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ipset.go
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ipset.go
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package ipset
import (
"encoding/binary"
"fmt"
"net"
"strings"
"lukechampine.com/uint128"
)
// Set tells whether ip is covered by any of subnets contained, handles both ipv4 and ipv6
type Set interface {
Contains(net.IP) bool
ContainsRawIPv4(uint32) bool
}
// ipset is a set based on radix tree (r = 2, so called patricia tree)
type ipset struct {
root *treeNode
}
// NewSet constructs CIDRSet from list of cidrs
func NewSet(cidrs ...*net.IPNet) Set {
s := &ipset{}
for _, cidr := range cidrs {
s.Add(cidr)
}
return s
}
// NewSetFromCSV constructs set from comma separated list of cidrs
func NewSetFromCSV(cidrsCSV string) (Set, error) {
cidrs, err := iPCidrListFromRaw(cidrsCSV)
if err != nil {
return nil, fmt.Errorf("from NewSetFromCSV: %w", err)
}
return NewSet(cidrs...), nil
}
func uint128FromIP(ip net.IP) (uint128.Uint128, error) {
ipv6 := ip.To16()
if ipv6 == nil {
return uint128.Zero, fmt.Errorf("invalid ip provided: %v", []byte(ip))
}
return uint128.New(binary.BigEndian.Uint64(ipv6[8:]), binary.BigEndian.Uint64(ipv6[:8])), nil
}
func (s *ipset) ContainsRawIPv4(ipRaw uint32) bool {
ipByte := make([]byte, 4)
binary.BigEndian.PutUint32(ipByte, ipRaw)
ip := net.IP(ipByte)
return s.Contains(ip)
}
func (s *ipset) Contains(ip net.IP) bool {
if s.root == nil {
return false
}
addr, err := uint128FromIP(ip)
if err != nil {
return false
}
curr := s.root
offset := uint32(0)
for {
matching := matchingPrefix(addr, curr.addr)
offset += curr.prefix
if matching < offset {
return false
}
if curr.left == nil || matching == 128 {
return true
}
if addr.Rsh(uint(128-(offset+1))).And64(0x01) == uint128.Zero {
curr = curr.left
} else {
curr = curr.right
}
}
}
func (s *ipset) Add(subnet *net.IPNet) {
node, err := nodeFromNet(subnet)
if err != nil {
panic(err)
}
if s.root == nil {
s.root = node
return
}
curr := s.root
offset := uint32(0)
for {
matching := matchingPrefix(node.addr, curr.addr)
offset += curr.prefix
// incoming subnet has shorter prefix, discard remaining parts of the tree
if matching >= node.prefix && node.prefix < offset {
curr.prefix += node.prefix - offset
curr.left, curr.right = nil, nil
return
}
if matching < node.prefix && matching < offset {
// three way split
newNode := &treeNode{
addr: node.addr,
prefix: node.prefix - matching,
}
splittedNode := &treeNode{
addr: curr.addr,
prefix: offset - matching,
left: curr.left,
right: curr.right,
}
if curr.addr.Rsh(uint(128-(matching+1))).And64(0x01) == uint128.Zero {
curr.left, curr.right = splittedNode, newNode
} else {
curr.left, curr.right = newNode, splittedNode
}
curr.prefix += matching - offset
return
}
if curr.left == nil {
// currently stored prefix is shorter than new one
// so new subnet is enclosed by existing subnet, nothing to do
return
}
// we are still traversing through prefix, decide which route next
if (node.addr.Rsh(uint(128 - (offset + 1)))).And64(0x01) == uint128.Zero {
curr = curr.left
} else {
curr = curr.right
}
}
}
type treeNode struct {
addr uint128.Uint128
prefix uint32
left *treeNode
right *treeNode
}
func nodeFromNet(cidr *net.IPNet) (*treeNode, error) {
if cidr == nil {
return nil, fmt.Errorf("nil node passed")
}
addr, err := uint128FromIP(cidr.IP)
if err != nil {
return nil, err
}
prefixLen, size := cidr.Mask.Size()
if size < 128 {
// ipv4, translate to ipv6 mask
// 0x0000000000ffff - static prefix used in ipv6 mapped ipv4 addrs, len = 96
// 96 + prefixLen = ipv6 subnet mask
prefixLen += 96
}
return &treeNode{addr: addr, prefix: uint32(prefixLen)}, nil
}
func (n *treeNode) String() string {
return fmt.Sprintf("%s:%d", n.addr, n.prefix)
}
func (n *treeNode) Equals(node *treeNode) bool {
if node == nil {
return false
}
return n.addr.Equals(node.addr) && n.prefix == node.prefix
}
func matchingPrefix(l, r uint128.Uint128) uint32 {
return uint32(l.Xor(r).LeadingZeros())
}
// IPCidrListFromRaw normalizes list of comma separates ips and/or cidrs into net.IPnet, works on v4 and v6 ips
// errors out on non ip string parts (doesn't support csv escaping by the way)
func iPCidrListFromRaw(raw string) (cidrs []*net.IPNet, _ error) {
if len(raw) == 0 {
return
}
ipCidrs := strings.Split(raw, ",")
cidrs = make([]*net.IPNet, len(ipCidrs))
for i, ipCidr := range ipCidrs {
network, err := netFromIPCidr2(ipCidr)
if err != nil {
return nil, fmt.Errorf("from IPCidrListFromRaw: %w", err)
}
cidrs[i] = network
}
return
}
// netFromIPCidr2 returns network from ip or cidr string representation including ipv6
func netFromIPCidr2(ipCidr string) (*net.IPNet, error) {
ipCidr = strings.TrimSpace(ipCidr)
if !strings.Contains(ipCidr, "/") {
if strings.Contains(ipCidr, ":") {
ipCidr += "/128"
} else {
ipCidr += "/32"
}
}
_, wlnet, err := net.ParseCIDR(ipCidr)
if err != nil {
err = fmt.Errorf("NetFromIPCidr: %w", err)
}
return wlnet, err
}