[DPDK/testpmd Bug 1479] mlx5: Not able to create rte_flows to match head fragments and sub fragments

[DPDK/testpmd Bug 1479] mlx5: Not able to create rte_flows to match head fragments and sub fragments

[bugzilla]

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https://bugs.dpdk.org/show_bug.cgi?id=1479

            Bug ID: 1479
           Summary: mlx5: Not able to create rte_flows to match head
                    fragments and sub fragments
           Product: DPDK
           Version: 21.11
          Hardware: All
                OS: All
            Status: UNCONFIRMED
          Severity: major
          Priority: Normal
         Component: testpmd
          Assignee: dev@dpdk.org
          Reporter: pingtosiva@gmail.com
  Target Milestone: ---

I am trying to create an RTE flow rule to match head and non-head fragments to
compute NIC RSS based on 5tuple/3tuple respectively on connectX-6 DX NIC and
mlx5 driver. 

As part of it when trying to install RTE flow rule using testpmd on dpdk
21.11/23.07 version, the following errors are thrown.

Flow rule to match head fragment
=================================
testpmd>  flow create 0 ingress pattern eth / ipv4 fragment_offset spec 0x2000
fragment_offset mask 0x3fff / end actions drop / count / end
port_flow_complain(): Caught PMD error type 13 (specific pattern item): cause:
0x7ffd1954c548, match on first fragment not supported: Operation not supported

Flow rule to match non-head fragments
======================================
testpmd> flow validate 0 ingress pattern eth / ipv4 fragment_offset is 0x2001
fragment_offset last 0x1fff / end actions drop / end
port_flow_complain(): Caught PMD error type 11 (item specification range):
cause: 0x7ffc6f629534, specified range not supported: Operation not supported

When I browsed mlx5_flow_dv.c driver file, there are set of conditions
implemented to block this configurations.

Could you kindly help is there a way to compute different RSS hash for
fragments and non-fragments using RTE flow rules on mellanox?

Thanks! in advance.

       /*
         * Match on fragment_offset 0x2000 means MF is 1 and frag-offset is 0,
         * indicating this is 1st fragment of fragmented packet.
         * This is not yet supported in MLX5, return appropriate error message.
         */
        if (fragment_offset_spec == RTE_BE16(RTE_IPV4_HDR_MF_FLAG))
                return rte_flow_error_set(error, ENOTSUP,
                                          RTE_FLOW_ERROR_TYPE_ITEM, item,
                                          "match on first fragment not "
                                          "supported");
        if (fragment_offset_spec && !last)
                return rte_flow_error_set(error, ENOTSUP,
                                          RTE_FLOW_ERROR_TYPE_ITEM, item,
                                          "specified value not supported");
        /*
         * Match on fragment_offset spec 0x2001 and last 0x3fff
         * means MF is 1 and frag-offset is > 0.
         * This packet is fragment 2nd and onward, excluding last.
         * This is not yet supported in MLX5, return appropriate
         * error message.
         */
        if (fragment_offset_spec == RTE_BE16(RTE_IPV4_HDR_MF_FLAG + 1) &&
            fragment_offset_last == RTE_BE16(MLX5_IPV4_FRAG_OFFSET_MASK))
                return rte_flow_error_set(error, ENOTSUP,
                                          RTE_FLOW_ERROR_TYPE_ITEM_LAST,
                                          last, "match on following "
                                          "fragments not supported");
        /*
         * Match on fragment_offset spec 0x0001 and last 0x1fff
         * means MF is 0 and frag-offset is > 0.
         * This packet is last fragment of fragmented packet.
         * This is not yet supported in MLX5, return appropriate
         * error message.
         */
        if (fragment_offset_spec == RTE_BE16(1) &&
            fragment_offset_last == RTE_BE16(RTE_IPV4_HDR_OFFSET_MASK))
                return rte_flow_error_set(error, ENOTSUP,
                                          RTE_FLOW_ERROR_TYPE_ITEM_LAST,
                                          last, "match on last "
                                          "fragment not supported");

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RE: [DPDK/testpmd Bug 1479] mlx5: Not able to create rte_flows to match head fragments and sub fragments

[Asaf Penso]

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Hello

Mlx5 pmd supports only these two modes:

  1.  fragment_offset=0x0000 with mask 0xffff means MF is 0 and frag-offset is 0.​
This is an unfragmented packet.​
  2.  fragment_offset spec 0x0001 and last 0x3fff with mask 0xffff, means MF and/or frag-offset is not 0.​
This is a fragmented packet.
To answer your questions, mlx5 doesn’t support match on head fragment and to match on non-head fragment, try mode 2 above.

