openvswitch: Add support for unique flow IDs.

Previously, flows were manipulated by userspace specifying a full,
unmasked flow key. This adds significant burden onto flow
serialization/deserialization, particularly when dumping flows.

This patch adds an alternative way to refer to flows using a
variable-length "unique flow identifier" (UFID). At flow setup time,
userspace may specify a UFID for a flow, which is stored with the flow
and inserted into a separate table for lookup, in addition to the
standard flow table. Flows created using a UFID must be fetched or
deleted using the UFID.

All flow dump operations may now be made more terse with OVS_UFID_F_*
flags. For example, the OVS_UFID_F_OMIT_KEY flag allows responses to
omit the flow key from a datapath operation if the flow has a
corresponding UFID. This significantly reduces the time spent assembling
and transacting netlink messages. With all OVS_UFID_F_OMIT_* flags
enabled, the datapath only returns the UFID and statistics for each flow
during flow dump, increasing ovs-vswitchd revalidator performance by 40%
or more.

Signed-off-by: Joe Stringer <joestringer@nicira.com>
Acked-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/openvswitch.txt

@@ -131,6 +131,19 @@ performs best-effort detection of overlapping wildcarded flows and may reject
 some but not all of them. However, this behavior may change in future versions.
 
 
+Unique flow identifiers
+-----------------------
+
+An alternative to using the original match portion of a key as the handle for
+flow identification is a unique flow identifier, or "UFID". UFIDs are optional
+for both the kernel and user space program.
+
+User space programs that support UFID are expected to provide it during flow
+setup in addition to the flow, then refer to the flow using the UFID for all
+future operations. The kernel is not required to index flows by the original
+flow key if a UFID is specified.
+
+
 Basic rule for evolving flow keys
 ---------------------------------
 

include/uapi/linux/openvswitch.h

@@ -459,6 +459,14 @@ struct ovs_key_nd {
  * a wildcarded match. Omitting attribute is treated as wildcarding all
  * corresponding fields. Optional for all requests. If not present,
  * all flow key bits are exact match bits.
+ * @OVS_FLOW_ATTR_UFID: A value between 1-16 octets specifying a unique
+ * identifier for the flow. Causes the flow to be indexed by this value rather
+ * than the value of the %OVS_FLOW_ATTR_KEY attribute. Optional for all
+ * requests. Present in notifications if the flow was created with this
+ * attribute.
+ * @OVS_FLOW_ATTR_UFID_FLAGS: A 32-bit value of OR'd %OVS_UFID_F_*
+ * flags that provide alternative semantics for flow installation and
+ * retrieval. Optional for all requests.
  *
  * These attributes follow the &struct ovs_header within the Generic Netlink
  * payload for %OVS_FLOW_* commands.
@@ -474,11 +482,23 @@ enum ovs_flow_attr {
 	OVS_FLOW_ATTR_MASK,      /* Sequence of OVS_KEY_ATTR_* attributes. */
 	OVS_FLOW_ATTR_PROBE,     /* Flow operation is a feature probe, error
 				  * logging should be suppressed. */
+	OVS_FLOW_ATTR_UFID,      /* Variable length unique flow identifier. */
+	OVS_FLOW_ATTR_UFID_FLAGS,/* u32 of OVS_UFID_F_*. */
 	__OVS_FLOW_ATTR_MAX
 };
 
 #define OVS_FLOW_ATTR_MAX (__OVS_FLOW_ATTR_MAX - 1)
 
+/**
+ * Omit attributes for notifications.
+ *
+ * If a datapath request contains an %OVS_UFID_F_OMIT_* flag, then the datapath
+ * may omit the corresponding %OVS_FLOW_ATTR_* from the response.
+ */
+#define OVS_UFID_F_OMIT_KEY      (1 << 0)
+#define OVS_UFID_F_OMIT_MASK     (1 << 1)
+#define OVS_UFID_F_OMIT_ACTIONS  (1 << 2)
+
 /**
  * enum ovs_sample_attr - Attributes for %OVS_ACTION_ATTR_SAMPLE action.
  * @OVS_SAMPLE_ATTR_PROBABILITY: 32-bit fraction of packets to sample with