diff options
| author | Laurent Vivier <lvivier@redhat.com> | 2026-03-04 16:43:38 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2026-03-19 18:15:25 +0300 |
| commit | 577fbb14390a11bd7366bf94ab026576bfba44b7 (patch) | |
| tree | ce4825daa5e04096986562902db056ac7dbe0c41 /drivers | |
| parent | 83f7b54242d0abbfce35a55c01322f50962ed3ee (diff) | |
| download | linux-577fbb14390a11bd7366bf94ab026576bfba44b7.tar.xz | |
qmi_wwan: allow max_mtu above hard_mtu to control rx_urb_size
commit 55f854dd5bdd8e19b936a00ef1f8d776ac32c7b0 upstream.
Commit c7159e960f14 ("usbnet: limit max_mtu based on device's hard_mtu")
capped net->max_mtu to the device's hard_mtu in usbnet_probe(). While
this correctly prevents oversized packets on standard USB network
devices, it breaks the qmi_wwan driver.
qmi_wwan relies on userspace (e.g. ModemManager) setting a large MTU on
the wwan0 interface to configure rx_urb_size via usbnet_change_mtu().
QMI modems negotiate USB transfer sizes of 16,383 or 32,767 bytes, and
the USB receive buffers must be sized accordingly. With max_mtu capped
to hard_mtu (~1500 bytes), userspace can no longer raise the MTU, the
receive buffers remain small, and download speeds drop from >300 Mbps
to ~0.8 Mbps.
Introduce a FLAG_NOMAXMTU driver flag that allows individual usbnet
drivers to opt out of the max_mtu cap. Set this flag in qmi_wwan's
driver_info structures to restore the previous behavior for QMI devices,
while keeping the safety fix in place for all other usbnet drivers.
Fixes: c7159e960f14 ("usbnet: limit max_mtu based on device's hard_mtu")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/lkml/CAPh3n803k8JcBPV5qEzUB-oKzWkAs-D5CU7z=Vd_nLRCr5ZqQg@mail.gmail.com/
Reported-by: Koen Vandeputte <koen.vandeputte@citymesh.com>
Tested-by: Daniele Palmas <dnlplm@gmail.com>
Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Link: https://patch.msgid.link/20260304134338.1785002-1-lvivier@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/net/usb/qmi_wwan.c | 4 | ||||
| -rw-r--r-- | drivers/net/usb/usbnet.c | 7 |
2 files changed, 6 insertions, 5 deletions
diff --git a/drivers/net/usb/qmi_wwan.c b/drivers/net/usb/qmi_wwan.c index 3a4985b582cb..05acac10cd2b 100644 --- a/drivers/net/usb/qmi_wwan.c +++ b/drivers/net/usb/qmi_wwan.c @@ -928,7 +928,7 @@ err: static const struct driver_info qmi_wwan_info = { .description = "WWAN/QMI device", - .flags = FLAG_WWAN | FLAG_SEND_ZLP, + .flags = FLAG_WWAN | FLAG_NOMAXMTU | FLAG_SEND_ZLP, .bind = qmi_wwan_bind, .unbind = qmi_wwan_unbind, .manage_power = qmi_wwan_manage_power, @@ -937,7 +937,7 @@ static const struct driver_info qmi_wwan_info = { static const struct driver_info qmi_wwan_info_quirk_dtr = { .description = "WWAN/QMI device", - .flags = FLAG_WWAN | FLAG_SEND_ZLP, + .flags = FLAG_WWAN | FLAG_NOMAXMTU | FLAG_SEND_ZLP, .bind = qmi_wwan_bind, .unbind = qmi_wwan_unbind, .manage_power = qmi_wwan_manage_power, diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c index 9280ef544bbb..f9f7506d9427 100644 --- a/drivers/net/usb/usbnet.c +++ b/drivers/net/usb/usbnet.c @@ -1821,11 +1821,12 @@ usbnet_probe(struct usb_interface *udev, const struct usb_device_id *prod) if ((dev->driver_info->flags & FLAG_NOARP) != 0) net->flags |= IFF_NOARP; - if (net->max_mtu > (dev->hard_mtu - net->hard_header_len)) + if ((dev->driver_info->flags & FLAG_NOMAXMTU) == 0 && + net->max_mtu > (dev->hard_mtu - net->hard_header_len)) net->max_mtu = dev->hard_mtu - net->hard_header_len; - if (net->mtu > net->max_mtu) - net->mtu = net->max_mtu; + if (net->mtu > (dev->hard_mtu - net->hard_header_len)) + net->mtu = dev->hard_mtu - net->hard_header_len; } else if (!info->in || !info->out) status = usbnet_get_endpoints(dev, udev); |