Merge branch 'net-openvswitch-add-sample-multicasting'

Adrian Moreno says:

====================
net: openvswitch: Add sample multicasting.

** Background **
Currently, OVS supports several packet sampling mechanisms (sFlow,
per-bridge IPFIX, per-flow IPFIX). These end up being translated into a
userspace action that needs to be handled by ovs-vswitchd's handler
threads only to be forwarded to some third party application that
will somehow process the sample and provide observability on the
datapath.

A particularly interesting use-case is controller-driven
per-flow IPFIX sampling where the OpenFlow controller can add metadata
to samples (via two 32bit integers) and this metadata is then available
to the sample-collecting system for correlation.

** Problem **
The fact that sampled traffic share netlink sockets and handler thread
time with upcalls, apart from being a performance bottleneck in the
sample extraction itself, can severely compromise the datapath,
yielding this solution unfit for highly loaded production systems.

Users are left with little options other than guessing what sampling
rate will be OK for their traffic pattern and system load and dealing
with the lost accuracy.

Looking at available infrastructure, an obvious candidated would be
to use psample. However, it's current state does not help with the
use-case at stake because sampled packets do not contain user-defined
metadata.

** Proposal **
This series is an attempt to fix this situation by extending the
existing psample infrastructure to carry a variable length
user-defined cookie.

The main existing user of psample is tc's act_sample. It is also
extended to forward the action's cookie to psample.

Finally, a new OVS action (OVS_SAMPLE_ATTR_PSAMPLE) is created.
It accepts a group and an optional cookie and uses psample to
multicast the packet and the metadata.
====================

Link: https://patch.msgid.link/20240704085710.353845-1-amorenoz@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 30 insertions, 1 deletions

diff --git a/include/uapi/linux/openvswitch.h b/include/uapi/linux/openvswitch.h
index efc82c318fa2..3a701bd1f31b 100644
--- a/include/uapi/linux/openvswitch.h
+++ b/include/uapi/linux/openvswitch.h
@@ -649,7 +649,8 @@ enum ovs_flow_attr {
  * Actions are passed as nested attributes.
  *
  * Executes the specified actions with the given probability on a per-packet
- * basis.
+ * basis. Nested actions will be able to access the probability value of the
+ * parent @OVS_ACTION_ATTR_SAMPLE.
  */
 enum ovs_sample_attr {
 	OVS_SAMPLE_ATTR_UNSPEC,
@@ -914,6 +915,31 @@ struct check_pkt_len_arg {
 };
 #endif
 
+#define OVS_PSAMPLE_COOKIE_MAX_SIZE 16
+/**
+ * enum ovs_psample_attr - Attributes for %OVS_ACTION_ATTR_PSAMPLE
+ * action.
+ *
+ * @OVS_PSAMPLE_ATTR_GROUP: 32-bit number to identify the source of the
+ * sample.
+ * @OVS_PSAMPLE_ATTR_COOKIE: An optional variable-length binary cookie that
+ * contains user-defined metadata. The maximum length is
+ * OVS_PSAMPLE_COOKIE_MAX_SIZE bytes.
+ *
+ * Sends the packet to the psample multicast group with the specified group and
+ * cookie. It is possible to combine this action with the
+ * %OVS_ACTION_ATTR_TRUNC action to limit the size of the sample.
+ */
+enum ovs_psample_attr {
+	OVS_PSAMPLE_ATTR_GROUP = 1,	/* u32 number. */
+	OVS_PSAMPLE_ATTR_COOKIE,	/* Optional, user specified cookie. */
+
+	/* private: */
+	__OVS_PSAMPLE_ATTR_MAX
+};
+
+#define OVS_PSAMPLE_ATTR_MAX (__OVS_PSAMPLE_ATTR_MAX - 1)
+
 /**
  * enum ovs_action_attr - Action types.
  *
@@ -966,6 +992,8 @@ struct check_pkt_len_arg {
  * of l3 tunnel flag in the tun_flags field of OVS_ACTION_ATTR_ADD_MPLS
  * argument.
  * @OVS_ACTION_ATTR_DROP: Explicit drop action.
+ * @OVS_ACTION_ATTR_PSAMPLE: Send a sample of the packet to external observers
+ * via psample.
  *
  * Only a single header can be set with a single %OVS_ACTION_ATTR_SET.  Not all
  * fields within a header are modifiable, e.g. the IPv4 protocol and fragment
@@ -1004,6 +1032,7 @@ enum ovs_action_attr {
 	OVS_ACTION_ATTR_ADD_MPLS,     /* struct ovs_action_add_mpls. */
 	OVS_ACTION_ATTR_DEC_TTL,      /* Nested OVS_DEC_TTL_ATTR_*. */
 	OVS_ACTION_ATTR_DROP,         /* u32 error code. */
+	OVS_ACTION_ATTR_PSAMPLE,      /* Nested OVS_PSAMPLE_ATTR_*. */
 
 	__OVS_ACTION_ATTR_MAX,	      /* Nothing past this will be accepted
 				       * from userspace. */