net/tap: add deprecation notice for RTE_FLOW_ACTION_RSS

The BPF infrastructure in kernel changed which broke the method being used to load the RSS part of rte_flow in the TAP device. Since this is a little used feature, and fixing the problem would be moderately complex and create new dependency on libbpf, mark the feature as deprecated and plan for removal.

Signed-off-by Stephen Hemminger <[email protected]>

---
 doc/guides/rel_notes/deprecation.rst | 5 +++++
 1 file changed, 5 insertions(+)

doc/guides/rel_notes/deprecation.rst +0 -0

index 81b93515cbd9..7d9012ada2d7 100644

The BPF infrastructure in kernel changed which broke the method being used to load the RSS part of rte_flow in the TAP device. Since this is a little used feature, and fixing the problem would be moderately complex and create new dependency on libbpf, mark the feature as deprecated and plan for removal.

Signed-off-by Stephen Hemminger <[email protected]>

---
 doc/guides/rel_notes/deprecation.rst | 5 +++++
 1 file changed, 5 insertions(+)

doc/guides/rel_notes/deprecation.rst +5 -1

index 81b93515cbd9..7d9012ada2d7 100644
@@ -146,3 +146,8 @@ Deprecation Notices
   will be deprecated and subsequently removed in DPDK 24.11 release.
   Before this, the new port library API (functions rte_swx_port_*)
   will gradually transition from experimental to stable status.
+
+* tap: The support for RTE_FLOW_ACTION_TYPE_RSS is deprecated and
+  will be removed in DPDK 24.11 release. It is already broken on recent
+  Linux kernels due to changes in how BPF programs are loaded,
+  and will not be fixed.
--

2.43.0

Quoted 5 lines · Stephen Hemminger

The BPF infrastructure in kernel changed which broke the method being used to load the RSS part of rte_flow in the TAP device. Since this is a little used feature, and fixing the problem would be moderately complex and create new dependency on libbpf, mark the feature as deprecated and plan for removal.

Does this mean that RSS will not work with netvsc as netvsc is using
tap and mellanox ? Or will that not be affected .

Quoted 1 line · On Fri, 15 Dec 2023 00:18:41 +0530 kumaraparameshwaran rathinavel…

On Thu, Dec 14, 2023, 11:20 PM Stephen Hemminger <

[email protected]>

Quoted 10 lines

Quoted 5 lines · wrote:

The BPF infrastructure in kernel changed which broke the method being used to load the RSS part of rte_flow in the TAP device. Since this is a little used feature, and fixing the problem would be moderately complex and create new dependency on libbpf, mark the feature as deprecated and plan for removal.

Does this mean that RSS will not work with netvsc as netvsc is using
tap and mellanox ? Or will that not be affected .

The netvsc driver does not support rte_flow because the packets arrive direct from host (over vmbus). It does have normal RSS.
It many ways netvsc is equivalent in functionality to virtio and vmxnet3.

The tap BPF stuff was only useful for doing flow steering to a set of queues. It was a hack to get the kernel to do flow steering.

The BPF infrastructure in kernel changed which broke the method being used to load the RSS part of rte_flow in the TAP device. Since this is a little used feature, and fixing the problem would be moderately complex and create new dependency on libbpf, mark the feature as deprecated and plan for removal.

Signed-off-by Stephen Hemminger <[email protected]>

---
 doc/guides/rel_notes/deprecation.rst | 5 +++++
 1 file changed, 5 insertions(+)

doc/guides/rel_notes/deprecation.rst +0 -0

index 81b93515cbd9..7d9012ada2d7 100644