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From: John Fastabend <john.fastabend@gmail.com>
To: Jakub Sitnicki <jakub@cloudflare.com>,
	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 07:18:55 -0700	[thread overview]
Message-ID: <5db3044f82e10_36802aec12c585b83b@john-XPS-13-9370.notmuch> (raw)
In-Reply-To: <87lft9ch0k.fsf@cloudflare.com>

Jakub Sitnicki wrote:
> 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:

Right, so its not required for your series just letting you know I will
probably look to do this shortly. It would be useful for some use cases
we have.

> 
> /* 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 14:19 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
2019-10-25 14:18     ` John Fastabend [this message]
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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