netdev - Re: [PATCH v2 net-next] ipv6: Convert gateway validation to use fib6

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Date:   Thu, 27 Jun 2019 11:11:32 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     dsahern@...nel.org
Cc:     netdev@...r.kernel.org, kafai@...com, weiwan@...gle.com,
        dsahern@...il.com
Subject: Re: [PATCH v2 net-next] ipv6: Convert gateway validation to use
 fib6_info

From: David Ahern <dsahern@...nel.org>
Date: Mon, 24 Jun 2019 13:44:51 -0700

> From: David Ahern <dsahern@...il.com>
> 
> Gateway validation does not need a dst_entry, it only needs the fib
> entry to validate the gateway resolution and egress device. So,
> convert ip6_nh_lookup_table from ip6_pol_route to fib6_table_lookup
> and ip6_route_check_nh to use fib6_lookup over rt6_lookup.
> 
> ip6_pol_route is a call to fib6_table_lookup and if successful a call
> to fib6_select_path. From there the exception cache is searched for an
> entry or a dst_entry is created to return to the caller. The exception
> entry is not relevant for gateway validation, so what matters are the
> calls to fib6_table_lookup and then fib6_select_path.
> 
> Similarly, rt6_lookup can be replaced with a call to fib6_lookup with
> RT6_LOOKUP_F_IFACE set in flags. Again, the exception cache search is
> not relevant, only the lookup with path selection. The primary difference
> in the lookup paths is the use of rt6_select with fib6_lookup versus
> rt6_device_match with rt6_lookup. When you remove complexities in the
> rt6_select path, e.g.,
> 1. saddr is not set for gateway validation, so RT6_LOOKUP_F_HAS_SADDR
>    is not relevant
> 2. rt6_check_neigh is not called so that removes the RT6_NUD_FAIL_DO_RR
>    return and round-robin logic.
> 
> the code paths are believed to be equivalent for the given use case -
> validate the gateway and optionally given the device. Furthermore, it
> aligns the validation with onlink code path and the lookup path actually
> used for rx and tx.
> 
> Adjust the users, ip6_route_check_nh_onlink and ip6_route_check_nh to
> handle a fib6_info vs a rt6_info when performing validation checks.
> 
> Existing selftests fib-onlink-tests.sh and fib_tests.sh are used to
> verify the changes.
> 
> Signed-off-by: David Ahern <dsahern@...il.com>
> ---
> v2
> - use in6_dev_get versus __in6_dev_get + in6_dev_hold (comment from Wei)
> - updated commit message

Applied, thanks.