netdev - Re: [PATCH bpf-next 1/2] libbpf: separate XDP program load with xsk socket creation

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Message-ID: <CADm5B_NEt14sqhi6V_cx48sOViweYi_GXO8GgrvpXJjYSueg3w@mail.gmail.com>
Date:   Thu, 5 Nov 2020 14:58:27 +0100
From:   Mariusz Dudek <mariusz.dudek@...il.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     Magnus Karlsson <magnus.karlsson@...el.com>,
        Björn Töpel <bjorn.topel@...el.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Networking <netdev@...r.kernel.org>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        bpf <bpf@...r.kernel.org>,
        Mariusz Dudek <mariuszx.dudek@...el.com>
Subject: Re: [PATCH bpf-next 1/2] libbpf: separate XDP program load with xsk
 socket creation

On Wed, Nov 4, 2020 at 10:07 PM Andrii Nakryiko
<andrii.nakryiko@...il.com> wrote:
>
> On Wed, Nov 4, 2020 at 1:47 AM <mariusz.dudek@...il.com> wrote:
> >
> > From: Mariusz Dudek <mariuszx.dudek@...el.com>
> >
> >         Add support for separation of eBPF program load and xsk socket
> >         creation.
> >
> >         This is needed for use-case when you want to privide as little
> >         privileges as possible to the data plane application that will
> >         handle xsk socket creation and incoming traffic.
> >
> >         With this patch the data entity container can be run with only
> >         CAP_NET_RAW capability to fulfill its purpose of creating xsk
> >         socket and handling packages. In case your umem is larger or
> >         equal process limit for MEMLOCK you need either increase the
> >         limit or CAP_IPC_LOCK capability.
> >
> >         To resolve privileges issue two APIs are introduced:
> >
> >         - xsk_setup_xdp_prog - prepares bpf program if given and
> >         loads it on a selected network interface or loads the built in
> >         XDP program, if no XDP program is supplied. It can also return
> >         xsks_map_fd which is needed by unprivileged process to update
> >         xsks_map with AF_XDP socket "fd"
> >
> >         - xsk_update_xskmap - inserts an AF_XDP socket into an xskmap
> >         for a particular xsk_socket
> >
>
> Your commit message seems to be heavily shifted right...
>
Will be fixed
>
> > Signed-off-by: Mariusz Dudek <mariuszx.dudek@...el.com>
> > ---
> >  tools/lib/bpf/libbpf.map |   2 +
> >  tools/lib/bpf/xsk.c      | 157 ++++++++++++++++++++++++++++++++-------
> >  tools/lib/bpf/xsk.h      |  13 ++++
> >  3 files changed, 146 insertions(+), 26 deletions(-)
> >
>
> [...]
>
> > diff --git a/tools/lib/bpf/xsk.h b/tools/lib/bpf/xsk.h
> > index 1069c46364ff..c42b91935d3c 100644
> > --- a/tools/lib/bpf/xsk.h
> > +++ b/tools/lib/bpf/xsk.h
> > @@ -201,6 +201,19 @@ struct xsk_umem_config {
> >         __u32 flags;
> >  };
> >
> > +struct bpf_prog_cfg {
> > +       struct bpf_insn *prog;
> > +       const char *license;
> > +       size_t insns_cnt;
> > +       int xsks_map_fd;
> > +};
>
> This config will have problems with backward/forward compatibility.
> Please check how xxx_opts are done and use them for extensible options
> structs.
>
I will add struct size as first parameter and #define for __last_field
to be inline with xxx_opts
>
> > +
> > +LIBBPF_API int xsk_setup_xdp_prog(int ifindex,
> > +                                 struct bpf_prog_cfg *cfg,
> > +                                 int *xsks_map_fd);
> > +LIBBPF_API int xsk_update_xskmap(struct xsk_socket *xsk,
> > +                                int xsks_map_fd);
>
> this should be called xsk_socket__update_map? BTW, what's xskmap? Is
> that a special BPF map type?
>
I will change the API name as you suggested. XSKMAP is a special
BPF_MAP_TYPE_XSKMAP.
It defines how packets are being distributed from an XDP program to the XSKs.
> > +
> >  /* Flags for the libbpf_flags field. */
> >  #define XSK_LIBBPF_FLAGS__INHIBIT_PROG_LOAD (1 << 0)
> >
> > --
> > 2.20.1
> >