linux-kernel - Re: [PATCH v1 bpf-next 09/11] bpf: Support bpf_get_socket_cookie_sock() for BPF_PROG_TYPE_SK

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Date:   Sun, 6 Dec 2020 13:36:01 +0900
From:   Kuniyuki Iwashima <kuniyu@...zon.co.jp>
To:     <kuniyu@...zon.co.jp>
CC:     <kuni1840@...il.com>, <netdev@...r.kernel.org>,
        <bpf@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 bpf-next 09/11] bpf: Support bpf_get_socket_cookie_sock() for BPF_PROG_TYPE_SK_REUSEPORT.

I'm sending this mail just for logging because I failed to send mails only 
to LKML, netdev, and bpf yesterday.


From:   Martin KaFai Lau <kafai@...com>
Date:   Fri, 4 Dec 2020 11:58:07 -0800
> On Tue, Dec 01, 2020 at 11:44:16PM +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 makes the sk pointer available in sk_reuseport_md so that we can
> > get the ID by BPF_FUNC_get_socket_cookie() in the eBPF program.
> > 
> > Link: https://lore.kernel.org/netdev/20201119001154.kapwihc2plp4f7zc@kafai-mbp.dhcp.thefacebook.com/
> > Suggested-by: Martin KaFai Lau <kafai@...com>
> > Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.co.jp>
> > ---
> >  include/uapi/linux/bpf.h       |  8 ++++++++
> >  net/core/filter.c              | 12 +++++++++++-
> >  tools/include/uapi/linux/bpf.h |  8 ++++++++
> >  3 files changed, 27 insertions(+), 1 deletion(-)
> > 
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index efe342bf3dbc..3e9b8bd42b4e 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -1650,6 +1650,13 @@ union bpf_attr {
> >   * 		A 8-byte long non-decreasing number on success, or 0 if the
> >   * 		socket field is missing inside *skb*.
> >   *
> > + * u64 bpf_get_socket_cookie(struct bpf_sock *sk)
> > + * 	Description
> > + * 		Equivalent to bpf_get_socket_cookie() helper that accepts
> > + * 		*skb*, but gets socket from **struct bpf_sock** context.
> > + * 	Return
> > + * 		A 8-byte long non-decreasing number.
> > + *
> >   * u64 bpf_get_socket_cookie(struct bpf_sock_addr *ctx)
> >   * 	Description
> >   * 		Equivalent to bpf_get_socket_cookie() helper that accepts
> > @@ -4420,6 +4427,7 @@ struct sk_reuseport_md {
> >  	__u32 bind_inany;	/* Is sock bound to an INANY address? */
> >  	__u32 hash;		/* A hash of the packet 4 tuples */
> >  	__u8 migration;		/* Migration type */
> > +	__bpf_md_ptr(struct bpf_sock *, sk); /* current listening socket */
> >  };
> >  
> >  #define BPF_TAG_SIZE	8
> > diff --git a/net/core/filter.c b/net/core/filter.c
> > index 0a0634787bb4..1059d31847ef 100644
> > --- a/net/core/filter.c
> > +++ b/net/core/filter.c
> > @@ -4628,7 +4628,7 @@ static const struct bpf_func_proto bpf_get_socket_cookie_sock_proto = {
> >  	.func		= bpf_get_socket_cookie_sock,
> >  	.gpl_only	= false,
> >  	.ret_type	= RET_INTEGER,
> > -	.arg1_type	= ARG_PTR_TO_CTX,
> > +	.arg1_type	= ARG_PTR_TO_SOCKET,
> This will break existing bpf prog (BPF_PROG_TYPE_CGROUP_SOCK)
> using this proto.  A new proto is needed and there is
> an on-going patch doing this [0].
> 
> [0]: https://lore.kernel.org/bpf/20201203213330.1657666-1-revest@google.com/

Thank you for notifying me of this patch!
I will define another proto, but may drop the part if the above patch is
already merged then.