Merge branch 'mitigate-double-allocations-in-ioam6_iptunnel'

Justin Iurman says:

====================
Mitigate double allocations in ioam6_iptunnel

Commit dce525185bc9 ("net: ipv6: ioam6_iptunnel: mitigate 2-realloc
issue") fixed the double allocation issue in ioam6_iptunnel. However,
since commit 92191dd10730 ("net: ipv6: fix dst ref loops in rpl, seg6
and ioam6 lwtunnels"), the fix was left incomplete. Because the cache is
now empty when the dst_entry is the same post transformation in order to
avoid a reference loop, the double reallocation is back for such cases
(e.g., inline mode) which are valid for IOAM. This patch provides a way
to detect such cases without having a reference loop in the cache, and
so to avoid the double reallocation issue for all cases again.

v1: https://lore.kernel.org/netdev/20250410152432.30246-1-justin.iurman@uliege.be/T/#t
====================

Link: https://patch.msgid.link/20250415112554.23823-1-justin.iurman@uliege.be
Signed-off-by: Paolo Abeni <pabeni@redhat.com>