global: use netip where possible now

There are more places where we'll need to add it later, when Go 1.18
comes out with support for it in the "net" package. Also, allowedips
still uses slices internally, which might be suboptimal.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

conn/conn.go

@@ -9,10 +9,11 @@ package conn
 import (
 	"errors"
 	"fmt"
-	"net"
 	"reflect"
 	"runtime"
 	"strings"
+
+	"golang.zx2c4.com/go118/netip"
 )
 
 // A ReceiveFunc receives a single inbound packet from the network.
@@ -68,8 +69,8 @@ type Endpoint interface {
 	SrcToString() string // returns the local source address (ip:port)
 	DstToString() string // returns the destination address (ip:port)
 	DstToBytes() []byte  // used for mac2 cookie calculations
-	DstIP() net.IP
-	SrcIP() net.IP
+	DstIP() netip.Addr
+	SrcIP() netip.Addr
 }
 
 var (
@@ -119,33 +120,3 @@ func (fn ReceiveFunc) PrettyName() string {
 	}
 	return name
 }
-
-func parseEndpoint(s string) (*net.UDPAddr, error) {
-	// ensure that the host is an IP address
-
-	host, _, err := net.SplitHostPort(s)
-	if err != nil {
-		return nil, err
-	}
-	if i := strings.LastIndexByte(host, '%'); i > 0 && strings.IndexByte(host, ':') >= 0 {
-		// Remove the scope, if any. ResolveUDPAddr below will use it, but here we're just
-		// trying to make sure with a small sanity test that this is a real IP address and
-		// not something that's likely to incur DNS lookups.
-		host = host[:i]
-	}
-	if ip := net.ParseIP(host); ip == nil {
-		return nil, errors.New("Failed to parse IP address: " + host)
-	}
-
-	// parse address and port
-
-	addr, err := net.ResolveUDPAddr("udp", s)
-	if err != nil {
-		return nil, err
-	}
-	ip4 := addr.IP.To4()
-	if ip4 != nil {
-		addr.IP = ip4
-	}
-	return addr, err
-}