Re: rfc/patch: user-agent distro-description for debuginfod http traffic

[Mark Wielaard <mark at klomp dot org>]

Hi Frank,

On Wed, Jan 08, 2020 at 10:11:25AM -0500, Frank Ch. Eigler wrote:
> > Eep. We really should pick up this info during runtime instead of
> > during build time. 
> 
> That's what I thought at first too.  However, doing it at run time
> means doing work - a popen() etc. - over and over or saving in a
> locked global.  Since on a normal machine, the distro doesn't change
> without elfutils also changing, it's practically a literal.

We are already opening some files to scan for cached files, open a
socket, download data, etc. I don't think one or two extra syscalls
are that much overhead.

> > We do want a reproducible build. 
> 
> Can you give an example?  Bootstrapping a new distro version/arch?

Probably best explained at https://reproducible-builds.org/ most
distributions are participating.

> > And this will most likely produce wrong information if the package
> > build server is on a different OS or release than the OS/release it
> > is producing packages for. uname -sm might be "stable", but probably
> > not when cross- compiling.
> 
> I wonder if the cross-compiled debuginfod-client case is worth
> worrying about.

I think it is.

> > But where does lsb_release come from? I don't have that on my
> > systems.
> 
> BuildRequires: /usr/bin/lsb_release :-) It's a different package on
> different distros.  And running at run time would make a Require:
> rather than a one-time BuildRequire:.

It looks like the new standard (since about 8 years) is os-release:
http://man7.org/linux/man-pages/man5/os-release.5.html

It looks like an easily parsable file format.  The attached produces
some reasonable looking identification strings on a couple of my
systems out of the box:

Linux/i686 4.19.0-6-686-pae
debian/10

Linux/x86_64 3.10.0-1062.9.1.el7.x86_64
rhel/7.7

Linux/x86_64 4.19.0-5-amd64
pureos/9.0

Maybe something like that is usable?

Cheers,

Mark

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/utsname.h>

int
main ()
{
  struct utsname uts;
  if (uname (&uts) == 0)
    printf ("%s/%s %s\n", uts.sysname, uts.machine, uts.release);
  
  FILE *f;
  f = fopen ("/etc/os-release", "r");
  if (f == NULL)
    f = fopen ("/usr/lib/os-release", "r");

  char *id = NULL;
  char *version = NULL;
  if (f != NULL)
    {
      while (id == NULL || version == NULL)
	{
	  char buf[128];
	  char *s = &buf[0];
	  if (fgets (s, 128, f) == NULL)
	    break;

	  int len = strlen (s);
	  if (len < 3)
	    continue;

	  if (s[len - 1] == '\n')
	    {
	      s[len - 1] = '\0';
	      len--;
	    }
	  
	  char *v = strchr (s, '=');
	  if (v == NULL || strlen (v) < 2)
	    continue;

	  /* Split var and value. */
	  *v = '\0';
	  v++;

	  /* Remove optional quotes around value string. */
	  if (*v == '"' || *v == '\'')
	    {
	      v++;
	      s[len - 1] = '\0';
	    }
	  
	  if (strcmp (s, "ID") == 0)
	    id = strdup (v);
	  if (strcmp (s, "VERSION_ID") == 0)
	    version = strdup (v);
	}
      fclose (f);
    }

  printf ("%s/%s\n", id, version);

  free (id);
  free (version);

  return 0;
}