76 lines
1.7 KiB
Go
76 lines
1.7 KiB
Go
package gateway
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import (
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"bytes"
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"io/ioutil"
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"net"
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"os/exec"
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)
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func discoverGatewayUsingIp() (ip net.IP, err error) {
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routeCmd := exec.Command("ip", "route", "show")
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stdOut, err := routeCmd.StdoutPipe()
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if err != nil {
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return
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}
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if err = routeCmd.Start(); err != nil {
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return
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}
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output, err := ioutil.ReadAll(stdOut)
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if err != nil {
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return
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}
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// Linux 'ip route show' format looks like this:
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// default via 192.168.178.1 dev wlp3s0 metric 303
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// 192.168.178.0/24 dev wlp3s0 proto kernel scope link src 192.168.178.76 metric 303
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outputLines := bytes.Split(output, []byte("\n"))
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for _, line := range outputLines {
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if bytes.Contains(line, []byte("default")) {
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ipFields := bytes.Fields(line)
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ip = net.ParseIP(string(ipFields[2]))
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break
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}
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}
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err = routeCmd.Wait()
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return
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}
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func discoverGatewayUsingRoute() (ip net.IP, err error) {
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routeCmd := exec.Command("route", "-n")
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stdOut, err := routeCmd.StdoutPipe()
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if err != nil {
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return
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}
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if err = routeCmd.Start(); err != nil {
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return
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}
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output, err := ioutil.ReadAll(stdOut)
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if err != nil {
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return
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}
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// Linux route out format is always like this:
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// Kernel IP routing table
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// Destination Gateway Genmask Flags Metric Ref Use Iface
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// 0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 eth0
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outputLines := bytes.Split(output, []byte("\n"))
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for _, line := range outputLines {
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if bytes.Contains(line, []byte("0.0.0.0")) {
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ipFields := bytes.Fields(line)
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ip = net.ParseIP(string(ipFields[1]))
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break
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}
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}
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err = routeCmd.Wait()
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return
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}
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func DiscoverGateway() (ip net.IP, err error) {
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ip, err = discoverGatewayUsingRoute()
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if err != nil {
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ip, err = discoverGatewayUsingIp()
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}
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return
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}
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