Yes, I did. On Tue, Dec 13, 2022 at 1:23 PM Daniele Palmas <dnlplm@xxxxxxxxx> wrote: > > Hello Seija, > > Il giorno mar 13 dic 2022 alle ore 18:44 Seija K. > <doremylover123@xxxxxxxxx> ha scritto: > > > > When a packet larger than MTU arrives in Linux from the modem, it is > > discarded with -EOVERFLOW error (Babble error). > > > > This is seen on USB3.0 and USB2.0 buses. > > > > This is because the MRU (Max Receive Size) is not a separate entity > > from the MTU (Max Transmit Size), and the received packets can be > > larger than those transmitted. > > > > Following the babble error, there was an endless supply of zero-length > > URBs that were rejected with -EPROTO (increasing the rx input error > > counter each time). > > > > This is only seen on USB3.0. These continue to come ad infinitum until > > the modem is shut down. > > > > There appears to be a bug in the core USB handling code in Linux that > > doesn't deal with network MTUs smaller than 1500 bytes well. > > > > By default, the dev->hard_mtu (the real MTU) is in lockstep with > > dev->rx_urb_size (essentially an MRU), and the latter is causing > > trouble. > > > > This has nothing to do with the modems; the issue can be reproduced by > > getting a USB-Ethernet dongle, setting the MTU to 1430, and pinging > > with size greater than 1406. > > > > Signed-off-by: Seija Kijin <doremylover123@xxxxxxxxx> > > > > Co-Authored-By: TarAldarion <gildeap@xxxxxx> > > --- > > drivers/net/usb/qmi_wwan.c | 7 +++++++ > > 1 file changed, 7 insertions(+) > > > > diff --git a/drivers/net/usb/qmi_wwan.c b/drivers/net/usb/qmi_wwan.c > > index 554d4e2a84a4..39db53a74b5a 100644 > > --- a/drivers/net/usb/qmi_wwan.c > > +++ b/drivers/net/usb/qmi_wwan.c > > @@ -842,6 +842,13 @@ static int qmi_wwan_bind(struct usbnet *dev, > > struct usb_interface *intf) > > } > > dev->net->netdev_ops = &qmi_wwan_netdev_ops; > > dev->net->sysfs_groups[0] = &qmi_wwan_sysfs_attr_group; > > + /* LTE Networks don't always respect their own MTU on the receiving side; > > + * e.g. AT&T pushes 1430 MTU but still allows 1500 byte packets from > > + * far-end networks. Make the receive buffer large enough to accommodate > > + * them, and add four bytes so MTU does not equal MRU on network > > + * with 1500 MTU. Otherwise, usbnet_change_mtu() will change both. > > + */ > > + dev->rx_urb_size = ETH_DATA_LEN + 4; > > Did you test this change with QMAP? > > To support qmap dl aggregated blocks qmi_wwan relies on the > usbnet_change_mtu behavior of changing the rx_urb_size. > > Thanks, > Daniele > > > err: > > return status; > > } > > -- > > 2.38.2
