Add a new rss_multiqueue Python test variant that exercises multi-queue
zero-copy receive on a single listening socket, where the server
dispatches accepted connections to worker threads by SO_INCOMING_NAPI_ID.

The setup creates an RSS context spanning N receive queues and a single
flow rule that uses that context, then queries the NAPI ID for each
queue at runtime via netlink queue_get(). The NAPI IDs are passed to
the C binary via a new -n option so it can map each accepted connection
to the worker handling that NAPI's queue. The client spawns more
connections than worker threads to exercise multiple connections per
worker.

Signed-off-by: Juanlu Herrero <juanlu@fastmail.com>
---
 .../selftests/drivers/net/hw/iou-zcrx.py      | 59 ++++++++++++++++++-
 1 file changed, 57 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/drivers/net/hw/iou-zcrx.py b/tools/testing/selftests/drivers/net/hw/iou-zcrx.py
index e81724cb5542a..896376b26e01a 100755
--- a/tools/testing/selftests/drivers/net/hw/iou-zcrx.py
+++ b/tools/testing/selftests/drivers/net/hw/iou-zcrx.py
@@ -29,6 +29,12 @@ def create_rss_ctx(cfg):
     return int(values)
 
 
+def create_rss_ctx_multi(cfg, start, count):
+    output = ethtool(f"-X {cfg.ifname} context new start {start} equal {count}").stdout
+    values = re.search(r'New RSS context is (\d+)', output).group(1)
+    return int(values)
+
+
 def set_flow_rule(cfg):
     output = ethtool(f"-N {cfg.ifname} flow-type tcp6 dst-port {cfg.port} action {cfg.target}").stdout
     values = re.search(r'ID (\d+)', output).group(1)
@@ -100,16 +106,65 @@ def rss(cfg):
     defer(ethtool, f"-N {cfg.ifname} delete {flow_rule_id}")
 
 
+def rss_multiqueue(cfg):
+    channels = cfg.ethnl.channels_get({'header': {'dev-index': cfg.ifindex}})
+    channels = channels['combined-count']
+    if channels < 3:
+        raise KsftSkipEx('Test requires NETIF with at least 3 combined channels')
+
+    rings = cfg.ethnl.rings_get({'header': {'dev-index': cfg.ifindex}})
+    rx_rings = rings['rx']
+    hds_thresh = rings.get('hds-thresh', 0)
+
+    cfg.ethnl.rings_set({'header': {'dev-index': cfg.ifindex},
+                         'tcp-data-split': 'enabled',
+                         'hds-thresh': 0,
+                         'rx': 64})
+    defer(cfg.ethnl.rings_set, {'header': {'dev-index': cfg.ifindex},
+                                'tcp-data-split': 'unknown',
+                                'hds-thresh': hds_thresh,
+                                'rx': rx_rings})
+    defer(mp_clear_wait, cfg)
+
+    cfg.num_threads = 2
+    cfg.target = channels - cfg.num_threads
+    ethtool(f"-X {cfg.ifname} equal {cfg.target}")
+    defer(ethtool, f"-X {cfg.ifname} default")
+
+    rss_ctx_id = create_rss_ctx_multi(cfg, cfg.target, cfg.num_threads)
+    defer(ethtool, f"-X {cfg.ifname} delete context {rss_ctx_id}")
+
+    flow_rule_id = set_flow_rule_rss(cfg, rss_ctx_id)
+    defer(ethtool, f"-N {cfg.ifname} delete {flow_rule_id}")
+
+    napi_ids = []
+    for i in range(cfg.num_threads):
+        queue = cfg.netnl.queue_get({'ifindex': cfg.ifindex,
+                                     'id': cfg.target + i,
+                                     'type': 'rx'})
+        napi_ids.append(str(queue['napi-id']))
+    cfg.napi_ids = ','.join(napi_ids)
+
+
 @ksft_variants([
     KsftNamedVariant("single", single),
     KsftNamedVariant("rss", rss),
+    KsftNamedVariant("rss_multiqueue", rss_multiqueue),
 ])
 def test_zcrx(cfg, setup) -> None:
     cfg.require_ipver('6')
 
+    cfg.num_threads = 1
+    cfg.napi_ids = None
+
     setup(cfg)
-    rx_cmd = f"{cfg.bin_local} -s -p {cfg.port} -i {cfg.ifname} -q {cfg.target}"
-    tx_cmd = f"{cfg.bin_remote} -c -h {cfg.addr_v['6']} -p {cfg.port} -l 12840"
+
+    rx_cmd = (f"{cfg.bin_local} -s -p {cfg.port} -i {cfg.ifname} "
+              f"-q {cfg.target} -t {cfg.num_threads}")
+    if cfg.napi_ids:
+        rx_cmd += f" -n {cfg.napi_ids}"
+    tx_cmd = (f"{cfg.bin_remote} -c -h {cfg.addr_v['6']} -p {cfg.port} "
+              f"-l 12840 -t {cfg.num_threads}")
     with bkg(rx_cmd, exit_wait=True):
         wait_port_listen(cfg.port, proto="tcp")
         cmd(tx_cmd, host=cfg.remote)
-- 
2.52.0