Fix point-to-point VPN tunnel sockets for BACnet/IP by using IFF_POINTTOPOINT flag when getting the broadcast address. (#1066)

ports/bsd/bip-init.c

@@ -32,6 +32,8 @@ static struct in_addr BIP_Broadcast_Addr;
 /* broadcast binding mechanism */
 static bool BIP_Broadcast_Binding_Address_Override;
 static struct in_addr BIP_Broadcast_Binding_Address;
+/* point-to-point interface flag - uses the unicast socket for broadcast */
+static bool BIP_Point_To_Point = false;
 /* enable debugging */
 static bool BIP_Debug = false;
 /* interface name */
@@ -449,11 +451,15 @@ bool bip_get_addr_by_name(const char *host_name, BACNET_IP_ADDRESS *addr)
 static void *get_addr_ptr(struct sockaddr *sockaddr_ptr)
 {
     void *addr_ptr = NULL;
+
+    if (sockaddr_ptr) {
         if (sockaddr_ptr->sa_family == AF_INET) {
             addr_ptr = &((struct sockaddr_in *)sockaddr_ptr)->sin_addr;
         } else if (sockaddr_ptr->sa_family == AF_INET6) {
             addr_ptr = &((struct sockaddr_in6 *)sockaddr_ptr)->sin6_addr;
         }
+    }
+
     return addr_ptr;
 }
 
@@ -492,7 +498,9 @@ int bip_get_local_address_ioctl(
     char rv = '\0'; /* return value */
 
     struct ifaddrs *ifaddrs_ptr;
+    void *addr_ptr = NULL;
     int status;
+
     status = getifaddrs(&ifaddrs_ptr);
     if (status == -1) {
         fprintf(
@@ -500,17 +508,25 @@ int bip_get_local_address_ioctl(
     }
     while (ifaddrs_ptr) {
         if ((ifaddrs_ptr->ifa_addr->sa_family == AF_INET) &&
-            (strcmp(ifaddrs_ptr->ifa_name, ifname) == 0)) {
+            (ifname && strcmp(ifaddrs_ptr->ifa_name, ifname) == 0)) {
-            void *addr_ptr = NULL;
-            if (!ifaddrs_ptr->ifa_addr) {
-                return rv;
-            }
             switch (request) {
                 case SIOCGIFADDR:
                     addr_ptr = get_addr_ptr(ifaddrs_ptr->ifa_addr);
                     break;
                 case SIOCGIFBRDADDR:
+                    /*  Depending on whether the bit
+                        IFF_BROADCAST or IFF_POINTOPOINT is set
+                        in ifa_flags (only one can be set at a time),
+                        either ifa_broadaddr will contain the broadcast
+                        address associated with ifa_addr or ifa_dstaddr
+                        will contain the destination address of the
+                        point-to-point interface.*/
+                    if (ifaddrs_ptr->ifa_flags & IFF_POINTOPOINT) {
+                        BIP_Point_To_Point = true;
+                        addr_ptr = get_addr_ptr(ifaddrs_ptr->ifa_dstaddr);
+                    } else {
                         addr_ptr = get_addr_ptr(ifaddrs_ptr->ifa_broadaddr);
+                    }
                     break;
                 case SIOCGIFNETMASK:
                     addr_ptr = get_addr_ptr(ifaddrs_ptr->ifa_netmask);
@@ -525,6 +541,7 @@ int bip_get_local_address_ioctl(
         ifaddrs_ptr = ifaddrs_ptr->ifa_next;
     }
     freeifaddrs(ifaddrs_ptr);
+
     return rv;
 }
 
@@ -571,6 +588,9 @@ void bip_set_interface(const char *ifname)
     struct in_addr broadcast_address;
     int rv = 0;
 
+    local_address.s_addr = 0;
+    broadcast_address.s_addr = 0;
+    BIP_Point_To_Point = false;
     /* setup local address */
     rv = bip_get_local_address_ioctl(ifname, &local_address, SIOCGIFADDR);
     if (rv < 0) {
@@ -611,9 +631,12 @@ void bip_set_interface(const char *ifname)
     if (rv < 0) {
         BIP_Broadcast_Addr.s_addr = ~0;
     } else {
-        BIP_Broadcast_Addr = local_address;
+        if (BIP_Point_To_Point) {
+            BIP_Broadcast_Addr.s_addr = local_address.s_addr;
+        } else {
             BIP_Broadcast_Addr.s_addr = broadcast_address.s_addr;
         }
+    }
 #endif
     if (BIP_Debug) {
         fprintf(
@@ -626,6 +649,11 @@ void bip_set_interface(const char *ifname)
     }
 }
 
+const char *bip_get_interface(void)
+{
+    return BIP_Interface_Name;
+}
+
 static int createSocket(const struct sockaddr_in *sin)
 {
     int status = 0; /* return from socket lib calls */
@@ -710,18 +738,20 @@ bool bip_init(char *ifname)
         fflush(stderr);
         return false;
     }
-
     sin.sin_family = AF_INET;
     sin.sin_port = BIP_Port;
     memset(&(sin.sin_zero), '\0', sizeof(sin.sin_zero));
-
     sin.sin_addr.s_addr = BIP_Address.s_addr;
     sock_fd = createSocket(&sin);
     BIP_Socket = sock_fd;
     if (sock_fd < 0) {
         return false;
     }
-
+    if (BIP_Point_To_Point) {
+        /* point-to-point interface flag
+           uses the unicast socket for broadcast */
+        BIP_Broadcast_Socket = BIP_Socket;
+    } else {
         broadcast_sin_config.sin_family = AF_INET;
         broadcast_sin_config.sin_port = BIP_Port;
         memset(
@@ -752,7 +782,7 @@ bool bip_init(char *ifname)
                 return false;
             }
         }
-
+    }
     bvlc_init();
 
     return true;