Populate link address cache at dispatch

This allows the stack to learn remote link addresses on incoming
packets, reducing the need to ARP to send responses.

This also reduces the number of round trips to the system clock,
since that may also prove to be performance-sensitive.

Fixes #739.

PiperOrigin-RevId: 265815816

1 files changed, 7 insertions, 7 deletions

diff --git a/pkg/tcpip/header/ipv6.go b/pkg/tcpip/header/ipv6.go
index 31be42ce0..bc4e56535 100644
--- a/pkg/tcpip/header/ipv6.go
+++ b/pkg/tcpip/header/ipv6.go
@@ -27,7 +27,7 @@ const (
 	nextHdr    = 6
 	hopLimit   = 7
 	v6SrcAddr  = 8
-	v6DstAddr  = 24
+	v6DstAddr  = v6SrcAddr + IPv6AddressSize
 )
 
 // IPv6Fields contains the fields of an IPv6 packet. It is used to describe the
@@ -119,13 +119,13 @@ func (b IPv6) Payload() []byte {
 
 // SourceAddress returns the "source address" field of the ipv6 header.
 func (b IPv6) SourceAddress() tcpip.Address {
-	return tcpip.Address(b[v6SrcAddr : v6SrcAddr+IPv6AddressSize])
+	return tcpip.Address(b[v6SrcAddr:][:IPv6AddressSize])
 }
 
 // DestinationAddress returns the "destination address" field of the ipv6
 // header.
 func (b IPv6) DestinationAddress() tcpip.Address {
-	return tcpip.Address(b[v6DstAddr : v6DstAddr+IPv6AddressSize])
+	return tcpip.Address(b[v6DstAddr:][:IPv6AddressSize])
 }
 
 // Checksum implements Network.Checksum. Given that IPv6 doesn't have a
@@ -153,13 +153,13 @@ func (b IPv6) SetPayloadLength(payloadLength uint16) {
 
 // SetSourceAddress sets the "source address" field of the ipv6 header.
 func (b IPv6) SetSourceAddress(addr tcpip.Address) {
-	copy(b[v6SrcAddr:v6SrcAddr+IPv6AddressSize], addr)
+	copy(b[v6SrcAddr:][:IPv6AddressSize], addr)
 }
 
 // SetDestinationAddress sets the "destination address" field of the ipv6
 // header.
 func (b IPv6) SetDestinationAddress(addr tcpip.Address) {
-	copy(b[v6DstAddr:v6DstAddr+IPv6AddressSize], addr)
+	copy(b[v6DstAddr:][:IPv6AddressSize], addr)
 }
 
 // SetNextHeader sets the value of the "next header" field of the ipv6 header.
@@ -178,8 +178,8 @@ func (b IPv6) Encode(i *IPv6Fields) {
 	b.SetPayloadLength(i.PayloadLength)
 	b[nextHdr] = i.NextHeader
 	b[hopLimit] = i.HopLimit
-	copy(b[v6SrcAddr:v6SrcAddr+IPv6AddressSize], i.SrcAddr)
-	copy(b[v6DstAddr:v6DstAddr+IPv6AddressSize], i.DstAddr)
+	b.SetSourceAddress(i.SrcAddr)
+	b.SetDestinationAddress(i.DstAddr)
 }
 
 // IsValid performs basic validation on the packet.