enabled edge to bind to a specified IP address (-b) (#753)

edge.8

@@ -40,6 +40,10 @@ TOS for packets, e.g. 0x48 for SSH like priority
 enable PMTU discovery, it can reduce fragmentation but
 causes connections to stall if not properly supported
 .TP
+\fB\-b \fR<\fIbind ip\fR>
+binds edge to the provided local IP address only, defaults to 'any' ip address
+if not provided
+.TP
 \fB\-S1\fR ... \fB\-S2\fR
 do not connect p2p, always use the supernode,
 \-S1 = via UDP, \-S2 = via TCP

include/n2n.h

@@ -220,7 +220,7 @@ int memxor (uint8_t *destination, const uint8_t *source, size_t len);
 char* sock_to_cstr (n2n_sock_str_t out,
                     const n2n_sock_t * sock);
 char * ip_subnet_to_str (dec_ip_bit_str_t buf, const n2n_ip_subnet_t *ipaddr);
-SOCKET open_socket (int local_port, int bind_any, int type);
+SOCKET open_socket (int local_port, int bind_any, in_addr_t address, int type);
 int sock_equal (const n2n_sock_t * a,
                 const n2n_sock_t * b);
 

include/n2n_typedefs.h

@@ -646,6 +646,7 @@ typedef struct n2n_edge_conf {
     char                     *encrypt_key;
     int                      register_interval;      /**< Interval for supernode registration, also used for UDP NAT hole punching. */
     int                      register_ttl;           /**< TTL for registration packet when UDP NAT hole punching through supernode. */
+    in_addr_t                bind_address;           /**< The address to bind to if provided (-b) */
     int                      local_port;
     int                      mgmt_port;
     uint8_t                  connect_tcp;            /** connection to supernode 0 = UDP; 1 = TCP */

src/edge.c

@@ -177,7 +177,7 @@ static void help (int level) {
                "[-H] "
                "[-z<compression>]"
             "\n                      "
-               "[-S<level of solitude>]"
+               "[-b <bind IP address>][-S<level of solitude>]"
           "\n\n tap device and       "
                "[-a [static:|dhcp:]<tap IP address>[/<cidr suffix>]] "
             "\n overlay network      "
@@ -252,6 +252,8 @@ static void help (int level) {
         printf(" -D                | enable PMTU discovery, it can reduce fragmentation but\n"
                "                   | causes connections to stall if not properly supported\n");
 #endif
+        printf(" -b <bind ip>      | bind the edge to the provided local IP address only,\n"
+               "                   | defaults to 'any' ip address if not provided\n");
         printf(" -S1 ... -S2       | do not connect p2p, always use the supernode,\n"
                "                   | -S1 = via UDP"
 
@@ -589,6 +591,20 @@ static int setOption (int optkey, char *optargument, n2n_tuntap_priv_config_t *e
             break;
         }
 
+        case 'b': {
+            if(optargument) {
+                conf->bind_address = inet_addr(optargument);
+
+                if(conf->bind_address == INADDR_NONE) {
+                    traceEvent(TRACE_WARNING, "Bad address to bind to, binding to any IP address.");
+                    conf->bind_address = INADDR_ANY;
+                    break;
+                }
+            }
+
+            break;
+        }
+
         case 't': {
             conf->mgmt_port = atoi(optargument);
             break;
@@ -711,6 +727,7 @@ static const struct option long_options[] =
         { "tap-device",        required_argument, NULL, 'd' },
         { "euid",              required_argument, NULL, 'u' },
         { "egid",              required_argument, NULL, 'g' },
+        { "bind",              required_argument, NULL, 'b' },
         { "help"     ,         no_argument,       NULL, '@' }, /* special character '@' to identify long help case */
         { "verbose",           no_argument,       NULL, 'v' },
         { NULL,                0,                 NULL,  0  }
@@ -724,7 +741,7 @@ static int loadFromCLI (int argc, char *argv[], n2n_edge_conf_t *conf, n2n_tunta
     u_char c;
 
     while ((c = getopt_long(argc, argv,
-                            "k:a:bc:Eu:g:m:M:s:d:l:p:fvhrt:i:I:J:P:S::DL:z::A::Hn:R:"
+                            "k:a:b:c:Eu:g:m:M:s:d:l:p:fvhrt:i:I:J:P:S::DL:z::A::Hn:R:"
 #ifdef __linux__
                             "T:"
 #endif

src/edge_utils.c

@@ -214,7 +214,8 @@ int supernode_connect(n2n_edge_t *eee) {
                                      (eee->conf.connect_tcp) ? 0 : eee->conf.local_port);
 
         eee->sock = open_socket((eee->conf.connect_tcp) ?  0 : eee->conf.local_port,
-                                 1 /* bind ANY */, eee->conf.connect_tcp);
+                                 2 /* bind as provided with next parameter */, eee->conf.bind_address,
+                                 eee->conf.connect_tcp);
 
         if(eee->sock < 0) {
             traceEvent(TRACE_ERROR, "Failed to bind main UDP port %u",
@@ -3090,7 +3091,7 @@ static int edge_init_sockets (n2n_edge_t *eee) {
         closesocket(eee->udp_multicast_sock);
 #endif
 
