Merge branch 'act_vlan-allow-modify-zero'

Boris Sukholitko says:

====================
net/sched: act_vlan: Fix modify to allow 0

Currently vlan modification action checks existence of vlan priority by
comparing it to 0. Therefore it is impossible to modify existing vlan
tag to have priority 0.

For example, the following tc command will change the vlan id but will
not affect vlan priority:

tc filter add dev eth1 ingress matchall action vlan modify id 300 \
        priority 0 pipe mirred egress redirect dev eth2

The incoming packet on eth1:

ethertype 802.1Q (0x8100), vlan 200, p 4, ethertype IPv4

will be changed to:

ethertype 802.1Q (0x8100), vlan 300, p 4, ethertype IPv4

although the user has intended to have p == 0.

The fix is to add tcfv_push_prio_exists flag to struct tcf_vlan_params
and rely on it when deciding to set the priority.

The same flag is used to avoid dumping unset vlan priority.

Change Log:
v3 -> v4:
- revert tcf_vlan_get_fill_size change: total size calculation may race vs dump

v2 -> v3:
- Push assumes that the priority is being set
- tcf_vlan_get_fill_size accounts for priority existence

v1 -> v2:
- Do not dump unset priority and fix tests accordingly
- Test for priority 0 modification
====================

Reviewed-by: Davide Caratti <dcaratti@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/tc_act/tc_vlan.h

@@ -16,6 +16,7 @@ struct tcf_vlan_params {
 	u16               tcfv_push_vid;
 	__be16            tcfv_push_proto;
 	u8                tcfv_push_prio;
+	bool              tcfv_push_prio_exists;
 	struct rcu_head   rcu;
 };
 

net/sched/act_vlan.c

@@ -70,7 +70,7 @@ static int tcf_vlan_act(struct sk_buff *skb, const struct tc_action *a,
 		/* replace the vid */
 		tci = (tci & ~VLAN_VID_MASK) | p->tcfv_push_vid;
 		/* replace prio bits, if tcfv_push_prio specified */
-		if (p->tcfv_push_prio) {
+		if (p->tcfv_push_prio_exists) {
 			tci &= ~VLAN_PRIO_MASK;
 			tci |= p->tcfv_push_prio << VLAN_PRIO_SHIFT;
 		}
@@ -121,6 +121,7 @@ static int tcf_vlan_init(struct net *net, struct nlattr *nla,
 	struct tc_action_net *tn = net_generic(net, vlan_net_id);
 	struct nlattr *tb[TCA_VLAN_MAX + 1];
 	struct tcf_chain *goto_ch = NULL;
+	bool push_prio_exists = false;
 	struct tcf_vlan_params *p;
 	struct tc_vlan *parm;
 	struct tcf_vlan *v;
@@ -189,7 +190,8 @@ static int tcf_vlan_init(struct net *net, struct nlattr *nla,
 			push_proto = htons(ETH_P_8021Q);
 		}
 
-		if (tb[TCA_VLAN_PUSH_VLAN_PRIORITY])
+		push_prio_exists = !!tb[TCA_VLAN_PUSH_VLAN_PRIORITY];
+		if (push_prio_exists)
 			push_prio = nla_get_u8(tb[TCA_VLAN_PUSH_VLAN_PRIORITY]);
 		break;
 	case TCA_VLAN_ACT_POP_ETH:
@@ -241,6 +243,7 @@ static int tcf_vlan_init(struct net *net, struct nlattr *nla,
 	p->tcfv_action = action;
 	p->tcfv_push_vid = push_vid;
 	p->tcfv_push_prio = push_prio;
+	p->tcfv_push_prio_exists = push_prio_exists || action == TCA_VLAN_ACT_PUSH;
 	p->tcfv_push_proto = push_proto;
 
 	if (action == TCA_VLAN_ACT_PUSH_ETH) {
@@ -304,8 +307,8 @@ static int tcf_vlan_dump(struct sk_buff *skb, struct tc_action *a,
 	    (nla_put_u16(skb, TCA_VLAN_PUSH_VLAN_ID, p->tcfv_push_vid) ||
 	     nla_put_be16(skb, TCA_VLAN_PUSH_VLAN_PROTOCOL,
 			  p->tcfv_push_proto) ||
-	     (nla_put_u8(skb, TCA_VLAN_PUSH_VLAN_PRIORITY,
-					      p->tcfv_push_prio))))
+	     (p->tcfv_push_prio_exists &&
+	      nla_put_u8(skb, TCA_VLAN_PUSH_VLAN_PRIORITY, p->tcfv_push_prio))))
 		goto nla_put_failure;
 
 	if (p->tcfv_action == TCA_VLAN_ACT_PUSH_ETH) {

tools/testing/selftests/tc-testing/tc-tests/actions/vlan.json

@@ -445,6 +445,30 @@
         "matchCount": "0",
         "teardown": []
     },
+    {
+        "id": "ba5b",
+        "name": "Add vlan modify action for protocol 802.1Q setting priority 0",
+        "category": [
+            "actions",
+            "vlan"
+        ],
+        "setup": [
+            [
+                "$TC actions flush action vlan",
+                0,
+                1,
+                255
+            ]
+        ],
+        "cmdUnderTest": "$TC actions add action vlan modify protocol 802.1Q id 5 priority 0 index 100",
+        "expExitCode": "0",
+        "verifyCmd": "$TC actions get action vlan index 100",
+        "matchPattern": "action order [0-9]+: vlan.*modify id 100 priority 0 protocol 802.1Q pipe.*index 100 ref",
+        "matchCount": "0",
+        "teardown": [
+            "$TC actions flush action vlan"
+        ]
+    },
     {
         "id": "6812",
         "name": "Add vlan modify action for protocol 802.1Q",
@@ -463,7 +487,7 @@
         "cmdUnderTest": "$TC actions add action vlan modify protocol 802.1Q id 5 index 100",
         "expExitCode": "0",
         "verifyCmd": "$TC actions get action vlan index 100",
-        "matchPattern": "action order [0-9]+: vlan.*modify id 100 protocol 802.1Q priority 0 pipe.*index 100 ref",
+        "matchPattern": "action order [0-9]+: vlan.*modify id 100 protocol 802.1Q pipe.*index 100 ref",
         "matchCount": "0",
         "teardown": [
             "$TC actions flush action vlan"
@@ -487,7 +511,7 @@
         "cmdUnderTest": "$TC actions add action vlan modify protocol 802.1ad id 500 reclassify index 12",
         "expExitCode": "0",
         "verifyCmd": "$TC actions get action vlan index 12",
-        "matchPattern": "action order [0-9]+: vlan.*modify id 500 protocol 802.1ad priority 0 reclassify.*index 12 ref",
+        "matchPattern": "action order [0-9]+: vlan.*modify id 500 protocol 802.1ad reclassify.*index 12 ref",
         "matchCount": "1",
         "teardown": [
             "$TC actions flush action vlan"