Introducing SNMP4Nagios

[Peter Gritsch]

On Monday 30 January 2006 11:45, Andre Heine wrote:

Okay, here is what I found:

The interface did indeed change. Quote rrd.h:
 * Revision 1.7  2003/11/12 22:14:26  oetiker
 * allow to pass an open filehandle into rrd_graph as an extra
argument
/Quote



> [...]
> But I get some problems to compile it with RRDtool 1.2.11.
>
> gcc -O2     -I. `net-snmp-config --cflags` -ansi -pedantic -Wall
> -D_GNU_SOURCE -DRRDDIR='"/usr/local/nagios/perflog/rrd"'
> -DPNGDIR='"/usr/local/nagios/perflog/img"' -c -o rrdif.o rrdif.c
> rrdif.c: In function ‘RRDGraph’:
> rrdif.c:545: error: syntax error before ‘/’ token
> rrdif.c:545:13: error: too many decimal points in number
> rrdif.c:546: error: too few arguments to function ‘rrd_graph’
> rrdif.c:546: error: syntax error before ‘/’ token
> make: *** [rrdif.o] Fehler 1
> [...]
I looks different on my test machine (a Debian Sarge this time,
using home-built rrdtool 1.2.12:

gcc -O2     -I. `net-snmp-config --cflags` -ansi -pedantic -Wall
-D_GNU_SOURCE -DRRDDIR='"/usr/local/nagios/perflog/rrd"'
-DPNGDIR='"/usr/local/nagios/perflog/img"' -c -o rrdif.o rrdif.c
rrdif.c: In function `RRDGraph':
rrdif.c:545: error: too few arguments to function `rrd_graph'
make: *** [rrdif.o] Error 1

but it is basically the same error.

> [...]
> chk = rrd_graph (aParamCnt, aParams, &results, &w, &h, NULL,
> NULL,NULL);
>
> Now, it compiles cleanly. But it's untested yet...

The function is declare like this:

rrd_graph(int argc, char **argv, char ***prdata, int *xsize, int 
*ysize,
FILE *stream, double *ymin, double *ymax)


"stream" is only used this way:

    im.graphhandle = stream;


"im.graphhandle" in turn is used like this:

=== BEGIN ===
  if (strcmp(im->graphfile,"-")==0) {
    fo = im->graphhandle ? im->graphhandle : stdout;
#if defined(_WIN32) && !defined(__CYGWIN__) && !defined(__CYGWIN32__)
    /* Change translation mode for stdout to BINARY */
    _setmode( _fileno( fo ), O_BINARY );
#endif
  } else {
    if ((fo = fopen(im->graphfile,"wb")) == NULL) {
      rrd_set_error("Opening '%s' for write: %s",im->graphfile,
                    rrd_strerror(errno));
      return (-1);
    }
  }
  gfx_render (im->canvas,im->ximg,im->yimg,0x00000000,fo);
=== END ===

Which roughly translates to:
If the filename is equal to "-" and "stream" is not NULL, then write
the graph to the file "stream". So NULL would be ok 'cause the
filename is never set to "-"


"ymin" and "ymax" are only used like this:
    *ymin=im.minval;
    *ymax=im.maxval;

IOW: They are used to pass values back to the caller.

Now I'm no C guru at all but dereferencing a NULL pointer
seems like a bad idea to me. Sorry, my test maching just crashed,
the Mainboard hangs during POST and I can't find the manual
(of course) so I can't give you a decent diff for now.

However replacing the head of RRDGraph with this should work:

void RRDGraph ( int aParamCnt, char** aParams, tFN* aFN, tPP* aPP )
{
    int chk = -1;
    int w;
    int h;
    char** results;
    int j = 0;
    double junk1;
    double junk2;

    LogParams ( aParamCnt, aParams );
    optind = 1; /* rrd_*'s weired interface */
    rrd_clear_error ();
    /* rrd_* functions return 0 on success. */
    chk = rrd_graph ( aParamCnt, aParams, &results, &w, &h,
            NULL, &junk1, &junk2 );


I'll fix it in the release once I've figured out how to check for
the version of rrd.h (without actually using autoconf/automake right
now).

So long,
Peter

-- 
Peter Gritsch
mail: s4nag at no-where.at
web:  http://snmp4nagios.sourceforge.net/


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