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![Paddy](/assets/img/avatar_default.png)
Switch to using Go modules. This migrates our vendor.json to use Go 1.11's modules system, and replaces the vendor folder with the output of go mod vendor. The vendored code should remain basically the same; I believe some tree shaking of packages and support scripts/licenses/READMEs/etc. happened. This also fixes Travis and our Makefile to no longer use govendor.
211 lines
6.5 KiB
Go
211 lines
6.5 KiB
Go
// Package cidr is a collection of assorted utilities for computing
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// network and host addresses within network ranges.
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//
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// It expects a CIDR-type address structure where addresses are divided into
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// some number of prefix bits representing the network and then the remaining
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// suffix bits represent the host.
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//
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// For example, it can help to calculate addresses for sub-networks of a
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// parent network, or to calculate host addresses within a particular prefix.
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//
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// At present this package is prioritizing simplicity of implementation and
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// de-prioritizing speed and memory usage. Thus caution is advised before
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// using this package in performance-critical applications or hot codepaths.
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// Patches to improve the speed and memory usage may be accepted as long as
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// they do not result in a significant increase in code complexity.
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package cidr
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import (
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"fmt"
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"math/big"
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"net"
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)
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// Subnet takes a parent CIDR range and creates a subnet within it
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// with the given number of additional prefix bits and the given
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// network number.
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//
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// For example, 10.3.0.0/16, extended by 8 bits, with a network number
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// of 5, becomes 10.3.5.0/24 .
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func Subnet(base *net.IPNet, newBits int, num int) (*net.IPNet, error) {
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ip := base.IP
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mask := base.Mask
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parentLen, addrLen := mask.Size()
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newPrefixLen := parentLen + newBits
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if newPrefixLen > addrLen {
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return nil, fmt.Errorf("insufficient address space to extend prefix of %d by %d", parentLen, newBits)
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}
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maxNetNum := uint64(1<<uint64(newBits)) - 1
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if uint64(num) > maxNetNum {
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return nil, fmt.Errorf("prefix extension of %d does not accommodate a subnet numbered %d", newBits, num)
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}
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return &net.IPNet{
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IP: insertNumIntoIP(ip, num, newPrefixLen),
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Mask: net.CIDRMask(newPrefixLen, addrLen),
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}, nil
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}
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// Host takes a parent CIDR range and turns it into a host IP address with
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// the given host number.
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//
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// For example, 10.3.0.0/16 with a host number of 2 gives 10.3.0.2.
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func Host(base *net.IPNet, num int) (net.IP, error) {
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ip := base.IP
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mask := base.Mask
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parentLen, addrLen := mask.Size()
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hostLen := addrLen - parentLen
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maxHostNum := uint64(1<<uint64(hostLen)) - 1
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numUint64 := uint64(num)
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if num < 0 {
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numUint64 = uint64(-num) - 1
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num = int(maxHostNum - numUint64)
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}
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if numUint64 > maxHostNum {
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return nil, fmt.Errorf("prefix of %d does not accommodate a host numbered %d", parentLen, num)
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}
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var bitlength int
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if ip.To4() != nil {
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bitlength = 32
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} else {
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bitlength = 128
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}
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return insertNumIntoIP(ip, num, bitlength), nil
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}
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// AddressRange returns the first and last addresses in the given CIDR range.
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func AddressRange(network *net.IPNet) (net.IP, net.IP) {
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// the first IP is easy
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firstIP := network.IP
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// the last IP is the network address OR NOT the mask address
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prefixLen, bits := network.Mask.Size()
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if prefixLen == bits {
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// Easy!
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// But make sure that our two slices are distinct, since they
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// would be in all other cases.
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lastIP := make([]byte, len(firstIP))
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copy(lastIP, firstIP)
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return firstIP, lastIP
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}
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firstIPInt, bits := ipToInt(firstIP)
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hostLen := uint(bits) - uint(prefixLen)
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lastIPInt := big.NewInt(1)
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lastIPInt.Lsh(lastIPInt, hostLen)
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lastIPInt.Sub(lastIPInt, big.NewInt(1))
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lastIPInt.Or(lastIPInt, firstIPInt)
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return firstIP, intToIP(lastIPInt, bits)
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}
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// AddressCount returns the number of distinct host addresses within the given
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// CIDR range.
