Re: [PATCH net v4 4/4] ipv6: do not restart DAD for a dead ifaddr

On Thu, Oct 15, 2026 at 02:06:51PM +0900, Daehyeon Ko wrote:

addrconf_dad_failure() can create a stable-privacy replacement without
RTNL. After ipv6_add_addr() publishes it, addrconf_ifdown() can mark the
new ifaddr DEAD, clear its route, and unlink it before the recovery path
takes ifp2->lock.

The recovery path then unconditionally changes the state back to PREDAD
and queues delayed DAD work. The MTU teardown path can leave IF_READY
set. For an optimistic address, addrconf_dad_begin() can consequently
pass the cleared NULL route to ip6_ins_rt().

This follow-on was found by source review and was not separately
triggered at runtime.

The new ifaddr is already initialized in PREDAD. Under ifp2->lock, record
the retry and queue DAD only if teardown has not changed the state to
DEAD. If teardown wins after this check, the work observes DEAD and exits
without reviving the address.

This complements the existing lock_errdad check that preserves the original
ifaddr's DEAD state after the same function reacquires its lock.

Fixes: 5f40ef77adb2 ("ipv6: do retries on stable privacy addresses")
Cc: stable@vger.kernel.org
Reported-by: Sashiko <netdev-bot+sashiko@kernel.org>
Closes: https://lore.kernel.org/r/179161099408.434549.14449036924552933828@kernel.org (local)
Link: https://lore.kernel.org/r/20260513025509.3776405-1-lilinmao@kylinos.cn (local)
Assisted-by: LLM
Signed-off-by: Daehyeon Ko <redacted>

Same comment as on the previous patch. My diff [1] was simpler and your
commit message admits that it's fine:

"If teardown wins after this check, the work observes DEAD and exits
without reviving the address"

Reviewed-by: Ido Schimmel <idosch@nvidia.com>

[1] https://lore.kernel.org/netdev/20261012151316.GA798355@shredder/ (local)