netdev - Re: [v3,2/4] tools: bpftool: add net detach command to detach XDP on interface

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Date:   Wed, 7 Aug 2019 20:30:41 +0200
From:   Maciej Fijalkowski <maciejromanfijalkowski@...il.com>
To:     Y Song <ys114321@...il.com>
Cc:     "Daniel T. Lee" <danieltimlee@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        netdev <netdev@...r.kernel.org>
Subject: Re: [v3,2/4] tools: bpftool: add net detach command to detach XDP
 on interface

On Wed, 7 Aug 2019 10:02:04 -0700
Y Song <ys114321@...il.com> wrote:

> On Tue, Aug 6, 2019 at 7:25 PM Daniel T. Lee <danieltimlee@...il.com> wrote:
> >
> > By this commit, using `bpftool net detach`, the attached XDP prog can
> > be detached. Detaching the BPF prog will be done through libbpf
> > 'bpf_set_link_xdp_fd' with the progfd set to -1.
> >
> > Signed-off-by: Daniel T. Lee <danieltimlee@...il.com>
> > ---
> >  tools/bpf/bpftool/net.c | 42 ++++++++++++++++++++++++++++++++++++++++-
> >  1 file changed, 41 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/bpf/bpftool/net.c b/tools/bpf/bpftool/net.c
> > index c05a3fac5cac..7be96acb08e0 100644
> > --- a/tools/bpf/bpftool/net.c
> > +++ b/tools/bpf/bpftool/net.c
> > @@ -343,6 +343,43 @@ static int do_attach(int argc, char **argv)
> >         return 0;
> >  }
> >
> > +static int do_detach(int argc, char **argv)
> > +{
> > +       enum net_attach_type attach_type;
> > +       int progfd, ifindex, err = 0;
> > +
> > +       /* parse detach args */
> > +       if (!REQ_ARGS(3))
> > +               return -EINVAL;
> > +
> > +       attach_type = parse_attach_type(*argv);
> > +       if (attach_type == max_net_attach_type) {
> > +               p_err("invalid net attach/detach type");
> > +               return -EINVAL;
> > +       }
> > +
> > +       NEXT_ARG();
> > +       ifindex = net_parse_dev(&argc, &argv);
> > +       if (ifindex < 1)
> > +               return -EINVAL;
> > +
> > +       /* detach xdp prog */
> > +       progfd = -1;
> > +       if (is_prefix("xdp", attach_type_strings[attach_type]))
> > +               err = do_attach_detach_xdp(progfd, attach_type, ifindex, NULL);  
> 
> I found an issue here. This is probably related to do_attach_detach_xdp.
> 
> -bash-4.4$ sudo ./bpftool net attach x pinned /sys/fs/bpf/xdp_example dev v1
> -bash-4.4$ sudo ./bpftool net
> xdp:
> v1(4) driver id 1172
> 
> tc:
> eth0(2) clsact/ingress fbflow_icmp id 29 act []
> eth0(2) clsact/egress cls_fg_dscp_section id 27 act []
> eth0(2) clsact/egress fbflow_egress id 28
> eth0(2) clsact/egress fbflow_sslwall_egress id 35
> 
> flow_dissector:
> 
> -bash-4.4$ sudo ./bpftool net detach x dev v2

Shouldn't this be v1 as dev?

> -bash-4.4$ sudo ./bpftool net
> xdp:
> v1(4) driver id 1172
> 
> tc:
> eth0(2) clsact/ingress fbflow_icmp id 29 act []
> eth0(2) clsact/egress cls_fg_dscp_section id 27 act []
> eth0(2) clsact/egress fbflow_egress id 28
> eth0(2) clsact/egress fbflow_sslwall_egress id 35
> 
> flow_dissector:
> 
> -bash-4.4$
> 
> Basically detaching may fail due to wrong dev name or wrong type, etc.
> But the tool did not return an error. Is this expected?
> This may be related to this funciton "bpf_set_link_xdp_fd()".
> So this patch itself should be okay.
> 
> > +
> > +       if (err < 0) {
> > +               p_err("interface %s detach failed",
> > +                     attach_type_strings[attach_type]);
> > +               return err;
> > +       }
> > +
> > +       if (json_output)
> > +               jsonw_null(json_wtr);
> > +
> > +       return 0;
> > +}
> > +
> >  static int do_show(int argc, char **argv)
> >  {
> >         struct bpf_attach_info attach_info = {};
> > @@ -419,6 +456,7 @@ static int do_help(int argc, char **argv)
> >         fprintf(stderr,
> >                 "Usage: %s %s { show | list } [dev <devname>]\n"
> >                 "       %s %s attach ATTACH_TYPE PROG dev <devname> [ overwrite ]\n"
> > +               "       %s %s detach ATTACH_TYPE dev <devname>\n"
> >                 "       %s %s help\n"
> >                 "\n"
> >                 "       " HELP_SPEC_PROGRAM "\n"
> > @@ -429,7 +467,8 @@ static int do_help(int argc, char **argv)
> >                 "      to dump program attachments. For program types\n"
> >                 "      sk_{filter,skb,msg,reuseport} and lwt/seg6, please\n"
> >                 "      consult iproute2.\n",
> > -               bin_name, argv[-2], bin_name, argv[-2], bin_name, argv[-2]);
> > +               bin_name, argv[-2], bin_name, argv[-2], bin_name, argv[-2],
> > +               bin_name, argv[-2]);
> >
> >         return 0;
> >  }
> > @@ -438,6 +477,7 @@ static const struct cmd cmds[] = {
> >         { "show",       do_show },
> >         { "list",       do_show },
> >         { "attach",     do_attach },
> > +       { "detach",     do_detach },
> >         { "help",       do_help },
> >         { 0 }
> >  };
> > --
> > 2.20.1
> >