Re: [PATCH net-next v4 10/10] tsnep: Support XDP BPF program setup

On Tue, 10 Jan 2023 22:38:04 +0100 Gerhard Engleder wrote:

quoted

As I called out earlier the __TSNEP_DOWN is just !IFF_UP so you don't
need that bit.

The fact that netif_carrier_off is here also points out the fact that
the code in the Tx path isn't needed regarding __TSNEP_DOWN and you can
probably just check netif_carrier_ok if you need the check.  

tsnep_netdev_close() is called directly during bpf prog setup (see
tsnep_xdp_setup_prog() in this commit). If the following
tsnep_netdev_open() call fails, then this flag signals that the device
is already down and nothing needs to be cleaned up if
tsnep_netdev_close() is called later (because IFF_UP is still set).

TBH we've been pushing pretty hard for a while now to stop people
from implementing the:

	close()
	change config
	open()

sort of reconfiguration. I did that myself when I was a was
implementing my first Ethernet driver and DaveM nacked the change.
Must have been a decade ago.

Imagine you're working on a remote box via SSH and the box is under
transient memory pressure. Allocations fail, we don't want the machine
to fall off the network :(