implemented server_probe(int *pid) that used monitor interface

to probe server status.  Also returns PID if running (Linux only).

commandline.c

@@ -799,14 +799,23 @@ int app_server_status(int argc, const char *const *argv, struct command_line_opt
 {
   if (cli_arg(argc, argv, o, "instance path", &thisinstancepath, cli_absolute_path, NULL) == -1)
     return -1;
-  int pid = server_pid();
-  if (pid < 0)
-    return -1;
+  int pid=-1;
+  int status=server_probe(&pid);
+
   cli_puts("instancepath");
   cli_delim(":");
   cli_puts(serval_instancepath());
   cli_delim("\n");
-  if (pid) {
+  cli_puts("status");
+  cli_delim(":");
+  switch(status) {
+  case SERVER_NOTRESPONDING: cli_puts("not responding"); break;
+  case SERVER_NOTRUNNING: cli_puts("stopped"); break;
+  case SERVER_RUNNING: cli_puts("running"); break;
+  case SERVER_UNKNOWN: default: cli_puts("unknown"); break;
+  }
+  cli_delim("\n");
+  if (pid>-1) {
     cli_puts("pid");
     cli_delim(":");
     cli_printf("%d", pid);

monitor.c

@@ -693,3 +693,74 @@ int monitor_tell_clients(unsigned char *msg,int msglen,int mask)
     }
   return 0;
 }
+
+/* Check if there is a running server, and whether it is responding or not.
+ */
+int server_probe(int *pid)
+{
+  int fd=-1;
+  struct sockaddr_un addr;
+  if ( (fd = socket(AF_UNIX, SOCK_STREAM, 0)) == -1) {
+    return SERVER_UNKNOWN; 
+  }
+
+  memset(&addr, 0, sizeof(addr));
+  addr.sun_family = AF_UNIX;
+  addr.sun_path[0]=0;
+  snprintf(&addr.sun_path[1],100,"org.servalproject.servald.monitor.socket");
+  int len = 1+strlen(&addr.sun_path[1]) + sizeof(addr.sun_family);
+  char *p=(char *)&addr;
+  printf("last char='%c' %02x\n",p[len-1],p[len-1]);
+
+  if (connect(fd, (struct sockaddr*)&addr, len) == -1) {
+    close(fd);
+    return SERVER_NOTRUNNING;
+  }
+  
+  /* Give the server 2 seconds to send us something */
+  struct pollfd fds[1];
+  fds[0].fd=fd;
+  fds[0].events=POLLIN;
+  poll(fds,1,2000);
+  
+  fcntl(fd,F_SETFL,fcntl(fd, F_GETFL, NULL)|O_NONBLOCK);
+
+  *pid=-1;
+  if (pid!=NULL) {
+#if defined(HAVE_LINUX_STRUCT_UCRED)
+    struct ucred ucred;
+#elif defined(HAVE_BSD_STRUCT_UCRED)
+    struct xucred ucred;
+#else
+#error "Unknown ucred struct"
+#endif
+    socklen_t len=sizeof(ucred);
+    int res=getsockopt(fd,SOL_SOCKET,SO_PEERCRED,&ucred,&len);
+    if (len>sizeof(ucred)) {
+      WHYF("This is likely to be bad (memory overrun by getsockopt())");
+    }
+    if (res) { 
+      WHY("Failed to read credentials of monitor.socket client");
+    } else {
+#if defined(HAVE_LINUX_STRUCT_UCRED)
+      *pid = ucred.pid;
+#elif defined(HAVE_BSD_STRUCT_UCRED)
+#warning cannot get PID from ucred on BSD
+      *pid = -1;
+#endif
+    }
+  }
+  
+  char buff[1024];
+  int bytes=read(fd,buff,1024);
+  close(fd);
+  if (bytes<0) {
+    return SERVER_NOTRESPONDING;
+  } else if (bytes==0) {
+    // Could just be really busy.
+    return SERVER_NOTRESPONDING;
+  } else {
+    return SERVER_RUNNING;
+  }
+
+}

serval.h

@@ -1497,3 +1497,9 @@ int bufferAudioForPlayback(int codec,long long start_time,long long end_time,
 			   unsigned char *data,int dataLen);
 int startAudio();
 int stopAudio();
+
+#define SERVER_UNKNOWN 1
+#define SERVER_NOTRESPONDING 2
+#define SERVER_NOTRUNNING 3
+#define SERVER_RUNNING 4
+int server_probe(int *pid);