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master
Stephen McQuay 2 years ago
parent
commit
08019f5593
Signed by: sm GPG Key ID: 4E4B72F479BA3CE5
4 changed files with 298 additions and 5 deletions
  1. +79
    -0
      cidr.go
  2. +186
    -0
      cidr_test.go
  3. +3
    -5
      main.go
  4. +30
    -0
      wrangling.go

+ 79
- 0
cidr.go View File

@ -0,0 +1,79 @@
// Package cidr is a collection of assorted utilities for computing
// network and host addresses within network ranges.
//
// It expects a CIDR-type address structure where addresses are divided into
// some number of prefix bits representing the network and then the remaining
// suffix bits represent the host.
//
// For example, it can help to calculate addresses for sub-networks of a
// parent network, or to calculate host addresses within a particular prefix.
//
// At present this package is prioritizing simplicity of implementation and
// de-prioritizing speed and memory usage. Thus caution is advised before
// using this package in performance-critical applications or hot codepaths.
// Patches to improve the speed and memory usage may be accepted as long as
// they do not result in a significant increase in code complexity.
package main
import (
"fmt"
"math/big"
"net"
)
// AddressRange returns the first and last addresses in the given CIDR range.
func AddressRange(network *net.IPNet) (net.IP, net.IP) {
// the first IP is easy
firstIP := network.IP
// the last IP is the network address OR NOT the mask address
prefixLen, bits := network.Mask.Size()
if prefixLen == bits {
// Easy!
// But make sure that our two slices are distinct, since they
// would be in all other cases.
lastIP := make([]byte, len(firstIP))
copy(lastIP, firstIP)
return firstIP, lastIP
}
firstIPInt, bits := ipToInt(firstIP)
hostLen := uint(bits) - uint(prefixLen)
lastIPInt := big.NewInt(1)
lastIPInt.Lsh(lastIPInt, hostLen)
lastIPInt.Sub(lastIPInt, big.NewInt(1))
lastIPInt.Or(lastIPInt, firstIPInt)
return firstIP, intToIP(lastIPInt, bits)
}
// AddressCount returns the number of distinct host addresses within the given
// CIDR range.
//
// Since the result is a uint64, this function returns meaningful information
// only for IPv4 ranges and IPv6 ranges with a prefix size of at least 65.
func AddressCount(network *net.IPNet) uint64 {
prefixLen, bits := network.Mask.Size()
return 1 << (uint64(bits) - uint64(prefixLen))
}
//NoOverlap takes a list subnets and supernet (CIDRBlock) and verifies
//none of the subnets overlap and all subnets are in the supernet
//it returns an error if any of those conditions are not satisfied
func NoOverlap(subnets []*net.IPNet) error {
firstLastIP := make([][]net.IP, len(subnets))
for i, s := range subnets {
first, last := AddressRange(s)
firstLastIP[i] = []net.IP{first, last}
}
for i, s := range subnets {
for j := i + 1; j < len(subnets); j++ {
first := firstLastIP[j][0]
last := firstLastIP[j][1]
if s.Contains(first) || s.Contains(last) {
return fmt.Errorf("%s overlaps with %s", subnets[j].String(), s.String())
}
}
}
return nil
}

