From: Roy Marples <roy@marples.name>
Date: Fri, 1 Aug 2008 08:41:25 +0000 (+0000)
Subject: Tweak README about monotonic, and improve warning message.
X-Git-Tag: v4.0.2~97
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8fd2efb43e5d216dadd6386d7e26663b22f2144f;p=thirdparty%2Fdhcpcd.git

Tweak README about monotonic, and improve warning message.
---

diff --git a/README b/README
index d84ab755..ef7e7842 100644
--- a/README
+++ b/README
@@ -15,12 +15,15 @@ If you're cross compiling you may need to set the below knobs to avoid
 automatic tests.
 OS=BSD | Linux
 
-If you're building for a NOMMU system where fork() does not work, you should
-add -DTHERE_IS_NO_FORK to your CPPFLAGS.
+If you're building for an MMU-less system where fork() does not work, you
+should add -DTHERE_IS_NO_FORK to your CPPFLAGS.
 
 dhcpcd will try and use a monotonic clock when possible.
 Some libc implementations do not correctly report that they have a monotonic
 clock, but they have the headers to make it work. dhcpcd will warn about this.
+Without a monotonic clock, we fall victim of the year 2038 time_t bug on
+32-bit platforms AND the timers will be sufer from clock skew if the system
+clock changes.
 To force the use of a monotonic clock you can add -DFORCE_MONOTONIC
 to your CPPFLAGS.
 
diff --git a/client.c b/client.c
index f68bafa6..346da0ce 100644
--- a/client.c
+++ b/client.c
@@ -870,7 +870,7 @@ wait_for_fd(struct if_state *state, int *fd)
 		else if (iface->arp_fd != -1 && FD_ISSET(iface->arp_fd, &fds))
 			*fd = iface->arp_fd;
 	} else {
-		/* select and poll are CAN timeout BEFORE the timeout.
+		/* select and poll CAN timeout BEFORE the timeout.
 		 * This is a sad state of affairs, so we need to reduce the
 		 * lowest timeout to -1 so it REALLY has timed out. */
 		ref = get_lowest_timer(state);
diff --git a/common.c b/common.c
index 9911b345..9bedc6de 100644
--- a/common.c
+++ b/common.c
@@ -184,13 +184,14 @@ set_nonblock(int fd)
  * Which is why we use CLOCK_MONOTONIC, but it is not available on all
  * platforms.
  */
+#define NO_MONOTONIC "host does not support a montonic clock - timing can skew"
 int
 get_monotonic(struct timeval *tp)
 {
+	static int posix_clock_set = 0;
 #if defined(_POSIX_MONOTONIC_CLOCK) && defined(CLOCK_MONOTONIC)
 	struct timespec ts;
 	static clockid_t posix_clock;
-	static int posix_clock_set = 0;
 
 #ifdef FORCE_MONOTONIC
 	if (!posix_clock_set) {
@@ -205,7 +206,7 @@ get_monotonic(struct timeval *tp)
 			clock_monotonic = 1;
 		} else {
 			posix_clock = CLOCK_REALTIME;
-			logger(LOG_WARNING, "host does not support a monotonic clock");
+			logger(LOG_WARNING, NO_MONOTONIC);
 		}
 
 		posix_clock_set = 1;
@@ -219,6 +220,11 @@ get_monotonic(struct timeval *tp)
 	tp->tv_usec = ts.tv_nsec / 1000;
 	return 0;
 #else
+
+	if (!posix_clock_set) {
+		logger(LOG_WARNING, NO_MONOTONIC);
+		posix_clock_set = 1;
+	}
 	return gettimeofday(tp, NULL);
 #endif
 }