From 6336611bc76a0b04911583cfbfa6f6911a65f86c Mon Sep 17 00:00:00 2001
From: Oliver Jowett <oliver@mutability.co.uk>
Date: Thu, 29 Dec 2016 17:56:32 +0000
Subject: [PATCH] Turn on mode A/C if a Beast connection asks for it.

Add a --no-modeac-auto option to disable this.
---
 dump1090.c |  5 +++++
 dump1090.h |  1 +
 net_io.c   | 21 +++++++++++++++++++++
 3 files changed, 27 insertions(+)

diff --git a/dump1090.c b/dump1090.c
index f943f05..60e79ae 100644
--- a/dump1090.c
+++ b/dump1090.c
@@ -144,6 +144,7 @@ void modesInitConfig(void) {
     Modes.json_interval           = 1000;
     Modes.json_location_accuracy  = 1;
     Modes.maxRange                = 1852 * 300; // 300NM default max range
+    Modes.mode_ac_auto            = 1;
 }
 //
 //=========================================================================
@@ -666,6 +667,7 @@ void showHelp(void) {
 "--raw                    Show only messages hex values\n"
 "--net                    Enable networking\n"
 "--modeac                 Enable decoding of SSR Modes 3/A & 3/C\n"
+"--no-modeac-auto         Don't enable Mode A/C if requested by a Beast connection\n"
 "--net-only               Enable just networking, no RTL device or file used\n"
 "--net-bind-address <ip>  IP address to bind to (default: Any; Use 127.0.0.1 for private)\n"
 #ifdef ENABLE_WEBSERVER
@@ -954,6 +956,9 @@ int main(int argc, char **argv) {
             Modes.net = 1;
         } else if (!strcmp(argv[j],"--modeac")) {
             Modes.mode_ac = 1;
+            Modes.mode_ac_auto = 0;
+        } else if (!strcmp(argv[j],"--no-modeac-auto")) {
+            Modes.mode_ac_auto = 0;
         } else if (!strcmp(argv[j],"--net-beast")) {
             fprintf(stderr, "--net-beast ignored, use --net-bo-port to control where Beast output is generated\n");
         } else if (!strcmp(argv[j],"--net-only")) {
diff --git a/dump1090.h b/dump1090.h
index 5dab1ad..324d01d 100644
--- a/dump1090.h
+++ b/dump1090.h
@@ -313,6 +313,7 @@ struct {                             // Internal state
     int   check_crc;                 // Only display messages with good CRC
     int   raw;                       // Raw output format
     int   mode_ac;                   // Enable decoding of SSR Modes A & C
+    int   mode_ac_auto;              // allow toggling of A/C by Beast commands
     int   debug;                     // Debugging mode
     int   net;                       // Enable networking
     int   net_only;                  // Enable just networking
diff --git a/net_io.c b/net_io.c
index 64568de..4d2d88e 100644
--- a/net_io.c
+++ b/net_io.c
@@ -81,6 +81,8 @@ static void send_sbs_heartbeat(struct net_service *service);
 static void writeFATSVEvent(struct modesMessage *mm, struct aircraft *a);
 static void writeFATSVPositionUpdate(float lat, float lon, float alt);
 
+static void autoset_modeac();
+
 //
 //=========================================================================
 //
@@ -315,6 +317,8 @@ static void modesCloseClient(struct client *c) {
     c->fd = -1;
     c->service = NULL;
     c->modeac_requested = 0;
+
+    autoset_modeac();
 }
 //
 //=========================================================================
@@ -788,6 +792,22 @@ static void handle_radarcape_position(float lat, float lon, float alt)
     }
 }
 
+// recompute global Mode A/C setting
+static void autoset_modeac() {
+    struct client *c;
+
+    if (!Modes.mode_ac_auto)
+        return;
+
+    Modes.mode_ac = 0;
+    for (c = Modes.clients; c; c = c->next) {
+        if (c->modeac_requested) {
+            Modes.mode_ac = 1;
+            break;
+        }
+    }
+}
+
 // Send some Beast settings commands to a client
 void sendBeastSettings(struct client *c, const char *settings)
 {
@@ -826,6 +846,7 @@ static int handleBeastCommand(struct client *c, char *p) {
         break;
     }
 
+    autoset_modeac();
     return 0;
 }