net: core: synchronize link-watch when carrier is queried

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There are multiple ways to query for the carrier state: through
rtnetlink, sysfs, and (possibly) ethtool. Synchronize linkwatch
work before these operations so that we don't have a situation
where userspace queries the carrier state between the driver's
carrier off->on transition and linkwatch running and expects it
to work, when really (at least) TX cannot work until linkwatch
has run.

I previously posted a longer explanation of how this applies to
wireless [1] but with this wireless can simply query the state
before sending data, to ensure the kernel is ready for it.

[1] https://lore.kernel.org/all/346b21d87c69f817ea3c37caceb34f1f56255884.camel@sipsolutions.net/

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Link: https://lore.kernel.org/r/20231204214706.303c62768415.I1caedccae72ee5a45c9085c5eb49c145ce1c0dd5@changeid
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

...

This commit is contained in:

Johannes Berg 2023-12-04 21:47:07 +01:00 • committed by Jakub Kicinski

parent faf4cf7495

commit facd15dfd6

7 changed files with 29 additions and 4 deletions

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9

include/linux/netdevice.h

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2

net/core/dev.c

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1

net/core/dev.h

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2

net/core/link_watch.c

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8

net/core/net-sysfs.c

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8

net/core/rtnetlink.c

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3

net/ethtool/ioctl.c

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