Experimental code to hunt for a DGPSIP server.

7 files changed, 96 insertions, 21 deletions

diff --git a/dgpsip.c b/dgpsip.c
index 96b7771d..77615b4d 100644
--- a/dgpsip.c
+++ b/dgpsip.c
@@ -31,7 +31,8 @@ int dgpsip_open(struct gps_context_t *context, const char *dgpsserver)
 	(void)gethostname(hn, sizeof(hn));
 	(void)snprintf(buf,sizeof(buf), "HELO %s gpsd %s\r\nR\r\n",hn,VERSION);
 	(void)write(context->dsock, buf, strlen(buf));
-    }
+    } else
+	gpsd_report(1, "Can't connect to DGPS server, netlib error %d\n", context->dsock);
     opts = fcntl(context->dsock, F_GETFL);
 
     if (opts >= 0)
@@ -89,3 +90,47 @@ void dgpsip_report(struct gps_device_t *session)
     }
 }
 
+/* maximum distance from DGPS server for it to be useful (meters) */
+#define DGPS_THRESHOLD	1600000
+
+void dgpsip_autoconnect(struct gps_context_t *context,
+			double lat, double lon,
+			const char *serverlist)
+/* tell the library to talk to the nearest DGPSIP server */
+{
+    char buf[BUFSIZ];
+    struct dgps_server_t {
+	double lat, lon;
+	char server[255];
+	double dist;
+    } keep, hold;
+    FILE *sfp = fopen(serverlist, "r");
+
+    if (sfp == NULL) {
+	gpsd_report(1, "no DGPS server list found.\n");
+	context->dsock = -2;	/* don't try this again */
+	return;
+    }
+
+    keep.dist = DGPS_THRESHOLD;
+    keep.server[0] = '\0';
+    while (fgets(buf, (int)sizeof(buf), sfp)) {
+	char *cp = strchr(buf, '#');
+	if (cp)
+	    *cp = '\0';
+	if (sscanf(buf,"%lf %lf %256s",&hold.lat, &hold.lon, hold.server)==3) {
+	    hold.dist = earth_distance(lat, lon, hold.lat, hold.lon);
+	    if (hold.dist < keep.dist)
+		memcpy(&keep, &hold, sizeof(struct dgps_server_t));
+	}
+    }
+    (void)fclose(sfp);
+
+    if (keep.server[0] == '\0') {
+	gpsd_report(1, "no DGPS server within %d m\n", DGPS_THRESHOLD);
+	context->dsock = -2;	/* don't try this again */
+	return;
+    }
+
+    (void)dgpsip_open(context, keep.server);
+}
diff --git a/gps.h b/gps.h
index 5223bc75..263affcb 100644
--- a/gps.h
+++ b/gps.h
@@ -195,7 +195,7 @@ extern double timestamp(void);
 extern double iso8601_to_unix(char *);
 extern /*@observer@*/char *unix_to_iso8601(double t, /*@ out @*/char[], int len);
 extern double gpstime_to_unix(int, double);
-/* extern double earth_distance(double, double, double, double); */
+extern double earth_distance(double, double, double, double);
 extern double wgs84_separation(double lat, double lon);
 extern int gpsd_units(void);
 
diff --git a/gpsd.c b/gpsd.c
index b794fe32..c4482891 100644
--- a/gpsd.c
+++ b/gpsd.c
@@ -48,6 +48,10 @@
 
 #define QLEN			5
 
+/* Where to find the list of DGPS correction servers, if there is one */
+#define DGPS_SERVER_LIST	"/usr/share/gpsd/dgpsip-servers"
+
+
 /*
  * The name of a tty device from which to pick up whatever the local
  * owning group for tty devices is.  Used when we drop privileges.
@@ -60,7 +64,7 @@ static bool in_background = false;
 static jmp_buf restartbuf;
 /*@ -initallelements -nullassign -nullderef @*/
 static struct gps_context_t context = {0, 
-				       false, 0, 0, 0, {'\0'}, 0,
+				       false, 0, -1, 0, {'\0'}, 0,
 				       LEAP_SECONDS, CENTURY_BASE, 
 #ifdef NTPSHM_ENABLE
 				       {0},
@@ -138,13 +142,13 @@ void gpsd_report(int errlevel, const char *fmt, ... )
 
