From: Daniel Borkmann <daniel@iogearbox.net>
To: "David Ahern" <dsahern@gmail.com>,
"Toke Høiland-Jørgensen" <toke@redhat.com>
Cc: David Ahern <dsahern@kernel.org>,
netdev@vger.kernel.org, bpf@vger.kernel.org
Subject: Re: [PATCH bpf v2 2/3] bpf_fib_lookup: optionally skip neighbour lookup
Date: Tue, 20 Oct 2020 17:04:44 +0200 [thread overview]
Message-ID: <9506a687-64a7-8cf4-008f-c4a10f867c01@iogearbox.net> (raw)
In-Reply-To: <20784134-7f4c-c263-5d62-facbb2adb8a8@gmail.com>
On 10/20/20 3:49 PM, David Ahern wrote:
> On 10/20/20 4:51 AM, Toke Høiland-Jørgensen wrote:
>> From: Toke Høiland-Jørgensen <toke@redhat.com>
>>
>> The bpf_fib_lookup() helper performs a neighbour lookup for the destination
>> IP and returns BPF_FIB_LKUP_NO_NEIGH if this fails, with the expectation
>> that the BPF program will deal with this condition, either by passing the
>> packet up the stack, or by using bpf_redirect_neigh().
>>
>> The neighbour lookup is done via a hash table (through ___neigh_lookup_noref()),
>> which incurs some overhead. If the caller knows this is likely to fail
>> anyway, it may want to skip that and go unconditionally to
>> bpf_redirect_neigh(). For this use case, add a flag to bpf_fib_lookup()
>> that will make it skip the neighbour lookup and instead always return
>> BPF_FIB_LKUP_RET_NO_NEIGH (but still populate the gateway and target
>> ifindex).
>>
>> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
>> ---
>> include/uapi/linux/bpf.h | 10 ++++++----
>> net/core/filter.c | 16 ++++++++++++++--
>> tools/include/uapi/linux/bpf.h | 10 ++++++----
>> 3 files changed, 26 insertions(+), 10 deletions(-)
>
> Nack. Please don't.
>
> As I mentioned in my reply to Daniel, I would prefer such logic be
> pushed to the bpf programs. There is no reason for rare run time events
> to warrant a new flag and new check in the existing FIB helpers. The bpf
> programs can take the hit of the extra lookup.
Fair enough, lets push it to progs then.
next prev parent reply other threads:[~2020-10-20 15:04 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-20 10:51 [PATCH bpf v2 0/3] bpf: Rework bpf_redirect_neigh() to allow supplying nexthop from caller Toke Høiland-Jørgensen
2020-10-20 10:51 ` [PATCH bpf v2 1/3] bpf_redirect_neigh: Support supplying the nexthop as a helper parameter Toke Høiland-Jørgensen
2020-10-20 15:08 ` Daniel Borkmann
2020-10-20 18:08 ` Toke Høiland-Jørgensen
2020-10-20 16:30 ` Jakub Kicinski
2020-10-20 18:08 ` Toke Høiland-Jørgensen
2020-10-20 19:01 ` Jakub Kicinski
2020-10-20 19:47 ` Daniel Borkmann
2020-10-20 18:12 ` David Ahern
2020-10-20 18:56 ` Jakub Kicinski
2020-10-20 16:34 ` Jakub Kicinski
2020-10-20 18:03 ` Toke Høiland-Jørgensen
2020-10-20 18:14 ` David Ahern
2020-10-20 18:50 ` Jakub Kicinski
2020-10-20 10:51 ` [PATCH bpf v2 2/3] bpf_fib_lookup: optionally skip neighbour lookup Toke Høiland-Jørgensen
2020-10-20 13:49 ` David Ahern
2020-10-20 15:04 ` Daniel Borkmann [this message]
2020-10-20 18:10 ` Toke Høiland-Jørgensen
2020-10-20 10:51 ` [PATCH bpf v2 3/3] selftests: Update test_tc_redirect.sh to use the modified bpf_redirect_neigh() Toke Høiland-Jørgensen
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