Issues with TCP Timestamps allocation
Michael Tuexen
tuexen at freebsd.org
Wed Jul 17 12:16:42 UTC 2019
> On 17. Jul 2019, at 13:55, Vitalij Satanivskij <satan at ukr.net> wrote:
>
> MT> > MT> In the meantime you can deal with the buggy hosts by disabling the timestamps
> MT> > MT> or dropping extensions on SYN retransmits.
> MT> >
> MT> > You meen by some code changes?
> MT> No.
> MT>
> MT> Two options:
> MT>
> MT> Option 1: Drop the TCP timestamp option on the third retransmission
> MT> To enable this, you configure on the client
> MT> sudo sysctl -w net.inet.tcp.rexmit_drop_options=1
> MT> or put
> MT> net.inet.tcp.rexmit_drop_options=1
> MT> in /etc/sysctl.conf
> MT> and reboot
> MT> In case of the broken host, the first SYN retransmission will happen 1 second after the
> MT> initial SYN segment, the second retransmission will happen 1.2 seconds after the first. On the
> MT> third retransmission, which happens again 1.2 seconds later, the TCP timestamp option is
> MT> dropped and the connection setup will succeed. This gives you a total delay of 3.4 seconds
> MT> on connection setup instead of the longer timeout.
>
> First Option is not working. Steel see same behave.
Interesting. It works for me:
tuexen at head:~ % curl https://vitagramma.com > /dev/null
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 18265 0 18265 0 0 33637 0 --:--:-- --:--:-- --:--:-- 33575
tuexen at head:~ % curl https://vitagramma.com > /dev/null
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 18265 0 18265 0 0 4834 0 --:--:-- 0:00:03 --:--:-- 4833
tuexen at head:~ % curl https://vitagramma.com > /dev/null
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 18265 0 18265 0 0 35813 0 --:--:-- --:--:-- --:--:-- 35813
tuexen at head:~ % time curl https://vitagramma.com > /dev/null
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 18265 0 18265 0 0 48320 0 --:--:-- --:--:-- --:--:-- 48320
0.012u 0.031s 0:00.39 10.2% 140+245k 0+0io 0pf+0w
tuexen at head:~ % time curl https://vitagramma.com > /dev/null
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 18265 0 18265 0 0 4592 0 --:--:-- 0:00:03 --:--:-- 4591
0.031u 0.010s 0:03.99 1.0% 80+140k 0+0io 0pf+0w
tuexen at head:~ % curl https://vitagramma.com > /dev/null
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 18265 0 18265 0 0 37815 0 --:--:-- --:--:-- --:--:-- 37737
tuexen at head:~ % curl https://vitagramma.com > /dev/null
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 18265 0 18265 0 0 27261 0 --:--:-- --:--:-- --:--:-- 27220
tuexen at head:~ % curl https://vitagramma.com > /dev/null
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 18265 0 18265 0 0 4533 0 --:--:-- 0:00:04 --:--:-- 4533
tuexen at head:~ % curl https://vitagramma.com > /dev/null
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 18265 0 18265 0 0 48320 0 --:--:-- --:--:-- --:--:-- 48192
tuexen at head:~ % curl https://vitagramma.com > /dev/null
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 18265 0 18265 0 0 4746 0 --:--:-- 0:00:03 --:--:-- 4745
tuexen at head:~ % curl https://vitagramma.com > /dev/null
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 18265 0 18265 0 0 4500 0 --:--:-- 0:00:04 --:--:-- 4767
tuexen at head:~ % curl https://vitagramma.com > /dev/null
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 18265 0 18265 0 0 4726 0 --:--:-- 0:00:03 --:--:-- 4726
tuexen at head:~ % curl https://vitagramma.com > /dev/null
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 18265 0 18265 0 0 34268 0 --:--:-- --:--:-- --:--:-- 34332
tuexen at head:~ %
So it either works immediately or with a delay of 3 to 4 seconds...
Best regards
Michael
>
>
> MT>
> MT> Option 2: Disable the TCP timestamps (and window scaling)
> MT> To enable this, you configure on the client
> MT> sudo sysctl -w net.inet.tcp.rfc1323=0
> MT> or put
> MT> net.inet.tcp.rfc1323=0
> MT> in /etc/sysctl.conf
> MT> and reboot.
