construct/ircd: Add option to soft-indicate no listening sockets should be bound.

construct/construct.cc

@@ -52,6 +52,7 @@ lgetopt opts[] =
 	{ "debug",      &ircd::debugmode, lgetopt::BOOL,    "Enable options for debugging" },
 	{ "console",    &cmdline,         lgetopt::BOOL,    "Drop to a command line immediately after startup" },
 	{ "execute",    &execute,         lgetopt::STRING,  "Execute command lines immediately after startup" },
+	{ "nolisten",   &ircd::nolisten,  lgetopt::BOOL,    "Normal execution but without listening sockets" },
 	{ nullptr,      nullptr,          lgetopt::STRING,  nullptr },
 };
 

include/ircd/stdinc.h

@@ -184,7 +184,8 @@ namespace ircd
 	constexpr size_t BUFSIZE { 512 };
 	extern const enum runlevel &runlevel;
 	extern const std::string &config;
-	extern bool debugmode; ///< Toggle; available only ifdef RB_DEBUG
+	extern bool debugmode;             ///< Toggle; available only ifdef RB_DEBUG
+	extern bool nolisten;              ///< Init option to not bind listener socks.
 
 	std::string demangle(const std::string &symbol);
 	template<class T> std::string demangle();

ircd/ircd.cc

@@ -22,6 +22,7 @@ namespace ircd
 
 	ctx::ctx *main_context;                      // Main program loop
 	bool debugmode;                              // meaningful ifdef RB_DEBUG
+	bool nolisten;                               // indicates no listener binding
 
 	void set_runlevel(const enum runlevel &);
 	void at_main_exit() noexcept;

ircd/m/m.cc

@@ -158,6 +158,16 @@ namespace ircd::m
 void
 ircd::m::init::listeners()
 {
+	if(ircd::nolisten)
+	{
+		log::warning
+		{
+			"Not listening on any addresses because nolisten flag is set."
+		};
+
+		return;
+	}
+
 	const json::array listeners
 	{
 		config["listeners"]