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