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 (
    "errors"
    "net"
    "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
}

// 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
}