netdev - Re: [PATCH net-next 05/10] net: ipv4: Emit notification when fib hardware flags are changed

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Date:   Sat, 30 Jan 2021 17:36:51 +0200
From:   Ido Schimmel <idosch@...sch.org>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     David Ahern <dsahern@...il.com>, netdev@...r.kernel.org,
        davem@...emloft.net, amcohen@...dia.com, roopa@...dia.com,
        sharpd@...dia.com, bpoirier@...dia.com, mlxsw@...dia.com,
        Ido Schimmel <idosch@...dia.com>
Subject: Re: [PATCH net-next 05/10] net: ipv4: Emit notification when fib
 hardware flags are changed

On Thu, Jan 28, 2021 at 08:15:45PM -0800, Jakub Kicinski wrote:
> My impression from working on this problem in TC is that the definition
> of "all" becomes problematic especially if one takes into account
> drivers getting reloaded. But I think routing offload has stronger
> semantics than TC, so no objections.

During the teardown phase of the reload, all the routes using the
driver's netdevs (or their uppers) will be deleted by the kernel because
the netdevs will disappear. During the init phase of the reload, the
driver will re-register its FIB notifier and ask for a dump of all the
existing routes (usually only host routes). With this patchset, user
space will receive a notification that these routes are now in hardware.

# ip monitor route
broadcast 127.255.255.255 dev lo table local proto kernel scope link src 127.0.0.1 
local 127.0.0.1 dev lo table local proto kernel scope host src 127.0.0.1 
local 127.0.0.0/8 dev lo table local proto kernel scope host src 127.0.0.1 
broadcast 127.0.0.0 dev lo table local proto kernel scope link src 127.0.0.1 
broadcast 10.209.1.255 dev eth0 table local proto kernel scope link src 10.209.0.191 
local 10.209.0.191 dev eth0 table local proto kernel scope host src 10.209.0.191 
broadcast 10.209.0.0 dev eth0 table local proto kernel scope link src 10.209.0.191 
10.209.0.1 dev eth0 proto dhcp scope link src 10.209.0.191 metric 1024 
10.209.0.0/23 dev eth0 proto kernel scope link src 10.209.0.191 
default via 10.209.0.1 dev eth0 proto dhcp src 10.209.0.191 metric 1024 
<< init phase starts here >>
default via 10.209.0.1 dev eth0 proto dhcp src 10.209.0.191 metric 1024 rt_trap 
10.209.0.0/23 dev eth0 proto kernel scope link src 10.209.0.191 rt_trap 
10.209.0.1 dev eth0 proto dhcp scope link src 10.209.0.191 metric 1024 rt_trap 
broadcast 10.209.0.0 dev eth0 table local proto kernel scope link src 10.209.0.191 rt_trap 
local 10.209.0.191 dev eth0 table local proto kernel scope host src 10.209.0.191 rt_trap 
broadcast 10.209.1.255 dev eth0 table local proto kernel scope link src 10.209.0.191 rt_trap 
broadcast 127.0.0.0 dev lo table local proto kernel scope link src 127.0.0.1 rt_trap 
local 127.0.0.0/8 dev lo table local proto kernel scope host src 127.0.0.1 rt_trap 
local 127.0.0.1 dev lo table local proto kernel scope host src 127.0.0.1 rt_trap 
broadcast 127.255.255.255 dev lo table local proto kernel scope link src 127.0.0.1 rt_trap