> MT> This disables the timestamp option and window scaling completely. This allows you to
> MT> setup the connections without any delay. However, you don't have the benefits of the
> MT> extension.
> MT>
> MT> Both options don't require any code changes.
>
> This option was tested some time before. Yep it's help. But overal performance of tcp networking ... Let's say to bad :(
>
>
>
>
> MT> Best regards
> MT> Michael
> MT>
> MT>
> MT> >
> MT> >
> MT> > MT>
> MT> > MT> Best regards
> MT> > MT> Michael
> MT> > MT> >
> MT> > MT> >
> MT> > MT> >
> MT> > MT> > Michael Tuexen wrote:
> MT> > MT> > MT>
> MT> > MT> > MT>
> MT> > MT> > MT> > On 9. Jul 2019, at 14:58, Paul <devgs at ukr.net> wrote:
> MT> > MT> > MT> >
> MT> > MT> > MT> > Hi Michael,
> MT> > MT> > MT> >
> MT> > MT> > MT> > 9 July 2019, 15:34:29, by "Michael Tuexen" <tuexen at freebsd.org>:
> MT> > MT> > MT> >
> MT> > MT> > MT> >>
> MT> > MT> > MT> >>
> MT> > MT> > MT> >>> On 8. Jul 2019, at 17:22, Paul <devgs at ukr.net> wrote:
> MT> > MT> > MT> >>>
> MT> > MT> > MT> >>>
> MT> > MT> > MT> >>>
> MT> > MT> > MT> >>> 8 July 2019, 17:12:21, by "Michael Tuexen" <tuexen at freebsd.org>:
> MT> > MT> > MT> >>>
> MT> > MT> > MT> >>>>> On 8. Jul 2019, at 15:24, Paul <devgs at ukr.net> wrote:
> MT> > MT> > MT> >>>>>
> MT> > MT> > MT> >>>>> Hi Michael,
> MT> > MT> > MT> >>>>>
> MT> > MT> > MT> >>>>> 8 July 2019, 15:53:15, by "Michael Tuexen" <tuexen at freebsd.org>:
> MT> > MT> > MT> >>>>>
> MT> > MT> > MT> >>>>>>> On 8. Jul 2019, at 12:37, Paul <devgs at ukr.net> wrote:
> MT> > MT> > MT> >>>>>>>
> MT> > MT> > MT> >>>>>>> Hi team,
> MT> > MT> > MT> >>>>>>>
> MT> > MT> > MT> >>>>>>> Recently we had an upgrade to 12 Stable. Immediately after, we have started
> MT> > MT> > MT> >>>>>>> seeing some strange connection establishment timeouts to some fixed number
> MT> > MT> > MT> >>>>>>> of external (world) hosts. The issue was persistent and easy to reproduce.
> MT> > MT> > MT> >>>>>>> Thanks to a patience and dedication of our system engineer we have tracked
> MT> > MT> > MT> >>>>>>> this issue down to a specific commit:
> MT> > MT> > MT> >>>>>>>
> MT> > MT> > MT> >>>>>>> https://svnweb.freebsd.org/base?view=revision&revision=338053
> MT> > MT> > MT> >>>>>>>
> MT> > MT> > MT> >>>>>>> This patch was also back-ported into 11 Stable:
> MT> > MT> > MT> >>>>>>>
> MT> > MT> > MT> >>>>>>> https://svnweb.freebsd.org/base?view=revision&revision=348435
> MT> > MT> > MT> >>>>>>>
> MT> > MT> > MT> >>>>>>> Among other things this patch changes the timestamp allocation strategy,
> MT> > MT> > MT> >>>>>>> by introducing a deterministic randomness via a hash function that takes
> MT> > MT> > MT> >>>>>>> into account a random key as well as source address, source port, dest
> MT> > MT> > MT> >>>>>>> address and dest port. As the result, timestamp offsets of different
> MT> > MT> > MT> >>>>>>> tuples (SA,SP,DA,DP) will be wildly different and will jump from small
> MT> > MT> > MT> >>>>>>> to large numbers and back, as long as something in the tuple changes.
