Reimplemented bind_rtmgrp in pure Go

Getting rid of the Cgo dependency for listing on netlink.

Ported original patch from "syscall" to "golang.org/x/sys/unix".

Signed-off-by: Dominik Süß <dominik.suess@outlook.at>
Co-Authored-By: Mathias Hall-Andersen <mathias@hall-andersen.dk>

diff --git a/tun_linux.go b/tun_linux.go
index daa2462ad7650c27825cf4eec3074d0f57597f25..b35e08db52b5bfa8f5ec600560df454a9a8f72d0 100644 (file)
--- a/tun_linux.go
+++ b/tun_linux.go
@@ -16,38 +16,9 @@ import (
        "unsafe"
 )
 
-// #include <string.h>
-// #include <unistd.h>
-// #include <net/if.h>
-// #include <netinet/in.h>
-// #include <linux/netlink.h>
-// #include <linux/rtnetlink.h>
-//
-// /* Creates a netlink socket
-//  * listening to the RTMGRP_LINK multicast group
-//  */
-//
-// int bind_rtmgrp() {
-//   int nl_sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
-//   if (nl_sock < 0)
-//     return -1;
-//
-//      struct sockaddr_nl addr;
-//   memset ((void *) &addr, 0, sizeof (addr));
-//   addr.nl_family = AF_NETLINK;
-//   addr.nl_pid = getpid ();
-//   addr.nl_groups = RTMGRP_LINK | RTMGRP_IPV4_IFADDR | RTMGRP_IPV6_IFADDR;
-//
-//   if (bind(nl_sock, (struct sockaddr *) &addr, sizeof (addr)) < 0)
-//     return -1;
-//
-//   return nl_sock;
-// }
-import "C"
-
 const (
-       CloneDevicePath = "/dev/net/tun"
-       IFReqSize       = unix.IFNAMSIZ + 64
+       cloneDevicePath = "/dev/net/tun"
+       ifReqSize       = unix.IFNAMSIZ + 64
 )
 
 type NativeTun struct {
@@ -58,6 +29,26 @@ type NativeTun struct {
        events chan TUNEvent // device related events
 }
 
+func toRTMGRP(sc uint) uint {
+       return 1 << (sc - 1)
+}
+
+func (tun *NativeTun) bindRTMGRP() (int, error) {
+       groups := toRTMGRP(unix.RTNLGRP_LINK)
+       groups |= toRTMGRP(unix.RTNLGRP_IPV4_IFADDR)
+       groups |= toRTMGRP(unix.RTNLGRP_IPV6_IFADDR)
+       sock, err := unix.Socket(unix.AF_NETLINK, unix.SOCK_RAW, unix.NETLINK_ROUTE)
+       if err != nil {
+               return 0, err
+       }
+       saddr := &unix.SockaddrNetlink{
+               Family: unix.AF_NETLINK,
+               Pid:    uint32(os.Getpid()),
+               Groups: uint32(groups),
+       }
+       return sock, unix.Bind(sock, saddr)
+}
+
 func (tun *NativeTun) File() *os.File {
        return tun.fd
 }
@@ -81,9 +72,8 @@ func (tun *NativeTun) RoutineHackListener() {
 }
 
 func (tun *NativeTun) RoutineNetlinkListener() {
-
-       sock := int(C.bind_rtmgrp())
-       if sock < 0 {
+       sock, err := tun.bindRTMGRP()
+       if err != nil {
                tun.errors <- errors.New("Failed to create netlink event listener")
                return
        }
@@ -159,7 +149,7 @@ func getIFIndex(name string) (int32, error) {
 
        defer unix.Close(fd)
 
-       var ifr [IFReqSize]byte
+       var ifr [ifReqSize]byte
        copy(ifr[:], name)
        _, _, errno := unix.Syscall(
                unix.SYS_IOCTL,
@@ -194,7 +184,7 @@ func (tun *NativeTun) setMTU(n int) error {
 
        // do ioctl call
 
-       var ifr [IFReqSize]byte
+       var ifr [ifReqSize]byte
        copy(ifr[:], tun.name)
        binary.LittleEndian.PutUint32(ifr[16:20], uint32(n))
        _, _, errno := unix.Syscall(
@@ -229,7 +219,7 @@ func (tun *NativeTun) MTU() (int, error) {
 
        // do ioctl call
 
-       var ifr [IFReqSize]byte
+       var ifr [ifReqSize]byte
        copy(ifr[:], tun.name)
        _, _, errno := unix.Syscall(
                unix.SYS_IOCTL,
@@ -324,15 +314,15 @@ func CreateTUN(name string) (TUNDevice, error) {
 
        // open clone device
 
-       fd, err := os.OpenFile(CloneDevicePath, os.O_RDWR, 0)
+       fd, err := os.OpenFile(cloneDevicePath, os.O_RDWR, 0)
        if err != nil {
                return nil, err
        }
 
        // create new device
 
-       var ifr [IFReqSize]byte
-       var flags uint16 = unix.IFF_TUN // | unix.IFF_NO_PI
+       var ifr [ifReqSize]byte
+       var flags uint16 = unix.IFF_TUN // | unix.IFF_NO_PI (disabled for TUN status hack)
        nameBytes := []byte(name)
        if len(nameBytes) >= unix.IFNAMSIZ {
                return nil, errors.New("Interface name too long")