io_uring/zcrx: selftests: add test case for rss ctx

RSS contexts are used to shard work across multiple queues for an
application using io_uring zero copy receive. Add a test case checking
that steering flows into an RSS context works.

Until I add multi-thread support to the selftest binary, this test case
only has 1 queue in the RSS context.

Signed-off-by: David Wei <dw@davidwei.uk>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Joe Damato <jdamato@fastly.com>
Link: https://patch.msgid.link/20250425022049.3474590-4-dw@davidwei.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: spikeh

tools/testing/selftests/drivers/net/hw/iou-zcrx.py

@@ -21,12 +21,25 @@ def _get_combined_channels(cfg):
     return int(values[1])
 
 
+def _create_rss_ctx(cfg, chans):
+    output = ethtool(f"-X {cfg.ifname} context new start {chans - 1} equal 1", host=cfg.remote).stdout
+    values = re.search(r'New RSS context is (\d+)', output).group(1)
+    ctx_id = int(values)
+    return (ctx_id, defer(ethtool, f"-X {cfg.ifname} delete context {ctx_id}", host=cfg.remote))
+
+
 def _set_flow_rule(cfg, chan):
     output = ethtool(f"-N {cfg.ifname} flow-type tcp6 dst-port 9999 action {chan}", host=cfg.remote).stdout
     values = re.search(r'ID (\d+)', output).group(1)
     return int(values)
 
 
+def _set_flow_rule_rss(cfg, chan):
+    output = ethtool(f"-N {cfg.ifname} flow-type tcp6 dst-port 9999 action {chan}", host=cfg.remote).stdout
+    values = re.search(r'ID (\d+)', output).group(1)
+    return int(values)
+
+
 def test_zcrx(cfg) -> None:
     cfg.require_ipver('6')
 
@@ -79,6 +92,34 @@ def test_zcrx_oneshot(cfg) -> None:
         cmd(tx_cmd)
 
 
+def test_zcrx_rss(cfg) -> None:
+    cfg.require_ipver('6')
+
+    combined_chans = _get_combined_channels(cfg)
+    if combined_chans < 2:
+        raise KsftSkipEx('at least 2 combined channels required')
+    (rx_ring, hds_thresh) = _get_current_settings(cfg)
+
+    ethtool(f"-G {cfg.ifname} tcp-data-split on", host=cfg.remote)
+    defer(ethtool, f"-G {cfg.ifname} tcp-data-split auto", host=cfg.remote)
+    ethtool(f"-G {cfg.ifname} hds-thresh 0", host=cfg.remote)
+    defer(ethtool, f"-G {cfg.ifname} hds-thresh {hds_thresh}", host=cfg.remote)
+    ethtool(f"-G {cfg.ifname} rx 64", host=cfg.remote)
+    defer(ethtool, f"-G {cfg.ifname} rx {rx_ring}", host=cfg.remote)
+    ethtool(f"-X {cfg.ifname} equal {combined_chans - 1}", host=cfg.remote)
+    defer(ethtool, f"-X {cfg.ifname} default", host=cfg.remote)
+
+    (ctx_id, delete_ctx) = _create_rss_ctx(cfg, combined_chans)
+    flow_rule_id = _set_flow_rule_rss(cfg, ctx_id)
+    defer(ethtool, f"-N {cfg.ifname} delete {flow_rule_id}", host=cfg.remote)
+
+    rx_cmd = f"{cfg.bin_remote} -s -p 9999 -i {cfg.ifname} -q {combined_chans - 1}"
+    tx_cmd = f"{cfg.bin_local} -c -h {cfg.remote_addr_v['6']} -p 9999 -l 12840"
+    with bkg(rx_cmd, host=cfg.remote, exit_wait=True):
+        wait_port_listen(9999, proto="tcp", host=cfg.remote)
+        cmd(tx_cmd)
+
+
 def main() -> None:
     with NetDrvEpEnv(__file__) as cfg:
         cfg.bin_local = path.abspath(path.dirname(__file__) + "/../../../drivers/net/hw/iou-zcrx")