On Fri, Jul 25, 2008 at 5:35 PM, Frank Denis <[EMAIL PROTECTED]> wrote:
> Hello,
>
> Well, I didn't have enough sleep lately, so probably this is an obvious
> and expected result.
>
> But connecting to a closed TCP port (that replies with RST) from OpenBSD
> doesn't immediately return.
>
> Extremely trivial demo (assuming nothing listens on 4242):
>
> $ nc 127.0.0.1 4242
>
> It waits a while before throwing Connection refused. Same thing for a
> remote host:
>
> $ nc openbsd.org 4242
>
> The same command with any another OS immediately returns ECONNREFUSED.
>
> PF isn't enabled. The behavior is the same with -current, OpenBSD 4.1 and
> OpenBSD 3.9, so this is not new.
>
> Is it intentional? What is the point?
>
> Another thing, with -current :
>
> $ sudo tcpdump -nvi vge0 dst host 199.185.137.3 &
> $ nc 199.185.137.3 4242
> tcpdump: listening on vge0, link-type EN10MB
> 01:24:53.473955 88.191.38.240.48850 > 199.185.137.3.4242: SWE [bad tcp cksum
> d965!] 1361218769:1361218769(0) win 16384 <mss
> 1460,nop,nop,sackOK,nop,wscale 0,nop,nop,timestamp 138557634 0> (DF) (ttl
> 64, id 18485, len 64, bad cksum 14!)
> 01:24:59.462216 88.191.38.240.48850 > 199.185.137.3.4242: S [bad tcp cksum
> 8d66!] 1361218769:1361218769(0) win 16384 <mss
> 1460,nop,nop,sackOK,nop,wscale 0,nop,nop,timestamp 138557646 0> (DF) (ttl
> 64, id 52715, len 64, bad cksum 14!)
>
> This is with a vge NIC on OpenBSD/i386. I tried on completely different
> hardware, on OpenBSD/amd64 with a re NIC and also got those bad checksums
> everytime.
Can't reproduce on a 4.2 -stable box with fxp NICs:
$ time nc -v openbsd.org 4242
nc: connect to openbsd.org port 4242 (tcp) failed: Connection refused
0m0.11s real 0m0.00s user 0m0.00s system
$ sudo tcpdump -i pppoe0 port 4242
tcpdump: listening on pppoe0, link-type PPP_ETHER
17:48:40.849784 97.118.x.x.41008 > 199.185.137.3.4242: S
2945779380:2945779380(0) win 65535 <mss 1452,nop,nop,sackOK,nop,wscale
1,nop,nop,timestamp 1351199331 0> (DF)
17:48:40.959003 199.185.137.3.4242 > 97.118.x.x.41008: R 0:0(0) ack
2945779381 win 0 (DF)
