linux-kernel - Re: [RFC PATCH bpf-next 6/8] bpf: Add cookie in sk_reuseport

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Date:   Fri, 20 Nov 2020 07:10:39 +0900
From:   Kuniyuki Iwashima <kuniyu@...zon.co.jp>
To:     <kafai@...com>
CC:     <ast@...nel.org>, <benh@...zon.com>, <bpf@...r.kernel.org>,
        <daniel@...earbox.net>, <davem@...emloft.net>,
        <edumazet@...gle.com>, <kuba@...nel.org>, <kuni1840@...il.com>,
        <kuniyu@...zon.co.jp>, <linux-kernel@...r.kernel.org>,
        <netdev@...r.kernel.org>
Subject: Re: [RFC PATCH bpf-next 6/8] bpf: Add cookie in sk_reuseport_md.

From:   Martin KaFai Lau <kafai@...com>
Date:   Wed, 18 Nov 2020 16:11:54 -0800
> On Tue, Nov 17, 2020 at 06:40:21PM +0900, Kuniyuki Iwashima wrote:
> > We will call sock_reuseport.prog for socket migration in the next commit,
> > so the eBPF program has to know which listener is closing in order to
> > select the new listener.
> > 
> > Currently, we can get a unique ID for each listener in the userspace by
> > calling bpf_map_lookup_elem() for BPF_MAP_TYPE_REUSEPORT_SOCKARRAY map.
> > This patch exposes the ID to the eBPF program.
> > 
> > Reviewed-by: Benjamin Herrenschmidt <benh@...zon.com>
> > Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.co.jp>
> > ---
> >  include/linux/bpf.h            | 1 +
> >  include/uapi/linux/bpf.h       | 1 +
> >  net/core/filter.c              | 8 ++++++++
> >  tools/include/uapi/linux/bpf.h | 1 +
> >  4 files changed, 11 insertions(+)
> > 
> > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > index 581b2a2e78eb..c0646eceffa2 100644
> > --- a/include/linux/bpf.h
> > +++ b/include/linux/bpf.h
> > @@ -1897,6 +1897,7 @@ struct sk_reuseport_kern {
> >  	u32 hash;
> >  	u32 reuseport_id;
> >  	bool bind_inany;
> > +	u64 cookie;
> >  };
> >  bool bpf_tcp_sock_is_valid_access(int off, int size, enum bpf_access_type type,
> >  				  struct bpf_insn_access_aux *info);
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index 162999b12790..3fcddb032838 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -4403,6 +4403,7 @@ struct sk_reuseport_md {
> >  	__u32 ip_protocol;	/* IP protocol. e.g. IPPROTO_TCP, IPPROTO_UDP */
> >  	__u32 bind_inany;	/* Is sock bound to an INANY address? */
> >  	__u32 hash;		/* A hash of the packet 4 tuples */
> > +	__u64 cookie;		/* ID of the listener in map */
> Instead of only adding the cookie of a sk, lets make the sk pointer available:
> 
> 	__bpf_md_ptr(struct bpf_sock *, sk);
> 
> and then use the BPF_FUNC_get_socket_cookie to get the cookie.
> 
> Other fields of the sk can also be directly accessed too once
> the sk pointer is available.

Oh, I did not know BPF_FUNC_get_socket_cookie.
I will add the sk pointer and use the helper function in the next spin!
Thank you.