net: openvswitch: add last-action drop reason

Create a new drop reason subsystem for openvswitch and add the first
drop reason to represent last-action drops.

Last-action drops happen when a flow has an empty action list or there
is no action that consumes the packet (output, userspace, recirc, etc).
It is the most common way in which OVS drops packets.

Implementation-wise, most of these skb-consuming actions already call
"consume_skb" internally and return directly from within the
do_execute_actions() loop so with minimal changes we can assume that
any skb that exits the loop normally is a packet drop.

Signed-off-by: Adrian Moreno <amorenoz@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/dropreason.h b/include/net/dropreason.h
index 685fb37df8e8e5ff45f272868a57e154a3f3dbde..56cb7be92244c2459f0a1e374539672e84df7100 100644 (file)
--- a/include/net/dropreason.h
+++ b/include/net/dropreason.h
@@ -23,6 +23,12 @@ enum skb_drop_reason_subsys {
         */
        SKB_DROP_REASON_SUBSYS_MAC80211_MONITOR,
 
+       /**
+        * @SKB_DROP_REASON_SUBSYS_OPENVSWITCH: openvswitch drop reasons,
+        * see net/openvswitch/drop.h
+        */
+       SKB_DROP_REASON_SUBSYS_OPENVSWITCH,
+
        /** @SKB_DROP_REASON_SUBSYS_NUM: number of subsystems defined */
        SKB_DROP_REASON_SUBSYS_NUM
 };

diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
index cab1e02b63e051b14144c9a57bc5b6b269b432d8..8c8a7a82f76ffc4c8096387267eac106492dc224 100644 (file)
--- a/net/openvswitch/actions.c
+++ b/net/openvswitch/actions.c
@@ -27,6 +27,7 @@
 #include <net/sctp/checksum.h>
 
 #include "datapath.h"
+#include "drop.h"
 #include "flow.h"
 #include "conntrack.h"
 #include "vport.h"
@@ -1036,7 +1037,7 @@ static int sample(struct datapath *dp, struct sk_buff *skb,
        if ((arg->probability != U32_MAX) &&
            (!arg->probability || get_random_u32() > arg->probability)) {
                if (last)
-                       consume_skb(skb);
+                       ovs_kfree_skb_reason(skb, OVS_DROP_LAST_ACTION);
                return 0;
        }
 
@@ -1297,6 +1298,9 @@ static int do_execute_actions(struct datapath *dp, struct sk_buff *skb,
                if (trace_ovs_do_execute_action_enabled())
                        trace_ovs_do_execute_action(dp, skb, key, a, rem);
 
+               /* Actions that rightfully have to consume the skb should do it
+                * and return directly.
+                */
                switch (nla_type(a)) {
                case OVS_ACTION_ATTR_OUTPUT: {
                        int port = nla_get_u32(a);
@@ -1332,6 +1336,10 @@ static int do_execute_actions(struct datapath *dp, struct sk_buff *skb,
                        output_userspace(dp, skb, key, a, attr,
                                                     len, OVS_CB(skb)->cutlen);
                        OVS_CB(skb)->cutlen = 0;
+                       if (nla_is_last(a, rem)) {
+                               consume_skb(skb);
+                               return 0;
+                       }
                        break;
 
                case OVS_ACTION_ATTR_HASH:
@@ -1485,7 +1493,7 @@ static int do_execute_actions(struct datapath *dp, struct sk_buff *skb,
                }
        }
 
-       consume_skb(skb);
+       ovs_kfree_skb_reason(skb, OVS_DROP_LAST_ACTION);
        return 0;
 }
 

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index a6d2a0b1aa21eaae6041ec9a9321af2d615a5c38..d33cb739883f731120580f75dbb4771f984618a1 100644 (file)
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -41,6 +41,7 @@
 #include <net/pkt_cls.h>
 
 #include "datapath.h"
+#include "drop.h"
 #include "flow.h"
 #include "flow_table.h"
 #include "flow_netlink.h"
@@ -2702,6 +2703,17 @@ static struct pernet_operations ovs_net_ops = {
        .size = sizeof(struct ovs_net),
 };
 
+static const char * const ovs_drop_reasons[] = {
+#define S(x)   (#x),
+       OVS_DROP_REASONS(S)
+#undef S
+};
+
+static struct drop_reason_list drop_reason_list_ovs = {
+       .reasons = ovs_drop_reasons,
+       .n_reasons = ARRAY_SIZE(ovs_drop_reasons),
+};
+
 static int __init dp_init(void)
 {
        int err;
@@ -2743,6 +2755,9 @@ static int __init dp_init(void)
        if (err < 0)
                goto error_unreg_netdev;
 
+       drop_reasons_register_subsys(SKB_DROP_REASON_SUBSYS_OPENVSWITCH,
+                                    &drop_reason_list_ovs);
+
        return 0;
 
 error_unreg_netdev:
@@ -2769,6 +2784,7 @@ static void dp_cleanup(void)
        ovs_netdev_exit();
        unregister_netdevice_notifier(&ovs_dp_device_notifier);
        unregister_pernet_device(&ovs_net_ops);
+       drop_reasons_unregister_subsys(SKB_DROP_REASON_SUBSYS_OPENVSWITCH);
        rcu_barrier();
        ovs_vport_exit();
        ovs_flow_exit();

diff --git a/net/openvswitch/drop.h b/net/openvswitch/drop.h
new file mode 100644 (file)
index 0000000..a5b2b90
--- /dev/null
+++ b/net/openvswitch/drop.h
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * OpenvSwitch drop reason list.
+ */
+
+#ifndef OPENVSWITCH_DROP_H
+#define OPENVSWITCH_DROP_H
+#include <linux/skbuff.h>
+#include <net/dropreason.h>
+
+#define OVS_DROP_REASONS(R)                    \
+       R(OVS_DROP_LAST_ACTION)                 \
+       /* deliberate comment for trailing \ */
+
+enum ovs_drop_reason {
+       __OVS_DROP_REASON = SKB_DROP_REASON_SUBSYS_OPENVSWITCH <<
+                               SKB_DROP_REASON_SUBSYS_SHIFT,
+#define ENUM(x) x,
+       OVS_DROP_REASONS(ENUM)
+#undef ENUM
+
+       OVS_DROP_MAX,
+};
+
+static inline void
+ovs_kfree_skb_reason(struct sk_buff *skb, enum ovs_drop_reason reason)
+{
+       kfree_skb_reason(skb, (u32)reason);
+}
+
+#endif /* OPENVSWITCH_DROP_H */