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From: Jakub Sitnicki <jakub@cloudflare.com>
To: John Fastabend <john.fastabend@gmail.com>
Cc: bpf@vger.kernel.org, Martin KaFai Lau <kafai@fb.com>,
	netdev@vger.kernel.org, kernel-team@cloudflare.com
Subject: Re: [RFC bpf-next 0/5] Extend SOCKMAP to store listening sockets
Date: Fri, 25 Oct 2019 11:26:51 +0200	[thread overview]
Message-ID: <87lft9ch0k.fsf@cloudflare.com> (raw)
In-Reply-To: <5db1d7a810bdb_5c282ada047205c08f@john-XPS-13-9370.notmuch>

On Thu, Oct 24, 2019 at 06:56 PM CEST, John Fastabend wrote:
> Jakub Sitnicki wrote:

[...]

>> I'm looking for feedback if there's anything fundamentally wrong with
>> extending SOCKMAP map type like this that I might have missed.
>
> I think this looks good. The main reason I blocked it off before is mostly
> because I had no use-case for it and the complication with what to do with
> child sockets. Clearing the psock state seems OK to me if user wants to
> add it back to a map they can simply grab it again from a sockops
> event.

Thanks for taking a look at the code.

> By the way I would eventually like to see the lookup hook return the
> correct type (PTR_TO_SOCKET_OR_NULL) so that the verifier "knows" the type
> and the socket can be used the same as if it was pulled from a sk_lookup
> helper.

Wait... you had me scratching my head there for a minute.

I haven't whitelisted bpf_map_lookup_elem for SOCKMAP in
check_map_func_compatibility so verifier won't allow lookups from BPF.

If we wanted to do that, I don't actually have a use-case for it, I
think would have to extend get_func_proto for SK_SKB and SK_REUSEPORT
prog types. At least that's what docs for bpf_map_lookup_elem suggest:

/* If kernel subsystem is allowing eBPF programs to call this function,
 * inside its own verifier_ops->get_func_proto() callback it should return
 * bpf_map_lookup_elem_proto, so that verifier can properly check the arguments
 *
 * Different map implementations will rely on rcu in map methods
 * lookup/update/delete, therefore eBPF programs must run under rcu lock
 * if program is allowed to access maps, so check rcu_read_lock_held in
 * all three functions.
 */
BPF_CALL_2(bpf_map_lookup_elem, struct bpf_map *, map, void *, key)
{
	WARN_ON_ONCE(!rcu_read_lock_held());
	return (unsigned long) map->ops->map_lookup_elem(map, key);
}

-Jakub

  reply	other threads:[~2019-10-25  9:26 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-22 11:37 Jakub Sitnicki
2019-10-22 11:37 ` [RFC bpf-next 1/5] bpf, sockmap: Let BPF helpers use lookup operation on SOCKMAP Jakub Sitnicki
2019-10-24 16:59   ` John Fastabend
2019-10-22 11:37 ` [RFC bpf-next 2/5] bpf, sockmap: Allow inserting listening TCP sockets into SOCKMAP Jakub Sitnicki
2019-10-24 17:06   ` John Fastabend
2019-10-25  9:41     ` Jakub Sitnicki
2019-10-22 11:37 ` [RFC bpf-next 3/5] bpf, sockmap: Don't let child socket inherit psock or its ops on copy Jakub Sitnicki
2019-10-22 11:37 ` [RFC bpf-next 4/5] bpf: Allow selecting reuseport socket from a SOCKMAP Jakub Sitnicki
2019-10-22 11:37 ` [RFC bpf-next 5/5] selftests/bpf: Extend SK_REUSEPORT tests to cover SOCKMAP Jakub Sitnicki
2019-10-24 16:12 ` [RFC bpf-next 0/5] Extend SOCKMAP to store listening sockets Alexei Starovoitov
2019-10-24 16:56 ` John Fastabend
2019-10-25  9:26   ` Jakub Sitnicki [this message]
2019-10-25 14:18     ` John Fastabend
2019-10-28  5:52 ` Martin Lau
2019-10-28 12:35   ` Jakub Sitnicki
2019-10-28 19:04     ` John Fastabend
2019-10-29  8:56       ` Jakub Sitnicki
2019-10-28 20:42     ` Martin Lau
2019-10-28 21:05       ` John Fastabend
2019-10-28 21:38         ` Martin Lau
2019-10-29  8:52           ` Jakub Sitnicki

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