net/af_xdp: fix multi interface support for K8s

The original 'use_cni' implementation, was added
to enable support for the AF_XDP PMD in a K8s env
without any escalated privileges.
However 'use_cni' used a hardcoded socket rather
than a configurable one. If a DPDK pod is requesting
multiple net devices and these devices are from
different pools, then the AF_XDP PMD attempts to
mount all the netdev UDSes in the pod as /tmp/afxdp.sock.
Which means that at best only 1 netdev will handshake
correctly with the AF_XDP DP. This patch addresses
this by making the socket parameter configurable using
a new vdev param called 'dp_path' alongside the
original 'use_cni' param. If the 'dp_path' parameter
is not set alongside the 'use_cni' parameter, then
it's configured inside the AF_XDP PMD (transparently
to the user). This change has been tested
with the AF_XDP DP PR 81[1], with both single and
multiple interfaces.

[1] intel/afxdp-plugins-for-kubernetes#81

Fixes: 7fc6ae5 ("net/af_xdp: support CNI Integration")
Cc: [email protected]

Signed-off-by: Maryam Tahhan <[email protected]>
Signed-off-by: 0-day Robot <[email protected]>

Author: maryamtahhan

doc/guides/howto/af_xdp_dp.rst

@@ -52,29 +52,33 @@ should be used when creating the socket
 to instruct libbpf not to load the default libbpf program on the netdev.
 Instead the loading is handled by the AF_XDP Device Plugin.
 
-Limitations
------------
+The EAL vdev argument ``dp_path`` is used alongside the ``use_cni`` argument
+to explicitly tell the AF_XDP PMD where to find the UDS to interact with the
+AF_XDP Device Plugin. If this argument is not passed alongside the ``use_cni``
+argument then the AF_XDP PMD configures it internally.
 
-For DPDK versions <= v23.11 the Unix Domain Socket file path appears in
-the pod at "/tmp/afxdp.sock". The handshake implementation in the AF_XDP PMD
-is only compatible with the AF_XDP Device Plugin up to commit id `38317c2`_
-and the pod is limited to a single netdev.
+.. note::
+
+    DPDK AF_XDP PMD <= v23.11 will only work with the AF_XDP Device Plugin
+    <= commit id `38317c2`_.
 
 .. note::
 
-    DPDK AF_XDP PMD <= v23.11 will not work with the latest version of the
-    AF_XDP Device Plugin.
+    DPDK AF_XDP PMD > v23.11 will work with latest version of the
+    AF_XDP Device Plugin through a combination of the ``dp_path`` and/or
+    the ``use_cni`` parameter. In these versions of the PMD if a user doesn't
+    explicitly set the ``dp_path`` parameter when using ``use_cni`` then that
+    path is transparently configured in the AF_XDP PMD to the default
+    `AF_XDP Device Plugin for Kubernetes`_ mount point path. The path can
+    be overridden by explicitly setting the ``dp_path`` param.
 
-The issue is if a single pod requests different devices from different pools it
-results in multiple UDS servers serving the pod with the container using only a
-single mount point for their UDS as ``/tmp/afxdp.sock``. This means that at best one
-device might be able to complete the handshake. This has been fixed in the AF_XDP
-Device Plugin so that the mount point in the pods for the UDS appear at
-``/tmp/afxdp_dp/<netdev>/afxdp.sock``. Later versions of DPDK fix this hardcoded path
-in the PMD alongside the ``use_cni`` parameter.
+.. note::
 
-.. _38317c2: https://github.com/intel/afxdp-plugins-for-kubernetes/commit/38317c256b5c7dfb39e013a0f76010c2ded03669
+    DPDK AF_XDP PMD > v23.11 is backwards compatible with (older) versions
+    of the AF_XDP DP <= commit id `38317c2`_ by explicitly setting ``dp_path`` to
+    ``/tmp/afxdp.sock``.
 
