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// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
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// The derpprobe binary probes derpers.
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package main
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import (
"flag"
"fmt"
"html"
"io"
"log"
"net/http"
"sort"
"time"
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"tailscale.com/prober"
"tailscale.com/tsweb"
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"tailscale.com/version"
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)
var (
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derpMapURL = flag . String ( "derp-map" , "https://login.tailscale.com/derpmap/default" , "URL to DERP map (https:// or file://) or 'local' to use the local tailscaled's DERP map" )
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versionFlag = flag . Bool ( "version" , false , "print version and exit" )
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listen = flag . String ( "listen" , ":8030" , "HTTP listen address" )
probeOnce = flag . Bool ( "once" , false , "probe once and print results, then exit; ignores the listen flag" )
spread = flag . Bool ( "spread" , true , "whether to spread probing over time" )
interval = flag . Duration ( "interval" , 15 * time . Second , "probe interval" )
meshInterval = flag . Duration ( "mesh-interval" , 15 * time . Second , "mesh probe interval" )
stunInterval = flag . Duration ( "stun-interval" , 15 * time . Second , "STUN probe interval" )
tlsInterval = flag . Duration ( "tls-interval" , 15 * time . Second , "TLS probe interval" )
bwInterval = flag . Duration ( "bw-interval" , 0 , "bandwidth probe interval (0 = no bandwidth probing)" )
bwSize = flag . Int64 ( "bw-probe-size-bytes" , 1_000_000 , "bandwidth probe size" )
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)
func main ( ) {
flag . Parse ( )
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if * versionFlag {
fmt . Println ( version . Long ( ) )
return
}
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p := prober . New ( ) . WithSpread ( * spread ) . WithOnce ( * probeOnce ) . WithMetricNamespace ( "derpprobe" )
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opts := [ ] prober . DERPOpt {
prober . WithMeshProbing ( * meshInterval ) ,
prober . WithSTUNProbing ( * stunInterval ) ,
prober . WithTLSProbing ( * tlsInterval ) ,
}
if * bwInterval > 0 {
opts = append ( opts , prober . WithBandwidthProbing ( * bwInterval , * bwSize ) )
}
dp , err := prober . DERP ( p , * derpMapURL , opts ... )
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if err != nil {
log . Fatal ( err )
}
p . Run ( "derpmap-probe" , * interval , nil , dp . ProbeMap )
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if * probeOnce {
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log . Printf ( "Waiting for all probes (may take up to 1m)" )
p . Wait ( )
st := getOverallStatus ( p )
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for _ , s := range st . good {
log . Printf ( "good: %s" , s )
}
for _ , s := range st . bad {
log . Printf ( "bad: %s" , s )
}
return
}
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mux := http . NewServeMux ( )
tsweb . Debugger ( mux )
mux . HandleFunc ( "/" , http . HandlerFunc ( serveFunc ( p ) ) )
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log . Printf ( "Listening on %s" , * listen )
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log . Fatal ( http . ListenAndServe ( * listen , mux ) )
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}
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type overallStatus struct {
good , bad [ ] string
}
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func ( st * overallStatus ) addBadf ( format string , a ... any ) {
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st . bad = append ( st . bad , fmt . Sprintf ( format , a ... ) )
}
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func ( st * overallStatus ) addGoodf ( format string , a ... any ) {
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st . good = append ( st . good , fmt . Sprintf ( format , a ... ) )
}
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func getOverallStatus ( p * prober . Prober ) ( o overallStatus ) {
for p , i := range p . ProbeInfo ( ) {
if i . End . IsZero ( ) {
// Do not show probes that have not finished yet.
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continue
}
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if i . Result {
o . addGoodf ( "%s: %s" , p , i . Latency )
} else {
o . addBadf ( "%s: %s" , p , i . Error )
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}
}
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sort . Strings ( o . bad )
sort . Strings ( o . good )
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return
}
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func serveFunc ( p * prober . Prober ) func ( w http . ResponseWriter , r * http . Request ) {
return func ( w http . ResponseWriter , r * http . Request ) {
st := getOverallStatus ( p )
summary := "All good"
if ( float64 ( len ( st . bad ) ) / float64 ( len ( st . bad ) + len ( st . good ) ) ) > 0.25 {
// Returning a 500 allows monitoring this server externally and configuring
// an alert on HTTP response code.
w . WriteHeader ( 500 )
summary = fmt . Sprintf ( "%d problems" , len ( st . bad ) )
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}
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io . WriteString ( w , "<html><head><style>.bad { font-weight: bold; color: #700; }</style></head>\n" )
fmt . Fprintf ( w , "<body><h1>derp probe</h1>\n%s:<ul>" , summary )
for _ , s := range st . bad {
fmt . Fprintf ( w , "<li class=bad>%s</li>\n" , html . EscapeString ( s ) )
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}
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for _ , s := range st . good {
fmt . Fprintf ( w , "<li>%s</li>\n" , html . EscapeString ( s ) )
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}
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io . WriteString ( w , "</ul></body></html>\n" )
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}
}
