X-Git-Url: http://git.meshlink.io/?a=blobdiff_plain;f=utcp.c;h=3faf2381d9559af2e4f907c119e2bc469e9863e2;hb=bbd35b9f705bc7684cf469d87248c8fb3f7c85c7;hp=7c30246cb066d1edccaa1fd5a48a7ec0a0fcedde;hpb=cdfbebf0324cf685f5046b45873ad2ef063692cc;p=utcp

diff --git a/utcp.c b/utcp.c
index 7c30246..3faf238 100644
--- a/utcp.c
+++ b/utcp.c
@@ -128,7 +128,7 @@ static void print_packet(struct utcp_connection *c, const char *dir, const void
 }
 
 static void debug_cwnd(struct utcp_connection *c) {
-	debug(c, "snd.cwnd %u snd.ssthresh %u\n", c->snd.cwnd, c->snd.ssthresh);
+	debug(c, "snd.cwnd %u snd.ssthresh %u\n", c->snd.cwnd, ~c->snd.ssthresh ? c->snd.ssthresh : 0);
 }
 #else
 #define debug(...) do {} while(0)
@@ -171,12 +171,40 @@ static int32_t seqdiff(uint32_t a, uint32_t b) {
 }
 
 // Buffer functions
-// TODO: convert to ringbuffers to avoid memmove() operations.
+static bool buffer_wraps(struct buffer *buf) {
+	return buf->size - buf->offset < buf->used;
+}
+
+static bool buffer_resize(struct buffer *buf, uint32_t newsize) {
+	char *newdata = realloc(buf->data, newsize);
+
+	if(!newdata) {
+		return false;
+	}
+
+	buf->data = newdata;
+
+	if(buffer_wraps(buf)) {
+		// Shift the right part of the buffer until it hits the end of the new buffer.
+		// Old situation:
+		// [345......012]
+		// New situation:
+		// [345.........|........012]
+		uint32_t tailsize = buf->size - buf->offset;
+		uint32_t newoffset = newsize - tailsize;
+		memmove(buf + newoffset, buf + buf->offset, tailsize);
+		buf->offset = newoffset;
+	}
+
+	buf->size = newsize;
+	return true;
+}
 
 // Store data into the buffer
 static ssize_t buffer_put_at(struct buffer *buf, size_t offset, const void *data, size_t len) {
 	debug(NULL, "buffer_put_at %lu %lu %lu\n", (unsigned long)buf->used, (unsigned long)offset, (unsigned long)len);
 
+	// Ensure we don't store more than maxsize bytes in total
 	size_t required = offset + len;
 
 	if(required > buf->maxsize) {
@@ -188,32 +216,41 @@ static ssize_t buffer_put_at(struct buffer *buf, size_t offset, const void *data
 		required = buf->maxsize;
 	}
 
+	// Check if we need to resize the buffer
 	if(required > buf->size) {
 		size_t newsize = buf->size;
 
 		if(!newsize) {
-			newsize = required;
-		} else {
-			do {
-				newsize *= 2;
-			} while(newsize < required);
+			newsize = 4096;
 		}
 
+		do {
+			newsize *= 2;
+		} while(newsize < required);
+
 		if(newsize > buf->maxsize) {
 			newsize = buf->maxsize;
 		}
 
-		char *newdata = realloc(buf->data, newsize);
-
-		if(!newdata) {
+		if(!buffer_resize(buf, newsize)) {
 			return -1;
 		}
+	}
 
-		buf->data = newdata;
-		buf->size = newsize;
+	uint32_t realoffset = buf->offset + offset;
+
+	if(buf->size - buf->offset < offset) {
+		// The offset wrapped
+		realoffset -= buf->size;
 	}
 