-    eee->udp_mgmt_sock = open_socket(eee->conf.mgmt_port, 0 /* bind LOOPBACK */, 0 /* UDP */);
+    eee->udp_mgmt_sock = open_socket(eee->conf.mgmt_port, 0 /* bind LOOPBACK */, 0, 0 /* UDP */);
     if(eee->udp_mgmt_sock < 0) {
         traceEvent(TRACE_ERROR, "Failed to bind management UDP port %u", eee->conf.mgmt_port);
         return(-2);
@@ -3105,7 +3106,7 @@ static int edge_init_sockets (n2n_edge_t *eee) {
     eee->multicast_peer.addr.v4[2] = 0;
     eee->multicast_peer.addr.v4[3] = 68;
 
-    eee->udp_multicast_sock = open_socket(N2N_MULTICAST_PORT, 1 /* bind ANY */, 0 /* UDP */);
+    eee->udp_multicast_sock = open_socket(N2N_MULTICAST_PORT, 1 /* bind ANY */, 0, 0 /* UDP */);
     if(eee->udp_multicast_sock < 0)
         return(-3);
     else {
@@ -3523,6 +3524,7 @@ void edge_init_conf_defaults (n2n_edge_conf_t *conf) {
 
     memset(conf, 0, sizeof(*conf));
 
+    conf->bind_address = INADDR_ANY; /* any address */
     conf->local_port = 0 /* any port */;
     conf->mgmt_port = N2N_EDGE_MGMT_PORT; /* 5644 by default */
     conf->transop_id = N2N_TRANSFORM_ID_NULL;

src/example_sn_embed.c

@@ -29,12 +29,12 @@ int main () {
         sss_node.daemon = 0;   // Whether to daemonize
         sss_node.lport = 1234; // Main UDP listen port
 
-        sss_node.sock = open_socket(sss_node.lport, 1, 0);
+        sss_node.sock = open_socket(sss_node.lport, 1, 0, 0);
         if(-1 == sss_node.sock) {
             exit(-2);
         }
 
-        sss_node.mgmt_sock = open_socket(5645, 0, 0); // Main UDP management port
+        sss_node.mgmt_sock = open_socket(5645, 0, 0, 0); // Main UDP management port
         if(-1 == sss_node.mgmt_sock) {
             exit(-2);
         }

src/n2n.c

@@ -28,7 +28,7 @@
 
 /* ************************************** */
 
-SOCKET open_socket (int local_port, int bind_any, int type /* 0 = UDP, TCP otherwise */) {
+SOCKET open_socket (int local_port, int bind_any, in_addr_t address, int type /* 0 = UDP, TCP otherwise */) {
 
     SOCKET sock_fd;
     struct sockaddr_in local_address;
@@ -50,7 +50,14 @@ SOCKET open_socket (int local_port, int bind_any, int type /* 0 = UDP, TCP other
     memset(&local_address, 0, sizeof(local_address));
     local_address.sin_family = AF_INET;
     local_address.sin_port = htons(local_port);
+    if(bind_any == 2) {
+        // use the provided address for binding
+        // REVISIT: allow for multiple addresses to be provided, i.e. through several '-b' at cli,
+        //          internally requires a list of in_addr_t addresses
+        local_address.sin_addr.s_addr = address;
+    } else {
         local_address.sin_addr.s_addr = htonl(bind_any ? INADDR_ANY : INADDR_LOOPBACK);
+    }
 
     if(bind(sock_fd,(struct sockaddr*) &local_address, sizeof(local_address)) == -1) {
         traceEvent(TRACE_ERROR, "Bind error on local port %u [%s]\n", local_port, strerror(errno));

src/sn.c

@@ -577,7 +577,7 @@ int main (int argc, char * const argv[]) {
 
     traceEvent(TRACE_DEBUG, "traceLevel is %d", getTraceLevel());
 
-    sss_node.sock = open_socket(sss_node.lport, 1 /*bind ANY*/, 0 /* UDP */);
+    sss_node.sock = open_socket(sss_node.lport, 1 /*bind ANY*/, 0, 0 /* UDP */);
     if(-1 == sss_node.sock) {
         traceEvent(TRACE_ERROR, "Failed to open main socket. %s", strerror(errno));
         exit(-2);
@@ -586,7 +586,7 @@ int main (int argc, char * const argv[]) {
     }
 
 #ifdef N2N_HAVE_TCP
-    sss_node.tcp_sock = open_socket(sss_node.lport, 1 /*bind ANY*/, 1 /* TCP */);
+    sss_node.tcp_sock = open_socket(sss_node.lport, 1 /*bind ANY*/, 0, 1 /* TCP */);
     if(-1 == sss_node.tcp_sock) {
         traceEvent(TRACE_ERROR, "Failed to open auxiliary TCP socket. %s", strerror(errno));
         exit(-2);
@@ -602,7 +602,7 @@ int main (int argc, char * const argv[]) {
     }
 #endif
 
-    sss_node.mgmt_sock = open_socket(sss_node.mport, 0 /* bind LOOPBACK */, 0 /* UDP */);
+    sss_node.mgmt_sock = open_socket(sss_node.mport, 0 /* bind LOOPBACK */, 0, 0 /* UDP */);
     if(-1 == sss_node.mgmt_sock) {
         traceEvent(TRACE_ERROR, "Failed to open management socket. %s", strerror(errno));
         exit(-2);