Add configuration parameter that allows to skip discovering interfaces

This adds a new configuration parameter that allows the user to completly
skip calling `is_same_machine` which is very expensive once the machine
has a critical mass of interfaces.

This comes with the downside of having to do more work in setting up
potential unnecessary binds.

common.c

@@ -265,7 +265,7 @@ int bind_peer(int fd, int fd_from)
     CHECK_RES_RETURN(res, "getpeername", res);
 
     /* if the destination is the same machine, there's no need to do bind */
-    if (is_same_machine(&from))
+    if (!cfg.no_discover_interfaces && is_same_machine(&from))
         return 0;
 
 #ifndef IP_BINDANY /* use IP_TRANSPARENT */

echosrv-conf.c

@@ -1,5 +1,5 @@
 /* Generated by conf2struct (https://www.rutschle.net/tech/conf2struct/README)
- * on Sun Sep  8 23:10:29 2024. 
+ * on Mon Nov 11 20:36:23 2024. 
 
 # conf2struct: generate libconf parsers that read to structs
 # Copyright (C) 2018-2024  Yves Rutschle

echosrv-conf.h

@@ -1,5 +1,5 @@
 /* Generated by conf2struct (https://www.rutschle.net/tech/conf2struct/README)
- * on Sun Sep  8 23:10:29 2024. 
+ * on Mon Nov 11 20:36:23 2024. 
 
 # conf2struct: generate libconf parsers that read to structs
 # Copyright (C) 2018-2024  Yves Rutschle

example.cfg

@@ -47,6 +47,12 @@ udp_max_connections: 16;
 # "none" disables use of syslog
 syslog_facility: "auth"; 
 
+# Disable discovering of local interfaces (useful if you
+# have a lot of interfaces and don't want to spend time
+# probing them all)
+# Default is false
+#no-discover-interfaces: true;
+
 # List of interfaces on which we should listen
 # Options:
 listen:

sslh-conf.c

@@ -1,5 +1,5 @@
 /* Generated by conf2struct (https://www.rutschle.net/tech/conf2struct/README)
- * on Sun Sep  8 23:10:29 2024. 
+ * on Mon Nov 11 20:36:23 2024. 
 
 # conf2struct: generate libconf parsers that read to structs
 # Copyright (C) 2018-2024  Yves Rutschle
@@ -483,6 +483,7 @@ struct arg_file* sslhcfg_conffile;
  struct arg_str* sslhcfg_syslog_facility;
  struct arg_str* sslhcfg_logfile;
  struct arg_str* sslhcfg_on_timeout;
+ struct arg_lit* sslhcfg_no_discover_interfaces;
  struct arg_str* sslhcfg_prefix;
  	struct arg_str* sslhcfg_listen;
  	struct arg_str* sslhcfg_ssh;
@@ -830,7 +831,7 @@ static struct config_desc table_sslhcfg_listen[] = {
         },
 	{ 0 }
 };
-
+                                                                                                                                                                                                                                                    
 static struct config_desc table_sslhcfg[] = {
 
 
@@ -1234,6 +1235,22 @@ static struct config_desc table_sslhcfg[] = {
             /* default_val*/    .default_val.def_string = "ssh" 
         },
 
+        { 
+            /* name */          "no_discover_interfaces", 
+            /* type */          CFG_BOOL, 
+            /* sub_group*/      NULL,
+            /* arg_cl */        & sslhcfg_no_discover_interfaces,
+            /* base_addr */     NULL,
+            /* offset */        offsetof(struct sslhcfg_item, no_discover_interfaces),
+            /* offset_len */    0,
+            /* offset_present */ 0,
+            /* size */          sizeof(int), 
+            /* array_type */    -1,
+            /* mandatory */     0, 
+            /* optional */      0, 
+            /* default_val*/    .default_val.def_bool = 0 
+        },
+
         { 
             /* name */          "prefix", 
             /* type */          CFG_STRING, 
@@ -1404,7 +1421,7 @@ static struct compound_cl_arg compound_cl_args[] = {
         {   /* arg: listen */
             .regex =           "(.+):(\\w+)",
             .arg_cl =          & sslhcfg_listen,
-            .base_entry =      & table_sslhcfg [26],
+            .base_entry =      & table_sslhcfg [27],
             .targets =         sslhcfg_listen_targets,
 