-	memcpy(buf->data + offset, data, len);
+	if(buf->size - realoffset < len) {
+		// The new chunk of data must be wrapped
+		memcpy(buf->data + realoffset, data, buf->size - realoffset);
+		memcpy(buf->data, (char *)data + buf->size - realoffset, len - (buf->size - realoffset));
+	} else {
+		memcpy(buf->data + realoffset, data, len);
+	}
 
 	if(required > buf->used) {
 		buf->used = required;
@@ -226,52 +263,59 @@ static ssize_t buffer_put(struct buffer *buf, const void *data, size_t len) {
 	return buffer_put_at(buf, buf->used, data, len);
 }
 
-// Get data from the buffer. data can be NULL.
-static ssize_t buffer_get(struct buffer *buf, void *data, size_t len) {
-	if(len > buf->used) {
-		len = buf->used;
+// Copy data from the buffer without removing it.
+static ssize_t buffer_copy(struct buffer *buf, void *data, size_t offset, size_t len) {
+	// Ensure we don't copy more than is actually stored in the buffer
+	if(offset >= buf->used) {
+		return 0;
 	}
 
-	if(data) {
-		memcpy(data, buf->data, len);
+	if(buf->used - offset < len) {
+		len = buf->used - offset;
 	}
 
-	if(len < buf->used) {
-		memmove(buf->data, buf->data + len, buf->used - len);
+	uint32_t realoffset = buf->offset + offset;
+
+	if(buf->size - buf->offset < offset) {
+		// The offset wrapped
+		realoffset -= buf->size;
+	}
+
+	if(buf->size - realoffset < len) {
+		// The data is wrapped
+		memcpy(data, buf->data + realoffset, buf->size - realoffset);
+		memcpy((char *)data + buf->size - realoffset, buf->data, len - (buf->size - realoffset));
+	} else {
+		memcpy(data, buf->data + realoffset, len);
 	}
 
-	buf->used -= len;
 	return len;
 }
 
-// Copy data from the buffer without removing it.
-static ssize_t buffer_copy(struct buffer *buf, void *data, size_t offset, size_t len) {
-	if(offset >= buf->used) {
-		return 0;
+// Discard data from the buffer.
+static ssize_t buffer_discard(struct buffer *buf, size_t len) {
+	if(buf->used < len) {
+		len = buf->used;
 	}
 
-	if(offset + len > buf->used) {
-		len = buf->used - offset;
+	if(buf->size - buf->offset < len) {
+		buf->offset -= buf->size;
 	}
 
-	memcpy(data, buf->data + offset, len);
+	buf->offset += len;
+	buf->used -= len;
+
 	return len;
 }
 
-static bool buffer_init(struct buffer *buf, uint32_t len, uint32_t maxlen) {
-	memset(buf, 0, sizeof(*buf));
-
-	if(len) {
-		buf->data = malloc(len);
-
-		if(!buf->data) {
-			return false;
-		}
+static bool buffer_set_size(struct buffer *buf, uint32_t minsize, uint32_t maxsize) {
+	if(maxsize < minsize) {
+		maxsize = minsize;
 	}
 
-	buf->size = len;
-	buf->maxsize = maxlen;
-	return true;
+	buf->maxsize = maxsize;
+
+	return buf->size >= minsize || buffer_resize(buf, minsize);
 }
 
 static void buffer_exit(struct buffer *buf) {
@@ -378,12 +422,12 @@ static struct utcp_connection *allocate_connection(struct utcp *utcp, uint16_t s
 		return NULL;
 	}
 
-	if(!buffer_init(&c->sndbuf, DEFAULT_SNDBUFSIZE, DEFAULT_MAXSNDBUFSIZE)) {
+	if(!buffer_set_size(&c->sndbuf, DEFAULT_SNDBUFSIZE, DEFAULT_MAXSNDBUFSIZE)) {
 		free(c);
 		return NULL;
 	}
 
