Hi Ben,
Thank you for the detailed information! I read this part of the code,
and have some confusion. Can you please review the following to see if
my understanding of code is correct?
1) ofproto/ code is userspace code, and datapath/ code is the actual dp code.
2) ofproto handles the rule insertion from control plane, and datapath
handles the actual flow lookup.
3) resubmit is handled in userspace? I saw the resubmit logic
xlate_nicira_action() is in ofproto I didn't see find any code in
datapath that handles resubmit, not even in ovs-ofctl.c. Is
xlate_nicira_action() doing flow insertion with resubmit action or
actually performing the dp actions? I am confused.
What is the relationship between ofproto userspace and the dp code?
what is the difference between xlate table action and odp action?
I think I am very confused, if there is any documentation I can read
to understand this design better, would you please give me a pointer?
Thanks!
Yimin
On Thu, May 3, 2012 at 11:30 AM, Ben Pfaff <b...@nicira.com> wrote:
> It's documented in nicira-ext.h:
>
> /* Action structures for NXAST_RESUBMIT and NXAST_RESUBMIT_TABLE.
> *
> * These actions search one of the switch's flow tables:
> *
> * - For NXAST_RESUBMIT_TABLE only, if the 'table' member is not 255, then
> * it specifies the table to search.
> *
> * - Otherwise (for NXAST_RESUBMIT_TABLE with a 'table' of 255, or for
> * NXAST_RESUBMIT regardless of 'table'), it searches the current flow
> * table, that is, the OpenFlow flow table that contains the flow from
> * which this action was obtained. If this action did not come from a
> * flow table (e.g. it came from an OFPT_PACKET_OUT message), then table > 0
> * is the current table.
> *
> * The flow table lookup uses a flow that may be slightly modified from the
> * original lookup:
> *
> * - For NXAST_RESUBMIT, the 'in_port' member of struct nx_action_resubmit
> * is used as the flow's in_port.
> *
> * - For NXAST_RESUBMIT_TABLE, if the 'in_port' member is not OFPP_IN_PORT,
> * then its value is used as the flow's in_port. Otherwise, the original
> * in_port is used.
> *
> * - If actions that modify the flow (e.g. OFPAT_SET_VLAN_VID) precede the
> * resubmit action, then the flow is updated with the new values.
> *
> * Following the lookup, the original in_port is restored.
> *
> * If the modified flow matched in the flow table, then the corresponding
> * actions are executed. Afterward, actions following the resubmit in the
> * original set of actions, if any, are executed; any changes made to the
> * packet (e.g. changes to VLAN) by secondary actions persist when those
> * actions are executed, although the original in_port is restored.
> *
> * Resubmit actions may be used any number of times within a set of actions.
> *
> * Resubmit actions may nest to an implementation-defined depth. Beyond this
> * implementation-defined depth, further resubmit actions are simply ignored.
> *
> * NXAST_RESUBMIT ignores 'table' and 'pad'. NXAST_RESUBMIT_TABLE requires
> * 'pad' to be all-bits-zero.
> *
> * Open vSwitch 1.0.1 and earlier did not support recursion. Open vSwitch
> * before 1.2.90 did not support NXAST_RESUBMIT_TABLE.
> */
> struct nx_action_resubmit {
> ovs_be16 type; /* OFPAT_VENDOR. */
> ovs_be16 len; /* Length is 16. */
> ovs_be32 vendor; /* NX_VENDOR_ID. */
> ovs_be16 subtype; /* NXAST_RESUBMIT. */
> ovs_be16 in_port; /* New in_port for checking flow table. */
> uint8_t table; /* NXAST_RESUBMIT_TABLE: table to use. */
> uint8_t pad[3];
> };
> OFP_ASSERT(sizeof(struct nx_action_resubmit) == 16);
>
> and in ovs-ofctl(8):
>
> resubmit:port
> resubmit([port],[table])
> Re-searches this OpenFlow flow table (or the table whose
> number is specified by table) with the in_port field
> replaced by port (if port is specified) and executes the
> actions found, if any, in addition to any other actions
> in this flow entry.
>
> Recursive resubmit actions are obeyed up to an implemen‐
> tation-defined maximum depth. Open vSwitch 1.0.1 and
> earlier did not support recursion; Open vSwitch before
> 1.2.90 did not support table.
>
>
> On Thu, May 03, 2012 at 09:54:08AM +0800, YIMIN CHEN wrote:
>> Hi Ben,
>>
>> Thank you for your reply! I saw there is some code about resubmit
>> Nicira extension action, but that seems to be in userspace ofproto.c,
>> not in datapath, so I didn't know that is related. Could you help
>> clarify for me how does resubmit work?
>>
>>
>> Thanks!
>> Yimin
>>
>> On Wed, May 2, 2012 at 12:40 PM, Ben Pfaff <b...@nicira.com> wrote:
>> > On Wed, May 02, 2012 at 10:53:10AM +0800, YIMIN CHEN wrote:
>> >> I am looking at ovs dp code, and is looking at a correct way for a
>> >> flow to traverse the table twice. The goal is like this:
>> >>
>> >> flow lookup => tbl_lookup()
>> >> perform actions => execute_actions() which changes the packet
>> >> flow lookup using the new packet => tbl_lookup()
>> >> perform actions on the new packet => execute_actions.
>> >
>> > Do you want the "resubmit" Nicira extension action?
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