Downstream fragmentation now working. Currently fragment size is hardcoded to 1200. More tweaking left, as well as fragsize auto detection. (#7)

src/dns.c

@@ -269,7 +269,7 @@ dns_decode(char *buf, size_t buflen, struct query *q, qr_t qr, char *packet, siz
 		rv = MIN(rlen, sizeof(rdata));
 		rv = readdata(packet, &data, rdata, rv);
 
-		if(type == T_NULL && rv > 2 && buf) {
+		if(type == T_NULL && rv >= 2 && buf) {
 			rv = MIN(rv, buflen);
 			memcpy(buf, rdata, rv);
 		}

src/iodine.c

@@ -63,7 +63,8 @@ static int downstream_seqno;
 static int downstream_fragment;
 
 /* Current IP packet */
-static struct packet packet;
+static struct packet outpkt;
+static struct packet inpkt;
 
 /* My userid at the server */
 static char userid;
@@ -151,7 +152,7 @@ build_hostname(char *buf, size_t buflen,
 static int
 is_sending()
 {
-	return (packet.len != 0);
+	return (outpkt.len != 0);
 }
 
 static int
@@ -181,12 +182,12 @@ read_dns(int fd, char *buf, int buflen)
 
 	if (is_sending() && chunkid == q.id) {
 		/* Got ACK on sent packet */
-		packet.offset += packet.sentlen;
+		outpkt.offset += outpkt.sentlen;
-		if (packet.offset == packet.len) {
+		if (outpkt.offset == outpkt.len) {
 			/* Packet completed */
-			packet.offset = 0;
+			outpkt.offset = 0;
-			packet.len = 0;
+			outpkt.len = 0;
-			packet.sentlen = 0;
+			outpkt.sentlen = 0;
 		} else {
 			/* More to send */
 			send_chunk(fd);
@@ -212,12 +213,12 @@ tunnel_tun(int tun_fd, int dns_fd)
 	inlen = read;
 	compress2((uint8_t*)out, &outlen, (uint8_t*)in, inlen, 9);
 
-	memcpy(packet.data, out, MIN(outlen, sizeof(packet.data)));
+	memcpy(outpkt.data, out, MIN(outlen, sizeof(outpkt.data)));
-	packet.sentlen = 0;
+	outpkt.sentlen = 0;
-	packet.offset = 0;
+	outpkt.offset = 0;
-	packet.len = outlen;
+	outpkt.len = outlen;
-	packet.seqno++;
+	outpkt.seqno++;
-	packet.fragment = 0;
+	outpkt.fragment = 0;
 
 	send_chunk(dns_fd);
 
@@ -227,24 +228,40 @@ tunnel_tun(int tun_fd, int dns_fd)
 static int
 tunnel_dns(int tun_fd, int dns_fd)
 {
-	unsigned long outlen;
+	unsigned long datalen;
-	unsigned long inlen;
+	char buf[64*1024];
-	char out[64*1024];
-	char in[64*1024];
 	size_t read;
 
-	if ((read = read_dns(dns_fd, in, sizeof(in))) <= 2) 
+	if ((read = read_dns(dns_fd, buf, sizeof(buf))) <= 2) 
 		return -1;
 
-	outlen = sizeof(out);
+	if (downstream_seqno != inpkt.seqno) {
-	inlen = read;
+		/* New packet */
-
+		inpkt.seqno = downstream_seqno;
-	/* Skip 2 byte data header and uncompress */
+		inpkt.fragment = downstream_fragment;
-	if (uncompress((uint8_t*)out, &outlen, (uint8_t*) &in[2], inlen - 2) != Z_OK) {
+		inpkt.len = 0;
+	} else if (downstream_fragment <= inpkt.fragment) {
+		/* Duplicate fragment */
 		return -1;
 	}
+	inpkt.fragment = downstream_fragment;
 
-	write_tun(tun_fd, out, outlen);
+	datalen = MIN(read - 2, sizeof(inpkt.data) - inpkt.len);
+
+	/* Skip 2 byte data header and append to packet */
+	memcpy(&inpkt.data[inpkt.len], &buf[2], datalen);
+	inpkt.len += datalen;
+
+	if (buf[1] & 1) { /* If last fragment flag is set */
+		/* Uncompress packet and send to tun */
+		datalen = sizeof(buf);
+		if (uncompress((uint8_t*)buf, &datalen, (uint8_t*) inpkt.data, inpkt.len) == Z_OK) {
+			write_tun(tun_fd, buf, datalen);
+		}
+		inpkt.len = 0;
+	}
+
+	/* If we have nothing to send, send a ping to get more data */
 	if (!is_sending()) 
 		send_ping(dns_fd);
 	
