ofproto-dpif: Expose datapath capability to ovsdb.

The patch adds support for fetching the datapath's capabilities
from the result of 'check_support()', and write the supported capability
to a new database column, called 'capabilities' under Datapath table.

To see how it works, run:
 # ovs-vsctl -- add-br br0 -- set Bridge br0 datapath_type=netdev
 # ovs-vsctl -- --id=@m create Datapath datapath_version=0 \
     'ct_zones={}' 'capabilities={}' \
     -- set Open_vSwitch . datapaths:"netdev"=@m

 # ovs-vsctl list-dp-cap netdev
 ufid=true sample_nesting=true clone=true tnl_push_pop=true \
 ct_orig_tuple=true ct_eventmask=true ct_state=true \
 ct_clear=true max_vlan_headers=1 recirc=true ct_label=true \
 max_hash_alg=1 ct_state_nat=true ct_timeout=true \
 ct_mark=true ct_orig_tuple6=true check_pkt_len=true \
 masked_set_action=true max_mpls_depth=3 trunc=true ct_zone=true

Signed-off-by: William Tu <u9012063@gmail.com>
Tested-by: Greg Rose <gvrose8192@gmail.com>
Reviewed-by: Greg Rose <gvrose8192@gmail.com>
---
v5:
    Add improved documentation from Ben and
    fix checkpatch error (tab and line 79 char)
v4:
    rebase to master
v3:
    fix 32-bit build, reported by Greg
    travis: https://travis-ci.org/williamtu/ovs-travis/builds/599276267
v2:
	rebase to master

1 files changed, 11 insertions, 3 deletions

diff --git a/lib/meta-flow.xml b/lib/meta-flow.xml
index d8763eb0b..90b405c73 100644
--- a/lib/meta-flow.xml
+++ b/lib/meta-flow.xml
@@ -2488,7 +2488,7 @@ actions=clone(load:0->NXM_OF_IN_PORT[],output:123)
 
   <group title="Connection Tracking">
     <p>
-      Open vSwitch 2.5 and later support ``connection tracking,'' which allows
+      Open vSwitch supports ``connection tracking,'' which allows
       bidirectional streams of packets to be statefully grouped into
       connections.  Open vSwitch connection tracking, for example, identifies
       the patterns of TCP packets that indicates a successfully initiated
@@ -2524,7 +2524,14 @@ actions=clone(load:0->NXM_OF_IN_PORT[],output:123)
     </p>
 
     <p>
-      Connection tracking is an Open vSwitch extension to OpenFlow.
+      Connection tracking is an Open vSwitch extension to OpenFlow.  Open
+      vSwitch 2.5 added the initial support for connection tracking.
+      Subsequent versions of Open vSwitch added many refinements and extensions
+      to the initial support.  Many of these capabilities depend on the Open
+      vSwitch datapath rather than simply the userspace version.  The
+      <code>capabilities</code> column in the <code>Datapath</code> table (see
+      <code>ovs-vswitchd.conf.db</code>(5)) reports the detailed capabilities
+      of a particular Open vSwitch datapath.
     </p>
 
     <field id="MFF_CT_STATE" title="Connection Tracking State">
@@ -2713,7 +2720,8 @@ actions=clone(load:0->NXM_OF_IN_PORT[],output:123)
     </p>
 
     <p>
-      The following fields are populated by the ct action, and require a
+      The following fields are populated by the <code>ct</code>
+      action, and require a
       match to a valid connection tracking state as a prerequisite, in
       addition to the IP or IPv6 ethertype match.  Examples of valid
       connection tracking state matches include <code>ct_state=+new</code>,