limit_nsca_child_processes.diff

gistfile1.diff

--- nsca~/src/nsca.c	2014-12-03 20:44:00.000000000 -0800
+++ nsca/src/nsca.c	2014-12-03 20:46:29.098392130 -0800
@@ -21,6 +21,9 @@
 #include "../include/utils.h"
 #include "../include/nsca.h"

+#include <stdio.h>
+#include <errno.h>
+

 static int server_port=DEFAULT_SERVER_PORT;
 static char server_address[16]="0.0.0.0";
@@ -66,6 +69,9 @@
 int     nrhand=0;
 int     nwhand=0;
 int     npfds=0;
+
+int     live_children=0;
+int     max_children=100;

 #ifdef HAVE_LIBWRAP
 int     allow_severity=LOG_INFO;
@@ -457,6 +463,9 @@
 		else if(!strcmp(varname,"pid_file"))
 			pid_file=strdup(varvalue);

+		else if(!strcmp(varname,"max_children"))
+			max_children = strtoul(varvalue, NULL, 10);
+
 		else{
                         syslog(LOG_ERR,"Unknown option specified in config file '%s' - Line %d\n",filename,line);

@@ -475,7 +484,9 @@
 /* get rid of all the children we can... */
 static void reap_children(int sig){

-        while(waitpid(-1,NULL,WNOHANG)>0);
+        while(waitpid(-1,NULL,WNOHANG)>0) {
+		live_children--;
+		}

 	return;
         }
@@ -770,6 +781,11 @@
         /* wait for a connection request */
         while(1){

+		if(mode==MULTI_PROCESS_DAEMON) {
+			/* Check for children every loop interation */
+			reap_children(0);
+			}
+
 		/* we got a live one... */
                 if((new_sd=accept(sock,0,0))>=0)
                         break;
@@ -820,22 +836,6 @@
 		}
 #endif

-
-        /* fork() if we have to... */
-        if(mode==MULTI_PROCESS_DAEMON){
-
-                pid=fork();
-                if(pid){
-                        /* parent doesn't need the new connection */
-                        close(new_sd);
-                        return;
-                        }
-		else{
-                        /* child does not need to listen for connections */
-                        close(sock);
-                        }
-                }
-
         /* find out who just connected... */
         addrlen=sizeof(addr);
         rc=getpeername(new_sd,&addr,&addrlen);
@@ -853,17 +853,44 @@

         nptr=(struct sockaddr_in *)&addr;

+
+        /* fork() if we have to... */
+        if(mode==MULTI_PROCESS_DAEMON){
+		if (live_children >= max_children) {
+			syslog(LOG_ERR, "already have %d children, refusing connect from %s", live_children, inet_ntoa(nptr->sin_addr));
+			close(new_sd);
+			return;
+			}
+
+                pid=fork();
+                if(pid > 0){
+			live_children++;
+                        /* parent doesn't need the new connection */
+                        close(new_sd);
+                        return;
+                        }
+		else if (pid == 0){
+                        /* child does not need to listen for connections */
+                        close(sock);
+                        }
+                } else {
+			syslog(LOG_ERR, "fork failed! errno %d, %s", errno, strerror(errno));
+			close(new_sd);
+			return;
+		}
+
         /* log info to syslog facility */
         if(debug==TRUE)
                 syslog(LOG_DEBUG,"Connection from %s port %d",inet_ntoa(nptr->sin_addr),nptr->sin_port);

 	/* handle the connection */
-	if(mode==SINGLE_PROCESS_DAEMON)
+	if(mode==SINGLE_PROCESS_DAEMON) {
 		/* mark the connection as ready to be handled */
 		register_write_handler(new_sd, handle_connection, NULL);
-	else
+	} else {
 		/* handle the client connection */
 		handle_connection(new_sd, NULL);
+		}

 	return;
         }