netdev - Re: [PATCHv2 bpf-next 1/5] bpf: Add socket assign support

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Message-ID: <CAOftzPjhADm7Aq2d=Hcu12RYpHSpJZEojGCT_QZoqk+o6LHHpg@mail.gmail.com>
Date:   Wed, 25 Mar 2020 23:31:23 -0700
From:   Joe Stringer <joe@...d.net.nz>
To:     Martin KaFai Lau <kafai@...com>
Cc:     Joe Stringer <joe@...d.net.nz>, bpf <bpf@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Lorenz Bauer <lmb@...udflare.com>
Subject: Re: [PATCHv2 bpf-next 1/5] bpf: Add socket assign support

On Wed, Mar 25, 2020 at 11:23 PM Martin KaFai Lau <kafai@...com> wrote:
>
> On Tue, Mar 24, 2020 at 10:57:41PM -0700, Joe Stringer wrote:
> > Add support for TPROXY via a new bpf helper, bpf_sk_assign().
> >
> > This helper requires the BPF program to discover the socket via a call
> > to bpf_sk*_lookup_*(), then pass this socket to the new helper. The
> > helper takes its own reference to the socket in addition to any existing
> > reference that may or may not currently be obtained for the duration of
> > BPF processing. For the destination socket to receive the traffic, the
> > traffic must be routed towards that socket via local route. The
> > simplest example route is below, but in practice you may want to route
> > traffic more narrowly (eg by CIDR):
> >
> >   $ ip route add local default dev lo
> >
> > This patch avoids trying to introduce an extra bit into the skb->sk, as
> > that would require more invasive changes to all code interacting with
> > the socket to ensure that the bit is handled correctly, such as all
> > error-handling cases along the path from the helper in BPF through to
> > the orphan path in the input. Instead, we opt to use the destructor
> > variable to switch on the prefetch of the socket.
> >
> > Signed-off-by: Joe Stringer <joe@...d.net.nz>
> > ---
> > v2: Use skb->destructor to determine socket prefetch usage instead of
> >       introducing a new metadata_dst
> >     Restrict socket assign to same netns as TC device
> >     Restrict assigning reuseport sockets
> >     Adjust commit wording
> > v1: Initial version
> > ---
> >  include/net/sock.h             |  7 +++++++
> >  include/uapi/linux/bpf.h       | 25 ++++++++++++++++++++++++-
> >  net/core/filter.c              | 31 +++++++++++++++++++++++++++++++
> >  net/core/sock.c                |  9 +++++++++
> >  net/ipv4/ip_input.c            |  3 ++-
> >  net/ipv6/ip6_input.c           |  3 ++-
> >  net/sched/act_bpf.c            |  2 ++
> >  tools/include/uapi/linux/bpf.h | 25 ++++++++++++++++++++++++-
> >  8 files changed, 101 insertions(+), 4 deletions(-)
> >
>
> [ ... ]
>
> > diff --git a/net/sched/act_bpf.c b/net/sched/act_bpf.c
> > index 46f47e58b3be..6c7ed8fcc909 100644
> > --- a/net/sched/act_bpf.c
> > +++ b/net/sched/act_bpf.c
> > @@ -53,6 +53,8 @@ static int tcf_bpf_act(struct sk_buff *skb, const struct tc_action *act,
> >               bpf_compute_data_pointers(skb);
> >               filter_res = BPF_PROG_RUN(filter, skb);
> >       }
> > +     if (filter_res != TC_ACT_OK)
> Should skb_sk_is_prefetched() be checked also?

Yes, thanks, will fix.