init

pkg/iproute/ipip.go

@@ -0,0 +1,59 @@
+// Copyright 2019 the Kilo authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package iproute
+
+import (
+	"bytes"
+	"fmt"
+	"os/exec"
+
+	"github.com/vishvananda/netlink"
+)
+
+const (
+	ipipHeaderSize = 20
+	tunnelName     = "tunl0"
+)
+
+// NewIPIP creates an IPIP interface using the base interface
+// to derive the tunnel's MTU.
+func NewIPIP(baseIndex int) (int, error) {
+	link, err := netlink.LinkByName(tunnelName)
+	if err != nil {
+		// If we failed to find the tunnel, then it probably simply does not exist.
+		cmd := exec.Command("ip", "tunnel", "add", tunnelName, "mode", "ipip")
+		var stderr bytes.Buffer
+		cmd.Stderr = &stderr
+		if err := cmd.Run(); err != nil {
+			return 0, fmt.Errorf("failed to create IPIP tunnel: %s", stderr.String())
+		}
+		link, err = netlink.LinkByName(tunnelName)
+		if err != nil {
+			return 0, fmt.Errorf("failed to get tunnel device: %v", err)
+		}
+	}
+
+	base, err := netlink.LinkByIndex(baseIndex)
+	if err != nil {
+		return 0, fmt.Errorf("failed to get base device: %v", err)
+	}
+
+	mtu := base.Attrs().MTU - ipipHeaderSize
+	if err = netlink.LinkSetMTU(link, mtu); err != nil {
+		return 0, fmt.Errorf("failed to set tunnel MTU: %v", err)
+	}
+
+	return link.Attrs().Index, nil
+}