net/packet: remove NewIP, offer only a netaddr constructor.

Signed-off-by: David Anderson <danderson@tailscale.com>

net/packet/ip4.go

@@ -7,7 +7,6 @@ package packet
 import (
 	"encoding/binary"
 	"fmt"
-	"net"
 
 	"inet.af/netaddr"
 )
@@ -15,17 +14,7 @@ import (
 // IP4 is an IPv4 address.
 type IP4 uint32
 
-// NewIP converts a standard library IP address into an IP.
-// It panics if b is not an IPv4 address.
-func NewIP4(b net.IP) IP4 {
-	b4 := b.To4()
-	if b4 == nil {
-		panic(fmt.Sprintf("To4(%v) failed", b))
-	}
-	return IP4(binary.BigEndian.Uint32(b4))
-}
-
-// IPFromNetaddr converts a netaddr.IP to an IP.
+// IPFromNetaddr converts a netaddr.IP to an IP. Panics if !ip.Is4.
 func IP4FromNetaddr(ip netaddr.IP) IP4 {
 	ipbytes := ip.As4()
 	return IP4(binary.BigEndian.Uint32(ipbytes[:]))

net/packet/packet_test.go

@@ -6,7 +6,6 @@ package packet
 
 import (
 	"bytes"
-	"net"
 	"reflect"
 	"testing"
 
@@ -31,7 +30,7 @@ func mustIP6(s string) IP6 {
 
 func TestIP4String(t *testing.T) {
 	const str = "1.2.3.4"
-	ip := NewIP4(net.ParseIP(str))
+	ip := mustIP4(str)
 
 	var got string
 	allocs := testing.AllocsPerRun(1000, func() {

wgengine/filter/filter_test.go

@@ -9,7 +9,6 @@ import (
 	"encoding/hex"
 	"encoding/json"
 	"fmt"
-	"net"
 	"strconv"
 	"strings"
 	"testing"
@@ -25,6 +24,14 @@ var TCP = packet.TCP
 var UDP = packet.UDP
 var Fragment = packet.Fragment
 
+func mustIP4(s string) packet.IP4 {
+	ip, err := netaddr.ParseIP(s)
+	if err != nil {
+		panic(err)
+	}
+	return packet.IP4FromNetaddr(ip)
+}
+
 func pfx(s string) netaddr.IPPrefix {
 	pfx, err := netaddr.ParseIPPrefix(s)
 	if err != nil {
@@ -435,19 +442,19 @@ func TestOmitDropLogging(t *testing.T) {
 		},
 		{
 			name: "v4_multicast_out_low",
-			pkt:  &packet.Parsed{IPVersion: 4, DstIP4: packet.NewIP4(net.ParseIP("224.0.0.0"))},
+			pkt:  &packet.Parsed{IPVersion: 4, DstIP4: mustIP4("224.0.0.0")},
 			dir:  out,
 			want: true,
 		},
 		{
 			name: "v4_multicast_out_high",
-			pkt:  &packet.Parsed{IPVersion: 4, DstIP4: packet.NewIP4(net.ParseIP("239.255.255.255"))},
+			pkt:  &packet.Parsed{IPVersion: 4, DstIP4: mustIP4("239.255.255.255")},
 			dir:  out,
 			want: true,
 		},
 		{
 			name: "v4_link_local_unicast",
-			pkt:  &packet.Parsed{IPVersion: 4, DstIP4: packet.NewIP4(net.ParseIP("169.254.1.2"))},
+			pkt:  &packet.Parsed{IPVersion: 4, DstIP4: mustIP4("169.254.1.2")},
 			dir:  out,
 			want: true,
 		},

wgengine/userspace.go

@@ -515,7 +515,7 @@ func (p *pinger) run(ctx context.Context, peerKey wgcfg.Key, ips []wgcfg.IP, src
 	start := time.Now()
 	var dstIPs []packet.IP4
 	for _, ip := range ips {
-		dstIPs = append(dstIPs, packet.NewIP4(ip.IP()))
+		dstIPs = append(dstIPs, packet.IP4FromNetaddr(netaddr.IPFrom16(ip.Addr)))
 	}
 
 	payload := []byte("magicsock_spray") // no meaning
@@ -555,7 +555,7 @@ func (e *userspaceEngine) pinger(peerKey wgcfg.Key, ips []wgcfg.IP) {
 
 	e.wgLock.Lock()
 	if len(e.lastCfgFull.Addresses) > 0 {
-		srcIP = packet.NewIP4(e.lastCfgFull.Addresses[0].IP.IP())
+		srcIP = packet.IP4FromNetaddr(netaddr.IPFrom16(e.lastCfgFull.Addresses[0].IP.Addr))
 	}
 	e.wgLock.Unlock()