tun: openbsd: check for interface already being up

In some cases, we operate on an already-up interface, or the user brings
up the interface before we start monitoring. For those situations, we
should first check if the interface is already up.

This still technically races between the initial check and the start of
the route loop, but fixing that is a bit ugly and probably not worth it
at the moment.

Reported-by: Theo Buehler <tb@theobuehler.org>

diff --git a/tun/tun_openbsd.go b/tun/tun_openbsd.go
index bbc0432cbf1cd854cc0590c166646a5d44499fff..44cedaa463c119eb23075b3e5cc04b89ad9954a9 100644 (file)
--- a/tun/tun_openbsd.go
+++ b/tun/tun_openbsd.go
@@ -42,13 +42,41 @@ func (tun *NativeTun) routineRouteListener(tunIfindex int) {
 
        defer close(tun.events)
 
+       check := func() bool {
+               iface, err := net.InterfaceByIndex(tunIfindex)
+               if err != nil {
+                       tun.errors <- err
+                       return true
+               }
+
+               // Up / Down event
+               up := (iface.Flags & net.FlagUp) != 0
+               if up != statusUp && up {
+                       tun.events <- EventUp
+               }
+               if up != statusUp && !up {
+                       tun.events <- EventDown
+               }
+               statusUp = up
+
+               // MTU changes
+               if iface.MTU != statusMTU {
+                       tun.events <- EventMTUUpdate
+               }
+               statusMTU = iface.MTU
+               return false
+       }
+
+       if check() {
+               return
+       }
+
        data := make([]byte, os.Getpagesize())
        for {
-       retry:
                n, err := unix.Read(tun.routeSocket, data)
                if err != nil {
                        if errno, ok := err.(syscall.Errno); ok && errno == syscall.EINTR {
-                               goto retry
+                               continue
                        }
                        tun.errors <- err
                        return
@@ -65,28 +93,9 @@ func (tun *NativeTun) routineRouteListener(tunIfindex int) {
                if ifindex != tunIfindex {
                        continue
                }
-
-               iface, err := net.InterfaceByIndex(ifindex)
-               if err != nil {
-                       tun.errors <- err
+               if check() {
                        return
                }
-
-               // Up / Down event
-               up := (iface.Flags & net.FlagUp) != 0
-               if up != statusUp && up {
-                       tun.events <- EventUp
-               }
-               if up != statusUp && !up {
-                       tun.events <- EventDown
-               }
-               statusUp = up
-
-               // MTU changes
-               if iface.MTU != statusMTU {
-                       tun.events <- EventMTUUpdate
-               }
-               statusMTU = iface.MTU
        }
 }
 
@@ -140,7 +149,6 @@ func CreateTUN(name string, mtu int) (Device, error) {
 }
 
 func CreateTUNFromFile(file *os.File, mtu int) (Device, error) {
-
        tun := &NativeTun{
                tunFile: file,
                events:  make(chan Event, 10),