2021-12-21 21:52:50 +00:00
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// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package resolver
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import (
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"fmt"
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"html"
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"net/http"
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"strconv"
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"sync"
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"sync/atomic"
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"time"
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"tailscale.com/health"
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)
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func init() {
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health.RegisterDebugHandler("dnsfwd", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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n, _ := strconv.Atoi(r.FormValue("n"))
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if n <= 0 {
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n = 100
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} else if n > 10000 {
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n = 10000
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}
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2022-08-04 04:31:40 +00:00
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fl := fwdLogAtomic.Load()
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if fl == nil || n != len(fl.ent) {
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2021-12-21 21:52:50 +00:00
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fl = &fwdLog{ent: make([]fwdLogEntry, n)}
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fwdLogAtomic.Store(fl)
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}
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fl.ServeHTTP(w, r)
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}))
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}
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2022-08-04 04:31:40 +00:00
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var fwdLogAtomic atomic.Pointer[fwdLog]
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2021-12-21 21:52:50 +00:00
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type fwdLog struct {
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mu sync.Mutex
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pos int // ent[pos] is next entry
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ent []fwdLogEntry
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}
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type fwdLogEntry struct {
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Domain string
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Time time.Time
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}
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func (fl *fwdLog) addName(name string) {
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if fl == nil {
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return
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}
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fl.mu.Lock()
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defer fl.mu.Unlock()
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if len(fl.ent) == 0 {
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return
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}
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fl.ent[fl.pos] = fwdLogEntry{Domain: name, Time: time.Now()}
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fl.pos++
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if fl.pos == len(fl.ent) {
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fl.pos = 0
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}
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}
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func (fl *fwdLog) ServeHTTP(w http.ResponseWriter, r *http.Request) {
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fl.mu.Lock()
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defer fl.mu.Unlock()
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fmt.Fprintf(w, "<html><h1>DNS forwards</h1>")
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now := time.Now()
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for i := 0; i < len(fl.ent); i++ {
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ent := fl.ent[(i+fl.pos)%len(fl.ent)]
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if ent.Domain == "" {
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continue
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}
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fmt.Fprintf(w, "%v ago: %v<br>\n", now.Sub(ent.Time).Round(time.Second), html.EscapeString(ent.Domain))
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}
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}
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