path: root/Documentation/networking
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authorJoe Stringer <>2015-01-21 16:42:52 -0800
committerDavid S. Miller <>2015-01-26 15:45:50 -0800
commit74ed7ab9264c54471c7f057409d352052820d750 (patch)
treef90152a0560337fceaf55538a9e57e8c9aaa9182 /Documentation/networking
parent7b1883cefc288b2725966357edd2d8f321605622 (diff)
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 <> Acked-by: Pravin B Shelar <> Signed-off-by: David S. Miller <>
Diffstat (limited to 'Documentation/networking')
1 files changed, 13 insertions, 0 deletions
diff --git a/Documentation/networking/openvswitch.txt b/Documentation/networking/openvswitch.txt
index 37c20ee2455e..b3b9ac61d29d 100644
--- a/Documentation/networking/openvswitch.txt
+++ b/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