 static void usage(void)
 {
-    (void)printf("usage:  gpsd [options] \n\
+    (void)printf("usage: gpsd [-d dgpsip-server] [-D n] [-F sockfile] [-P pidfile] [-S port] [-h] device...\n\
   Options include: \n\
-  -f string              	= set GPS device name \n\
-  -S integer (default %s)	= set port for daemon \n\
   -d host[:port]         	= set DGPS server \n\
+  -F sockfile                   = specift control socket location\n\
   -P pidfile              	= set file to record process ID \n\
   -D integer (default 0)  	= set debug level \n\
+  -S integer (default %s)	= set port for daemon \n\
   -h                     	= help message \n",
 	   DEFAULT_GPSD_PORT);
 }
@@ -1037,10 +1041,8 @@ int main(int argc, char *argv[])
 
     if (dgpsserver) {
         int dsock = dgpsip_open(&context, dgpsserver);
-	if (dsock >= 0) {
+	if (dsock >= 0)
 	    FD_SET(dsock, &all_fds);
-	} else
-	    gpsd_report(1, "Can't connect to DGPS server, netlib error %d\n", dsock);
     }
 
 #ifdef NTPSHM_ENABLE
@@ -1192,9 +1194,8 @@ int main(int argc, char *argv[])
 	}
 
 	/* be ready for DGPSIP reports */
-	if (FD_ISSET(context.dsock, &rfds)) {
+	if (context.dsock >= 0 && FD_ISSET(context.dsock, &rfds))
 	    dgpsip_poll(&context);
-	}
 
 	/* read any commands that came in over control sockets */
 	for (cfd = 0; cfd < FD_SETSIZE; cfd++)
@@ -1212,7 +1213,6 @@ int main(int argc, char *argv[])
 
 	/* poll all active devices */
 	for (channel = channels; channel < channels + MAXDEVICES; channel++) {
-
 	    if (!allocated_channel(channel))
 		continue;
 
@@ -1270,6 +1270,19 @@ int main(int argc, char *argv[])
 #endif
 	}
 
+	/* may be time to hunt up a DGPSIP server */
+	if (context.fixcnt > 0 && context.dsock == -1) {
+	    for (channel=channels; channel < channels+MAXDEVICES; channel++) {
+		if (channel->gpsdata.fix.mode < MODE_NO_FIX) {
+		    dgpsip_autoconnect(&context,
+				       channel->gpsdata.fix.latitude,
+				       channel->gpsdata.fix.longitude,
+				       DGPS_SERVER_LIST);
+		    break;
+		}
+	    }
+	}
+
 	/* accept and execute commands for all clients */
 	for (cfd = 0; cfd < FD_SETSIZE; cfd++) {
 	    if (subscribers[cfd].active && FD_ISSET(cfd, &rfds)) {
diff --git a/gpsd.h b/gpsd.h
index 15e7179a..75096a3e 100644
--- a/gpsd.h
+++ b/gpsd.h
@@ -177,6 +177,8 @@ extern int dgpsip_open(struct gps_context_t *, const char *);
 extern void dgpsip_poll(struct gps_context_t *);
 extern void dgpsip_relay(struct gps_device_t *);
 extern void dgpsip_report(struct gps_device_t *);
+extern void dgpsip_autoconnect(struct gps_context_t *, 
+			       double, double, const char *);
 
 extern int gpsd_open(struct gps_device_t *);
 extern bool gpsd_next_hunt_setting(struct gps_device_t *);
diff --git a/gpsd.spec.in b/gpsd.spec.in
index e5434d18..ed494109 100644
--- a/gpsd.spec.in
+++ b/gpsd.spec.in
@@ -72,6 +72,7 @@ cp xgpsspeed.ad "$RPM_BUILD_ROOT"%{_libdir}/X11/app-defaults/xgpsspeed
 mkdir -p "$RPM_BUILD_ROOT"%{_sysconfdir}/hotplug/usb
 cp gpsd.hotplug gpsd.usermap "$RPM_BUILD_ROOT"%{_sysconfdir}/hotplug/usb/
 # additional gpsd-devel files
+mkdir -p "$RPM_BUILD_ROOT"%{_datadir}/gpsd
 PYVERSION=`python -c "import sys; print sys.version[:3]"`
 mkdir -p "$RPM_BUILD_ROOT"%{_libdir}/python${PYVERSION}/site-packages
 cp gps.py gpsfake.py "$RPM_BUILD_ROOT"%{_libdir}/python${PYVERSION}/site-packages
@@ -99,6 +100,7 @@ cp gps.py gpsfake.py "$RPM_BUILD_ROOT"%{_libdir}/python${PYVERSION}/site-package
 %{_mandir}/man1/sirfmon.1*
 %{_sysconfdir}/hotplug/usb/gpsd.hotplug
 %{_sysconfdir}/hotplug/usb/gpsd.usermap
+%{_datadir}/gpsd/dgps-servers
 %{_libdir}/python*/site-packages/gps.py*
 