Regards,
Asaf Penso

From: bugzilla@dpdk.org <bugzilla@dpdk.org>
Sent: Tuesday, 2 July 2024 17:21
To: dev@dpdk.org
Subject: [DPDK/testpmd Bug 1479] mlx5: Not able to create rte_flows to match head fragments and sub fragments

Bug ID
1479<https://bugs.dpdk.org/show_bug.cgi?id=1479>
Summary
mlx5: Not able to create rte_flows to match head fragments and sub fragments
Product
DPDK
Version
21.11
Hardware
All
OS
All
Status
UNCONFIRMED
Severity
major
Priority
Normal
Component
testpmd
Assignee
dev@dpdk.org<mailto:dev@dpdk.org>
Reporter
pingtosiva@gmail.com<mailto:pingtosiva@gmail.com>
Target Milestone
---

I am trying to create an RTE flow rule to match head and non-head fragments to

compute NIC RSS based on 5tuple/3tuple respectively on connectX-6 DX NIC and

mlx5 driver.



As part of it when trying to install RTE flow rule using testpmd on dpdk

21.11/23.07 version, the following errors are thrown.



Flow rule to match head fragment

=================================

testpmd>  flow create 0 ingress pattern eth / ipv4 fragment_offset spec 0x2000

fragment_offset mask 0x3fff / end actions drop / count / end

port_flow_complain(): Caught PMD error type 13 (specific pattern item): cause:

0x7ffd1954c548, match on first fragment not supported: Operation not supported



Flow rule to match non-head fragments

======================================

testpmd> flow validate 0 ingress pattern eth / ipv4 fragment_offset is 0x2001

fragment_offset last 0x1fff / end actions drop / end

port_flow_complain(): Caught PMD error type 11 (item specification range):

cause: 0x7ffc6f629534, specified range not supported: Operation not supported



When I browsed mlx5_flow_dv.c driver file, there are set of conditions

implemented to block this configurations.



Could you kindly help is there a way to compute different RSS hash for

fragments and non-fragments using RTE flow rules on mellanox?



Thanks! in advance.



       /*

         * Match on fragment_offset 0x2000 means MF is 1 and frag-offset is 0,

         * indicating this is 1st fragment of fragmented packet.

         * This is not yet supported in MLX5, return appropriate error message.

         */

        if (fragment_offset_spec == RTE_BE16(RTE_IPV4_HDR_MF_FLAG))

                return rte_flow_error_set(error, ENOTSUP,

                                          RTE_FLOW_ERROR_TYPE_ITEM, item,

                                          "match on first fragment not "

                                          "supported");

        if (fragment_offset_spec && !last)

                return rte_flow_error_set(error, ENOTSUP,

                                          RTE_FLOW_ERROR_TYPE_ITEM, item,

                                          "specified value not supported");

        /*

         * Match on fragment_offset spec 0x2001 and last 0x3fff

         * means MF is 1 and frag-offset is > 0.

         * This packet is fragment 2nd and onward, excluding last.

         * This is not yet supported in MLX5, return appropriate

         * error message.

         */

        if (fragment_offset_spec == RTE_BE16(RTE_IPV4_HDR_MF_FLAG + 1) &&

            fragment_offset_last == RTE_BE16(MLX5_IPV4_FRAG_OFFSET_MASK))

                return rte_flow_error_set(error, ENOTSUP,

                                          RTE_FLOW_ERROR_TYPE_ITEM_LAST,

                                          last, "match on following "

                                          "fragments not supported");

        /*

         * Match on fragment_offset spec 0x0001 and last 0x1fff

         * means MF is 0 and frag-offset is > 0.

         * This packet is last fragment of fragmented packet.

         * This is not yet supported in MLX5, return appropriate

         * error message.

         */

        if (fragment_offset_spec == RTE_BE16(1) &&

            fragment_offset_last == RTE_BE16(RTE_IPV4_HDR_OFFSET_MASK))

                return rte_flow_error_set(error, ENOTSUP,

                                          RTE_FLOW_ERROR_TYPE_ITEM_LAST,

                                          last, "match on last "

                                          "fragment not supported");



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[DPDK/testpmd Bug 1479] mlx5: Not able to create rte_flows to match head fragments and sub fragments

[bugzilla]

http://bugs.dpdk.org/show_bug.cgi?id=1479

mkashani@nvidia.com (mkashani@nvidia.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mkashani@nvidia.com
             Status|CONFIRMED                   |RESOLVED
         Resolution|---                         |FIXED

--- Comment #1 from mkashani@nvidia.com (mkashani@nvidia.com) ---
Hi, Siva,
Sorry for the late response,

You're correct that the mlx5 driver explicitly blocks the fragment matching
patterns you're trying to use.

For your use case (computing different RSS based on 5-tuple vs 3-tuple):
Create two flow rules:
One for ANY fragmented packets → RSS with 3-tuple (ipv4-frag)
One for non-fragmented packets → RSS with 5-tuple (ipv4-tcp, ipv4-udp)
The NIC will automatically:
Use 3-tuple for fragments (only IP src/dst/protocol available)
Use 5-tuple for non-fragments (full 5-tuple available)
You cannot differentiate between first, middle, and last fragments in flow
rules on ConnectX-6 DX.
The hardware RSS engine already handles this correctly by design - fragmented
packets can only use 3-tuple because port information is only in the first
fragment, and may not be available to all fragments.

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