net: add module parameter mars_port=

kernel/Kconfig

@@ -57,7 +57,8 @@ config MARS_DEFAULT_PORT
 	default 7777
 	---help---
 	Best practice is to uniformly use the same port number
-	in a cluster. Therefore, this is compiletime constant.
+	in a cluster. Therefore, this is a compiletime constant.
+	You may override this at insmod time via the mars_port= parameter.
 
 config MARS_MEM_RETRY
 	bool "make MARS memory allocation more robust"

kernel/mars_net.c

@@ -14,6 +14,7 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/string.h>
+#include <linux/moduleparam.h>
 
 #include "mars.h"
 #include "mars_net.h"
@@ -24,6 +25,10 @@
 /* Low-level network traffic
  */
 
+int mars_net_default_port = CONFIG_MARS_DEFAULT_PORT;
+EXPORT_SYMBOL_GPL(mars_net_default_port);
+module_param_named(mars_port, mars_net_default_port, int, 0);
+
 /* TODO: allow binding to specific source addresses instead of catch-all.
  * TODO: make all the socket options configurable.
  * TODO: implement signal handling.
@@ -58,7 +63,7 @@ int mars_create_sockaddr(struct sockaddr_storage *addr, const char *spec)
 
 	memset(addr, 0, sizeof(*addr));
 	sockaddr->sin_family = AF_INET;
-	sockaddr->sin_port = htons(CONFIG_MARS_DEFAULT_PORT);
+	sockaddr->sin_port = htons(mars_net_default_port);
 
 	/* Try to translate hostnames to IPs if possible.
 	 */

kernel/mars_net.h

@@ -8,6 +8,7 @@
 
 #include "brick.h"
 
+extern int mars_net_default_port;
 extern bool mars_net_is_alive;
 
 #define MAX_FIELD_LEN   32

kernel/sy_old/mars_proc.c

@@ -232,6 +232,8 @@ ctl_table mars_table[] = {
 #ifdef CONFIG_MARS_LOADAVG_LIMIT
 	INT_ENTRY("loadavg_limit",        mars_max_loadavg,       0600),
 #endif
+	// changing makes no sense because the server will immediately start upon modprobe
+	INT_ENTRY("mars_port",            mars_net_default_port,  0400),
 	INT_ENTRY("network_io_timeout",   global_net_io_timeout,  0600),
 	{
 		_CTL_NAME