Notify frotend of Speak version packets

This allows new versions of the protocol to send broadcast advertizements
without the older versions telling the sender to speak their version.

Version 1.0 of the reference implementation will still do that, but the
issue is not great enough to warrant pulling and replacing it.

ethermess-backend.c

@@ -22,12 +22,13 @@
 #include <time.h>
 #include <unistd.h>
 
-#define EM_PROTOCOL_VERSION 0
+#define EM_PROTOCOL_VERSION 1
 #define EM_MESSAGE_MAX_LENGTH (1500 - 2 - 2 - 2)
 #define EM_STATUS_BROADCAST_TIME (60 * 1000 + 1000 * random_byte() / 64)
 #define EM_RETRANSMIT_TIME (1000 + random_byte() * 2)
 #define EM_MAX_RETRANSMIT 5
 
+// Version 0
 #define EMT_SPEAK_VERSION 0
 #define EMT_STATUS_REQUEST 1
 #define EMT_STATUS 2
@@ -36,6 +37,9 @@
 #define EMT_MESSAGE 5
 #define EMT_ACK 6
 
+// Version 1
+#define EMT_FILE_OFFER 7
+
 #define EMS_AVAILABLE 0
 #define EMS_UNAVAILABLE 1
 #define EMS_OFFLINE 2
@@ -272,7 +276,7 @@ void send_frame(const unsigned char *frame, size_t frame_length) {
 	}
 }
 
-void write_headers(unsigned char frame[14], const unsigned char destination_mac[6], unsigned char packet_type) {
+void write_headers(unsigned char frame[14], const unsigned char destination_mac[6], unsigned char version, unsigned char packet_type) {
 	// Destination MAC
 	memcpy(&frame[0], destination_mac, 6);
 
@@ -284,7 +288,7 @@ void write_headers(unsigned char frame[14], const unsigned char destination_mac[
 	frame[13] = 0x7a;
 
 	// Ethermess version
-	frame[14] = EM_PROTOCOL_VERSION;
+	frame[14] = version;
 
 	// Ethermess packet type
 	frame[15] = packet_type;
@@ -293,7 +297,7 @@ void write_headers(unsigned char frame[14], const unsigned char destination_mac[
 void send_speak_version(const unsigned char destination[6]) {
 	unsigned char frame[14 + 2 + 1];
 
-	write_headers(frame, destination, EMT_SPEAK_VERSION);
+	write_headers(frame, destination, 0, EMT_SPEAK_VERSION);
 
 	// Version to speak
 	frame[16] = EM_PROTOCOL_VERSION;
@@ -304,7 +308,7 @@ void send_speak_version(const unsigned char destination[6]) {
 void send_status_request(const unsigned char destination[6]) {
 	unsigned char frame[14 + 2];
 
-	write_headers(frame, destination, EMT_STATUS_REQUEST);
+	write_headers(frame, destination, 0, EMT_STATUS_REQUEST);
 
 	send_frame(frame, sizeof(frame));
 }
@@ -312,7 +316,7 @@ void send_status_request(const unsigned char destination[6]) {
 void send_status(const unsigned char destination[6]) {
 	unsigned char frame[14 + 2 + 1 + 1 + own_nick_length];
 
-	write_headers(frame, destination, EMT_STATUS);
+	write_headers(frame, destination, 0, EMT_STATUS);
 
 	// Status
 	frame[16] = own_status;
@@ -329,7 +333,7 @@ void send_status(const unsigned char destination[6]) {
 void send_msgid_request(const unsigned char destination[6]) {
 	unsigned char frame[14 + 2];
 
-	write_headers(frame, destination, EMT_MSGID_REQUEST);
+	write_headers(frame, destination, 0, EMT_MSGID_REQUEST);
 
 	send_frame(frame, sizeof(frame));
 }
@@ -337,7 +341,7 @@ void send_msgid_request(const unsigned char destination[6]) {
 void send_msgid(const unsigned char destination[6]) {
 	unsigned char frame[14 + 2 + 2];
 
-	write_headers(frame, destination, EMT_MSGID);
+	write_headers(frame, destination, 0, EMT_MSGID);
 
 	// Look up destination in the ID cache
 	ssize_t cache_index = msgid_cache_lookup(destination);
@@ -366,7 +370,7 @@ void send_msgid(const unsigned char destination[6]) {
 void send_message(void) {
 	unsigned char frame[14 + 2 + 2 + 2 + own_message_length];
 
