[PATCH net-next v2 0/3] veth: link RX queues to their NAPI instances

[Tianyi Gao <tianyi@cloudflare.com>]

veth does not link its RX queues to their NAPI instances. queue-get
therefore reports no napi-id for them. napi-get lists the NAPI instances
of a veth, and their thread PIDs when NAPI is threaded. It does not show
which RX queue each instance polls. Userspace cannot tell which NAPI
thread to pin for a given queue, or which NAPI to change with napi-set.

There is also no way to busy poll an AF_XDP socket bound to a veth
queue. xsk_bind() takes the socket's NAPI ID from the RX queue, and a
veth RX queue has none.

Patch 1 is a cleanup to ease review of patch 2. veth_enable_xdp_range()
adds the NAPI instances only to pass their napi_id to
xdp_rxq_info_reg(), which no longer uses it. Patch 1 moves
netif_napi_add() into the loop that enables the NAPI instances. It also
removes the arguments and wrappers that came with adding the NAPI
instances in two places.

Patch 2 calls netif_queue_set_napi() in veth_napi_enable_range(), after
napi_enable(). In veth_napi_del_range(), it clears the link with NULL
before napi_disable().

Patch 3 adds RX queue NAPI link checks to veth.sh. The napi-id of every
RX queue must match a NAPI instance of the device. The queues must be
linked only while NAPI is enabled. The checks run with GRO on and with
XDP attached, and across RX channel changes and link down/up.

---
Changes in v2:
- Rebase on net-next. Patch 3 no longer applied after commit
  c1f04ea0aa0f ("selftests: net: check veth carrier after changing
  channel counts"). The conflict is in context only. No code change.
- v1: https://lore.kernel.org/all/20261105143356.17062-1-tianyi@cloudflare.com/

Tianyi Gao (3):
  veth: refactor NAPI enable paths
  veth: link RX queues to their NAPI instances
  selftests: net: veth: test RX queue NAPI links

 drivers/net/veth.c                  | 83 ++++++++---------------------
 tools/testing/selftests/net/veth.sh | 79 ++++++++++++++++++++++++++-
 2 files changed, 99 insertions(+), 63 deletions(-)


base-commit: 79ee9e6768721f337952e9b3edd14cedbbc03030
-- 
2.56.0