860ad5842b
ADDED: * num-addrs subcommand, to get the number of hosts/addresses in a given prefix length * get-net subcommand, to more easily get a single subnet from either the beginning or the end of a prefix. (MUCH FASTER than CIDR-splitting!)
90 lines
2.3 KiB
Go
90 lines
2.3 KiB
Go
package netsplit
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import (
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`math`
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"net/netip"
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"go4.org/netipx"
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)
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/*
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Split splits the network defined in a SubnetSplitter alongside its configuration and performs the subnetting.
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This strategy allows for splitting a network into exactly evenly sized specified number of subnets.
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remaining may or may not be nil depending on if the specified number of subnets fit cleanly into the network boundaries.
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An ErrNoNetSpace error will be returned if subnetting size exhaustion occurs before the specified number of subnets is reached
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(but nets will be populated and remaining will contain any left over subnets).
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*/
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func (s *SubnetSplitter) Split() (nets []*netip.Prefix, remaining *netipx.IPSet, err error) {
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var ok bool
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var pfxLen int
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var base netip.Prefix
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var vlsm *VLSMSplitter
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if s == nil || s.BaseSplitter == nil || s.network == nil || s.NumberSubnets == 0 {
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return
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}
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if err = validate.Struct(s); err != nil {
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return
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}
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if base, ok = netipx.FromStdIPNet(s.network); !ok {
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err = ErrBadBoundary
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return
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}
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if !base.IsValid() {
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err = ErrBadBoundary
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return
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}
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// Previously, this used (github.com/projectdiscovery/mapcidr).SplitIPNetIntoN.
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// It no longer does: https://github.com/projectdiscovery/mapcidr/issues/628
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// I am Noticing.
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// First the number of bits needed is calculated.
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pfxLen = int(math.Ceil(math.Log2(float64(s.NumberSubnets))))
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// And this is then added to the original prefix length to get the new prefix size.
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pfxLen = pfxLen + base.Bits()
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// I don't know how this would happen, but it'd be bad if it did.
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if pfxLen < base.Bits() {
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err = ErrBigPrefix
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return
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}
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// Likewise.
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if base.Addr().Is6() {
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ok = pfxLen <= int(maxBitsv6)
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} else {
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ok = pfxLen <= int(maxBitsv4)
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}
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if !ok {
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err = ErrBadPrefix
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return
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}
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// We can now VLSM.
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vlsm = &VLSMSplitter{
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// Ascenting and Explicit are pointless to set as all defined sizes are the same.
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Ascending: false,
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Explicit: false,
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PrefixLengths: make([]uint8, s.NumberSubnets),
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BaseSplitter: s.BaseSplitter,
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}
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for i := 0; i < int(s.NumberSubnets); i++ {
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vlsm.PrefixLengths[i] = uint8(pfxLen)
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}
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if nets, remaining, err = vlsm.Split(); err != nil {
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return
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}
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if s.Strict && remaining != nil && remaining.Prefixes() != nil && len(remaining.Prefixes()) > 0 {
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err = ErrBadNumNets
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return
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}
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return
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}
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