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// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
//go:build linux && !android
package derp
import (
"context"
"crypto/tls"
"net"
"time"
"tailscale.com/net/tcpinfo"
)
func (c *sclient) startStatsLoop(ctx context.Context) {
// Get the RTT initially to verify it's supported.
conn := c.tcpConn()
if conn == nil {
c.s.tcpRtt.Add("non-tcp", 1)
return
}
if _, err := tcpinfo.RTT(conn); err != nil {
c.logf("error fetching initial RTT: %v", err)
c.s.tcpRtt.Add("error", 1)
return
}
const statsInterval = 10 * time.Second
// Don't launch a goroutine; use a timer instead.
var gatherStats func()
gatherStats = func() {
// Do nothing if the context is finished.
if ctx.Err() != nil {
return
}
// Reschedule ourselves when this stats gathering is finished.
defer c.s.clock.AfterFunc(statsInterval, gatherStats)
// Gather TCP RTT information.
rtt, err := tcpinfo.RTT(conn)
if err == nil {
c.s.tcpRtt.Add(durationToLabel(rtt), 1)
}
// TODO(andrew): more metrics?
}
// Kick off the initial timer.
c.s.clock.AfterFunc(statsInterval, gatherStats)
}
// tcpConn attempts to get the underlying *net.TCPConn from this client's
// Conn; if it cannot, then it will return nil.
func (c *sclient) tcpConn() *net.TCPConn {
nc := c.nc
for {
switch v := nc.(type) {
case *net.TCPConn:
return v
case *tls.Conn:
nc = v.NetConn()
default:
return nil
}
}
}
func durationToLabel(dur time.Duration) string {
switch {
case dur <= 10*time.Millisecond:
return "10ms"
case dur <= 20*time.Millisecond:
return "20ms"
case dur <= 50*time.Millisecond:
return "50ms"
case dur <= 100*time.Millisecond:
return "100ms"
case dur <= 150*time.Millisecond:
return "150ms"
case dur <= 250*time.Millisecond:
return "250ms"
case dur <= 500*time.Millisecond:
return "500ms"
default:
return "inf"
}
}
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