flags & IFF_PROMISC -- rtnetlink and sysfs

[Tomas Janousek]

Hello,

while investigating the issue that ifconfig and ip link ls does not show the
PROMISC flag while tcpdump is running, I found that flags returned in
rtnetlink's ifinfo and /sys/class/net/eth0/flags differ.

rtnetlink (net/core/rtnetlink.c:rtnl_fill_ifinfo) calls dev_get_flags
(net/core/dev.c) to get the flags. Sysfs (net/core/net-sysfs.c) just shows
what is in net->flags. Is this difference intentional?

On the other hand, it's good that this net->flags is accessible somewhere,
because it shows the real state of the PROMISC flag.

If we want to show the real state in ip/ifconfig, what do you think we should
do? Read /sys/class/net/eth0/flags?

If this issue had been brought up before and decided, sorry.
-- 
Tomas Janousek, SW Engineer, Red Hat, Inc.
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