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iplist.go
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iplist.go
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// Package iplist handles the P2P Plaintext Format described by
// https://en.wikipedia.org/wiki/PeerGuardian#P2P_plaintext_format.
package iplist
import (
"bufio"
"bytes"
"errors"
"fmt"
"io"
"net"
"sort"
)
// An abstraction of IP list implementations.
type Ranger interface {
// Return a Range containing the IP.
Lookup(net.IP) (r Range, ok bool)
// If your ranges hurt, use this.
NumRanges() int
}
type IPList struct {
ranges []Range
}
type Range struct {
First, Last net.IP
Description string
}
func (r *Range) String() string {
return fmt.Sprintf("%s-%s (%s)", r.First, r.Last, r.Description)
}
// Create a new IP list. The given ranges must already sorted by the lower
// bound IP in each range. Behaviour is undefined for lists of overlapping
// ranges.
func New(initSorted []Range) *IPList {
return &IPList{
ranges: initSorted,
}
}
func (me *IPList) NumRanges() int {
if me == nil {
return 0
}
return len(me.ranges)
}
// Return the range the given IP is in. Returns nil if no range is found.
func (me *IPList) Lookup(ip net.IP) (r Range, ok bool) {
if me == nil {
return
}
// TODO: Perhaps all addresses should be converted to IPv6, if the future
// of IP is to always be backwards compatible. But this will cost 4x the
// memory for IPv4 addresses?
v4 := ip.To4()
if v4 != nil {
r, ok = me.lookup(v4)
if ok {
return
}
}
v6 := ip.To16()
if v6 != nil {
return me.lookup(v6)
}
if v4 == nil && v6 == nil {
r = Range{
Description: "bad IP",
}
ok = true
}
return
}
// Return a range that contains ip, or nil.
func lookup(
first func(i int) net.IP,
full func(i int) Range,
n int,
ip net.IP,
) (
r Range, ok bool,
) {
// Find the index of the first range for which the following range exceeds
// it.
i := sort.Search(n, func(i int) bool {
if i+1 >= n {
return true
}
return bytes.Compare(ip, first(i+1)) < 0
})
if i == n {
return
}
r = full(i)
ok = bytes.Compare(r.First, ip) <= 0 && bytes.Compare(ip, r.Last) <= 0
return
}
// Return the range the given IP is in. Returns nil if no range is found.
func (me *IPList) lookup(ip net.IP) (Range, bool) {
return lookup(func(i int) net.IP {
return me.ranges[i].First
}, func(i int) Range {
return me.ranges[i]
}, len(me.ranges), ip)
}
func minifyIP(ip *net.IP) {
v4 := ip.To4()
if v4 != nil {
*ip = append(make([]byte, 0, 4), v4...)
}
}
// Parse a line of the PeerGuardian Text Lists (P2P) Format. Returns !ok but
// no error if a line doesn't contain a range but isn't erroneous, such as
// comment and blank lines.
func ParseBlocklistP2PLine(l []byte) (r Range, ok bool, err error) {
l = bytes.TrimSpace(l)
if len(l) == 0 || bytes.HasPrefix(l, []byte("#")) {
return
}
// TODO: Check this when IPv6 blocklists are available.
colon := bytes.LastIndexAny(l, ":")
if colon == -1 {
err = errors.New("missing colon")
return
}
hyphen := bytes.IndexByte(l[colon+1:], '-')
if hyphen == -1 {
err = errors.New("missing hyphen")
return
}
hyphen += colon + 1
r.Description = string(l[:colon])
r.First = net.ParseIP(string(l[colon+1 : hyphen]))
minifyIP(&r.First)
r.Last = net.ParseIP(string(l[hyphen+1:]))
minifyIP(&r.Last)
if r.First == nil || r.Last == nil || len(r.First) != len(r.Last) {
err = errors.New("bad IP range")
return
}
ok = true
return
}
// Creates an IPList from a line-delimited P2P Plaintext file.
func NewFromReader(f io.Reader) (ret *IPList, err error) {
var ranges []Range
// There's a lot of similar descriptions, so we maintain a pool and reuse
// them to reduce memory overhead.
uniqStrs := make(map[string]string)
scanner := bufio.NewScanner(f)
lineNum := 1
for scanner.Scan() {
r, ok, lineErr := ParseBlocklistP2PLine(scanner.Bytes())
if lineErr != nil {
err = fmt.Errorf("error parsing line %d: %s", lineNum, lineErr)
return
}
lineNum++
if !ok {
continue
}
if s, ok := uniqStrs[r.Description]; ok {
r.Description = s
} else {
uniqStrs[r.Description] = r.Description
}
ranges = append(ranges, r)
}
err = scanner.Err()
if err != nil {
return
}
ret = New(ranges)
return
}