From 0d937847154b13725ae718abf4b9b07d9b924242 Mon Sep 17 00:00:00 2001
From: Masaq- <tilt@techie.com>
Date: Fri, 9 Jun 2017 03:50:46 +0000
Subject: [PATCH] option (-J0) to autodetect delay variance factor

---
 src/client.c | 11 ++++++++++-
 src/client.h |  1 +
 src/iodine.c |  7 ++++++-
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/src/client.c b/src/client.c
index 6730a46..343d2fb 100644
--- a/src/client.c
+++ b/src/client.c
@@ -285,6 +285,7 @@ got_response(int id, int immediate, int fail)
 {
 	struct timeval now, rtt;
 	time_t rtt_ms;
+	static time_t rtt_min_ms = 1;
 	gettimeofday(&now, NULL);
 
 	QTRACK_DEBUG(4, "Got answer id %d (%s)%s", id, immediate ? "immediate" : "lazy",
@@ -322,8 +323,16 @@ got_response(int id, int immediate, int fail)
 				this.rtt_total_ms += rtt_ms;
 				this.num_immediate++;
 
-				if (this.autodetect_server_timeout)
+				if (this.autodetect_server_timeout) {
+					if (this.autodetect_delay_variance) {
+						if (rtt_ms > 0 && (rtt_ms < rtt_min_ms || 1 == rtt_min_ms)) {
+							rtt_min_ms = rtt_ms;
+						}
+						this.downstream_delay_variance = (double) (this.rtt_total_ms /
+							this.num_immediate) / rtt_min_ms;
+					}
 					update_server_timeout(0);
+				}
 			}
 
 			/* Remove query info from buffer to mark it as answered */
diff --git a/src/client.h b/src/client.h
index 6d1f013..6a3645e 100644
--- a/src/client.h
+++ b/src/client.h
@@ -90,6 +90,7 @@ struct client_instance {
 	time_t downstream_timeout_ms;
 	double downstream_delay_variance;
 	int autodetect_server_timeout;
+	int autodetect_delay_variance;
 
 	/* Cumulative Round-Trip-Time in ms */
 	time_t rtt_total_ms;
diff --git a/src/iodine.c b/src/iodine.c
index ab389d9..0de74a2 100644
--- a/src/iodine.c
+++ b/src/iodine.c
@@ -83,6 +83,7 @@ struct client_instance this;
 	.num_immediate = 1, \
 	.rtt_total_ms = 200, \
 	.downstream_delay_variance = 2.0, \
+	.autodetect_delay_variance = 0, \
 	.remote_forward_addr = {.ss_family = AF_UNSPEC}
 
 static struct client_instance preset_default = {
@@ -265,7 +266,7 @@ help()
 	fprintf(stderr, "  -W  upstream fragment window size (default: 8 frags)\n");
 	fprintf(stderr, "  -i  server-side request timeout in lazy mode (default: auto)\n");
 	fprintf(stderr, "  -j  downstream fragment ACK timeout, implies -i4 (default: 2 sec)\n");
-	fprintf(stderr, "  -J  downstream fragment ACK delay variance factor (default: 2.0)\n");
+	fprintf(stderr, "  -J  downstream fragment ACK delay variance factor (default: 2.0), 0: auto\n");
 	//fprintf(stderr, "  --nodrop  disable TCP packet-dropping optimisations\n");
 	fprintf(stderr, "  -c 1: use downstream compression (default), 0: disable\n");
 	fprintf(stderr, "  -C 1: use upstream compression (default), 0: disable\n\n");
@@ -577,6 +578,10 @@ main(int argc, char **argv)
 			break;
 		case 'J':
 			this.downstream_delay_variance = strtod(optarg, NULL);
+			if (0.0 == this.downstream_delay_variance) {
+				this.autodetect_delay_variance = 1;
+				this.downstream_delay_variance = 2.0;
+			}
 			break;
 		case 's':
 			this.send_interval_ms = atoi(optarg);