+ 186
- 0
cidr_test.go View File

@ -0,0 +1,186 @@
package main
import (
"fmt"
"net"
"testing"
)
func TestAddressRange(t *testing.T) {
type Case struct {
Range string
First string
Last string
}
cases := []Case{
Case{
Range: "192.168.0.0/16",
First: "192.168.0.0",
Last: "192.168.255.255",
},
Case{
Range: "192.168.0.0/17",
First: "192.168.0.0",
Last: "192.168.127.255",
},
Case{
Range: "fe80::/64",
First: "fe80::",
Last: "fe80::ffff:ffff:ffff:ffff",
},
}
for _, testCase := range cases {
_, network, _ := net.ParseCIDR(testCase.Range)
firstIP, lastIP := AddressRange(network)
desc := fmt.Sprintf("AddressRange(%#v)", testCase.Range)
gotFirstIP := firstIP.String()
gotLastIP := lastIP.String()
if gotFirstIP != testCase.First {
t.Errorf("%s first is %s; want %s", desc, gotFirstIP, testCase.First)
}
if gotLastIP != testCase.Last {
t.Errorf("%s last is %s; want %s", desc, gotLastIP, testCase.Last)
}
}
}
func TestAddressCount(t *testing.T) {
type Case struct {
Range string
Count uint64
}
cases := []Case{
Case{
Range: "192.168.0.0/16",
Count: 65536,
},
Case{
Range: "192.168.0.0/17",
Count: 32768,
},
Case{
Range: "192.168.0.0/32",
Count: 1,
},
Case{
Range: "192.168.0.0/31",
Count: 2,
},
Case{
Range: "0.0.0.0/0",
Count: 4294967296,
},
Case{
Range: "0.0.0.0/1",
Count: 2147483648,
},
Case{
Range: "::/65",
Count: 9223372036854775808,
},
Case{
Range: "::/128",
Count: 1,
},
Case{
Range: "::/127",
Count: 2,
},
}
for _, testCase := range cases {
_, network, _ := net.ParseCIDR(testCase.Range)
gotCount := AddressCount(network)
desc := fmt.Sprintf("AddressCount(%#v)", testCase.Range)
if gotCount != testCase.Count {
t.Errorf("%s = %d; want %d", desc, gotCount, testCase.Count)
}
}
}
func TestVerifyNetowrk(t *testing.T) {
type testVerifyNetwork struct {
CIDRBlock string
CIDRList []string
}
testCases := []*testVerifyNetwork{
&testVerifyNetwork{
CIDRList: []string{
"192.168.8.0/24",
"192.168.9.0/24",
"192.168.10.0/24",
"192.168.11.0/25",
"192.168.11.128/25",
"192.168.12.0/25",
"192.168.12.128/26",
"192.168.12.192/26",
"192.168.13.0/26",
"192.168.13.64/27",
"192.168.13.96/27",
"192.168.13.128/27",
},
},
}
failCases := []*testVerifyNetwork{
&testVerifyNetwork{
CIDRList: []string{
"192.168.8.0/24",
"192.168.9.0/24",
"192.168.10.0/24",
"192.168.11.0/25",
"192.168.11.128/25",
"192.168.12.0/25",
"192.168.12.64/26",
"192.168.12.128/26",
},
},
&testVerifyNetwork{
CIDRList: []string{
"192.168.7.0/24",
"192.168.9.0/24",
"192.168.10.0/24",
"192.168.11.0/25",
"192.168.11.128/25",
"192.168.12.0/25",
"192.168.12.64/26",
"192.168.12.128/26",
},
},
}
for _, tc := range testCases {
subnets := make([]*net.IPNet, len(tc.CIDRList))
for i, s := range tc.CIDRList {
_, n, err := net.ParseCIDR(s)
if err != nil {
t.Errorf("Bad test data %s\n", s)
}
subnets[i] = n
}
test := NoOverlap(subnets)
if test != nil {
t.Errorf("Failed test with %v\n", test)
}
}
for _, tc := range failCases {
subnets := make([]*net.IPNet, len(tc.CIDRList))
for i, s := range tc.CIDRList {
_, n, err := net.ParseCIDR(s)
if err != nil {
t.Errorf("Bad test data %s\n", s)
}
subnets[i] = n
}
test := NoOverlap(subnets)
if test == nil {
t.Errorf("Test should have failed with CIDR %s\n", tc.CIDRBlock)
}
}
}

+ 3
- 5
main.go View File

@ -4,8 +4,6 @@ import (
"fmt"
"net"
"os"
"github.com/apparentlymart/go-cidr/cidr"
)
const usage = "sn <cidr>"
@ -24,11 +22,11 @@ func main() {
os.Exit(1)
}
nets = append(nets, net)
a, b := cidr.AddressRange(net)
l := cidr.AddressCount(net)
a, b := AddressRange(net)
l := AddressCount(net)
fmt.Printf("%-16s %-16s %10d\n", a, b, l)
}
if err := cidr.NoOverlap(nets); err != nil {
if err := NoOverlap(nets); err != nil {
fmt.Fprintf(os.Stderr, "overlaping networks: %v\n", err)
os.Exit(1)
}

+ 30
- 0
wrangling.go View File

@ -0,0 +1,30 @@
package main
import (
"fmt"
"math/big"
"net"
)
func ipToInt(ip net.IP) (*big.Int, int) {
val := &big.Int{}
val.SetBytes([]byte(ip))
if len(ip) == net.IPv4len {
return val, 32
} else if len(ip) == net.IPv6len {
return val, 128
} else {
panic(fmt.Errorf("Unsupported address length %d", len(ip)))
}
}
func intToIP(ipInt *big.Int, bits int) net.IP {
ipBytes := ipInt.Bytes()
ret := make([]byte, bits/8)
// Pack our IP bytes into the end of the return array,
// since big.Int.Bytes() removes front zero padding.
for i := 1; i <= len(ipBytes); i++ {
ret[len(ret)-i] = ipBytes[len(ipBytes)-i]
}
return net.IP(ret)
}

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