[PATCH net 0/1] ovpn: avoid caching stale IPv6 dst after FIB changes

[Ralf Lici <ralf@mandelbit.com>]

Hi,

This patch was originally part of a wider ovpn series addressing UDP
route-cache correctness when mutable socket routing properties or peer
endpoint state change while packets are being transmitted [1]. The
ovpn-specific fixes were resubmitted separately after dropping this
patch, which addresses an independent IPv6 FIB race reproduced in ovpn.

During review, Sabrina suggested submitting the patch directly to netdev
rather than through the ovpn pull request because it touches generic
dst_cache code and the underlying late-cookie sampling pattern is not
specific to ovpn. I first sent an RFC describing the race and a possible
kernel-wide solution [2], but it has not received any feedback so far.

After discussing the submission path with Antonio, we decided to post
the concrete ovpn fix directly to netdev. It prevents ovpn from caching
a route if the IPv6 FIB generation changed during lookup, without
attempting the broader network-stack refactoring discussed in the RFC.

[1] https://lore.kernel.org/openvpn-devel/cover.1785308184.git.ralf@mandelbit.com/
[2] https://lore.kernel.org/netdev/20260901122501.482920-1-ralf@mandelbit.com/

Compared with the version previously posted as part of the ovpn series,
this patch has been rebased on current net/main and made independent of
the pending ovpn route-cache and endpoint changes.

Thanks,

Ralf Lici
Mandelbit Srl

---
Ralf Lici (1):
  ovpn: avoid caching stale IPv6 dst after FIB changes

 drivers/net/ovpn/udp.c  | 20 +++++++++++++++++---
 include/net/dst_cache.h | 13 +++++++++++++
 net/core/dst_cache.c    | 19 +++++++++++++++----
 3 files changed, 45 insertions(+), 7 deletions(-)

base-commit: c9151088f1674fd29ff26a20f5fc687acf53a2f0
-- 
2.55.0