[ovs-dev] [PATCH 2/2] meta-flow: Make 'in_port' field writable.

[Ben Pfaff]

OpenFlow says that an "output" action to a flow's input port is ordinarily
dropped, unless the flow explicitly outputs to OFPP_IN_PORT.  We've
occasionally been asked to implement some way to avoid this behavior in
cases where it is not easily known in advance whether a given port is the
input port (so that OFPP_IN_PORT is not easy to use).

This commit implements such a feature.  With this commit, one may write:
    actions=load:0->NXM_OF_IN_PORT[],output:123
which will output to port 123 regardless of whether it is the input port.
If the input port is important, then one may save and restore it on the
stack:
    actions=push:NXM_OF_IN_PORT[],load:0->NXM_OF_IN_PORT[],output:123,
            pop:NXM_OF_IN_PORT[]

(Sometimes I am asked whether "resubmit" changes the in_port and would
therefore interact badly with this feature.  It does not.   "resubmit" only
(optionally) changes the in_port used for the resubmit's flow table lookup.
It does not otherwise have any effect on in_port.)

Bug #14091.
CC: Jarno Rajahalme <jarno.rajahalme at nsn.com>
CC: Ronghua Zhang <rzhang at nicira.com>
Signed-off-by: Ben Pfaff <blp at nicira.com>
---
 NEWS                          |    4 ++++
 include/openflow/nicira-ext.h |    2 ++
 lib/meta-flow.c               |    2 +-
 tests/ofproto-dpif.at         |    5 +++--
 4 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/NEWS b/NEWS
index 3a7123b..87f9bde 100644
--- a/NEWS
+++ b/NEWS
@@ -1,5 +1,9 @@
 post-v1.11.0
 ---------------------
+    - OpenFlow:
+      * The "load" and "set_field" actions can now modify the "in_port".  (This
+        allows one to enable output to a flow's input port by setting the
+        in_port to some unused value, such as OFPP_NONE.)
 
 
 v1.11.0 - xx xxx xxxx
diff --git a/include/openflow/nicira-ext.h b/include/openflow/nicira-ext.h
index c80ff95..8c9fab1 100644
--- a/include/openflow/nicira-ext.h
+++ b/include/openflow/nicira-ext.h
@@ -493,6 +493,8 @@ OFP_ASSERT(sizeof(struct nx_action_pop_queue) == 16);
  *     Modifying any of the above fields changes the corresponding packet
  *     header.
  *
+ *   - NXM_OF_IN_PORT
+ *
  *   - NXM_NX_REG(idx) for idx in the switch's accepted range.
  *
  *   - NXM_OF_VLAN_TCI.  Modifying this field's value has side effects on the
diff --git a/lib/meta-flow.c b/lib/meta-flow.c
index 9296faa..a75e526 100644
--- a/lib/meta-flow.c
+++ b/lib/meta-flow.c
@@ -114,7 +114,7 @@ static const struct mf_field mf_fields[MFF_N_IDS] = {
         MFM_NONE,
         MFS_OFP_PORT,
         MFP_NONE,
-        false,
+        true,
         NXM_OF_IN_PORT, "NXM_OF_IN_PORT",
         OXM_OF_IN_PORT, "OXM_OF_IN_PORT",
     }, {
diff --git a/tests/ofproto-dpif.at b/tests/ofproto-dpif.at
index 2b9df96..1fdbac3 100644
--- a/tests/ofproto-dpif.at
+++ b/tests/ofproto-dpif.at
@@ -92,18 +92,19 @@ AT_SETUP([ofproto-dpif - output])
 OVS_VSWITCHD_START
 ADD_OF_PORTS([br0], [1], [9], [10], [11], [55], [66], [77], [88])
 AT_DATA([flows.txt], [dnl
-in_port=1 actions=resubmit:2,resubmit:3,resubmit:4,resubmit:5,resubmit:6,resubmit:7
+in_port=1 actions=resubmit:2,resubmit:3,resubmit:4,resubmit:5,resubmit:6,resubmit:7,resubmit:8
 in_port=2 actions=output:9
 in_port=3 actions=load:55->NXM_NX_REG0[[]],output:NXM_NX_REG0[[]],load:66->NXM_NX_REG1[[]]
 in_port=4 actions=output:10,output:NXM_NX_REG0[[]],output:NXM_NX_REG1[[]],output:11
 in_port=5 actions=load:77->NXM_NX_REG0[[0..15]],load:88->NXM_NX_REG0[[16..31]]
 in_port=6 actions=output:NXM_NX_REG0[[0..15]],output:NXM_NX_REG0[[16..31]]
 in_port=7 actions=load:0x110000ff->NXM_NX_REG0[[]],output:NXM_NX_REG0[[]]
+in_port=8 actions=1,9,load:9->NXM_OF_IN_PORT[[]],1,9
 ])
 AT_CHECK([ovs-ofctl add-flows br0 flows.txt])
 AT_CHECK([ovs-appctl ofproto/trace br0 'in_port(1),eth(src=50:54:00:00:00:05,dst=50:54:00:00:00:07),eth_type(0x0800),ipv4(src=192.168.0.1,dst=192.168.0.2,proto=1,tos=0,ttl=128,frag=no),icmp(type=8,code=0)'], [0], [stdout])
 AT_CHECK([tail -1 stdout], [0],
-  [Datapath actions: 9,55,10,55,66,11,77,88
+  [Datapath actions: 9,55,10,55,66,11,77,88,9,1
 ])
 OVS_VSWITCHD_STOP
 AT_CLEANUP
-- 
1.7.2.5