Receiving broadcast messages and plausibility-checking

Now we're receiving the client broadcasts on the server side and
checking if they match the magic number we're expecting.

global.h

@@ -24,11 +24,6 @@
 #ifndef __GLOBAL_H__
 #define __GLOBAL_H__
 
-/* Magic is the prefix of announcement packages. It is the MD5SUM over the
- * string "luksrku v2". This only changes when the protocol that is spoken
- * changes. */
-#define UDP_MESSAGE_MAGIC									(const uint8_t[]){ 0x46, 0xf2, 0xf6, 0xc6, 0x63, 0x12, 0x2e, 0x00, 0xa0, 0x8a, 0xae, 0x42, 0x0c, 0x51, 0xf5, 0x65 }
-
 /* Size in bytes of the PSK that is used for TLS */
 #define PSK_SIZE_BYTES										32
 

msg.h

@@ -27,13 +27,19 @@
 #include <stdint.h>
 #include "global.h"
 
+/* Magic is the prefix of announcement packages. It is the MD5SUM over the
+ * string "luksrku v2". This only changes when the protocol that is spoken
+ * changes. */
+#define UDP_MESSAGE_MAGIC_SIZE								16
+#define UDP_MESSAGE_MAGIC									(const uint8_t[UDP_MESSAGE_MAGIC_SIZE]){ 0x46, 0xf2, 0xf6, 0xc6, 0x63, 0x12, 0x2e, 0x00, 0xa0, 0x8a, 0xae, 0x42, 0x0c, 0x51, 0xf5, 0x65 }
+
 struct udp_query_t {
-	uint8_t magic[16];
+	uint8_t magic[UDP_MESSAGE_MAGIC_SIZE];
 	uint8_t host_uuid[16];
 } __attribute__ ((packed));
 
 struct udp_response_t {
-	uint8_t magic[16];
+	uint8_t magic[UDP_MESSAGE_MAGIC_SIZE];
 } __attribute__ ((packed));
 
 struct msg_t {

server.c

@@ -174,10 +174,11 @@ static void udp_handler_thread(void *vctx) {
 
 	while (true) {
 		struct udp_query_t rx_msg;
-		if (!wait_udp_broadcast_message(client->udp_sd, client->port, &rx_msg, sizeof(rx_msg), 1000)) {
+		struct sockaddr_in origin;
+		if (!wait_udp_query(client->udp_sd, client->port, &rx_msg, &origin, 1000)) {
 			continue;
 		}
-		fprintf(stderr, "RXED!\n");
+		fprintf(stderr, "RXED! query\n");
 	}
 }
 

udp.c

@@ -62,15 +62,11 @@ int create_udp_socket(unsigned int listen_port, bool send_broadcast) {
 
 	return sd;
 }
-
+bool wait_udp_message(int sd, int port, void *data, unsigned int max_length, struct sockaddr_in *source, unsigned int timeout_millis) {
-bool wait_udp_broadcast_message(int sd, int port, void *data, unsigned int max_length, unsigned int timeout_millis) {
-	struct sockaddr_storage src_addr;
-	socklen_t src_addr_len = sizeof(src_addr);
-
 	fprintf(stderr, "RECV...\n");
-	ssize_t count=recvfrom(sd,data, max_length,0,(struct sockaddr*)&src_addr,&src_addr_len);
+	socklen_t socklen = sizeof(struct sockaddr_in);
-	fprintf(stderr, "RECV %ld\n", count);
+	ssize_t rx_bytes = recvfrom(sd,data, max_length, 0, (struct sockaddr*)source, &socklen);
-
+	fprintf(stderr, "RECV %ld\n", rx_bytes);
 	return true;
 }
 
@@ -87,3 +83,14 @@ bool send_udp_broadcast_message(int sd, int port, const void *data, unsigned int
 	}
 	return true;
 }
+
+bool wait_udp_query(int sd, int port, struct udp_query_t *query, struct sockaddr_in *source, unsigned int timeout_millis) {
+	bool rx_successful = wait_udp_message(sd, port, query, sizeof(struct udp_query_t), source, timeout_millis);
+	if (rx_successful) {
+		/* Also check if the message contains the correct magic */
+		if (!memcmp(query->magic, UDP_MESSAGE_MAGIC, UDP_MESSAGE_MAGIC_SIZE)) {
+			return true;
+		}
+	}
+	return false;
+}

udp.h

@@ -25,11 +25,13 @@
 #define __UDP_H__
 
 #include <stdbool.h>
+#include "msg.h"
 
 /*************** AUTO GENERATED SECTION FOLLOWS ***************/
 int create_udp_socket(unsigned int listen_port, bool send_broadcast);
-bool wait_udp_broadcast_message(int sd, int port, void *data, unsigned int max_length, unsigned int timeout_millis);
+bool wait_udp_message(int sd, int port, void *data, unsigned int max_length, struct sockaddr_in *source, unsigned int timeout_millis);
 bool send_udp_broadcast_message(int sd, int port, const void *data, unsigned int length);
+bool wait_udp_query(int sd, int port, struct udp_query_t *query, struct sockaddr_in *source, unsigned int timeout_millis);
 /***************  AUTO GENERATED SECTION ENDS   ***************/
 
 #endif