Re: [PATCH] passt-repair: Don't use perror(), accept ECONNRESET as termination

[Stefano Brivio <sbrivio@redhat.com>]

On Fri, 7 Feb 2025 13:38:10 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> On Fri, Feb 07, 2025 at 02:29:23AM +0100, Stefano Brivio wrote:
> > On Fri, 7 Feb 2025 12:15:35 +1100
> > David Gibson <david@gibson.dropbear.id.au> wrote:
> >   
> > > On Fri, Feb 07, 2025 at 01:54:39AM +0100, Stefano Brivio wrote:  
> > > > If we use glibc's perror(), we need to allow dup() and fcntl() in our
> > > > seccomp profiles, which are a bit too much for this simple helper. On
> > > > top of that, we would probably need a wrapper to avoid allocation for
> > > > translated messages.
> > > > 
> > > > While at it: ECONNRESET is just a close() from passt, treat it like
> > > > EOF.
> > > > 
> > > > Signed-off-by: Stefano Brivio <sbrivio@redhat.com>    
> > > 
> > > Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
> > >   
> > > > ---
> > > >  passt-repair.c | 10 +++++++---
> > > >  1 file changed, 7 insertions(+), 3 deletions(-)
> > > > 
> > > > diff --git a/passt-repair.c b/passt-repair.c
> > > > index 3c3247b..d137a18 100644
> > > > --- a/passt-repair.c
> > > > +++ b/passt-repair.c
> > > > @@ -95,7 +95,7 @@ int main(int argc, char **argv)
> > > >  	}
> > > >  
> > > >  	if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0) {
> > > > -		perror("Failed to create AF_UNIX socket");
> > > > +		fprintf(stderr, "Failed to create AF_UNIX socket:
> > > > %i\n", errno);    
> > > 
> > > We could use strerror_() here, couldn't we?  
> > 
> > We would need to link that, which is quite some code (the whole 
> > strerrordesc_np())... I mean, this runs privileged.  
> 
> Hrm, is the non-locale one really that much code though?  Shouldn't it
> be about 5 lines of code and a table of strings?  But then.. glibc is
> really good at making things complicated.

Right, and the "table of strings" is probably not great to have here.

But the lines of code I was referring to are the weak aliasing trick
(musl doesn't have strerrordesc_np(), which is not POSIX). I could
include util.h, but that means including even more code...

Really, I think numbers fit error messages printed by a privileged
component pretty well.

-- 
Stefano