> MT> > MT> > MT> >>>>>> Hi Paul,
> MT> > MT> > MT> >>>>>>
> MT> > MT> > MT> >>>>>> this is correct.
> MT> > MT> > MT> >>>>>>
> MT> > MT> > MT> >>>>>> Please note that the same happens with the old method, if two hosts with
> MT> > MT> > MT> >>>>>> different uptimes are bind a consumer grade NAT.
> MT> > MT> > MT> >>>>>
> MT> > MT> > MT> >>>>> If NAT does not replace timestamps then yes, it should be the case.
> MT> > MT> > MT> >>>>>
> MT> > MT> > MT> >>>>>>>
> MT> > MT> > MT> >>>>>>> After performing various tests of hosts that produce the above mentioned
> MT> > MT> > MT> >>>>>>> issue we came to conclusion that there are some interesting implementations
> MT> > MT> > MT> >>>>>>> that drop SYN packets with timestamps smaller than the largest timestamp
> MT> > MT> > MT> >>>>>>> value from streams of all recent or current connections from a specific
> MT> > MT> > MT> >>>>>>> address. This looks as some kind of SYN flood protection.
> MT> > MT> > MT> >>>>>> This also breaks multiple hosts with different uptimes behind a consumer
> MT> > MT> > MT> >>>>>> level NAT talking to such a server.
> MT> > MT> > MT> >>>>>>>
> MT> > MT> > MT> >>>>>>> To ensure that each external host is not going to see a wild jumps of
> MT> > MT> > MT> >>>>>>> timestamp values I propose a patch that removes ports from the equation
> MT> > MT> > MT> >>>>>>> all together, when calculating the timestamp offset:
> MT> > MT> > MT> >>>>>>>
> MT> > MT> > MT> >>>>>>> Index: sys/netinet/tcp_subr.c
> MT> > MT> > MT> >>>>>>> ===================================================================
> MT> > MT> > MT> >>>>>>> --- sys/netinet/tcp_subr.c (revision 348435)
> MT> > MT> > MT> >>>>>>> +++ sys/netinet/tcp_subr.c (working copy)
> MT> > MT> > MT> >>>>>>> @@ -2224,7 +2224,22 @@
> MT> > MT> > MT> >>>>>>> uint32_t
> MT> > MT> > MT> >>>>>>> tcp_new_ts_offset(struct in_conninfo *inc)
> MT> > MT> > MT> >>>>>>> {
> MT> > MT> > MT> >>>>>>> - return (tcp_keyed_hash(inc, V_ts_offset_secret));
> MT> > MT> > MT> >>>>>>> + /*
> MT> > MT> > MT> >>>>>>> + * Some implementations show a strange behaviour when a wildly random
> MT> > MT> > MT> >>>>>>> + * timestamps allocated for different streams. It seems that only the
> MT> > MT> > MT> >>>>>>> + * SYN packets are affected. Observed implementations drop SYN packets
> MT> > MT> > MT> >>>>>>> + * with timestamps smaller than the largest timestamp value of all
> MT> > MT> > MT> >>>>>>> + * recent or current connections from specific a address. To mitigate
> MT> > MT> > MT> >>>>>>> + * this we are going to ensure that each host will always observe
> MT> > MT> > MT> >>>>>>> + * timestamps as increasing no matter the stream: by dropping ports
> MT> > MT> > MT> >>>>>>> + * from the equation.
> MT> > MT> > MT> >>>>>>> + */
> MT> > MT> > MT> >>>>>>> + struct in_conninfo inc_copy = *inc;
> MT> > MT> > MT> >>>>>>> +
> MT> > MT> > MT> >>>>>>> + inc_copy.inc_fport = 0;
> MT> > MT> > MT> >>>>>>> + inc_copy.inc_lport = 0;
> MT> > MT> > MT> >>>>>>> +
> MT> > MT> > MT> >>>>>>> + return (tcp_keyed_hash(&inc_copy, V_ts_offset_secret));
> MT> > MT> > MT> >>>>>>> }
> MT> > MT> > MT> >>>>>>>
> MT> > MT> > MT> >>>>>>> /*
> MT> > MT> > MT> >>>>>>>
> MT> > MT> > MT> >>>>>>> In any case, the solution of the uptime leak, implemented in rev338053 is
> MT> > MT> > MT> >>>>>>> not going to suffer, because a supposed attacker is currently able to use
> MT> > MT> > MT> >>>>>>> any fixed values of SP and DP, albeit not 0, anyway, to remove them out
> MT> > MT> > MT> >>>>>>> of the equation.
