Re: [libvirt PATCH v8 3/3] Ignore EPERM on implicit clearing of VF VLAN ID

SmartNIC DPUs may not expose some privileged eswitch operations to the hypervisor hosts. For example, this happens with Bluefield devices running in the ECPF (default) mode for security reasons. While VF MAC address programming is possible via an RTM_SETLINK operation, trying to set a VLAN ID in the same operation will fail with EPERM. The equivalent ip link commands below provide an illustration: 1. This works: sudo ip link set enp130s0f0 vf 2 mac de:ad:be:ef:ca:fe 2. Setting (or clearing) a VLAN fails with EPERM: sudo ip link set enp130s0f0 vf 2 vlan 0 RTNETLINK answers: Operation not permitted 3. This is what Libvirt attempts to do today (when trying to clear a VF VLAN at the same time as programming a VF MAC). sudo ip link set enp130s0f0 vf 2 vlan 0 mac de:ad:be:ef:ca:fe RTNETLINK answers: Operation not permitted If setting an explicit VLAN ID results in an EPERM, clearing a VLAN (setting a VLAN ID to 0) can be handled gracefully by ignoring the EPERM error with the rationale being that if we cannot set this state in the first place, we cannot clear it either. In order to keep explicit clearing of VLAN ID working as it used to be passing a NULL pointer for VLAN ID is used. Signed-off-by: Dmitrii Shcherbakov <dmitrii.shcherbakov(a)canonical.com&gt; --- NEWS.rst | 14 ++++++++++++++ src/util/virnetdev.c | 11 ++++++++++- tests/virnetdevtest.c | 2 +- 3 files changed, 25 insertions(+), 2 deletions(-) diff --git a/NEWS.rst b/NEWS.rst index 666a593b58..f5453257ab 100644 --- a/NEWS.rst +++ b/NEWS.rst @@ -34,6 +34,20 @@ v8.1.0 (unreleased) to parse sysconfig files, in case they are created by the admin and filled with the desired key=value pairs. + * virnetdev: Ignore EPERM on implicit clearing of VF VLAN ID + + Libvirt will now ignore EPERM errors on attempts to implicitly clear a + VLAN ID (when a VLAN is not explicitly provided via an interface XML + using a 0 or a non-zero value) as SmartNIC DPUs do not expose VLAN + programming capabilities to the hypervisor host. This allows Libvirt + clients to avoid specifying a VLAN and expect VF configuration to work + since Libvirt tries to clear a VLAN in the same operation + as setting a MAC address for VIR_DOMAIN_NET_TYPE_HOSTDEV devices which + is now split into two distinct operations. EPERM errors received while + trying to program a non-zero VLAN ID or explicitly program a VLAN ID 0 + will still cause errors as before so there is no change in behavior + in those cases. + * **Bug fixes**

diff --git a/src/util/virnetdev.c b/src/util/virnetdev.c index eacdc3bf1f..cf9056f1bd 100644 --- a/src/util/virnetdev.c +++ b/src/util/virnetdev.c @@ -1613,12 +1613,21 @@ virNetDevSetVfVlan(const char *ifname, int vf, const int *vlanid) requestError = virNetDevSendVfSetLinkRequest(ifname, IFLA_VF_VLAN, &ifla_vf_vlan, sizeof(ifla_vf_vlan));