@@ -306,26 +323,26 @@ send_chunk(int fd)
 	int code;
 	char *p;
 
-	p = packet.data;
+	p = outpkt.data;
-	p += packet.offset;
+	p += outpkt.offset;
-	avail = packet.len - packet.offset;
+	avail = outpkt.len - outpkt.offset;
 
-	packet.sentlen = build_hostname(buf + 4, sizeof(buf) - 4, p, avail, topdomain, dataenc);
+	outpkt.sentlen = build_hostname(buf + 4, sizeof(buf) - 4, p, avail, topdomain, dataenc);
 
 	/* Build upstream data header (see doc/proto_xxxxxxxx.txt) */
 
 	buf[0] = hex[userid & 15]; /* First byte is 4 bits userid */
 
-	code = ((packet.seqno & 7) << 2) | ((packet.fragment & 15) >> 2);
+	code = ((outpkt.seqno & 7) << 2) | ((outpkt.fragment & 15) >> 2);
 	buf[1] = b32_5to8(code); /* Second byte is 3 bits seqno, 2 upper bits fragment count */
 
-	code = ((packet.fragment & 3) << 3) | (downstream_seqno & 7);
+	code = ((outpkt.fragment & 3) << 3) | (downstream_seqno & 7);
 	buf[2] = b32_5to8(code); /* Third byte is 2 bits lower fragment count, 3 bits downstream packet seqno */
 
-	code = ((downstream_fragment & 15) << 1) | (packet.sentlen == avail);
+	code = ((downstream_fragment & 15) << 1) | (outpkt.sentlen == avail);
 	buf[3] = b32_5to8(code); /* Fourth byte is 4 bits downstream fragment count, 1 bit compression flag */
 
-	packet.fragment++;
+	outpkt.fragment++;
 	send_query(fd, buf);
 }
 
@@ -352,13 +369,13 @@ send_ping(int fd)
 	char data[4];
 	
 	if (is_sending()) {
-		packet.sentlen = 0;
+		outpkt.sentlen = 0;
-		packet.offset = 0;
+		outpkt.offset = 0;
-		packet.len = 0;
+		outpkt.len = 0;
 	}
 
 	data[0] = userid;
-	data[1] = 0;
+	data[1] = ((downstream_seqno & 7) << 4) | (downstream_fragment & 15);
 	data[2] = (rand_seed >> 8) & 0xff;
 	data[3] = (rand_seed >> 0) & 0xff;
 	
@@ -722,7 +739,8 @@ main(int argc, char **argv)
 	device = NULL;
 	chunkid = 0;
 
-	packet.seqno = 0;
+	outpkt.seqno = 0;
+	inpkt.len = 0;
 
 	b32 = get_base32_encoder();
 	dataenc = get_base32_encoder();

src/iodined.c

@@ -118,7 +118,7 @@ tunnel_tun(int tun_fd, int dns_fd)
 		users[userid].outpacket.len = outlen;
 		users[userid].outpacket.offset = 0;
 		users[userid].outpacket.sentlen = 0;
-		users[userid].outpacket.seqno++;
+		users[userid].outpacket.seqno = (++users[userid].outpacket.seqno & 7);
 		users[userid].outpacket.fragment = 0;
 		return outlen;
 	} else {
@@ -162,47 +162,92 @@ static void
 send_chunk(int dns_fd, int userid) {
 	char pkt[4096];
 	int datalen;
+	int last;
 
-	datalen = MIN(sizeof(pkt) - 2, users[userid].outpacket.len);
+	/* TODO change this 1200b value to dynamic */
-	memcpy(&pkt[2], users[userid].outpacket.data, datalen);
+	datalen = MIN(1200, users[userid].outpacket.len - users[userid].outpacket.offset);
+
+	if (datalen && users[userid].outpacket.sentlen > 0 && 
+			(
+			users[userid].outpacket.seqno != users[userid].out_acked_seqno ||
+			users[userid].outpacket.fragment != users[userid].out_acked_fragment
+			)
+		) {
+
+		/* Still waiting on latest ack, send nothing */
+		datalen = 0;
+		last = 0;
+		/* TODO : count down and discard packet if no acks arrive within X queries */
+	} else {
+		memcpy(&pkt[2], &users[userid].outpacket.data[users[userid].outpacket.offset], datalen);
+		users[userid].outpacket.sentlen = datalen;
+		last = (users[userid].outpacket.len == users[userid].outpacket.offset + users[userid].outpacket.sentlen);
+
+		/* Increase fragment# when sending data with offset */
+		if (users[userid].outpacket.offset && datalen)
+			users[userid].outpacket.fragment++;
+	}
 