> MT> > MT> > MT> >>>>>> Can you describe how a peer can compute the uptime from two observed timestamps?
> MT> > MT> > MT> >>>>>> I don't see how you can do that...
> MT> > MT> > MT> >>>>>
> MT> > MT> > MT> >>>>> Supposed attacker could run a script that continuously monitors timestamps,
> MT> > MT> > MT> >>>>> for example via a periodic TCP connection from a fixed local port (eg 12345)
> MT> > MT> > MT> >>>>> and a fixed local address to the fixed victim's address and port (eg 80).
> MT> > MT> > MT> >>>>> Whenever large discrepancy is observed, attacker can assume that reboot has
> MT> > MT> > MT> >>>>> happened (due to V_ts_offset_secret re-generation), hence the received
> MT> > MT> > MT> >>>>> timestamp is considered an approximate point of reboot from which the uptime
> MT> > MT> > MT> >>>>> can be calculated, until the next reboot and so on.
> MT> > MT> > MT> >>>> Ahh, I see. The patch we are talking about is not intended to protect against
> MT> > MT> > MT> >>>> continuous monitoring, which is something you can always do. You could even
> MT> > MT> > MT> >>>> watch for service availability and detect reboots. A change of the local key
> MT> > MT> > MT> >>>> would also look similar to a reboot without a temporary loss of connectivity.
> MT> > MT> > MT> >>>>
> MT> > MT> > MT> >>>> Thanks for the clarification.
> MT> > MT> > MT> >>>>>
> MT> > MT> > MT> >>>>>>>
> MT> > MT> > MT> >>>>>>> There is the list of example hosts that we were able to reproduce the
> MT> > MT> > MT> >>>>>>> issue with:
> MT> > MT> > MT> >>>>>>>
> MT> > MT> > MT> >>>>>>> curl -v http://88.99.60.171:80
> MT> > MT> > MT> >>>>>>> curl -v http://163.172.71.252:80
> MT> > MT> > MT> >>>>>>> curl -v http://5.9.242.150:80
> MT> > MT> > MT> >>>>>>> curl -v https://185.134.205.105:443
> MT> > MT> > MT> >>>>>>> curl -v https://136.243.1.231:443
> MT> > MT> > MT> >>>>>>> curl -v https://144.76.196.4:443
> MT> > MT> > MT> >>>>>>> curl -v http://94.127.191.194:80
> MT> > MT> > MT> >>>>>>>
> MT> > MT> > MT> >>>>>>> To reproduce, call curl repeatedly with a same URL some number of times.
> MT> > MT> > MT> >>>>>>> You are going to see some of the requests stuck in
> MT> > MT> > MT> >>>>>>> `* Trying XXX.XXX.XXX.XXX...`
> MT> > MT> > MT> >>>>>>>
> MT> > MT> > MT> >>>>>>> For some reason, the easiest way to reproduce the issue is with nc:
> MT> > MT> > MT> >>>>>>>
> MT> > MT> > MT> >>>>>>> $ echo "foooooo" | nc -v 88.99.60.171 80
> MT> > MT> > MT> >>>>>>>
> MT> > MT> > MT> >>>>>>> Only a few such calls are required until one of them is stuck on connect():
> MT> > MT> > MT> >>>>>>> issuing SYN packets with an exponential backoff.
> MT> > MT> > MT> >>>>>> Thanks for providing an end-point to test with. I'll take a look.
> MT> > MT> > MT> >>>>>> Just to be clear: You are running a FreeBSD client against one of the above
> MT> > MT> > MT> >>>>>> servers and experience the problem with the new timestamp computations.