+.. _38317c2: https://github.com/intel/afxdp-plugins-for-kubernetes/commit/38317c256b5c7dfb39e013a0f76010c2ded03669
 
 Prerequisites
 -------------
@@ -105,10 +109,10 @@ Device Plugin and DPDK container prerequisites:
 
   .. code-block:: console
 
-     cat << EOF | sudo tee /etc/systemd/system/containerd.service.d/limits.conf
-     [Service]
-     LimitMEMLOCK=infinity
-     EOF
+    cat << EOF | sudo tee /etc/systemd/system/containerd.service.d/limits.conf
+    [Service]
+    LimitMEMLOCK=infinity
+    EOF
 
 * dpdk-testpmd application should have AF_XDP feature enabled.
 
@@ -284,7 +288,7 @@ Run dpdk-testpmd with the AF_XDP Device Plugin + CNI
         emptyDir:
           medium: HugePages
 
-  For further reference please use the `pod.yaml`_
+  For further reference please see the `pod.yaml`_
 
   .. _pod.yaml: https://github.com/intel/afxdp-plugins-for-kubernetes/blob/main/examples/pod-spec.yaml
 
@@ -297,3 +301,19 @@ Run dpdk-testpmd with the AF_XDP Device Plugin + CNI
            --vdev=net_af_xdp0,use_cni=1,iface=<interface name> \
            --no-mlockall --in-memory \
            -- -i --a --nb-cores=2 --rxq=1 --txq=1 --forward-mode=macswap;
+
+  Or
+
+  .. code-block:: console
+
+     kubectl exec -i <Pod name> --container <containers name> -- \
+           /<Path>/dpdk-testpmd -l 0,1 --no-pci \
+           --vdev=net_af_xdp0,use_cni=1,iface=<interface name>,dp_path="/tmp/afxdp_dp/<interface name>/afxdp.sock" \
+           --no-mlockall --in-memory \
+           -- -i --a --nb-cores=2 --rxq=1 --txq=1 --forward-mode=macswap;
+
+.. note::
+
+    If the ``dp_path`` parameter isn't explicitly set (like the example above)
+    the AF_XDP PMD will set the parameter value to
+    ``/tmp/afxdp_dp/<<interface name>>/afxdp.sock``.

doc/guides/nics/af_xdp.rst

@@ -171,6 +171,20 @@ enable the `AF_XDP Device Plugin for Kubernetes`_ with a DPDK application/pod.
    so enabling and disabling of the promiscuous mode through the DPDK application
    is also not supported.
 
+dp_path
+~~~~~~~
+
+The EAL vdev argument ``dp_path`` is used alongside the ``use_cni`` argument
+to explicitly tell the AF_XDP PMD where to find the UDS to interact with the
+`AF_XDP Device Plugin for Kubernetes`_. If this argument is not passed
+alongside the ``use_cni`` argument then the AF_XDP PMD configures it internally.
+
+.. _AF_XDP Device Plugin for Kubernetes: https://github.com/intel/afxdp-plugins-for-kubernetes
+
+.. code-block:: console
+
+   --vdev=net_af_xdp0,use_cni=1,dp_path="/tmp/afxdp_dp/<<interface name>>/afxdp.sock"
+
 Limitations
 -----------
 

doc/guides/rel_notes/release_24_03.rst

@@ -138,6 +138,13 @@ New Features
     to support TLS v1.2, TLS v1.3 and DTLS v1.2.
   * Added PMD API to allow raw submission of instructions to CPT.
 
+* **Enabled AF_XDP PMD multi interface (UDS) support with AF_XDP Device Plugin**.
+
+  The EAL vdev argument for the AF_XDP PMD ``use_cni`` previously limited
+  a pod to using only a single netdev/interface. The latest changes (adding
+  the ``dp_path`` parameter) remove this limitation and maintain backward
+  compatibility for any applications already using the ``use_cni`` vdev
+  argument with the AF_XDP Device Plugin.
 
 Removed Items
 -------------