[ovs-dev] [PATCH] FAQ: Add an entry describing the different ways to dump flows.

[Justin Pettit]

Signed-off-by: Justin Pettit <jpettit at nicira.com>
---
 FAQ |   35 +++++++++++++++++++++++++++++++++++
 1 files changed, 35 insertions(+), 0 deletions(-)

diff --git a/FAQ b/FAQ
index 0e7713b..177f992 100644
--- a/FAQ
+++ b/FAQ
@@ -283,6 +283,41 @@ A: No.  ERSPAN is an undocumented proprietary protocol.  As an
    alternative, Open vSwitch supports mirroring to a GRE tunnel (see
    above).
 
+Q: Why are there so many different ways to dump flows?
+
+A: There are four different ways to look at the flow tables in Open
+   vSwitch.  The fall into two categories: userspace flows and datapath
+   flows.
+
+   Userspace flows are the ones that define the switch's policy.  They
+   support wildcards, priorities, and multiple tables.  They are often
+   called the OpenFlow rules and may be configured by a controller or
+   ovs-ofctl utility.  There are two ways to look at these userspace
+   flows:
+
+       - "ovs-ofctl dump-flows <br>" dumps the user-visible flows.  This
+         is the most common method to look at flow table entries.
+
+       - "ovs-appctl bridge/dump-flows <br>" dumps both the user-visible
+         and "hidden" flows.  Hidden flows are set up by Open vSwitch
+         itself to implement local policies.  These flows are higher
+         priority than can be configured by a controller or user.  There
+         is more discussion about hidden flows in the "Controller"
+         section below.
+
+    Datapath flows are much simpler exact-match entries for efficient
+    lookup.  These commands are primarily useful for debugging Open
+    vSwitch, since they are simply a cache of recently seen traffic.
+    There are two ways to look at these datapath flows:
+
+        - "ovs-dpctl dump-flows [dp]" dumps the flow table entries for a
+          datapath instance.  If multiple bridges of the same type
+          exist, then the flows from all bridges of that type will be
+          shown.
+
+        - "ovs-appctl dpif/dump-flows <br>" dumps the datapath flows for
+          only the specified bridge, regardless of the type.
+
 
 Configuration Problems
 ----------------------
-- 
1.7.5.4