> MT> > MT> > MT> >>>>>>
> MT> > MT> > MT> >>>>>> You are not running arbitrary clients against a FreeBSD server...
> MT> > MT> > MT> >>>>>
> MT> > MT> > MT> >>>>> We are talking about FreeBSD being the client. Peers that yield this unwanted
> MT> > MT> > MT> >>>>> behaviour are unknown. Little bit of tinkering showed that some of them run
> MT> > MT> > MT> >>>>> Debian:
> MT> > MT> > MT> >>>>>
> MT> > MT> > MT> >>>>> telnet 88.99.60.171 22
> MT> > MT> > MT> >>>>> Trying 88.99.60.171...
> MT> > MT> > MT> >>>>> Connected to 88.99.60.171.
> MT> > MT> > MT> >>>>> Escape character is '^]'.
> MT> > MT> > MT> >>>>> SSH-2.0-OpenSSH_6.7p1 Debian-5+deb8u3
> MT> > MT> > MT> >>>> Also some are hosted by Hetzner, but not all. I'll will look into
> MT> > MT> > MT> >>>> this tomorrow, since I'm on a deadline today (well it is 2am tomorrow
> MT> > MT> > MT> >>>> morning, to be precise)...
> MT> > MT> > MT> >>>
> MT> > MT> > MT> >>> Thanks a lot, I would appreciate that.
> MT> > MT> > MT> >> Hi Paul,
> MT> > MT> > MT> >>
> MT> > MT> > MT> >> I have looked into this.
> MT> > MT> > MT> >>
> MT> > MT> > MT> >> * The FreeBSD behaviour is the one which is specified in the last bullet item
> MT> > MT> > MT> >> in https://tools.ietf.org/html/rfc7323#section-5.4
> MT> > MT> > MT> >> It is also the one, which is RECOMMENDED in
> MT> > MT> > MT> >> https://tools.ietf.org/html/rfc7323#section-7.1
> MT> > MT> > MT> >>
> MT> > MT> > MT> >> * My NAT box (a popular one in Germany) does NOT rewrite TCP timestamps.
> MT> > MT> > MT> >>
> MT> > MT> > MT> >> This means that the host you are referring to have some sort of protection,
> MT> > MT> > MT> >> which makes incorrect assumptions. It will also break multiple hosts behind
> MT> > MT> > MT> >> a NAT.
> MT> > MT> > MT> >>
> MT> > MT> > MT> >> I can run
> MT> > MT> > MT> >> curl -v http://88.99.60.171:80
> MT> > MT> > MT> >> in a loop without any problems from a FreeBSD head system. I tested 1000
> MT> > MT> > MT> >> iterations or so. The TS.val is jumping up and down as expected.
> MT> > MT> > MT> >> I'm wondering why you are observing errors in this case, too.
> MT> > MT> > MT> >>
> MT> > MT> > MT> >> However, doing something like
> MT> > MT> > MT> >> echo "foooooo" | nc -v 88.99.60.171 80
> MT> > MT> > MT> >> triggers the problem.
> MT> > MT> > MT> >>
> MT> > MT> > MT> >> So I think there is some functionality (in a middlebox or running on the host),
> MT> > MT> > MT> >> which incorrectly assume monotonic timestamps between multiple TCP connections
> MT> > MT> > MT> >> coming from the same IP address, but only in case of errors at the application layer.
> MT> > MT> > MT> >
> MT> > MT> > MT> > Yeah, exactly, some hosts seem to enable this only in case of an error in HTTP
> MT> > MT> > MT> > communication (some smart proxy?). However, there are some that behave this way
> MT> > MT> > MT> > regardless of errors, for example these:
> MT> > MT> > MT> >
> MT> > MT> > MT> > curl -v https://185.134.205.105:443
> MT> > MT> > MT> > curl -v https://136.243.1.231:443
> MT> > MT> > MT> Wireshark sees an Encrypted Alert in both cases. So I guess this is another indication
> MT> > MT> > MT> of "error at the application layer".
