skbedit: allow the user to specify bitmask for mark

The user may want to use only some bits of the skb mark in
his skbedit rules because the remaining part might be used by
something else.

Introduce the "mask" parameter to the skbedit actor in order
to implement such functionality.

When the mask is specified, only those bits selected by the
latter are altered really changed by the actor, while the
rest is left untouched.

Signed-off-by: Antonio Quartulli <antonio@open-mesh.com>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/tc_act/tc_skbedit.h

@@ -27,6 +27,7 @@ struct tcf_skbedit {
 	u32		flags;
 	u32		priority;
 	u32		mark;
+	u32		mask;
 	u16		queue_mapping;
 	u16		ptype;
 };

include/uapi/linux/tc_act/tc_skbedit.h

@@ -28,6 +28,7 @@
 #define SKBEDIT_F_QUEUE_MAPPING		0x2
 #define SKBEDIT_F_MARK			0x4
 #define SKBEDIT_F_PTYPE			0x8
+#define SKBEDIT_F_MASK			0x10
 
 struct tc_skbedit {
 	tc_gen;
@@ -42,6 +43,7 @@ enum {
 	TCA_SKBEDIT_MARK,
 	TCA_SKBEDIT_PAD,
 	TCA_SKBEDIT_PTYPE,
+	TCA_SKBEDIT_MASK,
 	__TCA_SKBEDIT_MAX
 };
 #define TCA_SKBEDIT_MAX (__TCA_SKBEDIT_MAX - 1)

net/sched/act_skbedit.c

@@ -46,8 +46,10 @@ static int tcf_skbedit(struct sk_buff *skb, const struct tc_action *a,
 	if (d->flags & SKBEDIT_F_QUEUE_MAPPING &&
 	    skb->dev->real_num_tx_queues > d->queue_mapping)
 		skb_set_queue_mapping(skb, d->queue_mapping);
-	if (d->flags & SKBEDIT_F_MARK)
-		skb->mark = d->mark;
+	if (d->flags & SKBEDIT_F_MARK) {
+		skb->mark &= ~d->mask;
+		skb->mark |= d->mark & d->mask;
+	}
 	if (d->flags & SKBEDIT_F_PTYPE)
 		skb->pkt_type = d->ptype;
 
@@ -61,6 +63,7 @@ static const struct nla_policy skbedit_policy[TCA_SKBEDIT_MAX + 1] = {
 	[TCA_SKBEDIT_QUEUE_MAPPING]	= { .len = sizeof(u16) },
 	[TCA_SKBEDIT_MARK]		= { .len = sizeof(u32) },
 	[TCA_SKBEDIT_PTYPE]		= { .len = sizeof(u16) },
+	[TCA_SKBEDIT_MASK]		= { .len = sizeof(u32) },
 };
 
 static int tcf_skbedit_init(struct net *net, struct nlattr *nla,
@@ -71,7 +74,7 @@ static int tcf_skbedit_init(struct net *net, struct nlattr *nla,
 	struct nlattr *tb[TCA_SKBEDIT_MAX + 1];
 	struct tc_skbedit *parm;
 	struct tcf_skbedit *d;
-	u32 flags = 0, *priority = NULL, *mark = NULL;
+	u32 flags = 0, *priority = NULL, *mark = NULL, *mask = NULL;
 	u16 *queue_mapping = NULL, *ptype = NULL;
 	bool exists = false;
 	int ret = 0, err;
@@ -108,6 +111,11 @@ static int tcf_skbedit_init(struct net *net, struct nlattr *nla,
 		mark = nla_data(tb[TCA_SKBEDIT_MARK]);
 	}
 
+	if (tb[TCA_SKBEDIT_MASK] != NULL) {
+		flags |= SKBEDIT_F_MASK;
+		mask = nla_data(tb[TCA_SKBEDIT_MASK]);
+	}
+
 	parm = nla_data(tb[TCA_SKBEDIT_PARMS]);
 
 	exists = tcf_hash_check(tn, parm->index, a, bind);
@@ -145,6 +153,10 @@ static int tcf_skbedit_init(struct net *net, struct nlattr *nla,
 		d->mark = *mark;
 	if (flags & SKBEDIT_F_PTYPE)
 		d->ptype = *ptype;
+	/* default behaviour is to use all the bits */
+	d->mask = 0xffffffff;
+	if (flags & SKBEDIT_F_MASK)
+		d->mask = *mask;
 
 	d->tcf_action = parm->action;
 
@@ -182,6 +194,9 @@ static int tcf_skbedit_dump(struct sk_buff *skb, struct tc_action *a,
 	if ((d->flags & SKBEDIT_F_PTYPE) &&
 	    nla_put_u16(skb, TCA_SKBEDIT_PTYPE, d->ptype))
 		goto nla_put_failure;
+	if ((d->flags & SKBEDIT_F_MASK) &&
+	    nla_put_u32(skb, TCA_SKBEDIT_MASK, d->mask))
+		goto nla_put_failure;
 
 	tcf_tm_dump(&t, &d->tcf_tm);
 	if (nla_put_64bit(skb, TCA_SKBEDIT_TM, sizeof(t), &t, TCA_SKBEDIT_PAD))