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6fe2703665
* Remove `make updatedeps` from Travis build. We'll follow up with more specific plans around dependency updating in subsequent PRs. * Update all `make` targets to set `GO15VENDOREXPERIMENT=1` and to filter out `/vendor/` from `./...` where appropriate. * Temporarily remove `vet` from the `make test` target until we can figure out how to get it to not vet `vendor/`. (Initial experimentation failed to yield the proper incantation.) Everything is pinned to current master, with the exception of: * Azure/azure-sdk-for-go which is pinned before the breaking change today * aws/aws-sdk-go which is pinned to the most recent tag The documentation still needs to be updated, which we can do in a follow up PR. The goal here is to unblock release.
106 lines
3.4 KiB
Go
106 lines
3.4 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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if uint64(num) > 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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return insertNumIntoIP(ip, num, 32), 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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