Fix bug of not explicitly binding to socket in send-linux

src/get_gateway-linux.h

@@ -271,7 +271,8 @@ int get_default_gw(struct in_addr *gw, char *iface)
 		    "The specified network (\"%s\") does not match "
 		    "the interface associated with the default gateway (%s). You will "
 		    "need to manually specify the MAC address of your gateway using "
-		    "the \"--gateway-mac\" flag.",
+		    "the \"--gateway-mac\" flag or use \"--iplayer\" to send IP packets and "
+		    "let the kernel take care of ethernet frame creation.",
 		    iface, _iface);
 	}
 	return EXIT_SUCCESS;

src/send-linux.c

@@ -51,13 +51,21 @@ int send_run_init(sock_t s)
 			  zconf.iface);
 		return EXIT_FAILURE;
 	}
+        // If we're sending IP packets (ie our socket is a AF_INET type, then we need to use the socket's SO_BINDTODEVICE option, only available for AF_INET sockets)
+	if (zconf.send_ip_pkts && setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, zconf.iface, strlen(zconf.iface)) < 0) {
+		log_error("send", "cannot bind to socket: %s", strerror(errno));
+		return EXIT_FAILURE;
+	}
+
+
 	strncpy(if_idx.ifr_name, zconf.iface, IFNAMSIZ - 1);
 	if (ioctl(sock, SIOCGIFINDEX, &if_idx) < 0) {
 		log_error("send", "%s", "SIOCGIFINDEX");
 		return EXIT_FAILURE;
 	}
 	int ifindex = if_idx.ifr_ifindex;
 
+
 	// destination address for the socket
 	memset((void *)&sockaddr, 0, sizeof(struct sockaddr_ll));
 	sockaddr.sll_ifindex = ifindex;