From 42749216453719dc255c56ff72848b5472138a54 Mon Sep 17 00:00:00 2001
From: Steven Barth <steven@midlink.org>
Date: Tue, 28 Oct 2014 09:57:24 +0100
Subject: [PATCH] Use monotonic clock for timeouts

Signed-off-by: Steven Barth <steven@midlink.org>
---
 cache.c   | 10 +++++-----
 service.c |  2 +-
 util.c    |  7 +++++++
 util.h    |  2 ++
 4 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/cache.c b/cache.c
index f2687e1..11d359d 100644
--- a/cache.c
+++ b/cache.c
@@ -63,7 +63,7 @@ cache_service_free(struct cache_service *s)
 static int
 cache_is_expired(time_t t, uint32_t ttl, int frac)
 {
-	if (time(NULL) - t >= ttl * frac / 100)
+	if (monotonic_time() - t >= ttl * frac / 100)
 		return 1;
 
 	return 0;
@@ -142,7 +142,7 @@ cache_service(struct interface *iface, char *entry, int hlen, int ttl)
 	avl_for_each_element_safe(&services, s, avl, t)
 		if (!strcmp(s->entry, entry)) {
 			s->refresh = 50;
-			s->time = time(NULL);
+			s->time = monotonic_time();
 			return s;
 		}
 
@@ -151,7 +151,7 @@ cache_service(struct interface *iface, char *entry, int hlen, int ttl)
 		&host_buf, hlen ? hlen + 1 : 0);
 
 	s->avl.key = s->entry = strcpy(entry_buf, entry);
-	s->time = time(NULL);
+	s->time = monotonic_time();
 	s->ttl = ttl;
 	s->iface = iface;
 	s->refresh = 50;
@@ -311,7 +311,7 @@ cache_answer(struct interface *iface, uint8_t *base, int blen, char *name, struc
 	if (r) {
 		if (!a->ttl) {
 			DBG(1, "D -> %s %s ttl:%d\n", dns_type_string(r->type), r->record, r->ttl);
-			r->time = time(0) + 1 - r->ttl;
+			r->time = monotonic_time() + 1 - r->ttl;
 		} else {
 			r->ttl = a->ttl;
 			DBG(1, "A -> %s %s ttl:%d\n", dns_type_string(r->type), r->record, r->ttl);
@@ -332,7 +332,7 @@ cache_answer(struct interface *iface, uint8_t *base, int blen, char *name, struc
 	r->ttl = a->ttl;
 	r->port = port;
 	r->rdlength = dlen;
-	r->time = time(NULL);
+	r->time = monotonic_time();
 	r->iface = iface;
 
 	if (tlen)
diff --git a/service.c b/service.c
index db4694e..0b42aee 100644
--- a/service.c
+++ b/service.c
@@ -113,7 +113,7 @@ service_add_srv(struct service *s, int ttl)
 static int
 service_timeout(struct service *s)
 {
-	time_t t = time(NULL);
+	time_t t = monotonic_time();
 
 	if (t - s->t <= TOUT_LOOKUP)
 		return 0;
diff --git a/util.c b/util.c
index f0517b4..d3d4d55 100644
--- a/util.c
+++ b/util.c
@@ -73,3 +73,10 @@ void get_hostname(void)
 	snprintf(mdns_hostname, sizeof(mdns_hostname), "%s", utsname.nodename);
 	snprintf(mdns_hostname_local, sizeof(mdns_hostname_local), "%s.local", utsname.nodename);
 }
+
+time_t monotonic_time(void)
+{
+	struct timespec ts;
+	clock_gettime(CLOCK_MONOTONIC, &ts);
+	return ts.tv_sec;
+}
diff --git a/util.h b/util.h
index 1a01fcc..efee5dc 100644
--- a/util.h
+++ b/util.h
@@ -15,6 +15,7 @@
 #define _UTIL_H__
 
 #include <stdint.h>
+#include <time.h>
 
 #define DBG(level, fmt, ...) do { \
 	if (debug >= level) \
@@ -31,5 +32,6 @@ extern char mdns_hostname_local[HOSTNAME_LEN + 6];
 
 extern void get_hostname(void);
 extern uint32_t rand_time_delta(uint32_t t);
+extern time_t monotonic_time(void);
 
 #endif
-- 
2.11.0