Re: [PATCH bpf] samples/bpf: Fix the error return code of xdp_redirect's main()

[wanghai (M)]

在 2021/7/2 18:29, Jesper Dangaard Brouer 写道:
> On 16/06/2021 06.25, Wang Hai wrote:
> > Fix to return a negative error code from the error handling
> > case instead of 0, as done elsewhere in this function.
>
> The main() function in C should never return a negative value on Unix 
> POSIX systems.
>
>
> There is a good explaination in exit(3p): `man 3p exit`
>
>    The  value  of  status may be 0, EXIT_SUCCESS, EXIT_FAILURE, or any 
> other value, though only the least significant 8 bits (that is, status 
> & 0377) shall be available to a waiting parent process.
>
> Thus, negative values are often seen as 255 in the $? program exit 
> status variable $?.
>
>
> Also explained in exit(3):
>
>     The C standard specifies two constants, EXIT_SUCCESS=0 and 
> EXIT_FAILURE=1.
>
> I see the 'samples/bpf/xdp_redirect_user.c' in most places just use 0 
> or 1.
Got it, thanks for the explanation, I will fix it to return 1, just like 
the other error paths in samples/bpf/xdp_redirect_user.c
> > If bpf_map_update_elem() failed, main() should return a negative error.
> >
> > Fixes: 832622e6bd18 ("xdp: sample program for new bpf_redirect helper")
> > Signed-off-by: Wang Hai <wanghai38@xxxxxxxxxx>
> > ---
> >   samples/bpf/xdp_redirect_user.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/samples/bpf/xdp_redirect_user.c 
> > b/samples/bpf/xdp_redirect_user.c
> > index 41d705c3a1f7..c903f1ccc15e 100644
> > --- a/samples/bpf/xdp_redirect_user.c
> > +++ b/samples/bpf/xdp_redirect_user.c
> > @@ -213,5 +213,5 @@ int main(int argc, char **argv)
> >       poll_stats(2, ifindex_out);
> >     out:
> > -    return 0;
> > +    return ret;
> >   }
>
>
> (Sorry, I didn't complain it time as I see this patch is already applied)
>
> .