Use big endian for handshake field values by default

At the moment the only multi-byte field is the MTU; it is kept in little endian
to provide backwards compatiblity. Future fields will be big endian.

2 files changed, 28 insertions, 15 deletions

diff --git a/src/handshake.c b/src/handshake.c
index 97c47cb..0a47987 100644
--- a/src/handshake.c
+++ b/src/handshake.c
@@ -62,19 +62,24 @@ static inline uint8_t as_uint8(const fastd_handshake_record_t *record) {
 	return record->data[0];
 }
 
-/** Reads a TLV record as a 16bit integer (little endian) */
+/** Reads a TLV record as a 16bit integer (big endian) */
 static inline uint16_t as_uint16(const fastd_handshake_record_t *record) {
-	return as_uint8(record) | (uint16_t)record->data[1] << 8;
+	return (uint16_t)as_uint8(record) << 8 | record->data[1];
 }
 
-/** Reads a TLV record as a 24bit integer (little endian) */
+/** Reads a TLV record as a 24bit integer (big endian) */
 static inline uint32_t as_uint24(const fastd_handshake_record_t *record) {
-	return as_uint16(record) | (uint32_t)record->data[2] << 16;
+	return (uint32_t)as_uint16(record) << 8 | record->data[2];
 }
 
-/** Reads a TLV record as a 32bit integer (little endian) */
+/** Reads a TLV record as a 32bit integer (big endian) */
 static inline uint32_t as_uint32(const fastd_handshake_record_t *record) {
-	return as_uint24(record) | (uint32_t)record->data[3] << 24;
+	return as_uint24(record) << 8 | record->data[3];
+}
+
+/** Reads a TLV record as a 16bit integer (little endian) */
+static inline uint16_t as_uint16_le(const fastd_handshake_record_t *record) {
+	return as_uint8(record) | (uint16_t)record->data[1] << 8;
 }
 
 /** Reads a TLV record as a variable-length integer (little endian) */
@@ -170,7 +175,7 @@ static fastd_buffer_t new_handshake(uint8_t type, const fastd_method_info_t *met
 
 	fastd_handshake_add_uint8(&buffer, RECORD_HANDSHAKE_TYPE, type);
 	fastd_handshake_add_uint8(&buffer, RECORD_MODE, conf.mode);
-	fastd_handshake_add_uint16(&buffer, RECORD_MTU, conf.mtu);
+	fastd_handshake_add_uint16_le(&buffer, RECORD_MTU, conf.mtu);
 
 	fastd_handshake_add(&buffer, RECORD_VERSION_NAME, version_len, FASTD_VERSION);
 	fastd_handshake_add(&buffer, RECORD_PROTOCOL_NAME, protocol_len, conf.protocol->name);
@@ -330,9 +335,9 @@ static inline bool check_records(fastd_socket_t *sock, const fastd_peer_address_
 
 	if (!conf.secure_handshakes || handshake->type > 1) {
 		if (handshake->records[RECORD_MTU].length == 2) {
-			if (as_uint16(&handshake->records[RECORD_MTU]) != conf.mtu) {
+			if (as_uint16_le(&handshake->records[RECORD_MTU]) != conf.mtu) {
 				pr_warn("MTU configuration differs with peer %I: local MTU is %u, remote MTU is %u",
-					remote_addr, conf.mtu, as_uint16(&handshake->records[RECORD_MTU]));
+					remote_addr, conf.mtu, as_uint16_le(&handshake->records[RECORD_MTU]));
 			}
 		}
 	}
diff --git a/src/handshake.h b/src/handshake.h
index a77b730..760d21b 100644
--- a/src/handshake.h
+++ b/src/handshake.h
@@ -156,27 +156,35 @@ static inline void fastd_handshake_add_uint8(fastd_buffer_t *buffer, fastd_hands
 static inline void fastd_handshake_add_uint16(fastd_buffer_t *buffer, fastd_handshake_record_type_t type, uint16_t value) {
 	uint8_t *dst = fastd_handshake_extend(buffer, type, 2);
 
-	dst[0] = value;
-	dst[1] = value >> 8;
+	dst[0] = value >> 8;
+	dst[1] = value;
 }
 
 /** Adds an uint24 TLV record of given type and value to a handshake buffer */
 static inline void fastd_handshake_add_uint24(fastd_buffer_t *buffer, fastd_handshake_record_type_t type, uint32_t value) {
 	uint8_t *dst = fastd_handshake_extend(buffer, type, 3);
 
-	dst[0] = value;
+	dst[0] = value >> 16;
 	dst[1] = value >> 8;
-	dst[2] = value >> 16;
+	dst[2] = value;
 }
 
 /** Adds an uint32 TLV record of given type and value to a handshake buffer */
 static inline void fastd_handshake_add_uint32(fastd_buffer_t *buffer, fastd_handshake_record_type_t type, uint32_t value) {
 	uint8_t *dst = fastd_handshake_extend(buffer, type, 4);
 
+	dst[0] = value >> 24;
+	dst[1] = value >> 16;
+	dst[2] = value >> 8;
+	dst[3] = value;
+}
+
+/** Adds an uint16 TLV record of given type and value to a handshake buffer encoded as little endian */
+static inline void fastd_handshake_add_uint16_le(fastd_buffer_t *buffer, fastd_handshake_record_type_t type, uint16_t value) {
+	uint8_t *dst = fastd_handshake_extend(buffer, type, 2);
+
 	dst[0] = value;
 	dst[1] = value >> 8;
-	dst[2] = value >> 16;
-	dst[3] = value >> 24;
 }
 
 /** Adds an TLV record of given type and value to a handshake buffer, automatically using a 1- to 4-byte value */