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vxlan: remove default_dst and use vxlan_config and lowerdev

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Now that vxlan->cfg is an RCU-protected pointer, storing default
destination attributes (remote_ip, remote_vni, remote_ifindex) in
vxlan->default_dst is redundant and creates potential data races for
lockless readers.

Furthermore, several fields of struct vxlan_rdst (remote_port,
offloaded, list, rcu, dst_cache) in default_dst were completely unused.
The remaining one, remote_dev, only tracked the lower device, a role
now taken by vxlan->lowerdev, so drop it from struct vxlan_rdst.

Replace vxlan->default_dst with a 'struct net_device *lowerdev' pointer
in struct vxlan_dev to track adjacent upper/lower netdev topology under
RTNL, and switch all remaining users over to reading configuration
attributes from vxlan->cfg.

Also update mlx5e_tc_tun_get_remote_ifindex() to read remote_ifindex
from vxlan->cfg under rcu_read_lock().

In vxlan_changelink(), pass lowerdev to vxlan_config_apply() to preserve
needed_headroom and needed_tailroom. The mtu is still only reconsidered
when the lower device changes, so that an unrelated changelink can not
shrink it.

cfg->remote_ifindex is now committed unconditionally, where
default_dst.remote_ifindex was left untouched when IFLA_VXLAN_LINK was
cleared, so a changelink dropping the lower device no longer leaves a
stale ifindex behind. For the same reason vxlan_changelink() no longer
needs to compute the ifindex that will actually be committed.

Setting IFLA_VXLAN_LINK to 0 now also tears down the upper/lower
adjacency, which netdev_adjacent_change_commit() used to skip for a NULL
new device, resets needed_tailroom, and is rejected if per-VNI multicast
groups are configured.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20260922181102.3989489-8-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2026-09-22 18:11:01 +00:00 • committed by Jakub Kicinski
commit 7e9e6844be
7 changed files with 213 additions and 163 deletions
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