Bug 34250 – Problem with FD_SETSIZE using netcat

• Status: RESOLVED FIXED
• Product: Gentoo Linux

[Description Frederic Mangeant 2003-11-24 03:44:28 UTC]

Problem with FD_SETSIZE using netcat

[Comment 1 Frederic Mangeant 2003-11-24 03:51:37 UTC]

Hi

here's what can be found in netcat.c (release 110-r4):

/* have to do this *before* including types.h. xxx: Linux still has it wrong */
#ifdef FD_SETSIZE               /* should be in types.h, butcha never know. */
#undef FD_SETSIZE               /* if we ever need more than 16 active */
#endif                          /* fd's, something is horribly wrong! */
#define FD_SETSIZE 16           /* <-- this'll give us a long anyways, wtf */
#include <sys/types.h>          /* *now* do it.  Sigh, this is broken */

As FD_SETSIZE does'nt seem to be included in /usr/include/sys/types.h (linux-headers 2.4.19-r1), FD_SETSIZE=16.

Later in the netcat's code, we have :

if (fd > FD_SETSIZE) {
    holler ("Preposterous fd value %d", fd);
    return (1);
}

So netcat does'nt work if more than 16 files are opened. I'm using netcat within cacti, a rrdtool frontend. As a lot of files are opened, I got :

nc -vv xxx.xxx.xxx.xxx 50000 -w 5, output:
Preposterous fd value 71
 sent 0, rcvd 0

I've tweaked FD_SETSIZE=16 to FD_SETSIZE=1024, and now it works as expected :

nc -vv xxx.xxx.xxx.xxx 50000 -w 5, output: xxxxxxxxxxx
 sent 0, rcvd 17

Could you add this as a patch to the ebuild ?

Thanks in advance.

Regards,

Fr

[Comment 2 Frederic Mangeant 2003-11-24 03:51:37 UTC]

Hi

here's what can be found in netcat.c (release 110-r4):

/* have to do this *before* including types.h. xxx: Linux still has it wrong */
#ifdef FD_SETSIZE               /* should be in types.h, butcha never know. */
#undef FD_SETSIZE               /* if we ever need more than 16 active */
#endif                          /* fd's, something is horribly wrong! */
#define FD_SETSIZE 16           /* <-- this'll give us a long anyways, wtf */
#include <sys/types.h>          /* *now* do it.  Sigh, this is broken */

As FD_SETSIZE does'nt seem to be included in /usr/include/sys/types.h (linux-headers 2.4.19-r1), FD_SETSIZE=16.

Later in the netcat's code, we have :

if (fd > FD_SETSIZE) {
    holler ("Preposterous fd value %d", fd);
    return (1);
}

So netcat does'nt work if more than 16 files are opened. I'm using netcat within cacti, a rrdtool frontend. As a lot of files are opened, I got :

nc -vv xxx.xxx.xxx.xxx 50000 -w 5, output:
Preposterous fd value 71
 sent 0, rcvd 0

I've tweaked FD_SETSIZE=16 to FD_SETSIZE=1024, and now it works as expected :

nc -vv xxx.xxx.xxx.xxx 50000 -w 5, output: xxxxxxxxxxx
 sent 0, rcvd 17

Could you add this as a patch to the ebuild ?

Thanks in advance.

Regards,

Frédéric Mangeant

[Comment 3 SpanKY 2003-11-24 09:49:00 UTC]

added this to -r4:
sed -i 's:#define FD_SETSIZE 16:#define FD_SETSIZE 1024:' netcat.c

[Comment 4 Frederic Mangeant 2003-11-26 06:08:00 UTC]

Created attachment 21312 [details, diff]
Change FD_SETSIZE from 16 to 1024