 
@@ -1416,7 +1433,7 @@ static struct compound_cl_arg compound_cl_args[] = {
         {   /* arg: ssh */
             .regex =           "(.+):(\\w+)",
             .arg_cl =          & sslhcfg_ssh,
-            .base_entry =      & table_sslhcfg [27],
+            .base_entry =      & table_sslhcfg [28],
             .targets =         sslhcfg_ssh_targets,
 
 
@@ -1428,7 +1445,7 @@ static struct compound_cl_arg compound_cl_args[] = {
         {   /* arg: tls */
             .regex =           "(.+):(\\w+)",
             .arg_cl =          & sslhcfg_tls,
-            .base_entry =      & table_sslhcfg [27],
+            .base_entry =      & table_sslhcfg [28],
             .targets =         sslhcfg_tls_targets,
 
 
@@ -1440,7 +1457,7 @@ static struct compound_cl_arg compound_cl_args[] = {
         {   /* arg: ssl */
             .regex =           "(.+):(\\w+)",
             .arg_cl =          & sslhcfg_ssl,
-            .base_entry =      & table_sslhcfg [27],
+            .base_entry =      & table_sslhcfg [28],
             .targets =         sslhcfg_ssl_targets,
 
 
@@ -1452,7 +1469,7 @@ static struct compound_cl_arg compound_cl_args[] = {
         {   /* arg: openvpn */
             .regex =           "(.+):(\\w+)",
             .arg_cl =          & sslhcfg_openvpn,
-            .base_entry =      & table_sslhcfg [27],
+            .base_entry =      & table_sslhcfg [28],
             .targets =         sslhcfg_openvpn_targets,
 
 
@@ -1464,7 +1481,7 @@ static struct compound_cl_arg compound_cl_args[] = {
         {   /* arg: tinc */
             .regex =           "(.+):(\\w+)",
             .arg_cl =          & sslhcfg_tinc,
-            .base_entry =      & table_sslhcfg [27],
+            .base_entry =      & table_sslhcfg [28],
             .targets =         sslhcfg_tinc_targets,
 
 
@@ -1476,7 +1493,7 @@ static struct compound_cl_arg compound_cl_args[] = {
         {   /* arg: wireguard */
             .regex =           "(.+):(\\w+)",
             .arg_cl =          & sslhcfg_wireguard,
-            .base_entry =      & table_sslhcfg [27],
+            .base_entry =      & table_sslhcfg [28],
             .targets =         sslhcfg_wireguard_targets,
 
 
@@ -1488,7 +1505,7 @@ static struct compound_cl_arg compound_cl_args[] = {
         {   /* arg: xmpp */
             .regex =           "(.+):(\\w+)",
             .arg_cl =          & sslhcfg_xmpp,
-            .base_entry =      & table_sslhcfg [27],
+            .base_entry =      & table_sslhcfg [28],
             .targets =         sslhcfg_xmpp_targets,
 
 
@@ -1500,7 +1517,7 @@ static struct compound_cl_arg compound_cl_args[] = {
         {   /* arg: http */
             .regex =           "(.+):(\\w+)",
             .arg_cl =          & sslhcfg_http,
-            .base_entry =      & table_sslhcfg [27],
+            .base_entry =      & table_sslhcfg [28],
             .targets =         sslhcfg_http_targets,
 
 
@@ -1512,7 +1529,7 @@ static struct compound_cl_arg compound_cl_args[] = {
         {   /* arg: adb */
             .regex =           "(.+):(\\w+)",
             .arg_cl =          & sslhcfg_adb,
-            .base_entry =      & table_sslhcfg [27],
+            .base_entry =      & table_sslhcfg [28],
             .targets =         sslhcfg_adb_targets,
 
 
@@ -1524,7 +1541,7 @@ static struct compound_cl_arg compound_cl_args[] = {
         {   /* arg: socks5 */
             .regex =           "(.+):(\\w+)",
             .arg_cl =          & sslhcfg_socks5,
-            .base_entry =      & table_sslhcfg [27],
+            .base_entry =      & table_sslhcfg [28],
             .targets =         sslhcfg_socks5_targets,
 
