From a6bf685ec3f64c3eae2d799aa1ebbdaa8f1de236 Mon Sep 17 00:00:00 2001
From: "Eric S. Raymond" <esr@thyrsus.com>
Date: Mon, 9 Mar 2009 14:55:20 +0000
Subject: Improve error detection from gpsd_hexpack().

---
 gpsd.c   | 13 +++++++++----
 gpsmon.c | 18 +++++++++---------
 hex.c    |  2 +-
 3 files changed, 19 insertions(+), 14 deletions(-)

diff --git a/gpsd.c b/gpsd.c
index 9362efa5..de0749bb 100644
--- a/gpsd.c
+++ b/gpsd.c
@@ -1332,13 +1332,18 @@ static void handle_control(int sfd, char *buf)
 	    *eq++ = '\0';
 	    len = strlen(eq)+5;
 	    if ((chp = find_device(stash)) != NULL) {
-		gpsd_report(LOG_INF,"<= control(%d): writing fromhex(%s) to %s\n", sfd, eq, stash);
 		/* NOTE: this destroys the original buffer contents */
 		len = (size_t)gpsd_hexpack(eq, eq, len);
-		ignore_return(write(chp->gpsdata.gps_fd, eq, len));
-		ignore_return(write(sfd, "OK\n", 3));
+		if (len < 0)
+		    gpsd_report(LOG_INF,"<= control(%d): invalid hex string (error %d)\n", sfd, len);
+		else
+		{
+		    gpsd_report(LOG_INF,"<= control(%d): writing fromhex(%s) to %s\n", sfd, eq, stash);
+		    ignore_return(write(chp->gpsdata.gps_fd, eq, len));
+		    ignore_return(write(sfd, "OK\n", 3));
+		}
 	    } else {
-		gpsd_report(LOG_INF,"<= control(%d): %s not active \n", sfd, stash);
+		gpsd_report(LOG_INF,"<= control(%d): %s not active\n", sfd, stash);
 		ignore_return(write(sfd, "ERROR\n", 6));
 	    }
 	}
diff --git a/gpsmon.c b/gpsmon.c
index b67722a2..cea6f63b 100644
--- a/gpsmon.c
+++ b/gpsmon.c
@@ -214,8 +214,6 @@ static void monitor_dump_send(void)
 
 bool monitor_control_send(/*@in@*/unsigned char *buf, size_t len)
 {
-    monitor_dump_send();
-
     if (controlfd == -1) 
 	return false;
     else {
@@ -246,7 +244,8 @@ bool monitor_control_send(/*@in@*/unsigned char *buf, size_t len)
 	    assert(read(controlfd, buf, 8) != -1);
 	    /*@ +sefparams @*/
 	}
-	return ((size_t)st == len);
+	monitor_dump_send();
+	return (st != -1);
     }
 }
 #endif /* ALLOW_CONTROLSEND */
@@ -817,15 +816,16 @@ int main (int argc, char **argv)
 		if (active == NULL)
 		    monitor_complain("No device defined yet");
 		else {
-		    len = gpsd_hexpack(arg, (char*)buf, len);
-		    if (len == -1)
-			monitor_complain("Invalid hex string");
-		    else if ((*active)->driver->control_send != NULL)
-			(void)monitor_control_send(buf, (size_t)len);
-		    else
+		    len = gpsd_hexpack(arg, (char*)buf, strlen(arg));
+		    if (len < 0)
+			monitor_complain("Invalid hex string (error %d)", len);
+		    else if ((*active)->driver->control_send == NULL)
 			monitor_complain("Device type has no control-send method.");
+		    else if (!monitor_control_send(buf, (size_t)len))
+			monitor_complain("Control send failed.");
 		}
 		break;
+
 #endif /* ALLOW_CONTROLSEND */
 
 	    default:
diff --git a/hex.c b/hex.c
index 2c7170a0..f09f6159 100644
--- a/hex.c
+++ b/hex.c
@@ -58,7 +58,7 @@ int gpsd_hexpack(char *src, char *dst, size_t len){
 
     l = (int)(strlen(src) / 2);
     if ((l < 1) || ((size_t)l > len))
-	return -1;
+	return -2;
 
     bzero(dst, (int)len);
     for (i = 0; i < l; i++)
-- 
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