Support for connection tracking of TCP packets.

Connection tracking is used to track packets in prerouting and
output hooks of iptables. The NAT rules modify the tuples in
connections. The connection tracking code modifies the packets by
looking at the modified tuples.

1 files changed, 19 insertions, 0 deletions

diff --git a/pkg/tcpip/stack/stack.go b/pkg/tcpip/stack/stack.go
index 4a2dc3dc6..e33fae4eb 100644
--- a/pkg/tcpip/stack/stack.go
+++ b/pkg/tcpip/stack/stack.go
@@ -1885,3 +1885,22 @@ func generateRandInt64() int64 {
 	}
 	return v
 }
+
+// FindNetworkEndpoint returns the network endpoint for the given address.
+func (s *Stack) FindNetworkEndpoint(netProto tcpip.NetworkProtocolNumber, address tcpip.Address) (NetworkEndpoint, *tcpip.Error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	for _, nic := range s.nics {
+		id := NetworkEndpointID{address}
+
+		if ref, ok := nic.mu.endpoints[id]; ok {
+			nic.mu.RLock()
+			defer nic.mu.RUnlock()
+
+			// An endpoint with this id exists, check if it can be used and return it.
+			return ref.ep, nil
+		}
+	}
+	return nil, tcpip.ErrBadAddress
+}