Rename tuntap package to tun

We haven't had TAP support in ages.

src/tun/tun_linux.go

@@ -0,0 +1,58 @@
+//go:build !mobile
+// +build !mobile
+
+package tun
+
+// The linux platform specific tun parts
+
+import (
+	"github.com/vishvananda/netlink"
+	wgtun "golang.zx2c4.com/wireguard/tun"
+)
+
+// Configures the TUN adapter with the correct IPv6 address and MTU.
+func (tun *TunAdapter) setup(ifname string, addr string, mtu uint64) error {
+	if ifname == "auto" {
+		ifname = "\000"
+	}
+	iface, err := wgtun.CreateTUN(ifname, int(mtu))
+	if err != nil {
+		panic(err)
+	}
+	tun.iface = iface
+	if mtu, err := iface.MTU(); err == nil {
+		tun.mtu = getSupportedMTU(uint64(mtu))
+	} else {
+		tun.mtu = 0
+	}
+	return tun.setupAddress(addr)
+}
+
+// Configures the TUN adapter with the correct IPv6 address and MTU. Netlink
+// is used to do this, so there is not a hard requirement on "ip" or "ifconfig"
+// to exist on the system, but this will fail if Netlink is not present in the
+// kernel (it nearly always is).
+func (tun *TunAdapter) setupAddress(addr string) error {
+	nladdr, err := netlink.ParseAddr(addr)
+	if err != nil {
+		return err
+	}
+	nlintf, err := netlink.LinkByName(tun.Name())
+	if err != nil {
+		return err
+	}
+	if err := netlink.AddrAdd(nlintf, nladdr); err != nil {
+		return err
+	}
+	if err := netlink.LinkSetMTU(nlintf, int(tun.mtu)); err != nil {
+		return err
+	}
+	if err := netlink.LinkSetUp(nlintf); err != nil {
+		return err
+	}
+	// Friendly output
+	tun.log.Infof("Interface name: %s", tun.Name())
+	tun.log.Infof("Interface IPv6: %s", addr)
+	tun.log.Infof("Interface MTU: %d", tun.mtu)
+	return nil
+}