 	/* Build downstream data header (see doc/proto_xxxxxxxx.txt) */
 
 	/* First byte is 1 bit compression flag, 3 bits upstream seqno, 4 bits upstream fragment */
 	pkt[0] = (1<<7) | ((users[userid].inpacket.seqno & 7) << 4) | (users[userid].inpacket.fragment & 15);
 	/* Second byte is 3 bits downstream seqno, 4 bits downstream fragment, 1 bit last flag */
-	pkt[1] = ((users[userid].outpacket.seqno & 7) << 5) | ((users[userid].outpacket.fragment & 15) << 1) | 1;
+	pkt[1] = ((users[userid].outpacket.seqno & 7) << 5) | 
-
+		((users[userid].outpacket.fragment & 15) << 1) | (last & 1);
 
 	if (debug >= 1) {
-		printf("OUT pkt seq# %d, frag %d (last=%d), fragsize %d, total %d, to user %d\n",
+		printf("OUT  pkt seq# %d, frag %d (last=%d), offset %d, fragsize %d, total %d, to user %d\n",
 			users[userid].outpacket.seqno & 7, users[userid].outpacket.fragment & 15, 
-			1, users[userid].outpacket.len, datalen, userid);
+			last, users[userid].outpacket.offset, datalen, users[userid].outpacket.len, userid);
 	}
 	write_dns(dns_fd, &users[userid].q, pkt, datalen + 2);
-	users[userid].outpacket.len = 0;
 	users[userid].q.id = 0;
+
+	if (users[userid].outpacket.len > 0 && 
+		users[userid].outpacket.len == users[userid].outpacket.sentlen) {
+
+		/* Whole packet was sent in one chunk, dont wait for ack */
+		users[userid].outpacket.len = 0;
+		users[userid].outpacket.offset = 0;
+		users[userid].outpacket.sentlen = 0;
+	}
 }
 
 static void
 update_downstream_seqno(int dns_fd, int userid, int down_seq, int down_frag)
 {
-	/* update outgoing seqno/frag */
+	/* If we just read a new packet from tun we have not sent a fragment of, just send it */
-	if (down_seq != users[userid].out_acked_seqno) {
+	if (users[userid].outpacket.len > 0 && users[userid].outpacket.sentlen == 0) {
-		/* First ack on new outgoing packet */
+		send_chunk(dns_fd, userid);
+		return;
+	}
+
+	/* otherwise, check if we received ack on a fragment and can send next */
+	if (users[userid].outpacket.len > 0 &&
+		users[userid].outpacket.seqno == down_seq && users[userid].outpacket.fragment == down_frag) {
+
+		if (down_seq != users[userid].out_acked_seqno || down_frag != users[userid].out_acked_fragment) {
+			/* Received ACK on downstream fragment */
+			users[userid].outpacket.offset += users[userid].outpacket.sentlen;
+			users[userid].outpacket.sentlen = 0;
+
+			/* Is packet done? */
+			if (users[userid].outpacket.offset == users[userid].outpacket.len) {
+				users[userid].outpacket.len = 0;
+				users[userid].outpacket.offset = 0;
+				users[userid].outpacket.sentlen = 0;
+			}
+
 			users[userid].out_acked_seqno = down_seq;
 			users[userid].out_acked_fragment = down_frag;
-	} else {
-		if (down_frag > users[userid].out_acked_fragment) {
-			/* Ack on later fragment */
-			users[userid].out_acked_fragment = down_frag;
-		}
-	}
 
 			/* Send reply if waiting */
 			if (users[userid].outpacket.len > 0) {
 				send_chunk(dns_fd, userid);
 			}
+		}
+	}
 }
 
 static void
@@ -345,6 +390,15 @@ handle_null_request(int tun_fd, int dns_fd, struct query *q, int domain_len)
 			return; /* illegal id */
 		}
 				
+		if (debug >= 1) {
+			printf("PING pkt from user %d\n", userid);
+		}
+
+		if (users[userid].q.id != 0) {
+			/* Send reply on earlier query before overwriting */
+			send_chunk(dns_fd, userid);
+		}
+
 		dn_seq = unpacked[1] >> 4;
 		dn_frag = unpacked[1] & 15;
 		memcpy(&(users[userid].q), q, sizeof(struct query));
@@ -379,6 +433,11 @@ handle_null_request(int tun_fd, int dns_fd, struct query *q, int domain_len)
 			int dn_frag = b32_8to5(in[3]) >> 1;
 			int lastfrag = b32_8to5(in[3]) & 1;
 
+			if (users[userid].q.id != 0) {
+				/* Send reply on earlier query before overwriting */
+				send_chunk(dns_fd, userid);
+			}
+
 			/* Update query and time info for user */
 			users[userid].last_pkt = time(NULL);
 			memcpy(&(users[userid].q), q, sizeof(struct query));