path: root/p2p/netutil/net.go

// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

// Package netutil contains extensions to the net package.
package netutil

import (
    "bytes"
    "errors"
    "fmt"
    "net"
    "sort"
    "strings"
)

var lan4, lan6, special4, special6 Netlist

func init() {
    // Lists from RFC 5735, RFC 5156,
    // https://www.iana.org/assignments/iana-ipv4-special-registry/
    lan4.Add("0.0.0.0/8")              // "This" network
    lan4.Add("10.0.0.0/8")             // Private Use
    lan4.Add("172.16.0.0/12")          // Private Use
    lan4.Add("192.168.0.0/16")         // Private Use
    lan6.Add("fe80::/10")              // Link-Local
    lan6.Add("fc00::/7")               // Unique-Local
    special4.Add("192.0.0.0/29")       // IPv4 Service Continuity
    special4.Add("192.0.0.9/32")       // PCP Anycast
    special4.Add("192.0.0.170/32")     // NAT64/DNS64 Discovery
    special4.Add("192.0.0.171/32")     // NAT64/DNS64 Discovery
    special4.Add("192.0.2.0/24")       // TEST-NET-1
    special4.Add("192.31.196.0/24")    // AS112
    special4.Add("192.52.193.0/24")    // AMT
    special4.Add("192.88.99.0/24")     // 6to4 Relay Anycast
    special4.Add("192.175.48.0/24")    // AS112
    special4.Add("198.18.0.0/15")      // Device Benchmark Testing
    special4.Add("198.51.100.0/24")    // TEST-NET-2
    special4.Add("203.0.113.0/24")     // TEST-NET-3
    special4.Add("255.255.255.255/32") // Limited Broadcast

    // http://www.iana.org/assignments/iana-ipv6-special-registry/
    special6.Add("100::/64")
    special6.Add("2001::/32")
    special6.Add("2001:1::1/128")
    special6.Add("2001:2::/48")
    special6.Add("2001:3::/32")
    special6.Add("2001:4:112::/48")
    special6.Add("2001:5::/32")
    special6.Add("2001:10::/28")
    special6.Add("2001:20::/28")
    special6.Add("2001:db8::/32")
    special6.Add("2002::/16")
}

// Netlist is a list of IP networks.
type Netlist []net.IPNet

// ParseNetlist parses a comma-separated list of CIDR masks.
// Whitespace and extra commas are ignored.
func ParseNetlist(s string) (*Netlist, error) {
    ws := strings.NewReplacer(" ", "", "\n", "", "\t", "")
    masks := strings.Split(ws.Replace(s), ",")
    l := make(Netlist, 0)
    for _, mask := range masks {
        if mask == "" {
            continue
        }
        _, n, err := net.ParseCIDR(mask)
        if err != nil {
            return nil, err
        }
        l = append(l, *n)
    }
    return &l, nil
}

// MarshalTOML implements toml.MarshalerRec.
func (l Netlist) MarshalTOML() interface{} {
    list := make([]string, 0, len(l))
    for _, net := range l {
        list = append(list, net.String())
    }
    return list
}

// UnmarshalTOML implements toml.UnmarshalerRec.
func (l *Netlist) UnmarshalTOML(fn func(interface{}) error) error {
    var masks []string
    if err := fn(&masks); err != nil {
        return err
    }
    for _, mask := range masks {
        _, n, err := net.ParseCIDR(mask)
        if err != nil {
            return err
        }
        *l = append(*l, *n)
    }
    return nil
}

// Add parses a CIDR mask and appends it to the list. It panics for invalid masks and is
// intended to be used for setting up static lists.
func (l *Netlist) Add(cidr string) {
    _, n, err := net.ParseCIDR(cidr)
    if err != nil {
        panic(err)
    }
    *l = append(*l, *n)
}

// Contains reports whether the given IP is contained in the list.
func (l *Netlist) Contains(ip net.IP) bool {
    if l == nil {
        return false
    }
    for _, net := range *l {
        if net.Contains(ip) {
            return true
        }
    }
    return false
}

// IsLAN reports whether an IP is a local network address.
func IsLAN(ip net.IP) bool {
    if ip.IsLoopback() {
        return true
    }
    if v4 := ip.To4(); v4 != nil {
        return lan4.Contains(v4)
    }
    return lan6.Contains(ip)
}

// IsSpecialNetwork reports whether an IP is located in a special-use network range
// This includes broadcast, multicast and documentation addresses.
func IsSpecialNetwork(ip net.IP) bool {
    if ip.IsMulticast() {
        return true
    }
    if v4 := ip.To4(); v4 != nil {
        return special4.Contains(v4)
    }
    return special6.Contains(ip)
}

var (
    errInvalid     = errors.New("invalid IP")
    errUnspecified = errors.New("zero address")
    errSpecial     = errors.New("special network")
    errLoopback    = errors.New("loopback address from non-loopback host")
    errLAN         = errors.New("LAN address from WAN host")
)

