Add --persistent flag to Linux edge

README.md

@@ -3,6 +3,8 @@
 
 # n2n
 
+NOTE: edge with `--persistent` flag will make the Linux TUNTAP device persistent, this is useful for routing.
+
 n2n is a light VPN software which makes it easy to create virtual networks bypassing intermediate firewalls.
 
 In order to start using n2n, two elements are required:

include/n2n_typedefs.h

@@ -222,6 +222,7 @@ typedef struct tuntap_dev {
     uint32_t             device_mask;
     uint16_t             mtu;
     char                 dev_name[N2N_IFNAMSIZ];
+    int                  persistent;
 } tuntap_dev;
 
 #define SOCKET int
@@ -676,6 +677,7 @@ typedef struct n2n_edge_conf {
     uint8_t                  sn_selection_strategy; /**< encodes currently chosen supernode selection strategy. */
     uint8_t                  number_max_sn_pings;   /**< Number of maximum concurrently allowed supernode pings. */
     uint64_t                 mgmt_password_hash;    /**< contains hash of managament port password. */
+    uint8_t                  persistent;            /**< Persistent TUNTAP */
 } n2n_edge_conf_t;
 
 

src/edge.c

@@ -305,6 +305,7 @@ static void help (int level) {
                "                   | '-m 10:20:30:40:50:60', random otherwise\n");
 #if defined(N2N_CAN_NAME_IFACE)
         printf(" -d <device>       | TAP device name\n");
+        printf(" --persistent      | Persistent TAP device\n");
 #endif
         printf(" -M <mtu>          | specify n2n MTU of TAP interface, default %d\n", DEFAULT_MTU);
         printf(" -r                | enable packet forwarding through n2n community\n");
@@ -568,6 +569,11 @@ static int setOption (int optkey, char *optargument, n2n_tuntap_priv_config_t *e
             ec->tuntap_dev_name[N2N_IFNAMSIZ - 1] = '\0';
             break;
         }
+        case '$': /* persistent TUNTAP */ {
+            traceEvent(TRACE_NORMAL, "persistent TUNTAP");
+            conf->persistent = 1;
+            break;
+        }
 #endif
         case 'I': /* Device Description (hint) or username */ {
             strncpy((char *)conf->dev_desc, optargument, N2N_DESC_SIZE);
@@ -807,6 +813,7 @@ static const struct option long_options[] =
         { "help",                no_argument,       NULL, '@' }, /* internal special character '@' to identify long help case */
         { "select-rtt",          no_argument,       NULL, '[' }, /*                            '['             rtt selection strategy */
         { "select-mac",          no_argument,       NULL, ']' }, /*                            ']'             mac selection strategy */
+        { "persistent",          no_argument,       NULL, '$'}, /*                             '$'             persistent tap device  */
         { "management-password", required_argument, NULL, '{' }, /*                            '{'             management port password */
         { NULL,                  0,                 NULL,  0  }
     };
@@ -1109,6 +1116,7 @@ int main (int argc, char* argv[]) {
     if(setuid(0) != 0)
         traceEvent(TRACE_ERROR, "unable to become root [%u/%s]", errno, strerror(errno));
     /* setgid(0); */
+    tuntap.persistent = conf.persistent;
 #endif
 
     if(conf.encrypt_key && !strcmp((char*)conf.community_name, conf.encrypt_key))

src/tuntap_linux.c

@@ -138,6 +138,14 @@ int tuntap_open (tuntap_dev *device,
         return -1;
     }
 
+    // persistent
+    rc = ioctl(device->fd, TUNSETPERSIST, device->persistent);
+    if (rc < 0) {
+        traceEvent(TRACE_ERROR, "tuntap ioctl(TUNSETPERSIST, IFF_TAP) error: %s[%d]\n", strerror(errno), rc);
+        close(device->fd);
+        return -1;
+    }
+
     // store the device name for later reuse
     strncpy(device->dev_name, ifr.ifr_name, MIN(IFNAMSIZ, N2N_IFNAMSIZ));
 
@@ -251,7 +259,6 @@ int tuntap_write (struct tuntap_dev *tuntap, unsigned char *buf, int len) {
 
 
 void tuntap_close (struct tuntap_dev *tuntap) {
-
     close(tuntap->fd);
 }