-	write_headers(frame, own_message_destination_mac, EMT_MESSAGE);
+	write_headers(frame, own_message_destination_mac, 0, EMT_MESSAGE);
 
 	// Message ID
 	frame[16] = own_message_msgid >> 8;
@@ -385,7 +389,7 @@ void send_message(void) {
 void send_ack(const unsigned char destination[6], uint16_t msgid) {
 	unsigned char frame[14 + 2 + 2];
 
-	write_headers(frame, destination, EMT_ACK);
+	write_headers(frame, destination, 0, EMT_ACK);
 
 	// Message ID
 	frame[16] = msgid >> 8;
@@ -394,6 +398,14 @@ void send_ack(const unsigned char destination[6], uint16_t msgid) {
 	send_frame(frame, sizeof(frame));
 }
 
+void send_file_offer(const unsigned char destination[6]) {
+	unsigned char frame[14 + 2];
+
+	write_headers(frame, destination, 1, EMT_FILE_OFFER);
+
+	send_frame(frame, sizeof(frame));
+}
+
 void readallx(int fd, unsigned char *buf, size_t length) {
 	size_t completed = 0;
 	while (completed < length) {
@@ -495,6 +507,10 @@ void read_command(void) {
 		send_status(broadcast_mac);
 	} else if (cmd == 'm') {
 		read_message();
+	} else if (cmd == 'f') {
+		unsigned char mac[6];
+		readallx(0, mac, sizeof(mac));
+		send_file_offer(mac);
 	} else {
 		errx(1, "Frontend sent an unknown command %c", cmd);
 	}
@@ -630,6 +646,29 @@ bool check_utf8(const unsigned char *data, size_t data_length, bool newline_tab_
 	return true;
 }
 
+void handle_speak_version(const unsigned char source_mac[6], const unsigned char *data, size_t data_length) {
+	if (data_length < 1) {
+		// Too short
+		return;
+	}
+
+	unsigned char version = data[0];
+
+	if (!check_padding(data, 1, data_length)) {
+		// Malformed padding
+		return;
+	}
+
+	// Type of event: Speak version
+	writeallx(1, "v", 1);
+
+	// MAC
+	writeallx(1, source_mac, 6);
+
+	// Version
+	writeallx(1, &version, 1);
+}
+
 void handle_status(const unsigned char source_mac[6], const unsigned char *data, size_t data_length) {
 	if (data_length < 2) {
 		// Too short
@@ -835,10 +874,13 @@ void process_frame(void) {
 		return;
 	}
 
+	bool broadcast;
 	if (memcmp(frame, own_mac, 6) == 0) {
 		// Targetted at us
+		broadcast = false;
 	} else if (memcmp(frame, broadcast_mac, 6) == 0) {
 		// Broadcast
+		broadcast = true;
 	} else {
 		// Does not concern us
 		return;
@@ -852,43 +894,58 @@ void process_frame(void) {
 	unsigned char version = frame[14];
 
 	// If they speak a version we don't understand, tell them to speak ours
+	// Exception: If it was a broadcast, just ingore it
 	if (version > EM_PROTOCOL_VERSION) {
-		send_speak_version(source_mac);
+		if (!broadcast) {
+			send_speak_version(source_mac);
+		}
 		return;
 	}
 
 	// Extract Ethermess packet type
 	unsigned char packet_type = frame[15];
 
-	// Process the packet based on the packet type
-	switch (packet_type) {
-		case EMT_STATUS_REQUEST:
-			if (check_padding(&frame[16], 0, packet_length - 16)) {
-				send_status(source_mac);
-			}
-			break;
+	// Process the packet based on the version and packet type
+	if (version == 0) {
+		switch (packet_type) {
+			case EMT_SPEAK_VERSION:
+				handle_speak_version(source_mac, &frame[16], packet_length - 16);
+				break;
 
-		case EMT_STATUS:
-			handle_status(source_mac, &frame[16], packet_length - 16);
-			break;
+			case EMT_STATUS_REQUEST:
+				if (check_padding(&frame[16], 0, packet_length - 16)) {
+					send_status(source_mac);
+				}
+				break;
 
-		case EMT_MSGID_REQUEST:
-			if (check_padding(&frame[16], 0, packet_length - 16)) {
-				send_msgid(source_mac);
-			}
-			break;
+			case EMT_STATUS:
+				handle_status(source_mac, &frame[16], packet_length - 16);
+				break;
 
-		case EMT_MSGID:
-			handle_msgid(source_mac, &frame[16], packet_length - 16);
-			break;
+			case EMT_MSGID_REQUEST:
+				if (check_padding(&frame[16], 0, packet_length - 16)) {
+					send_msgid(source_mac);
+				}
+				break;
 
