From: Johan Almbladh johan.almbladh@anyfinetworks.com
[ Upstream commit 79f5962baea74ce1cd4e5949598944bff854b166 ]
The maximum MTU was set to 2304, which is the maximum MSDU size. While this is valid for normal WLAN interfaces, it is too low for monitor interfaces. A monitor interface may receive and inject MPDU frames, and the maximum MPDU frame size is larger than 2304. The MPDU may also contain an A-MSDU frame, in which case the size may be much larger than the MTU limit. Since the maximum size of an A-MSDU depends on the PHY mode of the transmitting STA, it is not possible to set an exact MTU limit for a monitor interface. Now the maximum MTU for a monitor interface is unrestricted.
Signed-off-by: Johan Almbladh johan.almbladh@anyfinetworks.com Link: https://lore.kernel.org/r/20210628123246.2070558-1-johan.almbladh@anyfinetwo... Signed-off-by: Johannes Berg johannes.berg@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- net/mac80211/iface.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c index 1e5e9fc45523..cd96cd337aa8 100644 --- a/net/mac80211/iface.c +++ b/net/mac80211/iface.c @@ -2001,9 +2001,16 @@ int ieee80211_if_add(struct ieee80211_local *local, const char *name,
netdev_set_default_ethtool_ops(ndev, &ieee80211_ethtool_ops);
- /* MTU range: 256 - 2304 */ + /* MTU range is normally 256 - 2304, where the upper limit is + * the maximum MSDU size. Monitor interfaces send and receive + * MPDU and A-MSDU frames which may be much larger so we do + * not impose an upper limit in that case. + */ ndev->min_mtu = 256; - ndev->max_mtu = local->hw.max_mtu; + if (type == NL80211_IFTYPE_MONITOR) + ndev->max_mtu = 0; + else + ndev->max_mtu = local->hw.max_mtu;
ret = cfg80211_register_netdevice(ndev); if (ret) {