> MT> > MT> > MT> >
> MT> > MT> > MT> >>
> MT> > MT> > MT> >> Do you have any insights whether the hosts you are listed share something in
> MT> > MT> > MT> >> common. Some of them are hosted by Hetzner, but not all.
> MT> > MT> > MT> >
> MT> > MT> > MT> > Nope. A whole set of endpoints that we have detected so far is pretty diverse,
> MT> > MT> > MT> > containing a lot of different locations geographically, as well as different
> MT> > MT> > MT> > hosters.
> MT> > MT> > MT> OK. Thanks for the clarification.
> MT> > MT> > MT> >
> MT> > MT> > MT> >>
> MT> > MT> > MT> >> I think in general, it is the correct thing to include the port numbers in
> MT> > MT> > MT> >> the offset computation. We might add a sysctl variable to control the inclusion.
> MT> > MT> > MT> >> This would allow interworking with broken middleboxes.
> MT> > MT> > MT> >
> MT> > MT> > MT> > Yeah, I completely agree that these rare cases should not dictate the implementation.
> MT> > MT> > MT> > But an ability to enable a work-around via sysctl would be greatly appreciated.
> MT> > MT> > MT> > Currently we are unable to roll-out the upgrade across all servers because of this
> MT> > MT> > MT> > issue: even though it happens not so often, a lot of requests from our users
> MT> > MT> > MT> > get stuck or fail all together. For example, a host 185.134.205.105 is a kind of
> MT> > MT> > MT> > social network that our proxy servers connect to so securely access to content,
> MT> > MT> > MT> > such as images, on behalf of our users.
> MT> > MT> > MT> >
> MT> > MT> > MT> >>
> MT> > MT> > MT> >> Please note, this does not fix the case of multiple clients behind a NAT.
> MT> > MT> > MT> >
> MT> > MT> > MT> > Yeah, that's true. Fortunately we don't use NAT.
> MT> > MT> > MT> >
> MT> > MT> > MT> >>
> MT> > MT> > MT> >> I'm also trying to figure out how and why Linux and Windows are handling this.
> MT> > MT> > MT> >
> MT> > MT> > MT> > Thanks for bothering!
> MT> > MT> > MT> Will let you know what I figure out.
> MT> > MT> > MT>
> MT> > MT> > MT> Best regards
> MT> > MT> > MT> Michael
> MT> > MT> > MT> >
> MT> > MT> > MT> >>
> MT> > MT> > MT> >> Best regards
> MT> > MT> > MT> >> Michael
> MT> > MT> > MT> >>
> MT> > MT> > MT> >>>
> MT> > MT> > MT> >>>>
> MT> > MT> > MT> >>>> Best regards
> MT> > MT> > MT> >>>> Michael
> MT> > MT> > MT> >>>>>
> MT> > MT> > MT> >>>>>
> MT> > MT> > MT> >>>>>>
> MT> > MT> > MT> >>>>>> Best regards
> MT> > MT> > MT> >>>>>> Michael
> MT> > MT> > MT> >>>>>>
> MT> > MT> > MT> >>>>>>
> MT> > MT> > MT> >>>>
> MT> > MT> > MT> >>>>
> MT> > MT> > MT> >>
> MT> > MT> > MT> >>
> MT> > MT> > MT>
> MT> > MT> > MT> _______________________________________________
> MT> > MT> > MT> freebsd-net at freebsd.org mailing list
> MT> > MT> > MT> https://lists.freebsd.org/mailman/listinfo/freebsd-net
> MT> > MT> > MT> To unsubscribe, send any mail to "freebsd-net-unsubscribe at freebsd.org"
> MT> > MT>
> MT> > MT> _______________________________________________
> MT> > MT> freebsd-net at freebsd.org mailing list
> MT> > MT> https://lists.freebsd.org/mailman/listinfo/freebsd-net
> MT> > MT> To unsubscribe, send any mail to "freebsd-net-unsubscribe at freebsd.org"
> MT>
> _______________________________________________
> freebsd-net at freebsd.org mailing list
> https://lists.freebsd.org/mailman/listinfo/freebsd-net
> To unsubscribe, send any mail to "freebsd-net-unsubscribe at freebsd.org"
More information about the freebsd-net
mailing list