Fix occasional connection issues on startup due to bad MAC address read

android/edge_android.c

@@ -165,6 +165,9 @@ int start_edge(const n2n_edge_cmd_t* cmd)
     traceLevel = traceLevel < 0 ? 0 : traceLevel;   /* TRACE_ERROR */
     traceLevel = traceLevel > 4 ? 4 : traceLevel;   /* TRACE_DEBUG */
 
+    /* Random seed */
+    srand(time(NULL));
+
     if (-1 == edge_init(&eee) )
     {
         traceEvent( TRACE_ERROR, "Failed in edge_init" );

edge.c

@@ -666,6 +666,9 @@ int main(int argc, char* argv[]) {
 
   traceEvent(TRACE_NORMAL, "Starting n2n edge %s %s", PACKAGE_VERSION, PACKAGE_BUILDDATE);
 
+  /* Random seed */
+  srand(time(NULL));
+
   if(0 == strcmp("dhcp", ec.ip_mode)) {
     traceEvent(TRACE_NORMAL, "Dynamic IP address assignment enabled.");
 

edge_utils.c

@@ -171,10 +171,6 @@ n2n_edge_t* edge_init(const tuntap_dev *dev, const n2n_edge_conf_t *conf, int *r
   memcpy(&eee->device, dev, sizeof(*dev));
   eee->start_time = time(NULL);
 
-  /* REVISIT: BbMaj7 : Should choose something with less predictability
-           * particularly for embedded targets with no real-time clock. */
-  srand(eee->start_time);
-
   eee->known_peers    = NULL;
   eee->pending_peers  = NULL;
   eee->sup_attempts = N2N_EDGE_SUP_ATTEMPTS;

example_edge_embed.c

@@ -35,6 +35,9 @@ int main(int argc, char* argv[]) {
   /* Increase tracelevel to see what's happening */
   setTraceLevel(10);
 
+  /* Random seed */
+  srand(time(NULL));
+
   /* 
      NOTE
 

tuntap_linux.c

@@ -24,36 +24,10 @@
 #include <linux/netlink.h>
 #include <linux/rtnetlink.h>
 
-/* *************************************************** */
-
-static void read_mac(char *ifname, n2n_mac_t mac_addr) {
-  int _sock, res;
-  struct ifreq ifr;
-  macstr_t mac_addr_buf;
-
-  memset (&ifr,0,sizeof(struct ifreq));
-
-  /* Dummy socket, just to make ioctls with */
-  _sock=socket(PF_INET, SOCK_DGRAM, 0);
-  strcpy(ifr.ifr_name, ifname);
-  res = ioctl(_sock,SIOCGIFHWADDR,&ifr);
-  
-  if(res < 0) {
-    perror ("Get hw addr");
-    traceEvent(TRACE_ERROR, "Unable to read interfce %s MAC", ifname);
-  } else
-    memcpy(mac_addr, ifr.ifr_ifru.ifru_hwaddr.sa_data, 6);
-
-  traceEvent(TRACE_NORMAL, "Interface %s has MAC %s",
-	     ifname,
-	     macaddr_str(mac_addr_buf, mac_addr ));
-  close(_sock);
-}
-
 /* ********************************** */
 
 static int setup_ifname(int fd, const char *ifname, const char *ipaddr,
-          const char *netmask, const char *mac, int mtu) {
+          const char *netmask, uint8_t *mac, int mtu) {
   struct ifreq ifr;
 
   memset(&ifr, 0, sizeof(ifr));
@@ -61,14 +35,12 @@ static int setup_ifname(int fd, const char *ifname, const char *ipaddr,
   strncpy(ifr.ifr_name, ifname, IFNAMSIZ);
   ifr.ifr_name[IFNAMSIZ-1] = '\0';
 
-  if(mac && mac[0]) {
-    str2mac((uint8_t *)ifr.ifr_hwaddr.sa_data, mac);
-    ifr.ifr_hwaddr.sa_family = ARPHRD_ETHER;
+  ifr.ifr_hwaddr.sa_family = ARPHRD_ETHER;
+  memcpy(ifr.ifr_hwaddr.sa_data, mac, 6);
 
-    if(ioctl(fd, SIOCSIFHWADDR, &ifr) == -1) {
-      traceEvent(TRACE_ERROR, "ioctl(SIOCSIFHWADDR) failed [%d]: %s", errno, strerror(errno));
-      return(-1);
-    }
+  if(ioctl(fd, SIOCSIFHWADDR, &ifr) == -1) {
+    traceEvent(TRACE_ERROR, "ioctl(SIOCSIFHWADDR) failed [%d]: %s", errno, strerror(errno));
+    return(-1);
   }
 
   ifr.ifr_addr.sa_family = AF_INET;
@@ -168,6 +140,23 @@ int tuntap_open(tuntap_dev *device,
   /* Store the device name for later reuse */
   strncpy(device->dev_name, ifr.ifr_name, MIN(IFNAMSIZ, N2N_IFNAMSIZ) );
 
+  if(device_mac && device_mac[0]) {
+    /* Use the user-provided MAC */
+    str2mac(device->mac_addr, device_mac);
+  } else {
+    /* Set an explicit random MAC to know the exact MAC in use. Manually
+     * reading the MAC address is not safe as it may change internally
+     * also after the TAP interface UP status has been notified. */
+    int i;
+
+    for(i = 0; i < 6; i++)
+      device->mac_addr[i] = rand();
+
+    device->mac_addr[0] &= ~0x01; /* Clear multicast bit */
+    device->mac_addr[0] |= 0x02;  /* Set locally-assigned bit */
+  }
+
+  /* Initialize Netlink socket */
   if((nl_fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE)) == -1) {
     traceEvent(TRACE_ERROR, "netlink socket creation failed [%d]: %s", errno, strerror(errno));
     return -1;
@@ -198,7 +187,7 @@ int tuntap_open(tuntap_dev *device,
     return -1;
   }
 
-  if(setup_ifname(ioctl_fd, device->dev_name, device_ip, device_mask, device_mac, mtu) < 0) {
+  if(setup_ifname(ioctl_fd, device->dev_name, device_ip, device_mask, device->mac_addr, mtu) < 0) {
     close(nl_fd);
     close(ioctl_fd);
     close(device->fd);
@@ -240,7 +229,6 @@ int tuntap_open(tuntap_dev *device,
 
   device->ip_addr = inet_addr(device_ip);
   device->device_mask = inet_addr(device_mask);
-  read_mac(dev, device->mac_addr);
   return(device->fd);
 }