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// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
package netstack
import (
"html/template"
"net/http"
"net/netip"
"slices"
"time"
xmaps "golang.org/x/exp/maps"
"gvisor.dev/gvisor/pkg/tcpip"
)
var tcpForwarderTemplate = template.Must(template.New("").Parse(`
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<style>
body { font-family: monospace; font-size: 12; }
td { padding: 0.3em; }
</style>
</head>
<body>
<h1>TCP Forwarder</h1>
<h2>TCP Statistics</h2>
<table border=1>
<tr>
<th>Metric</th>
<th>Value</th>
</tr>
{{ range .Stats }}
<tr><td>{{ .Key }}</td><td>{{ .Value }}</td></tr>
{{ end }}
</table>
<h2>In-Flight Outbound Connections</h2>
<table border=1>
<tr>
<th>Start Time</th>
<th>Client IP</th>
<th>Remote IP</th>
</tr>
{{ range .InFlightDials }}
<tr>
<td>{{ .Start.Format "2006-01-02T15:04:05Z07:00" }} ({{ printf "%.2f" .DurationSecs }} seconds ago)</td>
<td>{{ .ClientIP }}</td>
<td>{{ .RemoteAddr }}</td>
</tr>
{{ end }}
</table>
</body>
</html>
`))
// DebugTCPForwarder writes debug information about this netstack
// implementation's current TCP forwarder in HTML format.
func (ns *Impl) DebugTCPForwarder(w http.ResponseWriter, r *http.Request) {
// Grab data while holding the mutex
ns.tcpDebugMu.Lock()
tcpDials := xmaps.Values(ns.inFlightDials)
ns.tcpDebugMu.Unlock()
slices.SortFunc(tcpDials, func(a, b tcpDialInfo) int {
return a.start.Compare(b.start)
})
type templateDataStats struct {
Key string
Value uint64
}
type templateDataDial struct {
Start time.Time
DurationSecs float64
ClientIP netip.Addr
RemoteAddr netip.AddrPort
}
type templateData struct {
Stats []templateDataStats
InFlightDials []templateDataDial
}
var data templateData
// Statistics from gVisor
tcpStats := ns.ipstack.Stats().TCP
tcpMetrics := []struct {
name string
field *tcpip.StatCounter
}{
{"Active Connection Openings", tcpStats.ActiveConnectionOpenings},
{"Passive Connection Openings", tcpStats.PassiveConnectionOpenings},
{"Established Connections", tcpStats.CurrentEstablished},
{"Connected Connections", tcpStats.CurrentConnected},
{"Dropped In-Flight Forwarder Connections", tcpStats.ForwardMaxInFlightDrop},
{"Established Resets", tcpStats.EstablishedResets},
{"Established Timeout", tcpStats.EstablishedTimedout},
{"Failed Connection Attempts", tcpStats.FailedConnectionAttempts},
{"Retransmits", tcpStats.Retransmits},
{"Timeouts", tcpStats.Timeouts},
{"Checksum Errors", tcpStats.ChecksumErrors},
{"Failed Port Reservations", tcpStats.FailedPortReservations},
}
for _, metric := range tcpMetrics {
data.Stats = append(data.Stats, templateDataStats{
Key: metric.name,
Value: metric.field.Value(),
})
}
// Any in-flight DialContext calls in the TCP forwarding path.
now := time.Now()
for _, dial := range tcpDials {
elapsed := now.Sub(dial.start)
data.InFlightDials = append(data.InFlightDials, templateDataDial{
Start: dial.start,
DurationSecs: elapsed.Seconds(),
ClientIP: dial.clientRemoteIP,
RemoteAddr: dial.dialAddr,
})
}
w.Header().Set("Content-Type", "text/html; charset=utf-8")
w.Header().Set("Cache-Control", "no-cache")
tcpForwarderTemplate.Execute(w, &data)
}
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