146 lines
3.4 KiB
Go
146 lines
3.4 KiB
Go
// Copyright 2017 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package sync
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import (
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"context"
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"fmt"
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"log"
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"math/rand"
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"net/http"
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"strings"
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"time"
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"golang.org/x/net/html"
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)
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var webCheck = []string{
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"http://checkip.dyndns.org/",
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"http://ipdetect.dnspark.com/",
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"http://dns.loopia.se/checkip/checkip.php",
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}
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// IPAddressPoller is a poller used to check the value
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// of the current public internet IP address.
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type IPAddressPoller struct {
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channels []chan string
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pollInterval time.Duration
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}
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func NewIPAddressPoller(pollInterval time.Duration) *IPAddressPoller {
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return &IPAddressPoller{
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pollInterval: pollInterval,
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}
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}
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// Channel() returns a channel that receives data whenever an
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// IP address value is received.
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func (p *IPAddressPoller) Channel() <-chan string {
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c := make(chan string, 1)
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p.channels = append(p.channels, c)
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return c
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}
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// poll() runs a single polling event and retrieving the internet IP.
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func (p *IPAddressPoller) poll() error {
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// Shuffle the list of URLs randomly so that they aren't
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// always used in the same order.
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urls := make([]string, len(webCheck))
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copy(urls, webCheck)
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for i := range urls {
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j := rand.Intn(i + 1)
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urls[i], urls[j] = urls[j], urls[i]
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}
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// Make a request to each url and send to the
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// channels if an IP is retrieved
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var lastErr error
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for i := range urls {
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ip, err := request(urls[i])
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if err != nil {
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lastErr = err
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continue
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}
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for _, c := range p.channels {
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select {
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case c <- ip:
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default:
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}
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}
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return nil
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}
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return fmt.Errorf("Could not obtain IP address: %s %#v", lastErr.Error(), lastErr)
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}
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// request() makes a request to a URL to get the internet IP address.
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func request(url string) (string, error) {
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req, err := http.NewRequest(http.MethodGet, url, nil)
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if err != nil {
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return "", err
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}
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ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
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defer cancel()
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req = req.WithContext(ctx)
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resp, err := http.DefaultClient.Do(req)
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if err != nil {
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return "", err
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}
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if resp.StatusCode != http.StatusOK {
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return "", fmt.Errorf("Got status code from %s: %s", url, resp.StatusCode)
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}
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z := html.NewTokenizer(resp.Body)
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for {
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tt := z.Next()
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switch tt {
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case html.ErrorToken:
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return "", z.Err()
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case html.TextToken:
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text := strings.Trim(string(z.Text()), " \n\t")
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if text != "" {
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ip := ""
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fmt.Sscanf(text, "Current IP Address: %s", &ip)
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if ip != "" {
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return strings.Trim(ip, " \n\t"), nil
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}
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}
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}
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}
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return "", fmt.Errorf("Could not obtain IP address from html body")
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}
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// Run() starts the main loop for the poller.
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func (i *IPAddressPoller) Run(stopCh <-chan struct{}) error {
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if err := i.poll(); err != nil {
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log.Printf("Error polling for IP: %s %#v", err.Error(), err)
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}
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for {
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select {
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case <-time.After(i.pollInterval):
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if err := i.poll(); err != nil {
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log.Printf("Error polling for IP: %s %#v", err.Error(), err)
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}
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case <-stopCh:
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return nil
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}
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}
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return nil
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}
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