Re: [PATCH net-next 3/3] ipv4: Initialise ->flowi4_scope properly in ICMP handlers.

[David Ahern <dsahern@kernel.org>]

On 4/20/22 5:21 PM, Guillaume Nault wrote:
> All the *_redirect() and *_update_pmtu() functions initialise their
> struct flowi4 variable with either __build_flow_key() or
> build_sk_flow_key(). When sk is provided, these functions use
> RT_CONN_FLAGS() to set ->flowi4_tos and always use RT_SCOPE_UNIVERSE
> for ->flowi4_scope. Then they rely on ip_rt_fix_tos() to adjust the
> scope based on the RTO_ONLINK bit and to mask the tos with
> IPTOS_RT_MASK.
> 
> This patch modifies __build_flow_key() and build_sk_flow_key() to
> properly initialise ->flowi4_tos and ->flowi4_scope, so that the
> ICMP redirects and PMTU handlers don't need an extra call to
> ip_rt_fix_tos() before doing a fib lookup. That is, we:
> 
>   * Drop RT_CONN_FLAGS(): use ip_sock_rt_tos() and ip_sock_rt_scope()
>     instead, so that we don't have to rely on ip_rt_fix_tos() to adjust
>     the scope anymore.
> 
>   * Apply IPTOS_RT_MASK to the tos, so that we don't need
>     ip_rt_fix_tos() to do it for us.
> 
>   * Drop the ip_rt_fix_tos() calls that now become useless.
> 
> The only remaining ip_rt_fix_tos() caller is ip_route_output_key_hash()
> which needs it as long as external callers still use the RTO_ONLINK
> flag.
> 
> Note:
>   This patch also drops some useless RT_TOS() calls as IPTOS_RT_MASK is
>   a stronger mask.
> 
> Signed-off-by: Guillaume Nault <gnault@redhat.com>
> ---
>  net/ipv4/route.c | 37 +++++++++++++++++--------------------
>  1 file changed, 17 insertions(+), 20 deletions(-)
> 

Reviewed-by: David Ahern <dsahern@kernel.org>