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//
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// Since the result is a uint64, this function returns meaningful information
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// only for IPv4 ranges and IPv6 ranges with a prefix size of at least 65.
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func AddressCount(network *net.IPNet) uint64 {
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prefixLen, bits := network.Mask.Size()
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return 1 << (uint64(bits) - uint64(prefixLen))
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}
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//VerifyNoOverlap takes a list subnets and supernet (CIDRBlock) and verifies
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//none of the subnets overlap and all subnets are in the supernet
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//it returns an error if any of those conditions are not satisfied
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func VerifyNoOverlap(subnets []*net.IPNet, CIDRBlock *net.IPNet) error {
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firstLastIP := make([][]net.IP, len(subnets))
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for i, s := range subnets {
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first, last := AddressRange(s)
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firstLastIP[i] = []net.IP{first, last}
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}
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for i, s := range subnets {
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if !CIDRBlock.Contains(firstLastIP[i][0]) || !CIDRBlock.Contains(firstLastIP[i][1]) {
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return fmt.Errorf("%s does not fully contain %s", CIDRBlock.String(), s.String())
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}
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for j := i + 1; j < len(subnets); j++ {
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first := firstLastIP[j][0]
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last := firstLastIP[j][1]
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if s.Contains(first) || s.Contains(last) {
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return fmt.Errorf("%s overlaps with %s", subnets[j].String(), s.String())
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}
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}
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}
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return nil
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}
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// PreviousSubnet returns the subnet of the desired mask in the IP space
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// just lower than the start of IPNet provided. If the IP space rolls over
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// then the second return value is true
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func PreviousSubnet(network *net.IPNet, prefixLen int) (*net.IPNet, bool) {
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startIP := checkIPv4(network.IP)
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previousIP := make(net.IP, len(startIP))
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copy(previousIP, startIP)
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cMask := net.CIDRMask(prefixLen, 8*len(previousIP))
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previousIP = Dec(previousIP)
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previous := &net.IPNet{IP: previousIP.Mask(cMask), Mask: cMask}
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if startIP.Equal(net.IPv4zero) || startIP.Equal(net.IPv6zero) {
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return previous, true
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}
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return previous, false
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}
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// NextSubnet returns the next available subnet of the desired mask size
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// starting for the maximum IP of the offset subnet
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// If the IP exceeds the maxium IP then the second return value is true
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func NextSubnet(network *net.IPNet, prefixLen int) (*net.IPNet, bool) {
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_, currentLast := AddressRange(network)
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mask := net.CIDRMask(prefixLen, 8*len(currentLast))
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currentSubnet := &net.IPNet{IP: currentLast.Mask(mask), Mask: mask}
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_, last := AddressRange(currentSubnet)
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last = Inc(last)
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next := &net.IPNet{IP: last.Mask(mask), Mask: mask}
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if last.Equal(net.IPv4zero) || last.Equal(net.IPv6zero) {
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return next, true
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}
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return next, false
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}
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//Inc increases the IP by one this returns a new []byte for the IP
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func Inc(IP net.IP) net.IP {
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IP = checkIPv4(IP)
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incIP := make([]byte, len(IP))
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copy(incIP, IP)
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for j := len(incIP) - 1; j >= 0; j-- {
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incIP[j]++
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if incIP[j] > 0 {
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break
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}
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}
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return incIP
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}
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//Dec decreases the IP by one this returns a new []byte for the IP
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func Dec(IP net.IP) net.IP {
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IP = checkIPv4(IP)
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decIP := make([]byte, len(IP))
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copy(decIP, IP)
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decIP = checkIPv4(decIP)
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for j := len(decIP) - 1; j >= 0; j-- {
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decIP[j]--
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if decIP[j] < 255 {
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break
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}
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}
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return decIP
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}
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func checkIPv4(ip net.IP) net.IP {
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// Go for some reason allocs IPv6len for IPv4 so we have to correct it
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if v4 := ip.To4(); v4 != nil {
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return v4
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}
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return ip
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}
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