Re: [PATCH] usbnet: ipheth: fix connectivity with iOS 14
From: Sam Bingner
Date: Sun Feb 21 2021 - 06:09:00 EST
There seems to be a problem with this patch:
Whenever the iPhone sends a packet to the tethered device that is 1500 bytes long, it gets the error "ipheth 1-1:4.2: ipheth_rcvbulk_callback: urb status: -79" on the connected device and stops passing traffic. I am able to bring it back up by shutting and unshutting the interface, but the same thing happens very quickly. I noticed that this patch dropped the max USB packet size from 1516 to 1514 bytes, so I decided to try lowering the MTU to 1498; this made the connection reliable and no more errors occurred.
It appears to me that the iPhone is still sending out 1516 bytes over USB for a 1500 byte packet and this patch makes USB abort when that happens? I could duplicate reliably by sending a ping from the iphone (ping -s 1472) to the connected device, or vice versa as the reply would then break it.
I apologize if this reply doesn't end up where it should - I tried to reply to the last message in this thread but I wasn't actually *on* the thread so I had to just build it as much as possible myself.
Sam