netdev - Re: [iproute PATCH v2 2/3] iproute_lwtunnel: Argument to strerror must be positive

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Date:   Fri, 18 Aug 2017 13:21:27 +0200
From:   Phil Sutter <phil@....cc>
To:     David Laight <David.Laight@...LAB.COM>
Cc:     Stephen Hemminger <stephen@...workplumber.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [iproute PATCH v2 2/3] iproute_lwtunnel: Argument to strerror
 must be positive

On Fri, Aug 18, 2017 at 09:21:34AM +0000, David Laight wrote:
> From: Phil Sutter
> > Sent: 17 August 2017 18:10
> > Signed-off-by: Phil Sutter <phil@....cc>
> > ---
> >  ip/iproute_lwtunnel.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/ip/iproute_lwtunnel.c b/ip/iproute_lwtunnel.c
> > index 398ab5e077ed8..1a3dc4d4c0ed9 100644
> > --- a/ip/iproute_lwtunnel.c
> > +++ b/ip/iproute_lwtunnel.c
> > @@ -643,7 +643,7 @@ static int lwt_parse_bpf(struct rtattr *rta, size_t len,
> >  	err = bpf_parse_common(bpf_type, &cfg, &bpf_cb_ops, &x);
> >  	if (err < 0) {
> >  		fprintf(stderr, "Failed to parse eBPF program: %s\n",
> > -			strerror(err));
> > +			strerror(-err));
> 
> If we are in userspace I'd expect errno values to be +ve.
> Returning a -ve errno is very non-standard.

This is because bpf_parse() returns the number of instructions parsed or
a negative return code. We could change it to return instructions * -1
or a positive return code, but that's even more insane than calling
strerror(-err), isn't it?

Cheers, Phil