act_mirred: use TC_ACT_REINSERT when possible

When mirred is invoked from the ingress path, and it wants to redirect
the processed packet, it can now use the TC_ACT_REINSERT action,
filling the tcf_result accordingly, and avoiding a per packet
skb_clone().

Overall this gives a ~10% improvement in forwarding performance for the
TC S/W data path and TC S/W performances are now comparable to the
kernel openvswitch datapath.

v1 -> v2: use ACT_MIRRED instead of ACT_REDIRECT
v2 -> v3: updated after action rename, fixed typo into the commit
	message
v3 -> v4: updated again after action rename, added more comments to
	the code (JiriP), skip the optimization if the control action
	need to touch the tcf_result (Paolo)
v4 -> v5: fix sparse warning (kbuild bot)

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c
index eeb335f031025a274a319a381f0f7c9b2a3f4097..b26d060da08ea350019c21e72c1494744a82f01f 100644 (file)
--- a/net/sched/act_mirred.c
+++ b/net/sched/act_mirred.c
@@ -25,6 +25,7 @@
 #include <net/net_namespace.h>
 #include <net/netlink.h>
 #include <net/pkt_sched.h>
+#include <net/pkt_cls.h>
 #include <linux/tc_act/tc_mirred.h>
 #include <net/tc_act/tc_mirred.h>
 
@@ -49,6 +50,18 @@ static bool tcf_mirred_act_wants_ingress(int action)
        }
 }
 
+static bool tcf_mirred_can_reinsert(int action)
+{
+       switch (action) {
+       case TC_ACT_SHOT:
+       case TC_ACT_STOLEN:
+       case TC_ACT_QUEUED:
+       case TC_ACT_TRAP:
+               return true;
+       }
+       return false;
+}
+
 static void tcf_mirred_release(struct tc_action *a)
 {
        struct tcf_mirred *m = to_mirred(a);
@@ -171,10 +184,13 @@ static int tcf_mirred(struct sk_buff *skb, const struct tc_action *a,
                      struct tcf_result *res)
 {
        struct tcf_mirred *m = to_mirred(a);
+       struct sk_buff *skb2 = skb;
        bool m_mac_header_xmit;
        struct net_device *dev;
-       struct sk_buff *skb2;
        int retval, err = 0;
+       bool use_reinsert;
+       bool want_ingress;
+       bool is_redirect;
        int m_eaction;
        int mac_len;
 
@@ -196,16 +212,25 @@ static int tcf_mirred(struct sk_buff *skb, const struct tc_action *a,
                goto out;
        }
 
-       skb2 = skb_clone(skb, GFP_ATOMIC);
-       if (!skb2)
-               goto out;
+       /* we could easily avoid the clone only if called by ingress and clsact;
+        * since we can't easily detect the clsact caller, skip clone only for
+        * ingress - that covers the TC S/W datapath.
+        */
+       is_redirect = tcf_mirred_is_act_redirect(m_eaction);
+       use_reinsert = skb_at_tc_ingress(skb) && is_redirect &&
+                      tcf_mirred_can_reinsert(retval);
+       if (!use_reinsert) {
+               skb2 = skb_clone(skb, GFP_ATOMIC);
+               if (!skb2)
+                       goto out;
+       }
 
        /* If action's target direction differs than filter's direction,
         * and devices expect a mac header on xmit, then mac push/pull is
         * needed.
         */
-       if (skb_at_tc_ingress(skb) != tcf_mirred_act_wants_ingress(m_eaction) &&
-           m_mac_header_xmit) {
+       want_ingress = tcf_mirred_act_wants_ingress(m_eaction);
+       if (skb_at_tc_ingress(skb) != want_ingress && m_mac_header_xmit) {
                if (!skb_at_tc_ingress(skb)) {
                        /* caught at egress, act ingress: pull mac */
                        mac_len = skb_network_header(skb) - skb_mac_header(skb);
@@ -216,15 +241,23 @@ static int tcf_mirred(struct sk_buff *skb, const struct tc_action *a,
                }
        }
 
+       skb2->skb_iif = skb->dev->ifindex;
+       skb2->dev = dev;
+
        /* mirror is always swallowed */
-       if (tcf_mirred_is_act_redirect(m_eaction)) {
+       if (is_redirect) {
                skb2->tc_redirected = 1;
                skb2->tc_from_ingress = skb2->tc_at_ingress;
+
+               /* let's the caller reinsert the packet, if possible */
+               if (use_reinsert) {
+                       res->ingress = want_ingress;
+                       res->qstats = this_cpu_ptr(m->common.cpu_qstats);
+                       return TC_ACT_REINSERT;
+               }
        }
 
-       skb2->skb_iif = skb->dev->ifindex;
-       skb2->dev = dev;
-       if (!tcf_mirred_act_wants_ingress(m_eaction))
+       if (!want_ingress)
                err = dev_queue_xmit(skb2);
        else
                err = netif_receive_skb(skb2);