process: make max number of children (connections) configurable

At least some Panasonic clients try to open more than 5 simultaneous
connections to the server.  If we keep the default of 5 max children,
it results in choppy playback on those clients.

Make this setting configurable, and default to 50 max connections.
Our process is pretty lightweight, so 50 children should not be a
problem on most systems.

minidlna.c

@@ -509,6 +509,7 @@ init(int argc, char **argv)
 	
 	runtime_vars.port = 8200;
 	runtime_vars.notify_interval = 895;	/* seconds between SSDP announces */
+	runtime_vars.max_connections = 50;
 	runtime_vars.root_container = NULL;
 	runtime_vars.ifaces[0] = NULL;
 
@@ -706,9 +707,12 @@ init(int argc, char **argv)
 		case FORCE_SORT_CRITERIA:
 			force_sort_criteria = ary_options[i].value;
 			break;
+		case MAX_CONNECTIONS:
+			runtime_vars.max_connections = atoi(ary_options[i].value);
+			break;
 		default:
 			DPRINTF(E_ERROR, L_GENERAL, "Unknown option in file %s\n",
-			        optionsfile);
+				optionsfile);
 		}
 	}
 	if (log_path[0] == '\0')

minidlna.conf

@@ -72,3 +72,7 @@ model_number=1
 
 # always force SortCriteria to this value, regardless of the SortCriteria passed by the client
 #force_sort_criteria=+upnp:class,+upnp:originalTrackNumber,+dc:title
+
+# maximum number of simultaneous connections
+# note: many clients open several simultaneous connections while streaming
+#max_connections=50

minidlnatypes.h

@@ -48,6 +48,7 @@ struct lan_addr_s {
 struct runtime_vars_s {
 	int port;	/* HTTP Port */
 	int notify_interval;	/* seconds between SSDP announces */
+	int max_connections;	/* max number of simultaneous conenctions */
 	char *root_container;	/* root ObjectID (instead of "0") */
 	char *ifaces[MAX_LAN_ADDR];	/* list of configured network interfaces */
 };

options.c

@@ -62,7 +62,8 @@ static const struct {
 	{ ENABLE_DLNA_STRICT, "strict_dlna" },
 	{ ROOT_CONTAINER, "root_container" },
 	{ USER_ACCOUNT, "user" },
-	{ FORCE_SORT_CRITERIA, "force_sort_criteria" }
+	{ FORCE_SORT_CRITERIA, "force_sort_criteria" },
+	{ MAX_CONNECTIONS, "max_connections" }
 };
 
 int

options.h

@@ -56,7 +56,8 @@ enum upnpconfigoptions {
 	ENABLE_DLNA_STRICT,		/* strictly adhere to DLNA specs */
 	ROOT_CONTAINER,			/* root ObjectID (instead of "0") */
 	USER_ACCOUNT,			/* user account to run as */
-	FORCE_SORT_CRITERIA		/* force sorting by a given sort criteria */
+	FORCE_SORT_CRITERIA,		/* force sorting by a given sort criteria */
+	MAX_CONNECTIONS			/* maximum number of simultaneous connections */
 };
 
 /* readoptionsfile()

process.c

@@ -38,18 +38,20 @@
 #include <signal.h>
 #include <sys/wait.h>
 
+#include "upnpglobalvars.h"
 #include "process.h"
 #include "config.h"
 #include "log.h"
 
-static const int max_number_of_children = 5;
 static int number_of_children = 0;
 
 pid_t
 process_fork(void)
 {
-	if (number_of_children >= max_number_of_children)
+	if (number_of_children >= runtime_vars.max_connections)
 	{
+		DPRINTF(E_WARN, L_GENERAL, "Exceeded max connections [%d], not forking\n",
+			runtime_vars.max_connections);
 		errno = EAGAIN;
 		return -1;
 	}
@@ -63,8 +65,21 @@ process_fork(void)
 void
 process_handle_child_termination(int signal)
 {
-	waitpid(-1, NULL, WNOHANG);
-	--number_of_children;
+	pid_t pid;
+
+	while ((pid = waitpid(-1, NULL, WNOHANG)))
+	{
+		if (pid == -1)
+		{
+			if (errno == EINTR)
+				continue;
+			else
+				break;
+		}
+		else if (pid == 0)
+			break;
+		--number_of_children;
+	}
 }
 
 int