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linux/net/decnet
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Hangbin Liu bd085ef678 net: add bool confirm_neigh parameter for dst_ops.update_pmtu 
The MTU update code is supposed to be invoked in response to real
networking events that update the PMTU. In IPv6 PMTU update function
__ip6_rt_update_pmtu() we called dst_confirm_neigh() to update neighbor
confirmed time.

But for tunnel code, it will call pmtu before xmit, like:
  - tnl_update_pmtu()
    - skb_dst_update_pmtu()
      - ip6_rt_update_pmtu()
        - __ip6_rt_update_pmtu()
          - dst_confirm_neigh()

If the tunnel remote dst mac address changed and we still do the neigh
confirm, we will not be able to update neigh cache and ping6 remote
will failed.

So for this ip_tunnel_xmit() case, _EVEN_ if the MTU is changed, we
should not be invoking dst_confirm_neigh() as we have no evidence
of successful two-way communication at this point.

On the other hand it is also important to keep the neigh reachability fresh
for TCP flows, so we cannot remove this dst_confirm_neigh() call.

To fix the issue, we have to add a new bool parameter for dst_ops.update_pmtu
to choose whether we should do neigh update or not. I will add the parameter
in this patch and set all the callers to true to comply with the previous
way, and fix the tunnel code one by one on later patches.

v5: No change.
v4: No change.
v3: Do not remove dst_confirm_neigh, but add a new bool parameter in
    dst_ops.update_pmtu to control whether we should do neighbor confirm.
    Also split the big patch to small ones for each area.
v2: Remove dst_confirm_neigh in __ip6_rt_update_pmtu.

Suggested-by: David Miller <davem@davemloft.net>
Reviewed-by: Guillaume Nault <gnault@redhat.com>
Acked-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2019-12-24 22:28:54 -08:00
..
netfilter treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 53 2019-05-24 17:36:42 +02:00
af_decnet.c net: use helpers to change sk_ack_backlog 2019-11-06 16:14:48 -08:00
dn_dev.c netlink: make validation more configurable for future strictness 2019-04-27 17:07:21 -04:00
dn_fib.c netlink: make validation more configurable for future strictness 2019-04-27 17:07:21 -04:00
dn_neigh.c proc: introduce proc_create_net{,_data} 2018-05-16 07:24:30 +02:00
dn_nsp_in.c net: use helpers to change sk_ack_backlog 2019-11-06 16:14:48 -08:00
dn_nsp_out.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 24 2019-05-21 11:52:39 +02:00
dn_route.c net: add bool confirm_neigh parameter for dst_ops.update_pmtu 2019-12-24 22:28:54 -08:00
dn_rules.c decnet: whitespace fixes 2018-07-24 14:10:42 -07:00
dn_table.c net: fix two coding style issues 2019-04-27 17:03:44 -04:00
dn_timer.c treewide: setup_timer() -> timer_setup() 2017-11-21 15:57:07 -08:00
Kconfig treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
Makefile decnet: whitespace fixes 2018-07-24 14:10:42 -07:00
README
sysctl_net_decnet.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
TODO decnet: whitespace fixes 2018-07-24 14:10:42 -07:00

README 

                       Linux DECnet Project
                      ======================

The documentation for this kernel subsystem is available in the
Documentation/networking subdirectory of this distribution and also
on line at http://www.chygwyn.com/DECnet/

Steve Whitehouse <SteveW@ACM.org>