Remove ipv4.endpoint.address

This field was added in the intial implementation, before Route existed
to pass the local and remote addresses to the packet-writing path.
Today, the Route's members should be respected. A similar bug was
previously fixed in 214650822.

PiperOrigin-RevId: 219474095
Change-Id: Id2a8ee4421d2841c8d88ccb3c193c455086350ee

pkg/tcpip/network/ipv4/ipv4.go

@@ -46,32 +46,29 @@ const (
 	buckets = 2048
 )
 
-type address [header.IPv4AddressSize]byte
-
 type endpoint struct {
 	nicid         tcpip.NICID
 	id            stack.NetworkEndpointID
-	address       address
 	linkEP        stack.LinkEndpoint
 	dispatcher    stack.TransportDispatcher
 	echoRequests  chan echoRequest
 	fragmentation *fragmentation.Fragmentation
 }
 
-func newEndpoint(nicid tcpip.NICID, addr tcpip.Address, dispatcher stack.TransportDispatcher, linkEP stack.LinkEndpoint) *endpoint {
+// NewEndpoint creates a new ipv4 endpoint.
+func (p *protocol) NewEndpoint(nicid tcpip.NICID, addr tcpip.Address, linkAddrCache stack.LinkAddressCache, dispatcher stack.TransportDispatcher, linkEP stack.LinkEndpoint) (stack.NetworkEndpoint, *tcpip.Error) {
 	e := &endpoint{
 		nicid:         nicid,
+		id:            stack.NetworkEndpointID{LocalAddress: addr},
 		linkEP:        linkEP,
 		dispatcher:    dispatcher,
 		echoRequests:  make(chan echoRequest, 10),
 		fragmentation: fragmentation.NewFragmentation(fragmentation.HighFragThreshold, fragmentation.LowFragThreshold, fragmentation.DefaultReassembleTimeout),
 	}
-	copy(e.address[:], addr)
-	e.id = stack.NetworkEndpointID{LocalAddress: tcpip.Address(e.address[:])}
 
 	go e.echoReplier()
 
-	return e
+	return e, nil
 }
 
 // DefaultTTL is the default time-to-live value for this endpoint.
@@ -122,7 +119,7 @@ func (e *endpoint) WritePacket(r *stack.Route, hdr buffer.Prependable, payload b
 		ID:          uint16(id),
 		TTL:         ttl,
 		Protocol:    uint8(protocol),
-		SrcAddr:     tcpip.Address(e.address[:]),
+		SrcAddr:     r.LocalAddress,
 		DstAddr:     r.RemoteAddress,
 	})
 	ip.SetChecksum(^ip.CalculateChecksum())
@@ -194,11 +191,6 @@ func (*protocol) ParseAddresses(v buffer.View) (src, dst tcpip.Address) {
 	return h.SourceAddress(), h.DestinationAddress()
 }
 
-// NewEndpoint creates a new ipv4 endpoint.
-func (p *protocol) NewEndpoint(nicid tcpip.NICID, addr tcpip.Address, linkAddrCache stack.LinkAddressCache, dispatcher stack.TransportDispatcher, linkEP stack.LinkEndpoint) (stack.NetworkEndpoint, *tcpip.Error) {
-	return newEndpoint(nicid, addr, dispatcher, linkEP), nil
-}
-
 // SetOption implements NetworkProtocol.SetOption.
 func (p *protocol) SetOption(option interface{}) *tcpip.Error {
 	return tcpip.ErrUnknownProtocolOption