net/packet: remove {get,put}{16,32} indirection to encoding/binary.

name              old time/op    new time/op    delta
Decode/tcp4-8       28.8ns ± 2%    13.1ns ± 4%  -54.44%  (p=0.008 n=5+5)
Decode/tcp6-8       20.6ns ± 1%    12.6ns ± 2%  -38.72%  (p=0.008 n=5+5)
Decode/udp4-8       28.2ns ± 1%    12.1ns ± 4%  -57.01%  (p=0.008 n=5+5)
Decode/udp6-8       20.0ns ± 6%    12.1ns ± 2%  -39.38%  (p=0.008 n=5+5)
Decode/icmp4-8      21.7ns ± 2%    11.5ns ± 1%  -47.01%  (p=0.008 n=5+5)
Decode/icmp6-8      14.1ns ± 2%    11.8ns ± 4%  -16.60%  (p=0.008 n=5+5)
Decode/unknown-8    9.43ns ± 2%    9.30ns ± 3%     ~     (p=0.222 n=5+5)

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

net/packet/icmp4.go

@@ -4,6 +4,8 @@
 
 package packet
 
+import "encoding/binary"
+
 type ICMP4Type uint8
 
 const (
@@ -66,7 +68,7 @@ func (h ICMP4Header) Marshal(buf []byte) error {
 
 	h.IP4Header.Marshal(buf)
 
-	put16(buf[22:24], ipChecksum(buf))
+	binary.BigEndian.PutUint16(buf[22:24], ipChecksum(buf))
 
 	return nil
 }

net/packet/ip4.go

@@ -5,6 +5,7 @@
 package packet
 
 import (
+	"encoding/binary"
 	"fmt"
 	"net"
 
@@ -21,13 +22,13 @@ func NewIP4(b net.IP) IP4 {
 	if b4 == nil {
 		panic(fmt.Sprintf("To4(%v) failed", b))
 	}
-	return IP4(get32(b4))
+	return IP4(binary.BigEndian.Uint32(b4))
 }
 
 // IPFromNetaddr converts a netaddr.IP to an IP.
 func IP4FromNetaddr(ip netaddr.IP) IP4 {
 	ipbytes := ip.As4()
-	return IP4(get32(ipbytes[:]))
+	return IP4(binary.BigEndian.Uint32(ipbytes[:]))
 }
 
 // Netaddr converts an IP to a netaddr.IP.
@@ -71,16 +72,16 @@ func (h IP4Header) Marshal(buf []byte) error {
 
 	buf[0] = 0x40 | (ip4HeaderLength >> 2) // IPv4
 	buf[1] = 0x00                          // DHCP, ECN
-	put16(buf[2:4], uint16(len(buf)))
+	binary.BigEndian.PutUint16(buf[2:4], uint16(len(buf)))
-	put16(buf[4:6], h.IPID)
+	binary.BigEndian.PutUint16(buf[4:6], h.IPID)
-	put16(buf[6:8], 0) // flags, offset
+	binary.BigEndian.PutUint16(buf[6:8], 0) // flags, offset
 	buf[8] = 64                             // TTL
 	buf[9] = uint8(h.IPProto)
-	put16(buf[10:12], 0) // blank IP header checksum
+	binary.BigEndian.PutUint16(buf[10:12], 0) // blank IP header checksum
-	put32(buf[12:16], uint32(h.SrcIP))
+	binary.BigEndian.PutUint32(buf[12:16], uint32(h.SrcIP))
-	put32(buf[16:20], uint32(h.DstIP))
+	binary.BigEndian.PutUint32(buf[16:20], uint32(h.DstIP))
 
-	put16(buf[10:12], ipChecksum(buf[0:20]))
+	binary.BigEndian.PutUint16(buf[10:12], ipChecksum(buf[0:20]))
 
 	return nil
 }
@@ -97,11 +98,11 @@ func (h IP4Header) MarshalPseudo(buf []byte) error {
 	}
 
 	length := len(buf) - ip4HeaderLength
-	put32(buf[8:12], uint32(h.SrcIP))
+	binary.BigEndian.PutUint32(buf[8:12], uint32(h.SrcIP))
-	put32(buf[12:16], uint32(h.DstIP))
+	binary.BigEndian.PutUint32(buf[12:16], uint32(h.DstIP))
 	buf[16] = 0x0
 	buf[17] = uint8(h.IPProto)
-	put16(buf[18:20], uint16(length))
+	binary.BigEndian.PutUint16(buf[18:20], uint16(length))
 	return nil
 }
 

net/packet/packet.go

@@ -21,14 +21,6 @@ const (
 	TCPSynAck = TCPSyn | TCPAck
 )
 
-var (
-	get16 = binary.BigEndian.Uint16
-	get32 = binary.BigEndian.Uint32
-
-	put16 = binary.BigEndian.PutUint16
-	put32 = binary.BigEndian.PutUint32
-)
-
 // Parsed is a minimal decoding of a packet suitable for use in filters.
 //
 // In general, it only supports IPv4. The IPv6 parsing is very minimal.
@@ -114,7 +106,7 @@ func ipChecksum(b []byte) uint16 {
 	i := 0
 	n := len(b)
 	for n >= 2 {
-		ac += uint32(get16(b[i : i+2]))
+		ac += uint32(binary.BigEndian.Uint16(b[i : i+2]))
 		n -= 2
 		i += 2
 	}
@@ -161,7 +153,7 @@ func (q *Parsed) decode4(b []byte) {
 
