l2/connection: refactoring

- split handle_packet() in two functions: the first does basic checks and calls
  the second one. This allows to do the basic checks externally (in the
  multi-connection management module) without duplicating them.
- use the new layer2_encode_packet() function.

impl/src/layer2/connection.c

@@ -80,19 +80,6 @@ result_t connection_handle_packet(connection_ctx_t *ctx, const uint8_t *buf, siz
 		return OK;
 	}
 
-	if(!ham64_is_equal(&header.src_addr, &ctx->peer_addr)) {
-		char fmt_src_addr[HAM64_FMT_MAX_LEN];
-		char fmt_peer_addr[HAM64_FMT_MAX_LEN];
-
-		ham64_format(&header.src_addr, fmt_src_addr);
-		ham64_format(&ctx->peer_addr, fmt_peer_addr);
-
-		LOG(LVL_ERR, "Packet has the wrong source address: got %s, expected %s",
-				fmt_src_addr, fmt_peer_addr);
-
-		return ERR_INVALID_ADDRESS;
-	}
-
 	if(!ham64_is_equal(&header.dst_addr, &ctx->my_addr)) {
 		char fmt_dst_addr[HAM64_FMT_MAX_LEN];
 		char fmt_my_addr[HAM64_FMT_MAX_LEN];
@@ -106,44 +93,85 @@ result_t connection_handle_packet(connection_ctx_t *ctx, const uint8_t *buf, siz
 		return ERR_INVALID_ADDRESS;
 	}
 
+	size_t header_size = layer2_get_encoded_header_size(&header);
+
+	const uint8_t *payload = buf + header_size;
+	size_t payload_len = packet_size - header_size;
+
+	return connection_handle_packet_prechecked(ctx, &header, payload, payload_len);
+}
+
+result_t connection_handle_packet_prechecked(
+		connection_ctx_t *ctx,
+		const layer2_packet_header_t *header,
+		const uint8_t *payload, size_t payload_len)
+{
+	// check the connection state
+	switch(ctx->conn_state) {
+		case CONN_STATE_UNINITIALIZED:
+		case CONN_STATE_INITIALIZED:
+		case CONN_STATE_CLOSED:
+			LOG(LVL_ERR, "Trying to pass packet to connection in state %u", ctx->conn_state);
+			return ERR_INVALID_STATE;
+
+		case CONN_STATE_CONNECTING:
+		case CONN_STATE_ESTABLISHED:
+			// in these states, packets can be handled
+			break;
+	}
+
+	// check if this packet is from our designated peer
+	if(!ham64_is_equal(&header->src_addr, &ctx->peer_addr)) {
+		char fmt_src_addr[HAM64_FMT_MAX_LEN];
+		char fmt_peer_addr[HAM64_FMT_MAX_LEN];
+
+		ham64_format(&header->src_addr, fmt_src_addr);
+		ham64_format(&ctx->peer_addr, fmt_peer_addr);
+
+		LOG(LVL_ERR, "Packet has the wrong source address: got %s, expected %s",
+				fmt_src_addr, fmt_peer_addr);
+
+		return ERR_INVALID_ADDRESS;
+	}
+
 	LOG(LVL_DEBUG, "Handling %s packet with rx_seq_nr %u, tx_seq_nr %u.",
-			layer2_msg_type_to_string(header.msg_type), header.rx_seq_nr, header.tx_seq_nr);
+			layer2_msg_type_to_string(header->msg_type), header->rx_seq_nr, header->tx_seq_nr);
 
-	ctx->last_acked_seq = header.rx_seq_nr;
+	ctx->last_acked_seq = header->rx_seq_nr;
 
 
-	switch(header.msg_type) {
+	switch(header->msg_type) {
 		case L2_MSG_TYPE_EMPTY:
 			LOG(LVL_DEBUG, "Empty packet: accepted ACK for %u.", ctx->last_acked_seq);
 			// handle the acknowledgement internally
-			connection_handle_ack(ctx, header.rx_seq_nr, false);
+			connection_handle_ack(ctx, header->rx_seq_nr, false);
 			return OK; // do not ACK and call back
 
 		case L2_MSG_TYPE_CONN_MGMT:
 		case L2_MSG_TYPE_CONNECTIONLESS:
-			LOG(LVL_WARN, "Message type %s is not implemented yet.", layer2_msg_type_to_string(header.msg_type));
+			LOG(LVL_WARN, "Message type %s is not implemented yet.", layer2_msg_type_to_string(header->msg_type));
 			return OK;
 
 		case L2_MSG_TYPE_DATA:
 			break;
 
 		default:
-			LOG(LVL_ERR, "Invalid message type %d.", header.msg_type);
+			LOG(LVL_ERR, "Invalid message type %d.", header->msg_type);
 			return ERR_INVALID_STATE;
 	}
 
-	if(ctx->next_expected_seq != header.tx_seq_nr) {
+	if(ctx->next_expected_seq != header->tx_seq_nr) {
-		LOG(LVL_ERR, "Expected sequence number %u, received %u.", ctx->next_expected_seq, header.tx_seq_nr);
+		LOG(LVL_ERR, "Expected sequence number %u, received %u.", ctx->next_expected_seq, header->tx_seq_nr);
 		return ERR_SEQUENCE;
 	}
 
 	ctx->next_expected_seq++;
 	ctx->next_expected_seq &= 0xF;
 
-	LOG(LVL_INFO, "Received ACK for seq_nr %u in packet seq_nr %u.", header.rx_seq_nr, header.tx_seq_nr);
+	LOG(LVL_INFO, "Received ACK for seq_nr %u in packet seq_nr %u.", header->rx_seq_nr, header->tx_seq_nr);
 
 	// handle the acknowledgement internally
-	connection_handle_ack(ctx, header.rx_seq_nr, true);
+	connection_handle_ack(ctx, header->rx_seq_nr, true);
 
 	size_t header_size = layer2_get_encoded_header_size(&header);
 
@@ -267,7 +295,7 @@ size_t connection_encode_next_packet(connection_ctx_t *ctx, uint8_t ack_seq_nr,
 		case CONN_STATE_INITIALIZED:
 		case CONN_STATE_CLOSED:
 			LOG(LVL_ERR, "Trying to encode packet in inactive state %u", ctx->conn_state);
-			return ERR_INVALID_STATE;
+			return 0;
 
 		case CONN_STATE_CONNECTING:
 		case CONN_STATE_ESTABLISHED:
@@ -282,30 +310,18 @@ size_t connection_encode_next_packet(connection_ctx_t *ctx, uint8_t ack_seq_nr,
 		return 0;
 	}
 
-	unsigned int crc_size = crc_sizeof_key(PAYLOAD_CRC_SCHEME);
-
-	assert(buf_len >= LAYER2_PACKET_HEADER_ENCODED_SIZE_MAX + crc_size + entry->data_len);
-
 	layer2_packet_header_t header = entry->header;
 	header.rx_seq_nr = ack_seq_nr;
 
 	// encode the header
 	LOG(LVL_DEBUG, "Encoding packet with rx_seq_nr %u, tx_seq_nr %u.", header.rx_seq_nr, header.tx_seq_nr);
 
-	size_t packet_size = layer2_encode_packet_header(&header, buf);
+	size_t packet_size = layer2_encode_packet(&header, entry->data, entry->data_len, buf, buf_len);
-
+	if(packet_size == 0) {
-	// add the payload data
+		LOG(LVL_ERR, "Buffer too small for encoded packet!");
-	if(entry->data) {
+		return 0;
-		memcpy(buf + packet_size, entry->data, entry->data_len);
 	}
 
-	packet_size += entry->data_len;
-
-	// calculate CRC of everything and append it to the packet
-	crc_append_key(PAYLOAD_CRC_SCHEME, buf, packet_size);
-
-	packet_size += crc_size;
-
 	ctx->next_packet_index++;
 
 	return packet_size;

impl/src/layer2/connection.h

@@ -71,6 +71,24 @@ void connection_destroy(connection_ctx_t *ctx);
  */
 result_t connection_handle_packet(connection_ctx_t *ctx, const uint8_t *buf, size_t buf_len);
 
+/*!\brief Handle a received packet where the header has already been decoded.
+ *
+ * This function assumes that the following basic checks were already done:
+ * - CRC is correct
+ * - Header can be decoded
+ * - Destination address is the local address
+ *
+ * \param ctx         The connection context.
+ * \param header      Pointer to the decoded header structure.
+ * \param payload     Pointer to the payload data.
+ * \param payload_len Length of the payload data.
+ * \returns           A result code from the packet handling procedure.
+ */
+result_t connection_handle_packet_prechecked(
+		connection_ctx_t *ctx,
+		const layer2_packet_header_t *header,
+		const uint8_t *payload, size_t payload_len);
+
 /*!\brief Return the sequence number expected next by our side.
  */
 uint8_t connection_get_next_expected_seq(const connection_ctx_t *ctx);