[PATCH net] selftests: drv-net: so_txtime: only send test traffic to sch_etf

[PATCH net] selftests: drv-net: so_txtime: only send test traffic to sch_etf

[Willem de Bruijn]

From: Willem de Bruijn <willemb@google.com>

The ETF qdiscs drops traffic without a socket or txtime. Even with
parameter skip_sock_check regular traffic is affected by ETF.

This test ran fine when run manually in a pure software environment.
But with drv-net across two hosts tests fail as early as when calling
cfg.remote.deploy due to effectively losing connectivity.

Isolate the intended test traffic:
- mark that with SO_MARK 100
- install a regular permissive root prio qdisc for background traffic
- install the ETF qdisc as leaf
- install a filter that only directs SO_MARK 100 traffic to this leaf

Technically other high prio traffic will map onto this leaf based on
ToS band mapping too. But that is immaterial in practice.

Fixes: 5c6baef3885c ("selftests: drv-net: convert so_txtime to drv-net")
Signed-off-by: Willem de Bruijn <willemb@google.com>
---
 tools/testing/selftests/drivers/net/config       |  2 ++
 tools/testing/selftests/drivers/net/so_txtime.py | 16 +++++++++++++---
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/drivers/net/config b/tools/testing/selftests/drivers/net/config
index 2070e890e064..de7af08a188d 100644
--- a/tools/testing/selftests/drivers/net/config
+++ b/tools/testing/selftests/drivers/net/config
@@ -6,6 +6,7 @@ CONFIG_IPV6=y
 CONFIG_MACSEC=m
 CONFIG_NET_CLS_ACT=y
 CONFIG_NET_CLS_BPF=y
+CONFIG_NET_CLS_FW=m
 CONFIG_NETCONSOLE=m
 CONFIG_NETCONSOLE_DYNAMIC=y
 CONFIG_NETCONSOLE_EXTENDED_LOG=y
@@ -14,6 +15,7 @@ CONFIG_NETKIT=y
 CONFIG_NET_SCH_ETF=m
 CONFIG_NET_SCH_FQ=m
 CONFIG_NET_SCH_INGRESS=y
+CONFIG_NET_SCH_PRIO=m
 CONFIG_PPP=y
 CONFIG_PPPOE=y
 CONFIG_VLAN_8021Q=m
diff --git a/tools/testing/selftests/drivers/net/so_txtime.py b/tools/testing/selftests/drivers/net/so_txtime.py
index adf6c848d6d8..9fbc0278d28b 100755
--- a/tools/testing/selftests/drivers/net/so_txtime.py
+++ b/tools/testing/selftests/drivers/net/so_txtime.py
@@ -27,7 +27,7 @@ def test_so_txtime(cfg, clockid, ipver, args_tx, args_rx, expect_success):
     cmd_addr = f"-S {cfg.addr_v[ipver]} -D {cfg.remote_addr_v[ipver]}"
     cmd_args = f"-{ipver} -c {clockid} -t {tstart} {cmd_addr}"
     cmd_rx = f"{cfg.bin_remote} {cmd_args} {args_rx} -r"
-    cmd_tx = f"{cfg.bin_local} {cmd_args} {args_tx}"
+    cmd_tx = f"{cfg.bin_local} -m 100 {cmd_args} {args_tx}"
 
     expect_fail = not expect_success
     if slow_machine:
@@ -45,7 +45,7 @@ def _qdisc_setup(ifname, qdisc, optargs=""):
     """
     orig = tc(f"qdisc show dev {ifname} root", json=True)[0].get("kind", None)
     defer(tc, f"qdisc replace dev {ifname} root {orig}")
-    tc(f"qdisc replace dev {ifname} root {qdisc} {optargs}")
+    tc(f"qdisc replace dev {ifname} root handle 1: {qdisc} {optargs}")
 
 
 def _test_variants_fq():
@@ -96,11 +96,21 @@ def _test_variants_etf():
 def test_so_txtime_etf(cfg, ipver, args_tx, args_rx, expect_fail):
     """Run all variants of etf tests."""
     cfg.require_ipver(ipver)
+
+    # root qdisc for background traffic (e.g., bkg())
+    _qdisc_setup(cfg.ifname, "prio")
+
+    # leaf ETF qdisc only for intended packets
     try:
-        _qdisc_setup(cfg.ifname, "etf", "clockid CLOCK_TAI delta 400000")
+        etf_args = "clockid CLOCK_TAI delta 400000"
+        tc(f"qdisc add dev {cfg.ifname} parent 1:1 handle 10: etf {etf_args}")
     except Exception as e:
         raise KsftSkipEx("tc does not support qdisc etf. skipping") from e
 
+    # redirect mark 100 to leaf
+    filter_args = "protocol all handle 100 fw flowid 1:1"
+    tc(f"filter add dev {cfg.ifname} parent 1: {filter_args}")
+
     test_so_txtime(cfg, "tai", ipver, args_tx, args_rx, expect_fail)
 
 
-- 
2.55.0.679.g6767b8d81c-goog

Re: [PATCH net] selftests: drv-net: so_txtime: only send test traffic to sch_etf

[Jakub Kicinski]

On Thu,  6 Aug 2026 13:36:57 -0400 Willem de Bruijn wrote:
> Subject: [PATCH net] selftests: drv-net: so_txtime: only send test traffic to sch_etf

This should probably go to net-next - where it does not apply.
I'm not sure if we documented this but selftests should not be treated
as fixes, unless they are packaged with a kernel fix. Or you _really_
need them in the current kernel version, but then you have to explain
why it matters specifically to you.
-- 
pw-bot: cr

Re: [PATCH net] selftests: drv-net: so_txtime: only send test traffic to sch_etf

[Willem de Bruijn]

Jakub Kicinski wrote:
> On Thu,  6 Aug 2026 13:36:57 -0400 Willem de Bruijn wrote:
> > Subject: [PATCH net] selftests: drv-net: so_txtime: only send test traffic to sch_etf
> 
> This should probably go to net-next - where it does not apply.

Ack, will address and send to net-next.

> I'm not sure if we documented this but selftests should not be treated
> as fixes, unless they are packaged with a kernel fix. Or you _really_
> need them in the current kernel version, but then you have to explain
> why it matters specifically to you.

No need from me. Makes total sense, but I was not aware. I do not yet
see it explicitly in maintainer-netdev.rst. If you want I can send
something like this:

@@ -66,7 +66,8 @@ driven by David Miller, the main network maintainer.  There is the
 ``net`` tree, and the ``net-next`` tree.  As you can probably guess from
 the names, the ``net`` tree is for fixes to existing code already in the
 mainline tree from Linus, and ``net-next`` is where the new code goes
-for the future release.  You can find the trees here:
+for the future release.  For selftests, all patches, including fixes,
+target net-next. You can find the trees here: