implement IPC messaging with queue loop

Makefile.am

@@ -2,7 +2,7 @@ INCLUDES=${gammu_CFLAGS}
 yasnd_LDADD = ${libconfuse_LIBS}
 yasnd_LDADD += ${gammu_LIBS}
 bin_PROGRAMS = yasnd
-yasnd_SOURCES = yasnd.c yasnd-gammu.c
+yasnd_SOURCES = yasnd.c yasnd-gammu.c yasnd-ipc.c
 
 distclean-local:
 	rm -rf aclocal.m4 autom4te.cache depcomp install-sh missing configure Makefile.in config.h* &>/dev/null

yasnd-ipc.c

@@ -0,0 +1,80 @@
+#include <sys/ipc.h>
+#include <sys/msg.h>
+
+#include "yasnd.h"
+
+pid_t ipc_clone_pid;
+
+int open_queue()
+{
+	key_t keyval=ftok(".",'m');
+        int qid;
+	if((qid = msgget( keyval, IPC_CREAT | 0660 )) == -1)
+	{
+		log_event("Error opening/creating IPC message queue");
+		exit(EXIT_FAILURE);
+	}
+	return qid;
+}
+
+int send_message(int qid, mymsgbuf* qbuf)
+{
+	int result;
+        /* The length is essentially the size of the structure minus sizeof(mtype) */
+	int length = sizeof(mymsgbuf) - sizeof(long);
+
+	if((result = msgsnd( qid, qbuf, length, 0)) == -1)
+	{
+		return -1;
+	}
+
+	return result;
+}
+
+int read_message(int qid, mymsgbuf* qbuf, long type)
+{
+	int result;
+	int length = sizeof(mymsgbuf) - sizeof(long);
+        if((result = msgrcv( qid, qbuf, length, type,  0)) == -1)
+        {
+                return -1;
+        }
+	return result;
+}
+
+int remove_queue( int qid )
+{
+        if( msgctl(qid, IPC_RMID, 0) == -1)
+        {
+                return -1;
+        }
+        return 0;
+}
+
+int ipc_queue_loop()
+{
+	// set default signal handlers
+	signal(SIGTERM,SIG_DFL);
+	signal(SIGHUP,SIG_DFL);
+	//
+	mymsgbuf qbuf;
+	while(1)
+	{
+		int result=read_message(qid, &qbuf, 1);
+		if (result==-1)
+		{
+			log_event("Error: finishing IPC loop process...");
+			return 1;
+		}
+		char dbg_txt[150];
+		sprintf(dbg_txt,"Read IPC message - Type: %ld Text: %s", qbuf.mtype, qbuf.mtext);
+		log_debug(dbg_txt,DEBUG_ALL);
+	}
+}
+
+void ipc_init()
+{
+	qid = open_queue();
+	unsigned char ipc_child_stack[16384];
+	ipc_clone_pid=clone(ipc_queue_loop,ipc_child_stack+8192,CLONE_VM,NULL);
+}

yasnd.c

@@ -8,7 +8,6 @@
 #include <errno.h>
 #include <unistd.h>
 #include <syslog.h>
-#include <signal.h>
 #include <confuse.h>
 
 #include "yasnd.h"
@@ -16,6 +15,7 @@
 cfg_t *cfg; // pointer to configuration structure
 host_decl* hosts=NULL; // structure with hosts' definitions
 int hosts_count=0; // count of hosts
+int qid=-1; // IPC queue id
 int debug_flag=0;
 bool sms_send_enable=false; // send or not send alerts via SMS
 char* phone_device=NULL; // phone device for gammu, for example: "/dev/ttyACM0"
@@ -109,7 +109,6 @@ void init()
 	}
 	// initialize gammu structures
 	gammu_init();
-
 }
 
