Date: Thu, 09 Jun 2016 09:08:33 -0400 From: "Kristof Provost" <kp@FreeBSD.org> To: "Slawa Olhovchenkov" <slw@zxy.spb.ru> Cc: stable@freebsd.org, freebsd-net@freebsd.org Subject: Re: ipfw fwd to closed port Message-ID: <F1894D5E-0951-4E6B-8BCF-CB25CD25A9A8@FreeBSD.org> In-Reply-To: <20160609130601.GS75630@zxy.spb.ru> References: <20160608230240.GA51364@zxy.spb.ru> <20160609130017.GA4071@vega.codepro.be> <20160609130601.GS75630@zxy.spb.ru>
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On 9 Jun 2016, at 9:06, Slawa Olhovchenkov wrote: > On Thu, Jun 09, 2016 at 03:00:17PM +0200, Kristof Provost wrote: > >> On 2016-06-09 02:02:40 (+0300), Slawa Olhovchenkov <slw@zxy.spb.ru> wrote: >>> Forwarding by ipfw to closed local port generating RST packet with >>> incorrect checksun. Is this know ussuse? Need open PR? >> >> Where did you capture the packet? If you've captured the packet on the >> machine that generated it tcpdump may indeed claim that the checksum is >> wrong, because it's computed by the hardware (so after tcpdump captured >> it). > > On the tun0 (destination of RST packet routed to tun0). > tun0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> metric 0 mtu 1500 > options=80000<LINKSTATE> > inet 192.168.4.1 --> 192.168.4.1 netmask 0xffffff00 > inet6 fe80::240:63ff:fedc:ac9e%tun0 prefixlen 64 scopeid 0x9 > nd6 options=21<PERFORMNUD,AUTO\_LINKLOCAL> > Opened by PID 1345 > > tun0 don't computed checksum. I’m not sure I understand what you’re trying to say. In any case: either capture the packet outside the machine, or confirm that the checksum is wrong by watching the relevant netstat counters. Regards, Kristof
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