From: Johan Almbladh <johan.almbladh@xxxxxxxxxxxxxxxxx> [ 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@xxxxxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20210628123246.2070558-1-johan.almbladh@xxxxxxxxxxxxxxxxx Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- 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 137fa4c50e07..8df7ab34911c 100644 --- a/net/mac80211/iface.c +++ b/net/mac80211/iface.c @@ -1985,9 +1985,16 @@ 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) { -- 2.30.2
