Increase STUN RTOs to work better on poor networks, such as 2G networks.
BUG=b/34822484
Review-Url: https://codereview.webrtc.org/2677743002
Cr-Commit-Position: refs/heads/master@{#16503}
diff --git a/webrtc/p2p/base/stunrequest.cc b/webrtc/p2p/base/stunrequest.cc
index 57c3c2e..ef2bee8 100644
--- a/webrtc/p2p/base/stunrequest.cc
+++ b/webrtc/p2p/base/stunrequest.cc
@@ -22,9 +22,22 @@
const uint32_t MSG_STUN_SEND = 1;
-const int MAX_SENDS = 9;
-const int DELAY_UNIT = 100; // 100 milliseconds
-const int DELAY_MAX_FACTOR = 16;
+// RFC 5389 says SHOULD be 500ms.
+// For years, this was 100ms, but for networks that
+// experience moments of high RTT (such as 2G networks), this doesn't
+// work well.
+const int STUN_INITIAL_RTO = 250; // milliseconds
+
+// The timeout doubles each retransmission, up to this many times
+// RFC 5389 says SHOULD retransmit 7 times.
+// This has been 8 for years (not sure why).
+const int STUN_MAX_RETRANSMISSIONS = 8; // Total sends: 9
+
+// We also cap the doubling, even though the standard doesn't say to.
+// This has been 1.6 seconds for years, but for networks that
+// experience moments of high RTT (such as 2G networks), this doesn't
+// work well.
+const int STUN_MAX_RTO = 8000; // milliseconds, or 5 doublings
StunRequestManager::StunRequestManager(rtc::Thread* thread)
: thread_(thread) {
@@ -226,7 +239,8 @@
void StunRequest::OnSent() {
count_ += 1;
- if (count_ == MAX_SENDS) {
+ int retransmissions = (count_ - 1);
+ if (retransmissions >= STUN_MAX_RETRANSMISSIONS) {
timeout_ = true;
}
LOG(LS_VERBOSE) << "Sent STUN request " << count_
@@ -237,7 +251,9 @@
if (count_ == 0) {
return 0;
}
- return DELAY_UNIT * std::min(1 << (count_-1), DELAY_MAX_FACTOR);
+ int retransmissions = (count_ - 1);
+ int rto = STUN_INITIAL_RTO << retransmissions;
+ return std::min(rto, STUN_MAX_RTO);
}
} // namespace cricket