Re: [PATCH net v4] ipv4: bump rt_genid when a relevant devconf value changes through netlink

[Jakub Kicinski <kuba@kernel.org>]

On Fri, 13 Mar 2026 16:13:20 +0100 Fernando Fernandez Mancera wrote:
> > Also, you are flushing the cache for more values than sysfs does.  
> 
> I don't think so. The problem is that the handling of sysctl is 
> scattered in several places.
> 
> IPV4_DEVCONF_FORWARDING is flushed at devinet_sysctl_forward().
> 
> IPV4_DEVCONF_NOXFRM, IPV4_DEVCONF_NOPOLICY, 
> IPV4_DEVCONF_PROMOTE_SECONDARIES, IPV4_DEVCONF_ROUTE_LOCALNET, and 
> IPV4_DEVCONF_DROP_UNICAST_IN_L2_MULTICAST are flushed at 
> ipv4_doint_and_flush() used by macro DEVINET_SYSCTL_FLUSHING_ENTRY.
> 
> Finally, IPV4_DEVCONF_BC_FORWARDING and IPV4_DEVCONF_ACCEPT_LOCAL are 
> flushed at devinet_conf_proc().
> 
> Yes, I know, the fact that they are scattered around is quite confusing. 
> This could be all unified in a single place but that would be too much 
> for net tree IMHO.
> 
> Please let me know if I am missing something.

I think David means that for some knobs procfs only flushes when value
changes "in one direct", eg

                if (i == IPV4_DEVCONF_ACCEPT_LOCAL - 1 ||                       
                    i == IPV4_DEVCONF_ROUTE_LOCALNET - 1)                       
                        if ((new_value == 0) && (old_value != 0))               
                                rt_cache_flush(net);       

which means only flush on the 1 -> 0 transition.