 
@@ -1536,7 +1553,7 @@ static struct compound_cl_arg compound_cl_args[] = {
         {   /* arg: syslog */
             .regex =           "(.+):(\\w+)",
             .arg_cl =          & sslhcfg_syslog,
-            .base_entry =      & table_sslhcfg [27],
+            .base_entry =      & table_sslhcfg [28],
             .targets =         sslhcfg_syslog_targets,
 
 
@@ -1548,7 +1565,7 @@ static struct compound_cl_arg compound_cl_args[] = {
         {   /* arg: msrdp */
             .regex =           "(.+):(\\w+)",
             .arg_cl =          & sslhcfg_msrdp,
-            .base_entry =      & table_sslhcfg [27],
+            .base_entry =      & table_sslhcfg [28],
             .targets =         sslhcfg_msrdp_targets,
 
 
@@ -1560,7 +1577,7 @@ static struct compound_cl_arg compound_cl_args[] = {
         {   /* arg: anyprot */
             .regex =           "(.+):(\\w+)",
             .arg_cl =          & sslhcfg_anyprot,
-            .base_entry =      & table_sslhcfg [27],
+            .base_entry =      & table_sslhcfg [28],
             .targets =         sslhcfg_anyprot_targets,
 
 
@@ -2250,6 +2267,7 @@ int sslhcfg_cl_parse(int argc, char* argv[], struct sslhcfg_item* cfg)
          sslhcfg_syslog_facility = arg_strn(NULL, "syslog-facility", "<str>", 0, 1, "Facility to syslog to"),
          sslhcfg_logfile = arg_strn(NULL, "logfile", "<str>", 0, 1, "Log messages to a file"),
          sslhcfg_on_timeout = arg_strn(NULL, "on-timeout", "<str>", 0, 1, "Target to connect to when timing out"),
+         sslhcfg_no_discover_interfaces = arg_litn(NULL, "no-discover-interfaces", 0, 1, "Do not discover interfaces"),
          sslhcfg_prefix = arg_strn(NULL, "prefix", "<str>", 0, 1, "Reserved for testing"),
  	sslhcfg_listen = arg_strn("p", "listen", "<host:port>", 0, 10, "Listen on host:port"),
  	sslhcfg_ssh = arg_strn(NULL, "ssh", "<host:port>", 0, 10, "Set up ssh target"),
@@ -2504,6 +2522,9 @@ void sslhcfg_fprint(
         fprintf(out, "on_timeout: %s", sslhcfg->on_timeout);
         fprintf(out, "\n");
         indent(out, depth);
+        fprintf(out, "no_discover_interfaces: %d", sslhcfg->no_discover_interfaces);
+        fprintf(out, "\n");
+        indent(out, depth);
         fprintf(out, "prefix: %s", sslhcfg->prefix);
         fprintf(out, "\n");
 

sslh-conf.h

@@ -1,5 +1,5 @@
 /* Generated by conf2struct (https://www.rutschle.net/tech/conf2struct/README)
- * on Sun Sep  8 23:10:29 2024. 
+ * on Mon Nov 11 20:36:23 2024. 
 
 # conf2struct: generate libconf parsers that read to structs
 # Copyright (C) 2018-2024  Yves Rutschle
@@ -105,6 +105,7 @@ struct sslhcfg_item {
 	int	logfile_is_present;
 	char*	logfile;
 	char*	on_timeout;
+	int	no_discover_interfaces;
 	char*	prefix;
 	size_t	listen_len;
 	struct sslhcfg_listen_item* listen;

sslhconf.cfg

@@ -89,6 +89,9 @@ config: {
             { name: "on-timeout"; type: "string"; default: "ssh"; 
               description: "Target to connect to when timing out"; },
 
+            { name: "no-discover-interfaces"; type: "bool"; default: false;
+              description: "Do not discover interfaces"; },
+
             { name: "prefix"; type: "string"; default: ""; description: "Reserved for testing" }, # For echosrv only, not sslh
 
             { name: "listen",