-	if(!buffer_init(&c->rcvbuf, DEFAULT_RCVBUFSIZE, DEFAULT_MAXRCVBUFSIZE)) {
+	if(!buffer_set_size(&c->rcvbuf, DEFAULT_RCVBUFSIZE, DEFAULT_MAXRCVBUFSIZE)) {
 		buffer_exit(&c->sndbuf);
 		free(c);
 		return NULL;
@@ -401,12 +445,8 @@ static struct utcp_connection *allocate_connection(struct utcp *utcp, uint16_t s
 	c->snd.una = c->snd.iss;
 	c->snd.nxt = c->snd.iss + 1;
 	c->snd.last = c->snd.nxt;
-	c->snd.cwnd = (utcp->mtu > 2190 ? 2 : utcp->mtu > 1095 ? 3 : 4) * utcp->mtu;
-#if UTCP_DEBUG
-	c->snd.ssthresh = c->sndbuf.maxsize;
-#else
+	c->snd.cwnd = (utcp->mss > 2190 ? 2 : utcp->mss > 1095 ? 3 : 4) * utcp->mss;
 	c->snd.ssthresh = ~0;
-#endif
 	debug_cwnd(c);
 	c->utcp = utcp;
 
@@ -539,8 +579,8 @@ static void ack(struct utcp_connection *c, bool sendatleastone) {
 	} else if(cwndleft < left) {
 		left = cwndleft;
 
-		if(!sendatleastone || cwndleft > c->utcp->mtu) {
-			left -= left % c->utcp->mtu;
+		if(!sendatleastone || cwndleft > c->utcp->mss) {
+			left -= left % c->utcp->mss;
 		}
 	}
 
@@ -553,13 +593,7 @@ static void ack(struct utcp_connection *c, bool sendatleastone) {
 	struct {
 		struct hdr hdr;
 		uint8_t data[];
-	} *pkt;
-
-	pkt = malloc(sizeof(pkt->hdr) + c->utcp->mtu);
-
-	if(!pkt) {
-		return;
-	}
+	} *pkt = c->utcp->pkt;
 
 	pkt->hdr.src = c->src;
 	pkt->hdr.dst = c->dst;
@@ -569,7 +603,7 @@ static void ack(struct utcp_connection *c, bool sendatleastone) {
 	pkt->hdr.aux = 0;
 
 	do {
-		uint32_t seglen = left > c->utcp->mtu ? c->utcp->mtu : left;
+		uint32_t seglen = left > c->utcp->mss ? c->utcp->mss : left;
 		pkt->hdr.seq = c->snd.nxt;
 
 		buffer_copy(&c->sndbuf, pkt->data, seqdiff(c->snd.nxt, c->snd.una), seglen);
@@ -592,8 +626,6 @@ static void ack(struct utcp_connection *c, bool sendatleastone) {
 		print_packet(c, "send", pkt, sizeof(pkt->hdr) + seglen);
 		c->utcp->send(c->utcp, pkt, sizeof(pkt->hdr) + seglen);
 	} while(left);
-
-	free(pkt);
 }
 
 ssize_t utcp_send(struct utcp_connection *c, const void *data, size_t len) {
@@ -680,7 +712,7 @@ ssize_t utcp_send(struct utcp_connection *c, const void *data, size_t len) {
 
 	if(!is_reliable(c)) {
 		c->snd.una = c->snd.nxt = c->snd.last;
-		buffer_get(&c->sndbuf, NULL, c->sndbuf.used);
+		buffer_discard(&c->sndbuf, c->sndbuf.used);
 	}
 
 	if(is_reliable(c) && !timerisset(&c->rtrx_timeout)) {
@@ -714,7 +746,7 @@ static void fast_retransmit(struct utcp_connection *c) {
 		uint8_t data[];
 	} *pkt;
 
