Re: [PATCH] samples/bpf: Fix tc and ip path in xdp2skb_meta.sh

[Taeung Song]

On 07/10/2018 04:20 AM, Jesper Dangaard Brouer wrote:
> On Tue, 10 Jul 2018 02:44:06 +0900
> Taeung Song <treeze.taeung@xxxxxxxxx> wrote:
>
> > Hi Jesper Dangaard Brouer,
> >
> > On 07/10/2018 12:40 AM, Jesper Dangaard Brouer wrote:
> > > On Tue, 10 Jul 2018 00:04:18 +0900
> > > Taeung Song <treeze.taeung@xxxxxxxxx> wrote:
> > >    
> > > > The below path error can occur:
> > > >
> > > >     # ./xdp2skb_meta.sh --dev eth0 --list
> > > >     ./xdp2skb_meta.sh: line 61: /usr/sbin/tc: No such file or directory
> > > >
> > > >     # which tc
> > > >     /sbin/tc
> > > >
> > > > So use 'which' command instead of absolute path of tc and ip
> > > >
> > > > Fixes: 36e04a2d78d9 ("samples/bpf: xdp2skb_meta shows transferring info from XDP to SKB")
> > > > Cc: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
> > > > Signed-off-by: Taeung Song <treeze.taeung@xxxxxxxxx>
> > > > ---
> > > >    samples/bpf/xdp2skb_meta.sh | 4 ++--
> > > >    1 file changed, 2 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/samples/bpf/xdp2skb_meta.sh b/samples/bpf/xdp2skb_meta.sh
> > > > index b9c9549c4c27..67cf7b5f336d 100755
> > > > --- a/samples/bpf/xdp2skb_meta.sh
> > > > +++ b/samples/bpf/xdp2skb_meta.sh
> > > > @@ -16,8 +16,8 @@
> > > >    BPF_FILE=xdp2skb_meta_kern.o
> > > >    DIR=$(dirname $0)
> > > >    
> > > > -export TC=/usr/sbin/tc
> > > > -export IP=/usr/sbin/ip
> > > > +export TC=`which tc`
> > > > +export IP=`which ip`
> > >
> > > This is not a good solution, as 'which' can return something else.
> > > E.g. on my system I've aliased 'tc' to 'sudo tc', and `which tc` returns:
> > >
> > > $ which tc
> > > alias tc='sudo tc'
> > > 	/usr/bin/sudo
> > >
> > > The easiest solution is to simply do:
> > >
> > >    export TC=tc
> > >    export IP=ip
> > >
> > > The more fancy solution is to allow callers to redefine $IP and $TC:
> > >
> > > [ -z "$TC" ] && TC=tc
> > > [ -z "$IP" ] && IP=ip
> > >    
> >
> > Yep, you are right, I'll change it.
> >
> > > And then you should also fix the use of 'basename', see below patch...
> > >    
> >
> > I thought it'd be fine to leave 'basename' as it is,
> > because if callers redefine TC=/home/taeung/tc and give
> > the options --verbose or --dry-run, 'basename' can more tidily show outputs.
>
> The 'basename' does not work correctly if e.g. TC='sudo tc'.
>
> Below output is with 'basename' removed, else it would say "sudo qdisc del ..."
>
> TC='sudo tc' IP='sudo ip' ./xdp2skb_meta.sh -v --dev mlx5p1 --dry-run
> # Device set to: DEV=mlx5p1
> # Dry-run mode: enable VERBOSE and don't call TC+IP
> sudo tc qdisc del dev mlx5p1 clsact
> sudo tc qdisc add dev mlx5p1 clsact
> sudo tc filter add dev mlx5p1 ingress prio 1 handle 1 bpf da obj ./xdp2skb_meta_kern.o sec tc_mark
> # Flush XDP on device: mlx5p1
> sudo ip link set dev mlx5p1 xdp off
> sudo ip link set dev mlx5p1 xdp obj ./xdp2skb_meta_kern.o sec xdp_mark

Oops, right. I missed the alias case.

> > But it seems to be trivial, I'll resend this patch as v2 based on your
> > comment !
>
> Thx, already ACKed it :-)

--
Thanks a lot !

Taeung