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