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4a2c3e2a0a
To not allocate 1MB up front on iOS. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
123 lines
2.7 KiB
Go
123 lines
2.7 KiB
Go
// Copyright (c) 2021 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 controlclient
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import (
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"bytes"
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"compress/gzip"
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"context"
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"fmt"
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"log"
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"net/http"
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"runtime"
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"strconv"
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"time"
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)
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func dumpGoroutinesToURL(c *http.Client, targetURL string) {
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ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
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defer cancel()
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zbuf := new(bytes.Buffer)
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zw := gzip.NewWriter(zbuf)
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zw.Write(scrubbedGoroutineDump())
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zw.Close()
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req, err := http.NewRequestWithContext(ctx, "PUT", targetURL, zbuf)
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if err != nil {
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log.Printf("dumpGoroutinesToURL: %v", err)
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return
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}
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req.Header.Set("Content-Encoding", "gzip")
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t0 := time.Now()
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_, err = c.Do(req)
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d := time.Since(t0).Round(time.Millisecond)
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if err != nil {
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log.Printf("dumpGoroutinesToURL error: %v to %v (after %v)", err, targetURL, d)
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} else {
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log.Printf("dumpGoroutinesToURL complete to %v (after %v)", targetURL, d)
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}
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}
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// scrubbedGoroutineDump returns the list of all current goroutines, but with the actual
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// values of arguments scrubbed out, lest it contain some private key material.
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func scrubbedGoroutineDump() []byte {
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var buf []byte
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// Grab stacks multiple times into increasingly larger buffer sizes
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// to minimize the risk that we blow past our iOS memory limit.
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for size := 1 << 10; size <= 1<<20; size += 1 << 10 {
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buf = make([]byte, size)
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buf = buf[:runtime.Stack(buf, true)]
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if len(buf) < size {
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// It fit.
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break
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}
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}
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return scrubHex(buf)
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}
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func scrubHex(buf []byte) []byte {
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saw := map[string][]byte{} // "0x123" => "v1%3" (unique value 1 and its value mod 8)
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foreachHexAddress(buf, func(in []byte) {
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if string(in) == "0x0" {
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return
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}
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if v, ok := saw[string(in)]; ok {
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for i := range in {
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in[i] = '_'
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}
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copy(in, v)
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return
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}
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inStr := string(in)
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u64, err := strconv.ParseUint(string(in[2:]), 16, 64)
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for i := range in {
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in[i] = '_'
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}
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if err != nil {
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in[0] = '?'
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return
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}
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v := []byte(fmt.Sprintf("v%d%%%d", len(saw)+1, u64%8))
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saw[inStr] = v
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copy(in, v)
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})
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return buf
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}
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var ohx = []byte("0x")
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// foreachHexAddress calls f with each subslice of b that matches
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// regexp `0x[0-9a-f]*`.
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func foreachHexAddress(b []byte, f func([]byte)) {
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for len(b) > 0 {
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i := bytes.Index(b, ohx)
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if i == -1 {
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return
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}
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b = b[i:]
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hx := hexPrefix(b)
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f(hx)
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b = b[len(hx):]
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}
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}
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func hexPrefix(b []byte) []byte {
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for i, c := range b {
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if i < 2 {
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continue
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}
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if !isHexByte(c) {
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return b[:i]
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}
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}
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return b
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}
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func isHexByte(b byte) bool {
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return '0' <= b && b <= '9' || 'a' <= b && b <= 'f' || 'A' <= b && b <= 'F'
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}
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