Turns out FreeBSD is a bit different so restrict this to OpenBSD for now

src/yggdrasil/tun_openbsd.go

@@ -0,0 +1,121 @@
+// +build openbsd
+
+package yggdrasil
+
+import "os/exec"
+import "strings"
+import "unsafe"
+import "syscall"
+import "golang.org/x/sys/unix"
+
+import water "github.com/neilalexander/water"
+
+// This is to catch OpenBSD
+
+// Warning! When porting this to other BSDs, the tuninfo struct can appear with
+// the fields in a different order, and the consts below might also have
+// different values
+
+type tuninfo struct {
+	tun_mtu     uint16
+	tun_type    uint32
+	tun_flags   uint32
+	tun_dummy   uint16
+}
+
+const TUNSIFINFO = (0x80000000) | ((12 & 0x1fff) << 16) | uint32(byte('t'))<<8 | 91
+const TUNGIFINFO = (0x40000000) | ((12 & 0x1fff) << 16) | uint32(byte('t'))<<8 | 92
+const SIOCAIFADDR_IN6 = (0x80000000) | ((4 & 0x1fff) << 16) | uint32(byte('i'))<<8 | 27
+
+// Below this point seems to be fairly standard at least...
+
+type in6_addrlifetime struct {
+	ia6t_expire    float64
+	ia6t_preferred float64
+	ia6t_vltime    uint32
+	ia6t_pltime    uint32
+}
+
+type sockaddr_in6 struct {
+	sin6_len      uint8
+	sin6_family   uint8
+	sin6_port     uint8
+	sin6_flowinfo uint32
+	sin6_addr     [8]uint16
+	sin6_scope_id uint32
+}
+
+type in6_aliasreq struct {
+	ifra_name       [16]byte
+	ifra_addr       sockaddr_in6
+	ifra_dstaddr    sockaddr_in6
+	ifra_prefixmask sockaddr_in6
+	ifra_flags      uint32
+	ifra_lifetime   in6_addrlifetime
+}
+
+func (tun *tunDevice) setup(ifname string, iftapmode bool, addr string, mtu int) error {
+	var config water.Config
+	switch {
+	case iftapmode || ifname[:8] == "/dev/tap":
+		config = water.Config{DeviceType: water.TAP}
+	case !iftapmode || ifname[:8] == "/dev/tun":
+		config = water.Config{DeviceType: water.TUN}
+	default:
+		panic("TUN/TAP name must be in format /dev/tunX or /dev/tapX")
+	}
+	config.Name = ifname
+	iface, err := water.New(config)
+	if err != nil {
+		panic(err)
+	}
+	tun.iface = iface
+	tun.mtu = mtu //1280 // Lets default to the smallest thing allowed for now
+	return tun.setupAddress(addr)
+}
+
+func (tun *tunDevice) setupAddress(addr string) error {
+	fd := tun.iface.FD().Fd()
+	var err error
+	var ti tuninfo
+
+	// Get the existing interface flags
+	if _, _, errno := unix.Syscall(unix.SYS_IOCTL, uintptr(fd), uintptr(TUNGIFINFO), uintptr(unsafe.Pointer(&ti))); errno != 0 {
+		err = errno
+		tun.core.log.Printf("Error in TUNGIFINFO: %v", errno)
+		return err
+	}
+	tun.core.log.Printf("TUNGIFINFO: %+v", ti)
+
+	// Set the new MTU
+	ti.tun_mtu = uint16(tun.mtu)
+
+	// Set the new interface flags
+	ti.tun_flags |= syscall.IFF_UP
+	switch {
+	case tun.iface.IsTAP():
+		ti.tun_flags |= syscall.IFF_MULTICAST
+		ti.tun_flags |= syscall.IFF_BROADCAST
+	case tun.iface.IsTUN():
+		ti.tun_flags |= syscall.IFF_POINTOPOINT
+	}
+
+	// Set the new interface flags
+	tun.core.log.Printf("TUNSIFINFO: %+v", ti)
+	if _, _, errno := unix.Syscall(unix.SYS_IOCTL, uintptr(fd), uintptr(TUNSIFINFO), uintptr(unsafe.Pointer(&ti))); errno != 0 {
+		err = errno
+		tun.core.log.Printf("Error in TUNSIFINFO: %v", errno)
+		return err
+	}
+
+	// Set address
+	cmd := exec.Command("ifconfig", tun.iface.Name(), "inet6", addr)
+	tun.core.log.Printf("ifconfig command: %v", strings.Join(cmd.Args, " "))
+	output, err := cmd.CombinedOutput()
+	if err != nil {
+		tun.core.log.Printf("ifconfig failed: %v.", err)
+		tun.core.log.Println(string(output))
+	}
+
+	return nil
+}