Messages in this thread Patch in this message | | | From | Jesper Dangaard Brouer <> | Subject | Re: [PATCH bpf] samples/bpf: Fix the error return code of xdp_redirect's main() | Date | Fri, 2 Jul 2021 12:29:35 +0200 |
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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.
> 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@huawei.com> > --- > 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)
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