Re: [PATCH v3 net-next 1/1] net_sched: Introduce skbmod action

On Sun, 2016-08-28 at 08:19 -0400, Jamal Hadi Salim wrote:

From: Jamal Hadi Salim <jhs@mojatatu.com>

...

+static int tcf_skbmod_run(struct sk_buff *skb, const struct tc_action *a,
+			  struct tcf_result *res)
+{
+	struct tcf_skbmod *d = to_skbmod(a);
+
+	spin_lock(&d->tcf_lock);
+	tcf_lastuse_update(&d->tcf_tm);
+	bstats_update(&d->tcf_bstats, skb);
+
+	if (d->flags & SKBMOD_F_DMAC)
+		ether_addr_copy(eth_hdr(skb)->h_dest, d->eth_dst);
+	if (d->flags & SKBMOD_F_SMAC)
+		ether_addr_copy(eth_hdr(skb)->h_source, d->eth_src);
+	if (d->flags & SKBMOD_F_ETYPE)
+		eth_hdr(skb)->h_proto = d->eth_type;
+	if (d->flags & SKBMOD_F_SWAPMAC) {
+		u8 tmpaddr[ETH_ALEN];
+		/*XXX: I am sure we can come up with something more efficient */
+		ether_addr_copy(tmpaddr, eth_hdr(skb)->h_dest);
+		ether_addr_copy(eth_hdr(skb)->h_dest, eth_hdr(skb)->h_source);
+		ether_addr_copy(eth_hdr(skb)->h_source, tmpaddr);
+	}
+
+	spin_unlock(&d->tcf_lock);
+	return d->tcf_action;
+}

Adding an action with a spinlock held in fast path in 2016 is
a way to tell people : It is a toy, do not use it for real.

Sorry guys. Friends do not let friends do that anymore.