Function complementRanges

internal/server/network/network_utils.go:1557–1604

complementRanges returns the complement of the provided IP network ranges. It calculates the IP ranges that are *not* covered by the input slice.

(ranges []*iprange.Range, netAddr *net.IPNet)

// complementRanges returns the complement of the provided IP network ranges.
// It calculates the IP ranges that are *not* covered by the input slice.
func complementRanges(ranges []*iprange.Range, netAddr *net.IPNet) ([]iprange.Range, error) {
	var complement []iprange.Range

	ipv4NetPrefix, err := netip.ParsePrefix(netAddr.String())
	if err != nil {
		return nil, err
	}

	previousEnd := ipv4NetPrefix.Addr()

	for _, r := range ranges {
		startAddr, err := netip.ParseAddr(r.Start.String())
		if err != nil {
			return nil, err
		}

		endAddr, err := netip.ParseAddr(r.End.String())
		if err != nil {
			return nil, err
		}

		if startAddr.Compare(previousEnd.Next()) == 1 {
			newStart := previousEnd.Next()
			newEnd := startAddr.Prev()

			if newStart.Compare(newEnd) == 0 {
				complement = append(complement, iprange.Range{Start: net.ParseIP(newStart.String())})
			} else {
				complement = append(complement, iprange.Range{Start: net.ParseIP(newStart.String()), End: net.ParseIP(newEnd.String())})
			}
		}

		if endAddr.Compare(previousEnd) == 1 {
			previousEnd = endAddr
		}
	}

	endAddr, err := netip.ParseAddr(dhcpalloc.GetIP(netAddr, -2).String())
	if err != nil {
		return nil, err
	}

	if previousEnd.Compare(endAddr) == -1 {
		complement = append(complement, iprange.Range{Start: net.ParseIP(previousEnd.Next().String()), End: net.ParseIP(endAddr.String())})
	}

	return complement, nil
}

// ipInRanges checks whether the given IP address is contained within any of the
// provided IP network ranges.