-	pkt = malloc(sizeof(pkt->hdr) + c->utcp->mtu);
+	pkt = malloc(c->utcp->mtu);
 
 	if(!pkt) {
 		return;
@@ -735,7 +767,7 @@ static void fast_retransmit(struct utcp_connection *c) {
 		pkt->hdr.seq = c->snd.una;
 		pkt->hdr.ack = c->rcv.nxt;
 		pkt->hdr.ctl = ACK;
-		uint32_t len = min(seqdiff(c->snd.last, c->snd.una), utcp->mtu);
+		uint32_t len = min(seqdiff(c->snd.last, c->snd.una), utcp->mss);
 
 		if(fin_wanted(c, c->snd.una + len)) {
 			len--;
@@ -766,13 +798,7 @@ static void retransmit(struct utcp_connection *c) {
 	struct {
 		struct hdr hdr;
 		uint8_t data[];
-	} *pkt;
-
-	pkt = malloc(sizeof(pkt->hdr) + c->utcp->mtu);
-
-	if(!pkt) {
-		return;
-	}
+	} *pkt = c->utcp->pkt;
 
 	pkt->hdr.src = c->src;
 	pkt->hdr.dst = c->dst;
@@ -812,27 +838,24 @@ static void retransmit(struct utcp_connection *c) {
 		pkt->hdr.seq = c->snd.una;
 		pkt->hdr.ack = c->rcv.nxt;
 		pkt->hdr.ctl = ACK;
-		uint32_t len = seqdiff(c->snd.last, c->snd.una);
-
-		if(len > utcp->mtu) {
-			len = utcp->mtu;
-		}
+		uint32_t len = min(seqdiff(c->snd.last, c->snd.una), utcp->mss);
 
 		if(fin_wanted(c, c->snd.una + len)) {
 			len--;
 			pkt->hdr.ctl |= FIN;
 		}
 
-		c->snd.nxt = c->snd.una + len;
-
 		// RFC 5681 slow start after timeout
-		c->snd.ssthresh = max(c->snd.cwnd / 2, utcp->mtu * 2); // eq. 4
-		c->snd.cwnd = utcp->mtu;
+		uint32_t flightsize = seqdiff(c->snd.nxt, c->snd.una);
+		c->snd.ssthresh = max(flightsize / 2, utcp->mss * 2); // eq. 4
+		c->snd.cwnd = utcp->mss;
 		debug_cwnd(c);
 
 		buffer_copy(&c->sndbuf, pkt->data, 0, len);
 		print_packet(c, "rtrx", pkt, sizeof(pkt->hdr) + len);
 		utcp->send(utcp, pkt, sizeof(pkt->hdr) + len);
+
+		c->snd.nxt = c->snd.una + len;
 		break;
 
 	case CLOSED:
@@ -855,9 +878,10 @@ static void retransmit(struct utcp_connection *c) {
 	}
 
 	c->rtt_start.tv_sec = 0; // invalidate RTT timer
+	c->dupack = 0; // cancel any ongoing fast recovery
 
 cleanup:
-	free(pkt);
+	return;
 }
 
 /* Update receive buffer and SACK entries after consuming data.
@@ -887,7 +911,7 @@ static void sack_consume(struct utcp_connection *c, size_t len) {
 		return;
 	}
 
-	buffer_get(&c->rcvbuf, NULL, len);
+	buffer_discard(&c->rcvbuf, len);
 
 	for(int i = 0; i < NSACKS && c->sacks[i].len;) {
 		if(len < c->sacks[i].offset) {
@@ -1258,6 +1282,19 @@ synack:
 			// Otherwise, continue processing.
 			len = 0;
 		}
+	} else {
+#if UTCP_DEBUG
+		int32_t rcv_offset = seqdiff(hdr.seq, c->rcv.nxt);
+
+		if(rcv_offset) {
+			debug(c, "packet out of order, offset %u bytes", rcv_offset);
+		}
+
+		if(rcv_offset >= 0) {
+			c->rcv.nxt = hdr.seq + len;
+		}
+
+#endif
 	}
 
 	c->snd.wnd = hdr.wnd; // TODO: move below
@@ -1410,7 +1447,7 @@ synack:
 #endif
 
 		if(data_acked) {
-			buffer_get(&c->sndbuf, NULL, data_acked);
+			buffer_discard(&c->sndbuf, data_acked);
 		}
 
