Do not resolve routes immediately

When a response needs to be sent to an incoming packet, the stack should
consult its neighbour table to determine the remote address's link
address.

When an entry does not exist in the stack's neighbor table, the stack
should queue the packet while link resolution completes. See comments.

PiperOrigin-RevId: 336185457

1 files changed, 8 insertions, 40 deletions

diff --git a/pkg/tcpip/stack/route.go b/pkg/tcpip/stack/route.go
index cc39c9a6a..710a02ac3 100644
--- a/pkg/tcpip/stack/route.go
+++ b/pkg/tcpip/stack/route.go
@@ -72,21 +72,20 @@ func makeRoute(netProto tcpip.NetworkProtocolNumber, localAddr, remoteAddr tcpip
 		loop |= PacketLoop
 	}
 
-	linkEP := nic.LinkEndpoint()
 	r := Route{
 		NetProto:         netProto,
 		LocalAddress:     localAddr,
-		LocalLinkAddress: linkEP.LinkAddress(),
+		LocalLinkAddress: nic.LinkEndpoint.LinkAddress(),
 		RemoteAddress:    remoteAddr,
 		addressEndpoint:  addressEndpoint,
 		nic:              nic,
 		Loop:             loop,
 	}
 
-	if nic := r.nic; linkEP.Capabilities()&CapabilityResolutionRequired != 0 {
-		if linkRes, ok := nic.stack.linkAddrResolvers[r.NetProto]; ok {
+	if r.nic.LinkEndpoint.Capabilities()&CapabilityResolutionRequired != 0 {
+		if linkRes, ok := r.nic.stack.linkAddrResolvers[r.NetProto]; ok {
 			r.linkRes = linkRes
-			r.linkCache = nic.stack
+			r.linkCache = r.nic.stack
 		}
 	}
 
@@ -116,7 +115,7 @@ func (r *Route) PseudoHeaderChecksum(protocol tcpip.TransportProtocolNumber, tot
 
 // Capabilities returns the link-layer capabilities of the route.
 func (r *Route) Capabilities() LinkEndpointCapabilities {
-	return r.nic.LinkEndpoint().Capabilities()
+	return r.nic.LinkEndpoint.Capabilities()
 }
 
 // GSOMaxSize returns the maximum GSO packet size.
@@ -127,12 +126,6 @@ func (r *Route) GSOMaxSize() uint32 {
 	return 0
 }
 
-// ResolveWith immediately resolves a route with the specified remote link
-// address.
-func (r *Route) ResolveWith(addr tcpip.LinkAddress) {
-	r.RemoteLinkAddress = addr
-}
-
 // Resolve attempts to resolve the link address if necessary. Returns ErrWouldBlock in
 // case address resolution requires blocking, e.g. wait for ARP reply. Waker is
 // notified when address resolution is complete (success or not).
@@ -208,16 +201,7 @@ func (r *Route) WritePacket(gso *GSO, params NetworkHeaderParams, pkt *PacketBuf
 		return tcpip.ErrInvalidEndpointState
 	}
 
-	// WritePacket takes ownership of pkt, calculate numBytes first.
-	numBytes := pkt.Size()
-
-	if err := r.nic.getNetworkEndpoint(r.NetProto).WritePacket(r, gso, params, pkt); err != nil {
-		return err
-	}
-
-	r.nic.stats.Tx.Packets.Increment()
-	r.nic.stats.Tx.Bytes.IncrementBy(uint64(numBytes))
-	return nil
+	return r.nic.getNetworkEndpoint(r.NetProto).WritePacket(r, gso, params, pkt)
 }
 
 // WritePackets writes a list of n packets through the given route and returns
@@ -227,15 +211,7 @@ func (r *Route) WritePackets(gso *GSO, pkts PacketBufferList, params NetworkHead
 		return 0, tcpip.ErrInvalidEndpointState
 	}
 
-	n, err := r.nic.getNetworkEndpoint(r.NetProto).WritePackets(r, gso, pkts, params)
-	r.nic.stats.Tx.Packets.IncrementBy(uint64(n))
-	writtenBytes := 0
-	for i, pb := 0, pkts.Front(); i < n && pb != nil; i, pb = i+1, pb.Next() {
-		writtenBytes += pb.Size()
-	}
-
-	r.nic.stats.Tx.Bytes.IncrementBy(uint64(writtenBytes))
-	return n, err
+	return r.nic.getNetworkEndpoint(r.NetProto).WritePackets(r, gso, pkts, params)
 }
 
 // WriteHeaderIncludedPacket writes a packet already containing a network
@@ -245,15 +221,7 @@ func (r *Route) WriteHeaderIncludedPacket(pkt *PacketBuffer) *tcpip.Error {
 		return tcpip.ErrInvalidEndpointState
 	}
 
-	// WriteHeaderIncludedPacket takes ownership of pkt, calculate numBytes first.
-	numBytes := pkt.Data.Size()
-
-	if err := r.nic.getNetworkEndpoint(r.NetProto).WriteHeaderIncludedPacket(r, pkt); err != nil {
-		return err
-	}
-	r.nic.stats.Tx.Packets.Increment()
-	r.nic.stats.Tx.Bytes.IncrementBy(uint64(numBytes))
-	return nil
+	return r.nic.getNetworkEndpoint(r.NetProto).WriteHeaderIncludedPacket(r, pkt)
 }
 
 // DefaultTTL returns the default TTL of the underlying network endpoint.