Add support for obtaining active_ip from the local socket

As proposed in reply 4 at http://dev.yorhel.nl/ncdc/bug/76

This option is activated with a '/hset active_ip local'.

Author: Yorhel

src/doc.h

@@ -281,7 +281,11 @@ static const doc_set_t doc_sets[] = {
   " separated with a comma. When unset, '0.0.0.0,::' is assumed. Only the IP"
   " version used to connect to the hub is used. That is, if you connect to an"
   " IPv6 hub, then the configured IPv6 address is used and the IPv4 address is"
-  " ignored."
+  " ignored.\n\n"
+  "When set to the special value `local', ncdc will automatically get your IP"
+  " address from the local network interface that is used to connect to the"
+  " hub. This option should only be used if there is no NAT between you and"
+  " the hub, because this will give the wrong IP if you are behind a NAT."
 },
 { "active_port", 1, "<integer>",
   "The listen port for incoming connections in active mode. Set to `0' to"

src/hub.c

@@ -510,9 +510,10 @@ char *hub_ip(hub_t *hub) {
   if(!net_is_connected(hub->net))
     return NULL;
 
-  // Somewhat roundabout way of obtaining the IP for the correct version
   char *ip = var_get(hub->id, VAR_active_ip);
-  if(!net_is_ipv6(hub->net)) {
+  if(ip && strcmp(ip, "local") == 0) {
+    ip = (char *)net_localaddr(hub->net);
+  } else if(!net_is_ipv6(hub->net)) {
     struct in_addr ip4 = var_parse_ip4(ip);
     ip = ip4_isany(ip4) ? NULL : (char *)ip4_unpack(ip4);
   } else {

src/net.c

@@ -69,7 +69,8 @@ struct net_t {
   dnscon_t *dnscon; // state DNS,CON. Setting ->net to NULL 'cancels' DNS resolving.
   int sock; // state CON,ASY,SYN,DIS
   int socksrc; // state CON,ASY,DIS. Glib event source on 'sock'.
-  char addr[64]; // state ASY,SYN,DIS
+  char addr[56]; // state ASY,SYN,DIS, ip:port
+  char laddr[40]; // state ASY,SYN,DIS, ip only
 
   gnutls_session_t tls; // state ASY,SYN,DIS (only if tls is enabled)
   void (*cb_handshake)(net_t *, const char *); // state ASY, called after complete handshake.
@@ -1011,6 +1012,18 @@ void net_connected(net_t *n, int sock, const char *addr, gboolean v6) {
   n->wbuf = g_string_sized_new(1024);
   n->rbuf = g_string_sized_new(1024);
 
+  if(v6) {
+    struct sockaddr_in6 a;
+    socklen_t l = sizeof(a);
+    getsockname(sock, (void *)&a, &l);
+    strcpy(n->laddr, ip6_unpack(a.sin6_addr));
+  } else {
+    struct sockaddr_in a;
+    socklen_t l = sizeof(a);
+    getsockname(sock, (void *)&a, &l);
+    strcpy(n->laddr, ip4_unpack(a.sin_addr));
+  }
+
   ratecalc_reset(&n->rate_in);
   ratecalc_reset(&n->rate_out);
   ratecalc_register(&n->rate_in, RCC_DOWN);
@@ -1211,6 +1224,7 @@ void net_set_keepalive(net_t *n, const char *msg) {
 
 
 const char *net_remoteaddr(net_t *n) { return n->addr; }
+const char *net_localaddr(net_t *n)  { return n->laddr; }
 ratecalc_t *net_rate_in(net_t *n)    { return &n->rate_in; }
 ratecalc_t *net_rate_out(net_t *n)   { return &n->rate_out; }
 void       *net_handle(net_t *n)     { return n->handle; }

src/vars.c

@@ -143,6 +143,12 @@ static char *p_ip(const char *val, GError **err) {
   return g_strdup_printf("%s,%s", ip4_unpack(i4), ip6_unpack(i6));
 }
 
+static char *p_active_ip(const char *val, GError **err) {
+  if(strcmp(val, "local") == 0)
+    return g_strdup(val);
+  return p_ip(val, err);
+}
+
 static char *p_regex(const char *val, GError **err) {
   GRegex *r = g_regex_new(val, 0, 0, err);
   if(!r)
@@ -939,7 +945,7 @@ struct var_t {
 // name               g h  format          parse            suggest        getraw        setraw           default/init
 #define VARS\
   V(active,           1,1, f_bool,         p_bool,          su_bool,       NULL,         s_active_conf,   "false")\
-  V(active_ip,        1,1, f_id,           p_ip,            su_old,        NULL,         s_active_conf,   NULL)\
+  V(active_ip,        1,1, f_id,           p_active_ip,     su_old,        NULL,         s_active_conf,   NULL)\
   V(active_port,      1,1, f_int,          p_active_port,   NULL,          NULL,         s_active_conf,   NULL)\
   V(active_udp_port,  1,1, f_int,          p_active_port,   NULL,          g_active_udp, s_active_conf,   NULL)\
   V(adc_blom,         1,1, f_bool,         p_bool,          su_bool,       NULL,         NULL,            "false")\