p2p/netutil: new package for network utilities

The new package contains three things for now:

- IP network list parsing and matching
- The WSAEMSGSIZE workaround, which is duplicated in p2p/discover and
  p2p/discv5.

1 files changed, 166 insertions, 0 deletions

diff --git a/p2p/netutil/net.go b/p2p/netutil/net.go
new file mode 100644
index 000000000..3c3715788
--- /dev/null
+++ b/p2p/netutil/net.go
@@ -0,0 +1,166 @@
+// 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
+}