 void check_host(int num,host_decl* host)
@@ -121,6 +120,10 @@ void check_host(int num,host_decl* host)
         }
         // If pid == 0, then we are in the child
         if (pid == 0) {
+		// Set default signal handlers
+		signal(SIGTERM, SIG_DFL);
+		signal(SIGHUP, SIG_DFL);
+		//
 		char tmp[50];
 		sprintf(tmp, "Pinging host %s", host->hostname);
 		log_debug(tmp,DEBUG_BASE);
@@ -205,6 +208,10 @@ void signal_handler(int signum)
 {
 	void free_resources()
 	{
+		// Stop IPC loop and remove IPC queue
+		kill(ipc_clone_pid,SIGTERM);
+		waitpid(ipc_clone_pid,NULL,__WCLONE);
+		remove_queue(qid);
 		// free config structure
 		cfg_free(cfg);
 		// free gammu structure
@@ -224,6 +231,8 @@ void signal_handler(int signum)
 
 		// free all resources
 		free_resources();
+		// Init IPC loop again
+	        ipc_init();
 		// run init again
 		init();
 		// sleep 5 seconds and unlock Main Loop
@@ -234,8 +243,13 @@ void signal_handler(int signum)
 	if (signum==SIGTERM)
 	{
 		log_event("SIGTERM captured, daemon stopping");
+		// close log decriptor
 		closelog();
-		free_resources(); // free all other resources
+		// free resources
+		free_resources();
+		// remove IPC message queue
+		remove_queue(qid);
+		//
 		exit(EXIT_SUCCESS);
 	}
 }
@@ -278,21 +292,25 @@ int main(void) {
 	close(STDOUT_FILENO);
 	close(STDERR_FILENO);
 
-	// Set signal handlers
+	// initialize IPC queue and create process
-	signal(SIGTERM, signal_handler);
+	// that will watch for new messages in it
-	signal(SIGHUP, signal_handler);
+	ipc_init();
 
 	// Init apropriate structures
 	init();
 
+	// Set signal handlers
+	signal(SIGTERM, signal_handler);
+	signal(SIGHUP, signal_handler);
+
 	/* The Main Loop */
 	while (1) {
 		if (!loop_locked)
 		{
 			loop_function();
-//			sleep(60); /* wait 60 seconds */
+			sleep(60); /* wait 60 seconds */
-			log_event("Exiting");
+//			log_event("Exiting");
-			exit(EXIT_SUCCESS);
+//			exit(EXIT_SUCCESS);
 		}
 		else
 		{

yasnd.h

@@ -5,17 +5,14 @@
 #define DEBUG_BASE 1
 #define DEBUG_ALL 2
 
+#include <signal.h>
 #include <stdbool.h>
 #include <string.h>
 #include <gammu.h>
+#define _GNU_SOURCE
+#include <sched.h>
 
-// External functions
+// Structure, that described single checked host
-extern void log_event(const char *message);
-extern void log_debug(const char *message,int verbosity);
-extern bool check_gammu_error(GSM_Error err);
-extern bool gammu_init();
-extern bool gammu_send_sms(const char* message);
-
 typedef struct {
 	char* hostname; // address of host
 	pid_t helper_pid; // pid of helper('pinger') child process
@@ -23,6 +20,23 @@ typedef struct {
 	bool alert_sent; // variable, that changed when host goes online/offline
 } host_decl;
 
+// Structure, that described single IPC message
+typedef struct {
+	long mtype;         /* Message type */
+	char mtext[100];
+} mymsgbuf;
+
+// External functions
+extern void log_event(const char *message);
+extern void log_debug(const char *message,int verbosity);
+extern void* allocate_memory(int bytes);
+extern bool check_gammu_error(GSM_Error err);
+extern bool gammu_init();
+extern bool gammu_send_sms(const char* message);
+extern void ipc_init();
+extern int remove_queue(int qid);
+extern int send_message(int qid, mymsgbuf* qbuf);
+
 // External variables
 extern int hosts_count; // count of hosts
 extern int debug_flag;
@@ -32,5 +46,7 @@ extern char* recipient_number;
 extern char* phone_device; // phone device for gammu, for example: "/dev/ttyACM0"
 extern char* phone_model; // gammu phone model, for example: "at"
 extern char* phone_connection; // gammu phone connection type, for example: "at"
+extern int qid;
+extern pid_t ipc_clone_pid;
 
 #endif