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Message-ID: <20140206224121.GB5251@lianli> Date: Thu, 6 Feb 2014 23:41:21 +0100 From: Emil Goode <emilgoode@...il.com> To: David Laight <David.Laight@...LAB.COM> Cc: 'Igor Gnatenko' <i.gnatenko.brain@...il.com>, "David S. Miller" <davem@...emloft.net>, Ming Lei <ming.lei@...onical.com>, Mark Brown <broonie@...aro.org>, Jeff Kirsher <jeffrey.t.kirsher@...el.com>, Glen Turner <gdt@....id.au>, "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: Re: [PATCH] net: asix: fix bad header length bug On Thu, Feb 06, 2014 at 03:28:13PM +0000, David Laight wrote: > From: Igor Gnatenko > > On Thu, 2014-02-06 at 13:56 +0100, Emil Goode wrote: > > > The AX88772B occasionally send rx packets that cross urb boundaries > > > and the remaining partial packet is sent with no header. > > > When the buffer with a partial packet is of less number of octets > > > than the value of hard_header_len the buffer is discarded by the > > > usbnet module. This is causing dropped packages and error messages > > > in dmesg. > > > > > > This can be reproduced by using ping with a packet size > > > between 1965-1976. > > > > > > The bug has been reported here: > > > > > > https://bugzilla.kernel.org/show_bug.cgi?id=29082 > > > > > > Signed-off-by: Emil Goode <emilgoode@...il.com> > > Reported-and-tested-by: Igor Gnatenko <i.gnatenko.brain@...il.com> > > > --- > > > drivers/net/usb/asix_devices.c | 1 + > > > 1 file changed, 1 insertion(+) > > > > > > diff --git a/drivers/net/usb/asix_devices.c b/drivers/net/usb/asix_devices.c > > > index 9765a7d..120bb29 100644 > > > --- a/drivers/net/usb/asix_devices.c > > > +++ b/drivers/net/usb/asix_devices.c > > > @@ -455,6 +455,7 @@ static int ax88772_bind(struct usbnet *dev, struct usb_interface *intf) > > > dev->net->ethtool_ops = &ax88772_ethtool_ops; > > > dev->net->needed_headroom = 4; /* cf asix_tx_fixup() */ > > > dev->net->needed_tailroom = 4; /* cf asix_tx_fixup() */ > > > + dev->net->hard_header_len = 0; /* Partial packets have no header */ > > That is the wrong place for the fix. > > It should only be done when rx_urb_size is set to a multiple of the usb > packet size. > That is only done for some of the supported devices. > > In fact, if the rx_urb_size is a multiple of the usb frame size (or 1k) > then maybe the usbnet code should assume that the driver is capable > of processing ethernet frames that cross usb packet boundaries and > not delete short packets at all - regardless of the hard_header_len. > > David > I will do some more digging in the code, but the test of skb->len against hard_header_len is done already in the completion callback function passed to usb_fill_bulk_urb so it seems that buffers of less than hard_header_len number of octets will be dropped regardless. Best regards, Emil Goode -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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