[PATCH 15/15] WMM: Medium Time zero for an admitted downlink TS

[Andrei-Alexandru Bleortu]

WMM v1.2.0, 3.5.2 requires an AP to return a Medium Time equal to zero
when it accepts a unidirectional downlink TS request: the medium time
is what the STA itself may use, and a downlink stream uses none of it.
hostapd returned the medium time it estimated for the stream.

Assisted-by: LLM
Signed-off-by: Andrei-Alexandru Bleortu <me at andrei-z.com>
---
 src/ap/wmm.c                    |  8 ++++++--
 tests/hwsim/test_wpas_wmm_ac.py | 11 +++++++++++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/src/ap/wmm.c b/src/ap/wmm.c
index 8e2212263..d4e6b3d10 100644
--- a/src/ap/wmm.c
+++ b/src/ap/wmm.c
@@ -277,8 +277,12 @@ int wmm_process_tspec(struct wmm_tspec_element *tspec)
 		return WMM_ADDTS_STATUS_REFUSED;
 	}
 
-	/* Convert to 32 microseconds per second unit */
-	tspec->medium_time = host_to_le16(medium_time / 32);
+	/* Convert to 32 microseconds per second unit; a unidirectional
+	 * downlink TS gets a Medium Time of zero (WMM v1.2.0, 3.5.2) */
+	if (dir == 1)
+		tspec->medium_time = 0;
+	else
+		tspec->medium_time = host_to_le16(medium_time / 32);
 
 	return WMM_ADDTS_STATUS_ADMISSION_ACCEPTED;
 }
diff --git a/tests/hwsim/test_wpas_wmm_ac.py b/tests/hwsim/test_wpas_wmm_ac.py
index 32e6afe64..20666eca2 100644
--- a/tests/hwsim/test_wpas_wmm_ac.py
+++ b/tests/hwsim/test_wpas_wmm_ac.py
@@ -116,6 +116,17 @@ def test_tspec(dev, apdev):
     if "FAIL" not in dev[0].request("WMM_AC_ADDTS foo"):
         raise Exception("Invalid WMM_AC_ADDTS command accepted")
 
+def test_tspec_downlink_medium_time(dev, apdev):
+    """Downlink TS admitted with a Medium Time of zero"""
+    hapd = add_wmm_ap(apdev[0], ["VO", "VI"])
+    dev[0].connect("wmm_ac", key_mgmt="NONE", scan_freq="2462")
+    dev[0].add_ts(5, 6, direction="downlink")
+    status = dev[0].request("WMM_AC_STATUS")
+    if "Total admitted time = 0\n" not in status:
+        raise Exception("Downlink TS admitted with medium time: " + status)
+    dev[0].del_ts(5)
+
+
 def test_tspec_protocol(dev, apdev):
     """Protocol tests for addts/delts"""
     # configure ap with VO and VI requiring admission-control
-- 
2.47.3