-		case EMT_MESSAGE:
-			handle_message(source_mac, &frame[16], packet_length - 16);
-			break;
+			case EMT_MSGID:
+				handle_msgid(source_mac, &frame[16], packet_length - 16);
+				break;
 
-		case EMT_ACK:
-			handle_ack(source_mac, &frame[16], packet_length - 16);
-			break;
+			case EMT_MESSAGE:
+				handle_message(source_mac, &frame[16], packet_length - 16);
+				break;
+
+			case EMT_ACK:
+				handle_ack(source_mac, &frame[16], packet_length - 16);
+				break;
+		}
+	} else if (version == 1) {
+		switch (packet_type) {
+			case EMT_FILE_OFFER:
+				fprintf(stderr, "File offered\n"); //debg
+				break;
+		}
 	}
 }
 

ethermess.7

@@ -58,6 +58,10 @@ Version	1	EtherMess protocol version
 Tells the recipient to speak the given version of the protocol.
 Should be generated whenever an EtherMess packet with a version one doesn't
 speak is received.
+.Pp
+Note however that this packet shouldn't be generated if the packet was
+sent to the Ethernet broadcast address
+.Li ff:ff:ff:ff:ff:ff .
 .It Status request (0x01)
 Requests the recipient to announce its status and nick.
 Upon receiving this packet, a status packet should be sent to the sender.

ethermess.py

@@ -208,6 +208,9 @@ def set_status_nick(backend, status, nick):
 	encoded = nick.encode('utf-8')
 	writeall(backend, b's' + bytes([status.value, len(encoded)]) + encoded)
 
+def send_file_offer(backend, mac):
+	writeall(backend, b'f' + mac)
+
 def handle_user_command(backend, line):
 	global own_nick, own_status
 	global default_target_mac
@@ -290,13 +293,17 @@ def handle_user_command(backend, line):
 				# Set default target of messages
 				default_target_mac = mac_from_name(rest)
 
+			elif command == '/sendfile':
+				# Send an offer to transmit the file
+				send_file_offer(backend, mac_from_name(rest))
+
 			elif command == '/quit':
 				# Quit
 				return 'quit'
 
 			else:
 				# Display usage
-				print('--- / <message>; /msg <target> <message>; /status [<target>]; /peers; /available; /unavailable; /nick [<nick>]; /target <target>; /quit')
+				print('--- / <message>; /msg <target> <message>; /status [<target>]; /peers; /available; /unavailable; /nick [<nick>]; /target <target>; /sendfile <target>; /quit')
 
 		else:
 			# Send message
@@ -428,7 +435,14 @@ def eventloop(proc):
 		for fd, event in poll.poll(wait):
 			if fd == proc.stdout.fileno() and event & select.POLLIN:
 				event_type = readall(proc.stdout, 1)
-				if event_type == b's':
+				if event_type == b'v':
+					# Speak version
+					source_mac = readall(proc.stdout, 6)
+					version, = readall(proc.stdout, 1)
+
+					print('--- Speak version %s %i' % (format_mac(source_mac), version)) #debg
+
+				elif event_type == b's':
 					# Status
 					source_mac = readall(proc.stdout, 6)
 					status, = readall(proc.stdout, 1)

frontend-backend-protocol.md

@@ -70,6 +70,12 @@ Events
 
 Frontend receives events from the backend.
 
+### Speak version
+Format: 'v' + MAC + version (u8)
+
+Generated when an EtherMess Speak version packet is received by the
+backend.
+
 ### Status
 Format: 's' + MAC + status + nick length in bytes (u8) + nick
 

test.sh

@@ -1,4 +1,12 @@
 #!/bin/sh
-LIBEXECDIR=. make &&
-test -n "$(getcap ethermess-backend)" || sudo setcap CAP_NET_RAW=ep ethermess-backend &&
+LIBEXECDIR=. CFLAGS=-Werror make || exit 1
+test -n "$(getcap ethermess-backend)" || sudo setcap CAP_NET_RAW=ep ethermess-backend || exit 1
+if ip link show veth0a > /dev/null 2>&1 || ip link show veth0b > /dev/null 2>&1
+then
+	true
+else
+	sudo ip link add veth0a type veth peer name veth0b || exit 1
+	sudo ip link set veth0a up || exit 1
+	sudo ip link set veth0b up || exit 1
+fi
 ./ethermess "$@"