[PATCH net-next] ipv6: reset all.force_forwarding when disabling all.forwarding

[PATCH net-next] ipv6: reset all.force_forwarding when disabling all.forwarding

[Gabriel Goller]

Disabling all.forwarding resets force_forwarding on every interface, but
leaves all.force_forwarding set:

  # sysctl -wq net.ipv6.conf.all.forwarding=1
  # sysctl -wq net.ipv6.conf.all.force_forwarding=1
  # sysctl -wq net.ipv6.conf.all.forwarding=0
  # sysctl net.ipv6.conf.dummy1.force_forwarding
  net.ipv6.conf.dummy1.force_forwarding = 0
  # sysctl net.ipv6.conf.all.force_forwarding
  net.ipv6.conf.all.force_forwarding = 1

Writing 1 to all.force_forwarding afterwards is ignored because the
value did not change, so the interfaces are not re-enabled.

Reset all.force_forwarding too and notify netconf listeners.

Suggested-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Gabriel Goller <g.goller@proxmox.com>
---
 net/ipv6/addrconf.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index d9d13e78bf13..9007a58039e6 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -905,6 +905,14 @@ static int addrconf_fixup_forwarding(const struct ctl_table *table, int *p, int
 						     net->ipv6.devconf_dflt);
 
 		addrconf_forward_change(net, newf);
+		/* Disabling all.forwarding also resets all.force_forwarding */
+		if (newf == 0 && net->ipv6.devconf_all->force_forwarding) {
+			WRITE_ONCE(net->ipv6.devconf_all->force_forwarding, 0);
+			inet6_netconf_notify_devconf(net, RTM_NEWNETCONF,
+						     NETCONFA_FORCE_FORWARDING,
+						     NETCONFA_IFINDEX_ALL,
+						     net->ipv6.devconf_all);
+		}
 		if ((!newf) ^ (!old))
 			inet6_netconf_notify_devconf(net, RTM_NEWNETCONF,
 						     NETCONFA_FORWARDING,

---
base-commit: fa5196392691051963726787944db872420dfa75
base-tree: git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git main
change-id: 20261109-ipv6_reset_all-1452fdf29254

Best regards,
--  
Gabriel Goller <g.goller@proxmox.com>

Re: [PATCH net-next] ipv6: reset all.force_forwarding when disabling all.forwarding

[Nicolas Dichtel]

Le 09/11/2026 à 16:53, Gabriel Goller a écrit :
> Disabling all.forwarding resets force_forwarding on every interface, but
> leaves all.force_forwarding set:
> 
>   # sysctl -wq net.ipv6.conf.all.forwarding=1
>   # sysctl -wq net.ipv6.conf.all.force_forwarding=1
>   # sysctl -wq net.ipv6.conf.all.forwarding=0
>   # sysctl net.ipv6.conf.dummy1.force_forwarding
>   net.ipv6.conf.dummy1.force_forwarding = 0
>   # sysctl net.ipv6.conf.all.force_forwarding
>   net.ipv6.conf.all.force_forwarding = 1
> 
> Writing 1 to all.force_forwarding afterwards is ignored because the
> value did not change, so the interfaces are not re-enabled.
> 
> Reset all.force_forwarding too and notify netconf listeners.
> 
> Suggested-by: Ido Schimmel <idosch@nvidia.com>
> Signed-off-by: Gabriel Goller <g.goller@proxmox.com>

There is the same effect if an interface entry is reset:

$ sysctl -wq net.ipv6.conf.all.force_forwarding=1
$ sysctl net.ipv6.conf.ntfp1.force_forwarding net.ipv6.conf.all.force_forwarding
net.ipv6.conf.ntfp1.force_forwarding = 1
net.ipv6.conf.all.force_forwarding = 1
$ sysctl -wq net.ipv6.conf.ntfp1.force_forwarding=0
$ sysctl net.ipv6.conf.ntfp1.force_forwarding net.ipv6.conf.all.force_forwarding
net.ipv6.conf.ntfp1.force_forwarding = 0
net.ipv6.conf.all.force_forwarding = 1
$ sysctl -wq net.ipv6.conf.all.force_forwarding=1
$ sysctl net.ipv6.conf.ntfp1.force_forwarding net.ipv6.conf.all.force_forwarding
net.ipv6.conf.ntfp1.force_forwarding = 0
net.ipv6.conf.all.force_forwarding = 1

Maybe the new value should be applied whatever the old value was for the 'all'
entry (like for net.ipv6.conf.all.forwarding).

Note that, it is the same for ipv4 forwarding:

$ sysctl -wq net.ipv4.conf.all.forwarding=1
$ sysctl net.ipv4.conf.all.forwarding net.ipv4.conf.ntfp1.forwarding
net.ipv4.conf.all.forwarding = 1
net.ipv4.conf.ntfp1.forwarding = 1
$ sysctl -wq net.ipv4.conf.ntfp1.forwarding=0
$ sysctl net.ipv4.conf.all.forwarding net.ipv4.conf.ntfp1.forwarding
net.ipv4.conf.all.forwarding = 1
net.ipv4.conf.ntfp1.forwarding = 0
$ sysctl -wq net.ipv4.conf.all.forwarding=1
$ sysctl net.ipv4.conf.all.forwarding net.ipv4.conf.ntfp1.forwarding
net.ipv4.conf.all.forwarding = 1
net.ipv4.conf.ntfp1.forwarding = 0

but not for ipv6 forwarding:
$ sysctl -wq net.ipv6.conf.all.forwarding=1
$ sysctl net.ipv6.conf.all.forwarding net.ipv6.conf.ntfp1.forwarding
net.ipv6.conf.all.forwarding = 1
net.ipv6.conf.ntfp1.forwarding = 1
$ sysctl -wq net.ipv6.conf.ntfp1.forwarding=0
$ sysctl net.ipv6.conf.all.forwarding net.ipv6.conf.ntfp1.forwarding
net.ipv6.conf.all.forwarding = 1
net.ipv6.conf.ntfp1.forwarding = 0
$ sysctl -wq net.ipv6.conf.all.forwarding=1
$ sysctl net.ipv6.conf.all.forwarding net.ipv6.conf.ntfp1.forwarding
net.ipv6.conf.all.forwarding = 1
net.ipv6.conf.ntfp1.forwarding = 1