// CheckRelayIP reports whether an IP relayed from the given sender IP
// is a valid connection target.
//
// There are four rules:
//   - Special network addresses are never valid.
//   - Loopback addresses are OK if relayed by a loopback host.
//   - LAN addresses are OK if relayed by a LAN host.
//   - All other addresses are always acceptable.
func CheckRelayIP(sender, addr net.IP) error {
    if len(addr) != net.IPv4len && len(addr) != net.IPv6len {
        return errInvalid
    }
    if addr.IsUnspecified() {
        return errUnspecified
    }
    if IsSpecialNetwork(addr) {
        return errSpecial
    }
    if addr.IsLoopback() && !sender.IsLoopback() {
        return errLoopback
    }
    if IsLAN(addr) && !IsLAN(sender) {
        return errLAN
    }
    return nil
}

// SameNet reports whether two IP addresses have an equal prefix of the given bit length.
func SameNet(bits uint, ip, other net.IP) bool {
    ip4, other4 := ip.To4(), other.To4()
    switch {
    case (ip4 == nil) != (other4 == nil):
        return false
    case ip4 != nil:
        return sameNet(bits, ip4, other4)
    default:
        return sameNet(bits, ip.To16(), other.To16())
    }
}

func sameNet(bits uint, ip, other net.IP) bool {
    nb := int(bits / 8)
    mask := ^byte(0xFF >> (bits % 8))
    if mask != 0 && nb < len(ip) && ip[nb]&mask != other[nb]&mask {
        return false
    }
    return nb <= len(ip) && bytes.Equal(ip[:nb], other[:nb])
}

// DistinctNetSet tracks IPs, ensuring that at most N of them
// fall into the same network range.
type DistinctNetSet struct {
    Subnet uint // number of common prefix bits
    Limit  uint // maximum number of IPs in each subnet

    members map[string]uint
    buf     net.IP
}

// Add adds an IP address to the set. It returns false (and doesn't add the IP) if the
// number of existing IPs in the defined range exceeds the limit.
func (s *DistinctNetSet) Add(ip net.IP) bool {
    key := s.key(ip)
    n := s.members[string(key)]
    if n < s.Limit {
        s.members[string(key)] = n + 1
        return true
    }
    return false
}

// Remove removes an IP from the set.
func (s *DistinctNetSet) Remove(ip net.IP) {
    key := s.key(ip)
    if n, ok := s.members[string(key)]; ok {
        if n == 1 {
            delete(s.members, string(key))
        } else {
            s.members[string(key)] = n - 1
        }
    }
}

// Contains whether the given IP is contained in the set.
func (s DistinctNetSet) Contains(ip net.IP) bool {
    key := s.key(ip)
    _, ok := s.members[string(key)]
    return ok
}

// Len returns the number of tracked IPs.
func (s DistinctNetSet) Len() int {
    n := uint(0)
    for _, i := range s.members {
        n += i
    }
    return int(n)
}

// key encodes the map key for an address into a temporary buffer.
//
// The first byte of key is '4' or '6' to distinguish IPv4/IPv6 address types.
// The remainder of the key is the IP, truncated to the number of bits.
func (s *DistinctNetSet) key(ip net.IP) net.IP {
    // Lazily initialize storage.
    if s.members == nil {
        s.members = make(map[string]uint)
        s.buf = make(net.IP, 17)
    }
    // Canonicalize ip and bits.
    typ := byte('6')
    if ip4 := ip.To4(); ip4 != nil {
        typ, ip = '4', ip4
    }
    bits := s.Subnet
    if bits > uint(len(ip)*8) {
        bits = uint(len(ip) * 8)
    }
    // Encode the prefix into s.buf.
    nb := int(bits / 8)
    mask := ^byte(0xFF >> (bits % 8))
    s.buf[0] = typ
    buf := append(s.buf[:1], ip[:nb]...)
    if nb < len(ip) && mask != 0 {
        buf = append(buf, ip[nb]&mask)
    }
    return buf
}

// String implements fmt.Stringer
func (s DistinctNetSet) String() string {
    var buf bytes.Buffer
    buf.WriteString("{")
    keys := make([]string, 0, len(s.members))
    for k := range s.members {
        keys = append(keys, k)
    }
    sort.Strings(keys)
    for i, k := range keys {
        var ip net.IP
        if k[0] == '4' {
            ip = make(net.IP, 4)
        } else {
            ip = make(net.IP, 16)
        }
        copy(ip, k[1:])
        fmt.Fprintf(&buf, "%v×%d", ip, s.members[k])
        if i != len(keys)-1 {
            buf.WriteString(" ")
        }
    }
    buf.WriteString("}")
    return buf.String()
}