v0.2.4

FIXED:
* IPv6 split-nets splitter didn't work. It does not.
  https://github.com/projectdiscovery/mapcidr/issues/628
  Noticed.
  As such, this library/program has *completely removed*
  ALL use of the mapcidr library as it cannot be expected
  to be accurate.

cmd/subnetter/args.go

@@ -77,7 +77,7 @@ type SplitHostArgs struct {
 }
 
 type SplitSubnetArgs struct {
-	Strict  bool `short:"t" long:"strict" description:"If specified, an error will occur if the number of possible equally-sized subnets is not exactly -n/--num-nets."`
+	Strict  bool `short:"t" long:"strict" description:"If specified, an error will occur if the number of subnets is not exactly -n/--num-nets."`
 	NumNets uint `short:"n" long:"num-nets" required:"true" description:"Number of networks." validate:"required"`
 	splitArgs
 }

netsplit/errs.go

@@ -5,6 +5,7 @@ import "errors"
 var (
 	ErrBadBoundary  error = errors.New("subnet does not align on bit boundary")
 	ErrBadNumHosts  error = errors.New("bad number of hosts; cannot split into prefix exactly")
+	ErrBadNumNets   error = errors.New("bad number of nets; cannot split into prefix exactly")
 	ErrBadPrefix    error = errors.New("prefix is invalid")
 	ErrBadPrefixLen error = errors.New("prefix length exceeds maximum possible for prefix's inet family")
 	ErrBadSplitter  error = errors.New("invalid or unknown splitter when containing")

netsplit/funcs_subnetsplitter.go

@@ -1,10 +1,9 @@
 package netsplit
 
 import (
-	`net`
+	`math`
 	"net/netip"
 
-	`github.com/projectdiscovery/mapcidr`
 	"go4.org/netipx"
 )
 
@@ -22,10 +21,7 @@ func (s *SubnetSplitter) Split() (nets []*netip.Prefix, remaining *netipx.IPSet,
 	var ok bool
 	var pfxLen int
 	var base netip.Prefix
-	var sub netip.Prefix
+	var vlsm *VLSMSplitter
-	var subPtr *netip.Prefix
-	var split []*net.IPNet
-	var ipsb *netipx.IPSetBuilder = new(netipx.IPSetBuilder)
 
 	if s == nil || s.BaseSplitter == nil || s.network == nil || s.NumberSubnets == 0 {
 		return
@@ -40,65 +36,48 @@ func (s *SubnetSplitter) Split() (nets []*netip.Prefix, remaining *netipx.IPSet,
 		return
 	}
 
-	if split, err = mapcidr.SplitIPNetIntoN(s.network, int(s.NumberSubnets)); err != nil {
+	// Previously, this used (github.com/projectdiscovery/mapcidr).SplitIPNetIntoN.
-		return
+	// It no longer does: https://github.com/projectdiscovery/mapcidr/issues/628
-	}
+	// I am Noticing.
 
-	for _, n := range split {
+	// First the number of bits needed is calculated.
-		if sub, ok = netipx.FromStdIPNet(n); !ok {
+	pfxLen = int(math.Ceil(math.Log2(float64(s.NumberSubnets))))
-			// We bail early on this error.
+	// And this is then added to the original prefix length to get the new prefix size.
-			err = &SplitErr{
+	pfxLen = pfxLen + base.Bits()
-				Wrapped:            ErrBadBoundary,
+	// I don't know how this would happen, but it'd be bad if it did.
-				Nets:               nets,
+	if pfxLen < base.Bits() {
-				Remaining:          remaining,
+		err = ErrBigPrefix
-				LastSubnet:         subPtr,
-				RequestedPrefixLen: 0,
-			}
-			err = ErrBadBoundary
 		return
 	}
-		if sub.String() == base.String() {
+	// Likewise.
-			continue
+	if base.Addr().Is6() {
-		}
+		ok = pfxLen <= int(maxBitsv6)
-		if pfxLen == 0 {
-			pfxLen = sub.Bits()
-			if nets == nil {
-				nets = make([]*netip.Prefix, 0)
-			}
-			subPtr = new(netip.Prefix)
-			*subPtr = sub
-			nets = append(nets, subPtr)
 	} else {
-			if sub.Bits() != pfxLen {
+		ok = pfxLen <= int(maxBitsv4)
-				if err == nil {
-					// Return this err but don't return early; wait for the populate.
-					err = &SplitErr{
-						Wrapped:            ErrNoNetSpace,
-						Nets:               nets,
-						Remaining:          remaining,
-						LastSubnet:         subPtr,
-						RequestedPrefixLen: uint8(pfxLen),
 	}
-				}
+	if !ok {
-				ipsb.AddPrefix(sub)
+		err = ErrBadPrefix
-			} else {
-				subPtr = new(netip.Prefix)
-				*subPtr = sub
-				nets = append(nets, subPtr)
-			}
-		}
-	}
-
-	if remaining, err = ipsb.IPSet(); err != nil {
 		return
 	}
 
-	if len(nets) < int(s.NumberSubnets) {
+	// We can now VLSM.
-		err = &SplitErr{
+	vlsm = &VLSMSplitter{
-			Wrapped:   ErrNoNetSpace,
+		// Ascenting and Explicit are pointless to set as all defined sizes are the same.
-			Nets:      nets,
+		Ascending:     false,
-			Remaining: remaining,
+		Explicit:      false,
+		PrefixLengths: make([]uint8, s.NumberSubnets),
+		BaseSplitter:  s.BaseSplitter,
 	}
+	for i := 0; i < int(s.NumberSubnets); i++ {
+		vlsm.PrefixLengths[i] = uint8(pfxLen)
+	}
+
+	if nets, remaining, err = vlsm.Split(); err != nil {
+		return
+	}
+
+	if s.Strict && remaining != nil && remaining.Prefixes() != nil && len(remaining.Prefixes()) > 0 {
+		err = ErrBadNumNets
 		return
 	}