Date: Sat, 21 Jun 1997 10:58:23 +0200 From: sthaug@nethelp.no To: jkh@time.cdrom.com Cc: marcs@znep.com, hackers@FreeBSD.ORG Subject: Re: gethostbyname() and fds >255 Message-ID: <23110.866883503@verdi.nethelp.no> In-Reply-To: Your message of "Sat, 21 Jun 1997 01:08:36 -0700" References: <28274.866880516@time.cdrom.com>
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> > For comparison, it works fine on BSD/OS 2.1. Does it work in -current?
>
> It would appear to:
>
> 396: host = 198.161.84.2 (valis.worldgate.com)
> 397: host = 198.161.84.2 (valis.worldgate.com)
> 398: host = 198.161.84.2 (valis.worldgate.com)
> 399: host = 198.161.84.2 (valis.worldgate.com)
> root@make-> uname -a
> FreeBSD make.ican.net 3.0-CURRENT FreeBSD 3.0-CURRENT #0: Mon Jun 16 13:10:14 EDT 1997 jkh@make.ican.net:/a/local/src/sys/compile/MAKE i386
>
> It does indeed fall over on my 2.2-stable system.
The problem is in res_send(). In lib/libc/net/res_send.c line 577 in
FreeBSD-current we have:
if (s+1 > FD_SETSIZE) {
#ifdef DEBUG
if (_res.options & RES_DEBUG)
fprintf(stderr,
"res_send: too many files\n");
#endif
res_close();
goto next_ns;
}
and FD_SETSIZE is statically defined as 256 in /usr/include/sys/types.h.
For comparison, the following code was added between BIND-4.9.5-P1 and
what will become BIND-4.9.6:
if (s+1 > FD_SETSIZE) {
Perror(stderr, "s+1 > FD_SETSIZE", EMFILE);
res_close();
goto next_ns;
}
and BIND-8.1.1-T2B src/lib/resolv/res_send.c has at line 587:
if (s+1 > FD_SETSIZE) {
Perror(stderr, "s+1 > FD_SETSIZE", EMFILE);
res_close();
goto next_ns;
}
Since this code was added between 4.9.5-P1 and 4.9.6, my guess is that
it's an attempt to stop some sort of denial of service attack - but it
looks like it may not be the best way to fix it.
Steinar Haug, Nethelp consulting, sthaug@nethelp.no
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