Date: Tue, 12 Jun 2001 10:23:27 +0300 From: Ruslan Ermilov <ru@FreeBSD.ORG> To: William Wong <willwong@samurai.com> Cc: freebsd-questions@FreeBSD.ORG Subject: Re: man 4 blackhole Message-ID: <20010612102327.E95192@sunbay.com> In-Reply-To: <006801c0f2f5$98bce740$0300a8c0@anime.ca>; from willwong@samurai.com on Tue, Jun 12, 2001 at 12:10:20AM -0400 References: <006801c0f2f5$98bce740$0300a8c0@anime.ca>
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On Tue, Jun 12, 2001 at 12:10:20AM -0400, William Wong wrote:
> Hi there,
>
> I'm looking at the man page and I don't see a difference between setting
> net.inet.tcp.blackhole, to either 1 or 2. Here's a section from the
> manpage.
>
> "Normal behaviour, when a TCP SYN segment is received on a port where
> there is no socket accepting connections, is for the system to return a
> RST segment, and drop the connection. The connecting system will see
> this as a "Connection reset by peer". By turning the TCP black hole MIB
> on to a numeric value of one, the incoming SYN segment is merely dropped,
^^^^^^^^^^^
> and no RST is sent, making the system appear as a blackhole. By setting
> the MIB value to two, any segment arriving on a closed port is dropped
^^^^^^^^^^^
> without returning a RST. This provides some degree of protection against
> stealth port scans."
>
> Since I'm sure option 2 isn't there for no reason, I must be interpreting
> this wrong.
>
> Anyone know the difference?
>
> Regards,
> - Will
>
>
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