Clear any host-specific NDP state when becoming a router

This change supports clearing all host-only NDP state when NICs become routers.
All discovered routers, discovered on-link prefixes and auto-generated addresses
will be invalidated when becoming a router. This is because normally, routers do
not process Router Advertisements to discover routers or on-link prefixes, and
do not do SLAAC.

Tests: Unittest to make sure that all discovered routers, discovered prefixes
and auto-generated addresses get invalidated when transitioning from a host to
a router.
PiperOrigin-RevId: 286902309

1 files changed, 35 insertions, 0 deletions

diff --git a/pkg/tcpip/stack/ndp.go b/pkg/tcpip/stack/ndp.go
index 90664ba8a..d9ab59336 100644
--- a/pkg/tcpip/stack/ndp.go
+++ b/pkg/tcpip/stack/ndp.go
@@ -1155,3 +1155,38 @@ func (ndp *ndpState) autoGenAddrInvalidationTimer(addr tcpip.Address, vl time.Du
 		ndp.invalidateAutoGenAddress(addr)
 	})
 }
+
+// cleanupHostOnlyState cleans up any state that is only useful for hosts.
+//
+// cleanupHostOnlyState MUST be called when ndp's NIC is transitioning from a
+// host to a router. This function will invalidate all discovered on-link
+// prefixes, discovered routers, and auto-generated addresses as routers do not
+// normally process Router Advertisements to discover default routers and
+// on-link prefixes, and auto-generate addresses via SLAAC.
+//
+// The NIC that ndp belongs to MUST be locked.
+func (ndp *ndpState) cleanupHostOnlyState() {
+	for addr, _ := range ndp.autoGenAddresses {
+		ndp.invalidateAutoGenAddress(addr)
+	}
+
+	if got := len(ndp.autoGenAddresses); got != 0 {
+		log.Fatalf("ndp: still have auto-generated addresses after cleaning up, found = %d", got)
+	}
+
+	for prefix, _ := range ndp.onLinkPrefixes {
+		ndp.invalidateOnLinkPrefix(prefix)
+	}
+
+	if got := len(ndp.onLinkPrefixes); got != 0 {
+		log.Fatalf("ndp: still have discovered on-link prefixes after cleaning up, found = %d", got)
+	}
+
+	for router, _ := range ndp.defaultRouters {
+		ndp.invalidateDefaultRouter(router)
+	}
+
+	if got := len(ndp.defaultRouters); got != 0 {
+		log.Fatalf("ndp: still have discovered default routers after cleaning up, found = %d", got)
+	}
+}