys(ads,now);
 
   r= adns__internal_check(ads,query_io,answer_r,context_r);
diff --git a/src/internal.h b/src/internal.h
index 121c6d8..c03a77b 100644
--- a/src/internal.h
+++ b/src/internal.h
@@ -895,6 +895,8 @@ adns__timeout_clear(adns_query qu)
   { qu->timeout_ms= 0; timerclear(&qu->timeout_started); }
 
 
+int adns__gettimeofday(adns_state ads, struct timeval *tv_buf);
+
 void adns__must_gettimeofday(adns_state ads, const struct timeval **now_io,
 			     struct timeval *tv_buf);
 /* Call with care - might reentrantly cause queries to be completed! */
diff --git a/src/query.c b/src/query.c
index 4eba888..82adbdd 100644
--- a/src/query.c
+++ b/src/query.c
@@ -284,7 +284,7 @@ int adns_submit(adns_state ads,
   typei= adns__findtype(type);
   if (!typei) return ENOSYS;
 
-  r= gettimeofday(&now,0); if (r) goto x_errno;
+  r= adns__gettimeofday(ads,&now); if (r) goto x_errno;
   qu= query_alloc(ads,typei,type,flags,now); if (!qu) goto x_errno;
   
   qu->ctx.ext= context;
diff --git a/src/types.c b/src/types.c
index 59e9502..428dbfa 100644
--- a/src/types.c
+++ b/src/types.c
@@ -691,7 +691,7 @@ static void icb_addr(adns_query parent, adns_query child) {
      * settled on.
      */
     adns__cancel_children(parent);
-    r= gettimeofday(&now, 0);  if (r) goto x_gtod;
+    r= adns__gettimeofday(ads,&now);  if (r) goto x_gtod;
     qf= adns__qf_addr_cname;
     if (!(parent->flags & adns_qf_cname_loose)) qf |= adns_qf_cname_forbid;
     addr_subqueries(parent, now, qf, child->vb.buf, child->vb.used);
@@ -712,7 +712,7 @@ static void icb_addr(adns_query parent, adns_query child) {
     adns__cancel_children(parent);
     adns__free_interim(parent, pans->rrs.bytes);
     pans->rrs.bytes= 0; pans->nrrs= 0;
-    r= gettimeofday(&now, 0);  if (r) goto x_gtod;
+    r= adns__gettimeofday(ads,&now);  if (r) goto x_gtod;
     adns__search_next(ads, parent, now);
     return;
   }
@@ -737,7 +737,8 @@ x_gtod:
   /* We have our own error handling, because adns__must_gettimeofday
    * handles errors by calling adns_globalsystemfailure, which would
    * reenter the query processing logic. */
-  adns__diag(ads, -1, parent, "gettimeofday failed: %s", strerror(errno));
+  adns__diag(ads, -1, parent, "gettimeofday/clock_gettime failed: %s",
+	     strerror(errno));
   err= adns_s_systemfail;
   goto x_err;