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84 lines
2.1 KiB
84 lines
2.1 KiB
// Copyright (c) 2017 Uber Technologies, Inc.
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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 utils
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import (
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"errors"
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"net"
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)
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// This code is borrowed from https://github.com/uber/tchannel-go/blob/dev/localip.go
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// scoreAddr scores how likely the given addr is to be a remote address and returns the
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// IP to use when listening. Any address which receives a negative score should not be used.
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// Scores are calculated as:
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// -1 for any unknown IP addresses.
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// +300 for IPv4 addresses
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// +100 for non-local addresses, extra +100 for "up" interaces.
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func scoreAddr(iface net.Interface, addr net.Addr) (int, net.IP) {
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var ip net.IP
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if netAddr, ok := addr.(*net.IPNet); ok {
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ip = netAddr.IP
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} else if netIP, ok := addr.(*net.IPAddr); ok {
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ip = netIP.IP
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} else {
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return -1, nil
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}
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var score int
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if ip.To4() != nil {
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score += 300
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}
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if iface.Flags&net.FlagLoopback == 0 && !ip.IsLoopback() {
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score += 100
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if iface.Flags&net.FlagUp != 0 {
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score += 100
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}
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}
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return score, ip
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}
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// HostIP tries to find an IP that can be used by other machines to reach this machine.
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func HostIP() (net.IP, error) {
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interfaces, err := net.Interfaces()
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if err != nil {
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return nil, err
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}
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bestScore := -1
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var bestIP net.IP
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// Select the highest scoring IP as the best IP.
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for _, iface := range interfaces {
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addrs, err := iface.Addrs()
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if err != nil {
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// Skip this interface if there is an error.
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continue
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}
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for _, addr := range addrs {
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score, ip := scoreAddr(iface, addr)
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if score > bestScore {
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bestScore = score
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bestIP = ip
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}
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}
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}
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if bestScore == -1 {
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return nil, errors.New("no addresses to listen on")
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}
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return bestIP, nil
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}
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