Merge branch 'neighbour-fix-update-of-proxy-neighbour'

Sabrina Dubroca says:

====================
neighbour: fix update of proxy neighbour

While re-reading some "old" patches I ran into a small change of
behavior in commit dc2a27e ("neighbour: Update pneigh_entry in
pneigh_create().").

The old behavior was not consistent between ->protocol and ->flags,
and didn't offer a way to clear protocol, so maybe it's better to
change that (7-years-old [1]) behavior. But then we should change
non-proxy neighbours as well to keep neigh/pneigh consistent.

[1] df9b0e3 ("neighbor: Add protocol attribute")
====================

Link: https://patch.msgid.link/cover.1772894876.git.sd@queasysnail.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: kuba-moo

net/core/neighbour.c

@@ -820,7 +820,8 @@ int pneigh_create(struct neigh_table *tbl, struct net *net,
 update:
 	WRITE_ONCE(n->flags, flags);
 	n->permanent = permanent;
-	WRITE_ONCE(n->protocol, protocol);
+	if (protocol)
+		WRITE_ONCE(n->protocol, protocol);
 out:
 	mutex_unlock(&tbl->phash_lock);
 	return err;

tools/testing/selftests/net/rtnetlink.sh

@@ -28,6 +28,7 @@ ALL_TESTS="
 	kci_test_fdb_get
 	kci_test_fdb_del
 	kci_test_neigh_get
+	kci_test_neigh_update
 	kci_test_bridge_parent_id
 	kci_test_address_proto
 	kci_test_enslave_bonding
@@ -1160,6 +1161,60 @@ kci_test_neigh_get()
 	end_test "PASS: neigh get"
 }
 
+kci_test_neigh_update()
+{
+	dstip=10.0.2.4
+	dstmac=de:ad:be:ef:13:37
+	local ret=0
+
+	for proxy in "" "proxy" ; do
+		# add a neighbour entry without any flags
+		run_cmd ip neigh add $proxy $dstip dev "$devdummy" lladdr $dstmac nud permanent
+		run_cmd_grep $dstip ip neigh show $proxy
+		run_cmd_grep_fail "$dstip dev $devdummy .*\(managed\|use\|router\|extern\)" ip neigh show $proxy
+
+		# set the extern_learn flag, but no other
+		run_cmd ip neigh change $proxy $dstip dev "$devdummy" extern_learn
+		run_cmd_grep "$dstip dev $devdummy .* extern_learn" ip neigh show $proxy
+		run_cmd_grep_fail "$dstip dev $devdummy .* \(managed\|use\|router\)" ip neigh show $proxy
+
+		# flags are reset when not provided
+		run_cmd ip neigh change $proxy $dstip dev "$devdummy"
+		run_cmd_grep $dstip ip neigh show $proxy
+		run_cmd_grep_fail "$dstip dev $devdummy .* extern_learn" ip neigh show $proxy
+
+		# add a protocol
+		run_cmd ip neigh change $proxy $dstip dev "$devdummy" protocol boot
+		run_cmd_grep "$dstip dev $devdummy .* proto boot" ip neigh show $proxy
+
+		# protocol is retained when not provided
+		run_cmd ip neigh change $proxy $dstip dev "$devdummy"
+		run_cmd_grep "$dstip dev $devdummy .* proto boot" ip neigh show $proxy
+
+		# change protocol
+		run_cmd ip neigh change $proxy $dstip dev "$devdummy" protocol static
+		run_cmd_grep "$dstip dev $devdummy .* proto static" ip neigh show $proxy
+
+		# also check an extended flag for non-proxy neighs
+		if [ "$proxy" = "" ]; then
+			run_cmd ip neigh change $proxy $dstip dev "$devdummy" managed
+			run_cmd_grep "$dstip dev $devdummy managed" ip neigh show $proxy
+
+			run_cmd ip neigh change $proxy $dstip dev "$devdummy" lladdr $dstmac
+			run_cmd_grep_fail "$dstip dev $devdummy managed" ip neigh show $proxy
+		fi
+
+		run_cmd ip neigh del $proxy $dstip dev "$devdummy"
+	done
+
+	if [ $ret -ne 0 ];then
+		end_test "FAIL: neigh update"
+		return 1
+	fi
+
+	end_test "PASS: neigh update"
+}
+
 kci_test_bridge_parent_id()
 {
 	local ret=0