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resolve.go
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resolve.go
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// Copyright 2017 Istio 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 proxy
import (
"context"
"errors"
"fmt"
"net"
"time"
"istio.io/istio/pkg/log"
)
// ErrResolveNoAddress error occurs when IP address resolution is attempted,
// but no address was provided.
var ErrResolveNoAddress = errors.New("no address specified")
// ResolveAddr resolves an authority address to an IP address. Incoming
// addr can be an IP address or hostname. If addr is an IPv6 address, the IP
// part must be enclosed in square brackets.
//
// TODO: LookupIPAddr() may return multiple IP addresses, of which this function
// returns the first entry. We're assuming that IPv4 addresses will be listed
// first, meaning it has priority over IPv6. If this does not hold, then
// additional logic will be needed to enforce an IP mode priority.
//
// To use this function in an IPv6 only environment, either provide an IPv6
// address or ensure the hostname resolves to only IPv6 addresses.
func ResolveAddr(addr string) (string, error) {
if addr == "" {
return "", ErrResolveNoAddress
}
host, port, err := net.SplitHostPort(addr)
if err != nil {
return "", err
}
log.Infof("Attempting to lookup address: %s", host)
defer log.Infof("Finished lookup of address: %s", host)
// lookup the udp address with a timeout of 15 seconds.
ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
defer cancel()
addrs, lookupErr := net.DefaultResolver.LookupIPAddr(ctx, host)
if lookupErr != nil || len(addrs) == 0 {
return "", fmt.Errorf("lookup failed for IP address: %v", lookupErr)
}
var resolvedAddr string
ip := addrs[0].IP
if ip.To4() == nil {
resolvedAddr = fmt.Sprintf("[%s]:%s", ip, port)
} else {
resolvedAddr = fmt.Sprintf("%s:%s", ip, port)
}
log.Infof("Addr resolved to: %s", resolvedAddr)
return resolvedAddr, nil
}