github.com/google/cloudprober@v0.11.3/common/iputils/iputils.go (about)

     1  // Copyright 2020 The Cloudprober Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //      http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  /*
    16  Package iputils implements utilities to work with IP addresses.
    17  */
    18  package iputils
    19  
    20  import (
    21  	"fmt"
    22  	"net"
    23  )
    24  
    25  // IPVersion tells if an IP address is IPv4 or IPv6.
    26  func IPVersion(ip net.IP) int {
    27  	if len(ip.To4()) == net.IPv4len {
    28  		return 4
    29  	}
    30  	if len(ip) == net.IPv6len {
    31  		return 6
    32  	}
    33  	return 0
    34  }
    35  
    36  // Addr is used for tests, allowing net.InterfaceByName to be mocked.
    37  type Addr interface {
    38  	Addrs() ([]net.Addr, error)
    39  }
    40  
    41  // InterfaceByName is a mocking point for net.InterfaceByName, used for tests.
    42  var InterfaceByName = func(s string) (Addr, error) { return net.InterfaceByName(s) }
    43  
    44  // ResolveIntfAddr takes the name of a network interface and IP version, and
    45  // returns the first IP address of the interface that matches the specified IP
    46  // version. If no IP version is specified (ipVer is 0), simply the first IP
    47  // address is returned.
    48  // TODO(manugarg): This functions is currently tested through options_test. We
    49  // should fix that.
    50  func ResolveIntfAddr(intfName string, ipVer int) (net.IP, error) {
    51  	i, err := InterfaceByName(intfName)
    52  	if err != nil {
    53  		return nil, fmt.Errorf("resolveIntfAddr(%v, %d) got error getting interface: %v", intfName, ipVer, err)
    54  	}
    55  
    56  	addrs, err := i.Addrs()
    57  	if err != nil {
    58  		return nil, fmt.Errorf("resolveIntfAddr(%v, %d) got error getting addresses for interface: %v", intfName, ipVer, err)
    59  	} else if len(addrs) == 0 {
    60  		return nil, fmt.Errorf("resolveIntfAddr(%v, %d) go 0 addrs for interface", intfName, ipVer)
    61  	}
    62  
    63  	var ip net.IP
    64  
    65  	for _, addr := range addrs {
    66  		// i.Addrs() mostly returns network addresses of the form "172.17.90.252/23".
    67  		// This bit of code will pull the IP address from this address.
    68  		switch v := addr.(type) {
    69  		case *net.IPNet:
    70  			ip = v.IP
    71  		case *net.IPAddr:
    72  			ip = v.IP
    73  		default:
    74  			return nil, fmt.Errorf("resolveIntfAddr(%v, %d) found unknown type for first address: %T", intfName, ipVer, v)
    75  		}
    76  
    77  		if ipVer == 0 || IPVersion(ip) == ipVer {
    78  			return ip, nil
    79  		}
    80  	}
    81  	return nil, fmt.Errorf("resolveIntfAddr(%v, %d) found no apprpriate IP addresses in %v", intfName, ipVer, addrs)
    82  }