 %files -n gpsd-devel
@@ -134,7 +136,8 @@ cp gps.py gpsfake.py "$RPM_BUILD_ROOT"%{_libdir}/python${PYVERSION}/site-package
   and (3) a subtle error in the channel-assignment logic that only
   showed up with multiple sessions active.  In fact, the daemon code
   no longer uses dynamic-memory allocation at all.  Also, the code
-  no longer relies on FIONREAD working.
+  no longer relies on FIONREAD working.  The daemon now hunts for a 
+  DGPSIP server within 1600000m if the user didn't specify one.
 
 * Wed Jun 22 2005 Eric S. Raymond <esr@snark.thyrsus.com> - 2.26
 - Time DOP and total DOP are now passed on from GPSes that report 
diff --git a/gpsd.xml b/gpsd.xml
index 5bc3bb5f..77531a71 100644
--- a/gpsd.xml
+++ b/gpsd.xml
@@ -21,7 +21,7 @@
       <arg choice='opt'>-f <replaceable>GPS-devicename</replaceable></arg>
       <arg choice='opt'>-F <replaceable>control-socket</replaceable></arg>
       <arg choice='opt'>-S <replaceable>listener-port</replaceable></arg>
-      <arg choice='opt'>-d <replaceable>DGPS-server</replaceable></arg>
+      <arg choice='opt'>-d <replaceable>DGPSIP-server</replaceable></arg>
       <arg choice='opt'>-n </arg>      
       <arg choice='opt'>-N </arg>      
       <arg choice='opt'>-h </arg>
@@ -56,10 +56,12 @@ protocol used by the USB version of the Garmin 18 and other Garmin USB
 GPSes. <application>gpsd</application> effectively hides the
 differences among these.</para>
 
-<para>Optionally, <application>gpsd</application> may get
-differential-GPS corrections from a ground station running a RTCM-S104
-server; this will improve user error by roughly a factor of four.
-See <xref linkend='accuracy'/> for discussion.</para>
+<para><application>gpsd</application> can use differential-GPS
+corrections from a ground station running a DGPSIP server that reports
+RTCM-S104 data; this will improve user error by roughly a factor of
+four.  If no server is specified, <application>gpsd</application> will
+hunt for one.  See <xref linkend='accuracy'/> and <xref
+linkend='files'/> for discussion.</para>
 
 <para>The program accepts the following options:</para>
 <variablelist remap='TP'>
@@ -781,6 +783,18 @@ device if no GPS device was specified on the command line does not
 exist.</para>
 </listitem>
 </varlistentry>
+<varlistentry>
+<term><filename>/usr/share/gpsd/dgpsip-servers</filename></term>
+<listitem>
+<para>A text file listing DGPSIP servers worldwide.  If no DGPSIP
+server is specified at startup (via the -d option)
+<application>gpsd</application> will look here to find the 
+nearest one.  Each line has three space-separated fields: 
+latitude (decimal degrees), longitude (decimal degrees) and
+a server name (optionally followed by a colon and a port number).
+Text following # on a line is ignored.  Blank lines are ignored.</para>
+</listitem>
+</varlistentry>
 </variablelist>
 
 </refsect1>
diff --git a/gpsutils.c b/gpsutils.c
index dc9e68d1..2cc081ac 100644
--- a/gpsutils.c
+++ b/gpsutils.c
@@ -165,7 +165,6 @@ double gpstime_to_unix(int week, double tow)
 
 #define Deg2Rad(n)	((n) * DEG_2_RAD)
 
-#ifdef __UNUSED__
 static double CalcRad(double lat)
 /* earth's radius of curvature in meters at specified latitude.*/
 {
@@ -206,13 +205,12 @@ double earth_distance(double lat1, double lon1, double lat2, double lon2)
     // a very small amount due to rounding errors in the preceding
     // calculations (this is prone to happen when the argument points
     // are very close together).  Thus we constrain it here.
-    if (abs(a) > 1) 
+    if (fabs(a) > 1) 
 	a = 1;
     else if (a < -1) 
 	a = -1;
     return CalcRad((lat1+lat2) / 2) * acos(a);
 }
-#endif /* __UNUSED__ */
 
 /*****************************************************************************