 		// Also advance snd.nxt if possible
@@ -1431,9 +1468,9 @@ synack:
 
 		// Increase the congestion window according to RFC 5681
 		if(c->snd.cwnd < c->snd.ssthresh) {
-			c->snd.cwnd += min(advanced, utcp->mtu); // eq. 2
+			c->snd.cwnd += min(advanced, utcp->mss); // eq. 2
 		} else {
-			c->snd.cwnd += max(1, (utcp->mtu * utcp->mtu) / c->snd.cwnd); // eq. 3
+			c->snd.cwnd += max(1, (utcp->mss * utcp->mss) / c->snd.cwnd); // eq. 3
 		}
 
 		if(c->snd.cwnd > c->sndbuf.maxsize) {
@@ -1464,15 +1501,16 @@ synack:
 			break;
 		}
 	} else {
-		if(!len && is_reliable(c)) {
+		if(!len && is_reliable(c) && c->snd.una != c->snd.last) {
 			c->dupack++;
 			debug(c, "duplicate ACK %d\n", c->dupack);
 
 			if(c->dupack == 3) {
 				// RFC 5681 fast recovery
 				debug(c, "fast recovery started\n", c->dupack);
-				c->snd.ssthresh = max(c->snd.cwnd / 2, utcp->mtu * 2); // eq. 4
-				c->snd.cwnd = min(c->snd.ssthresh + 3 * utcp->mtu, c->sndbuf.maxsize);
+				uint32_t flightsize = seqdiff(c->snd.nxt, c->snd.una);
+				c->snd.ssthresh = max(flightsize / 2, utcp->mss * 2); // eq. 4
+				c->snd.cwnd = min(c->snd.ssthresh + 3 * utcp->mss, c->sndbuf.maxsize);
 
 				if(c->snd.cwnd > c->sndbuf.maxsize) {
 					c->snd.cwnd = c->sndbuf.maxsize;
@@ -1482,7 +1520,7 @@ synack:
 
 				fast_retransmit(c);
 			} else if(c->dupack > 3) {
-				c->snd.cwnd += utcp->mtu;
+				c->snd.cwnd += utcp->mss;
 
 				if(c->snd.cwnd > c->sndbuf.maxsize) {
 					c->snd.cwnd = c->sndbuf.maxsize;
@@ -1490,6 +1528,11 @@ synack:
 
 				debug_cwnd(c);
 			}
+
+			// We got an ACK which indicates the other side did get one of our packets.
+			// Reset the retransmission timer to avoid going to slow start,
+			// but don't touch the connection timeout.
+			start_retransmit_timer(c);
 		}
 	}
 
@@ -1978,7 +2021,7 @@ struct utcp *utcp_init(utcp_accept_t accept, utcp_pre_accept_t pre_accept, utcp_
 	utcp->pre_accept = pre_accept;
 	utcp->send = send;
 	utcp->priv = priv;
-	utcp->mtu = DEFAULT_MTU;
+	utcp_set_mtu(utcp, DEFAULT_MTU);
 	utcp->timeout = DEFAULT_USER_TIMEOUT; // sec
 	utcp->rto = START_RTO; // usec
 
@@ -2017,10 +2060,26 @@ uint16_t utcp_get_mtu(struct utcp *utcp) {
 }
 
 void utcp_set_mtu(struct utcp *utcp, uint16_t mtu) {
-	// TODO: handle overhead of the header
-	if(utcp) {
-		utcp->mtu = mtu;
+	if(!utcp) {
+		return;
+	}
+
+	if(mtu <= sizeof(struct hdr)) {
+		return;
 	}
+
+	if(mtu > utcp->mtu) {
+		char *new = realloc(utcp->pkt, mtu + sizeof(struct hdr));
+
+		if(!new) {
+			return;
+		}
+
+		utcp->pkt = new;
+	}
+
+	utcp->mtu = mtu;
+	utcp->mss = mtu - sizeof(struct hdr);
 }
 
 void utcp_reset_timers(struct utcp *utcp) {