Re: [PATCH 4.14] tcp/udp: Make early_demux back namespacified.

[Greg KH <greg@kroah.com>]

On Thu, Nov 03, 2022 at 04:50:33PM -0700, Kuniyuki Iwashima wrote:
> commit 11052589cf5c0bab3b4884d423d5f60c38fcf25d upstream
> 
> Commit e21145a9871a ("ipv4: namespacify ip_early_demux sysctl knob") made
> it possible to enable/disable early_demux on a per-netns basis.  Then, we
> introduced two knobs, tcp_early_demux and udp_early_demux, to switch it for
> TCP/UDP in commit dddb64bcb346 ("net: Add sysctl to toggle early demux for
> tcp and udp").  However, the .proc_handler() was wrong and actually
> disabled us from changing the behaviour in each netns.
> 
> We can execute early_demux if net.ipv4.ip_early_demux is on and each proto
> .early_demux() handler is not NULL.  When we toggle (tcp|udp)_early_demux,
> the change itself is saved in each netns variable, but the .early_demux()
> handler is a global variable, so the handler is switched based on the
> init_net's sysctl variable.  Thus, netns (tcp|udp)_early_demux knobs have
> nothing to do with the logic.  Whether we CAN execute proto .early_demux()
> is always decided by init_net's sysctl knob, and whether we DO it or not is
> by each netns ip_early_demux knob.
> 
> This patch namespacifies (tcp|udp)_early_demux again.  For now, the users
> of the .early_demux() handler are TCP and UDP only, and they are called
> directly to avoid retpoline.  So, we can remove the .early_demux() handler
> from inet6?_protos and need not dereference them in ip6?_rcv_finish_core().
> If another proto needs .early_demux(), we can restore it at that time.
> 
> Fixes: dddb64bcb346 ("net: Add sysctl to toggle early demux for tcp and udp")
> Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
> Link: https://lore.kernel.org/r/20220713175207.7727-1-kuniyu@amazon.com
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>

All now queued up, thanks.

greg k-h