ipv6: per-netns exclusive flowlabel checks
commit 0b0dff5b3b98c5c7ce848151df9da0b3cdf0cc8b upstream.
Ipv6 flowlabels historically require a reservation before use.
Optionally in exclusive mode (e.g., user-private).
Commit 59c820b2317f ("ipv6: elide flowlabel check if no exclusive
leases exist") introduced a fastpath that avoids this check when no
exclusive leases exist in the system, and thus any flowlabel use
will be granted.
That allows skipping the control operation to reserve a flowlabel
entirely. Though with a warning if the fast path fails:
This is an optimization. Robust applications still have to revert to
requesting leases if the fast path fails due to an exclusive lease.
Still, this is subtle. Better isolate network namespaces from each
other. Flowlabels are per-netns. Also record per-netns whether
exclusive leases are in use. Then behavior does not change based on
activity in other netns.
Changes
v2
- wrap in IS_ENABLED(CONFIG_IPV6) to avoid breakage if disabled
Fixes: 59c820b2317f ("ipv6: elide flowlabel check if no exclusive leases exist")
Link: https://lore.kernel.org/netdev/MWHPR2201MB1072BCCCFCE779E4094837ACD0329@MWHPR2201MB1072.namprd22.prod.outlook.com/
Reported-by: Congyu Liu <[email protected]>
Signed-off-by: Willem de Bruijn <[email protected]>
Tested-by: Congyu Liu <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
3 files changed
