Created
April 13, 2021 14:43
-
-
Save yujp/cc1743955f1ced31b5ab7b73c99f2b0b to your computer and use it in GitHub Desktop.
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| package main | |
| import ( | |
| "context" | |
| "flag" | |
| "fmt" | |
| "log" | |
| "net" | |
| "os" | |
| "os/exec" | |
| "os/signal" | |
| "strings" | |
| "syscall" | |
| ) | |
| func main() { | |
| var ( | |
| ifName = flag.String("ifname", "", "network-interface-name") | |
| ) | |
| flag.Parse() | |
| args := flag.Args() | |
| if len(args) < 1 || *ifName == "" { | |
| log.Println("Usage: drr -ifname <network-interface-name> <domain1> <domain2>...") | |
| return | |
| } | |
| var ifIP string | |
| { | |
| ifr, err := net.InterfaceByName(*ifName) | |
| if err != nil { | |
| log.Fatalf("failed to get the interface(%s): %v", *ifName, err) | |
| } | |
| addrs, err := ifr.Addrs() | |
| if err != nil || len(addrs) < 1 { | |
| log.Fatalf("failed to get the addresses of the interface(%s): %v", *ifName, err) | |
| } | |
| ip, _, err := net.ParseCIDR(addrs[0].String()) | |
| if err != nil { | |
| log.Fatalf("failed to get the address of the interface(%s): %v", *ifName, err) | |
| } | |
| ifIP = ip.String() | |
| // log.Printf("LocalIP: %s", ifIP) | |
| } | |
| type target struct { | |
| domain string | |
| ips []string | |
| } | |
| var targets []*target | |
| for _, arg := range args { | |
| ips, err := net.LookupIP(arg) | |
| if err != nil { | |
| log.Fatalf("failed to find the domain(%s): %v", arg, err) | |
| } | |
| var t target | |
| t.domain = arg | |
| for _, ip := range ips { | |
| _, bits := ip.DefaultMask().Size() | |
| addr := fmt.Sprintf("%s/%d", ip.To4().String(), bits) | |
| t.ips = append(t.ips, addr) | |
| } | |
| targets = append(targets, &t) | |
| } | |
| unregister := func() { | |
| for _, t := range targets { | |
| log.Printf("Unregistering routes for the domain '%s'", t.domain) | |
| for _, ip := range t.ips { | |
| //log.Println(strings.Join([]string{"route", "delete", ip}, " ")) | |
| o, err := exec.Command("route", "delete", ip).Output() | |
| if err != nil { | |
| log.Printf("%s\tFailed: %v", ip, err) | |
| } else { | |
| log.Printf("%s\t%s\n", ip, strings.TrimSpace(string(o))) | |
| } | |
| } | |
| } | |
| } | |
| register := func() { | |
| for _, t := range targets { | |
| log.Printf("Registering routes for the domain '%s'", t.domain) | |
| for _, ip := range t.ips { | |
| //log.Println(strings.Join([]string{"route", "add", ip, ifIP}, " ")) | |
| o, err := exec.Command("route", "add", ip, ifIP).Output() | |
| if err != nil { | |
| log.Printf("%s\tFailed: %v", ip, err) | |
| } else { | |
| log.Printf("%s\t%s", ip, strings.TrimSpace(string(o))) | |
| } | |
| } | |
| } | |
| } | |
| defer unregister() | |
| register() | |
| ctx, _ := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGINT, syscall.SIGTERM) | |
| <-ctx.Done() | |
| } |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment