[PATCH] net: loopback: use NET_NAME_PREDICTABLE for name_assign_type

From: Rasmus Villemoes
Date: Wed Nov 23 2022 - 09:18:43 EST


When the name_assign_type attribute was introduced (commit
685343fc3ba6, "net: add name_assign_type netdev attribute"), the
loopback device was explicitly mentioned as one which would make use
of NET_NAME_PREDICTABLE:

The name_assign_type attribute gives hints where the interface name of a
given net-device comes from. These values are currently defined:
...
NET_NAME_PREDICTABLE:
The ifname has been assigned by the kernel in a predictable way
that is guaranteed to avoid reuse and always be the same for a
given device. Examples include statically created devices like
the loopback device [...]

Switch to that so that reading /sys/class/net/lo/name_assign_type
produces something sensible instead of returning -EINVAL.

Signed-off-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
---

This is mostly cosmetic, but ideally I'd like to get to a situation
where I don't need to do

assign_type=$(cat /sys/class/net/$dev/name_assign_type 2> /dev/null || echo 0)

or otherwise special-case [ $dev = "lo" ].

As always, there's a small chance that this could cause a regression,
but it seems extremely unlikely that anybody relies on
/sys/class/net/lo/name_assign_type being unreadable and thus
effectively is known to be NET_NAME_UNKNOWN.

drivers/net/loopback.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/loopback.c b/drivers/net/loopback.c
index 14e8d04cb434..2e9742952c4e 100644
--- a/drivers/net/loopback.c
+++ b/drivers/net/loopback.c
@@ -211,7 +211,7 @@ static __net_init int loopback_net_init(struct net *net)
int err;

err = -ENOMEM;
- dev = alloc_netdev(0, "lo", NET_NAME_UNKNOWN, loopback_setup);
+ dev = alloc_netdev(0, "lo", NET_NAME_PREDICTABLE, loopback_setup);
if (!dev)
goto out;

--
2.37.2