 	// Check that it's IPv4.
 	q.IPProto = IPProto(b[9])
-	q.length = int(get16(b[2:4]))
+	q.length = int(binary.BigEndian.Uint16(b[2:4]))
 	if len(b) < q.length {
 		// Packet was cut off before full IPv4 length.
 		q.IPProto = Unknown
@@ -169,8 +161,8 @@ func (q *Parsed) decode4(b []byte) {
 	}
 
 	// If it's valid IPv4, then the IP addresses are valid
-	q.SrcIP4 = IP4(get32(b[12:16]))
+	q.SrcIP4 = IP4(binary.BigEndian.Uint32(b[12:16]))
-	q.DstIP4 = IP4(get32(b[16:20]))
+	q.DstIP4 = IP4(binary.BigEndian.Uint32(b[16:20]))
 
 	q.subofs = int((b[0] & 0x0F) << 2)
 	sub := b[q.subofs:]
@@ -187,7 +179,7 @@ func (q *Parsed) decode4(b []byte) {
 	// zero reason to send such a short first fragment, so we can treat
 	// it as Unknown. We can also treat any subsequent fragment that starts
 	// at such a low offset as Unknown.
-	fragFlags := get16(b[6:8])
+	fragFlags := binary.BigEndian.Uint16(b[6:8])
 	moreFrags := (fragFlags & 0x20) != 0
 	fragOfs := fragFlags & 0x1FFF
 	if fragOfs == 0 {
@@ -215,8 +207,8 @@ func (q *Parsed) decode4(b []byte) {
 				q.IPProto = Unknown
 				return
 			}
-			q.SrcPort = get16(sub[0:2])
+			q.SrcPort = binary.BigEndian.Uint16(sub[0:2])
-			q.DstPort = get16(sub[2:4])
+			q.DstPort = binary.BigEndian.Uint16(sub[2:4])
 			q.TCPFlags = sub[13] & 0x3F
 			headerLength := (sub[12] & 0xF0) >> 2
 			q.dataofs = q.subofs + int(headerLength)
@@ -226,8 +218,8 @@ func (q *Parsed) decode4(b []byte) {
 				q.IPProto = Unknown
 				return
 			}
-			q.SrcPort = get16(sub[0:2])
+			q.SrcPort = binary.BigEndian.Uint16(sub[0:2])
-			q.DstPort = get16(sub[2:4])
+			q.DstPort = binary.BigEndian.Uint16(sub[2:4])
 			q.dataofs = q.subofs + udpHeaderLength
 			return
 		default:
@@ -261,7 +253,7 @@ func (q *Parsed) decode6(b []byte) {
 	}
 
 	q.IPProto = IPProto(b[6])
-	q.length = int(get16(b[4:6])) + ip6HeaderLength
+	q.length = int(binary.BigEndian.Uint16(b[4:6])) + ip6HeaderLength
 	if len(b) < q.length {
 		// Packet was cut off before the full IPv6 length.
 		q.IPProto = Unknown
@@ -300,8 +292,8 @@ func (q *Parsed) decode6(b []byte) {
 			q.IPProto = Unknown
 			return
 		}
-		q.SrcPort = get16(sub[0:2])
+		q.SrcPort = binary.BigEndian.Uint16(sub[0:2])
-		q.DstPort = get16(sub[2:4])
+		q.DstPort = binary.BigEndian.Uint16(sub[2:4])
 		q.TCPFlags = sub[13] & 0x3F
 		headerLength := (sub[12] & 0xF0) >> 2
 		q.dataofs = q.subofs + int(headerLength)
@@ -311,8 +303,8 @@ func (q *Parsed) decode6(b []byte) {
 			q.IPProto = Unknown
 			return
 		}
-		q.SrcPort = get16(sub[0:2])
+		q.SrcPort = binary.BigEndian.Uint16(sub[0:2])
-		q.DstPort = get16(sub[2:4])
+		q.DstPort = binary.BigEndian.Uint16(sub[2:4])
 		q.dataofs = q.subofs + udpHeaderLength
 	default:
 		q.IPProto = Unknown
@@ -324,7 +316,7 @@ func (q *Parsed) IP4Header() IP4Header {
 	if q.IPVersion != 4 {
 		panic("IP4Header called on non-IPv4 Parsed")
 	}
-	ipid := get16(q.b[4:6])
+	ipid := binary.BigEndian.Uint16(q.b[4:6])
 	return IP4Header{
 		IPID:    ipid,
 		IPProto: q.IPProto,

net/packet/udp4.go

@@ -4,6 +4,8 @@
 
 package packet
 
+import "encoding/binary"
+
 // UDPHeader represents an UDP packet header.
 type UDP4Header struct {
 	IP4Header
@@ -32,15 +34,15 @@ func (h UDP4Header) Marshal(buf []byte) error {
 	h.IPProto = UDP
 
 	length := len(buf) - h.IP4Header.Len()
-	put16(buf[20:22], h.SrcPort)
+	binary.BigEndian.PutUint16(buf[20:22], h.SrcPort)
-	put16(buf[22:24], h.DstPort)
+	binary.BigEndian.PutUint16(buf[22:24], h.DstPort)
-	put16(buf[24:26], uint16(length))
+	binary.BigEndian.PutUint16(buf[24:26], uint16(length))
-	put16(buf[26:28], 0) // blank checksum
+	binary.BigEndian.PutUint16(buf[26:28], 0) // blank checksum
 
 	h.IP4Header.MarshalPseudo(buf)
 
 	// UDP checksum with IP pseudo header.
-	put16(buf[26:28], ipChecksum(buf[8:]))
+	binary.BigEndian.PutUint16(buf[26:28], ipChecksum(buf[8:]))
 
 	h.IP4Header.Marshal(buf)