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Date:      Thu, 28 Sep 2000 08:39:00 -0700
From:      "Timothy L. Robertson" <timothyr@timothyr.com>
To:        <freebsd-questions@freebsd.org>
Subject:   cvsup Problem
Message-ID:  <NEBBKDBFKKIDPAPJPFOPKEGKCFAA.timothyr@timothyr.com>

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Hello All,

I've been happily keeping up to date using cvsup when suddenly it
stopped working.  I tightend up my firewall, installed snort, and
configured my machine as a DHCP and pop3 server, but I don't think
any of these actions are the reason.  Basically, I connect to the
server, and then nothing happens.  Here's a typical session:

su-2.03# make update
cvsup -g -z -L2 -P m /home/standard-supfile 2>&1 | tee
/usr/tmp/standard-cvs.`date "+%m%d.%H.%M.%S"`;  cvsup -g -z -L2 -P m
/home/ports-supfile 2>&1 | tee /usr/tmp/ports-cvs.`date
"+%m%d.%H.%M.%S"`;
Parsing supfile "/home/standard-supfile"
Connecting to cvsup4.FreeBSD.org
Connected to cvsup4.FreeBSD.org
Server software version: REL_16_1
Negotiating file attribute support
Exchanging collection information
Establishing multiplexed-mode data connection
Running

then it just hangs until it times out.  I looked at tcpdump output to
try and figure out what's going on, and it seems like packets are not
getting past an interface with an MTU of 1450.  The thing is I don't
have any interface configured with this MTU.  I configure my
interfaces for an MTU of 1462, and it seems like this number is
always 12 bytes less than what I've configured the interface for. 
The tcpdump shows the connection is established, then I get a bunch
of host unreachable ICMP packets on myself.  Here's a sample.  (My IP
is 64.82.116.252)
su-2.03# tcpdump -v -X -i tun0
[...packets establishing connection...]
20:04:52.763520 64.82.116.252.iad1 > 129.250.31.140.cvsup: P
280:288(8) ack 614 win 17370 <nop,nop,timestamp 11680 30547826> (DF)
(ttl 64, id 1373)
0x0000   4500 003c 055d 4000 4006 de8a 4052 74fc       
E..<.]@.@...@Rt.
0x0010   81fa 1f8c 0406 176f 3bff b5fc ec54 53e2       
.......o;....TS.
0x0020   8018 43da f870 0000 0101 080a 0000 2da0       
..C..p........-.
0x0030   01d2 1f72 0301 0400 0000 4000                  ...r......@.
20:04:52.765404 64.82.116.252 > 64.82.116.252: icmp: 64.82.116.252
unreachable - need to frag (mtu 1450) (ttl 255, id 1376)
0x0000   4500 0038 0560 0000 ff01 4bc8 4052 74fc       
E..8.`....K.@Rt.
0x0010   4052 74fc 0304 aefa 0000 05aa 4500 05dc       
@Rt.........E...
0x0020   055e 4000 4006 0000 4052 74fc 4052 74fc       
.^@.@...@Rt.@Rt.
0x0030   0406 176f 3bff b604                            ...o;...
20:04:52.765506 64.82.116.252 > 64.82.116.252: icmp: 64.82.116.252
unreachable - need to frag (mtu 1450) (ttl 255, id 1376)
0x0000   4500 0038 0560 0000 ff01 4bc8 4052 74fc       
E..8.`....K.@Rt.
0x0010   4052 74fc 0304 aefa 0000 05aa 4500 05dc       
@Rt.........E...
0x0020   055e 4000 4006 0000 4052 74fc 4052 74fc       
.^@.@...@Rt.@Rt.
0x0030   0406 176f 3bff b604                            ...o;...
20:04:53.110039 129.250.31.140.cvsup > 64.82.116.252.iad1: . ack 288
win 16920 <nop,nop,timestamp 30547828 11680> (DF) (ttl 48, id 22993)
0x0000   4500 0034 59d1 4000 3006 9a1e 81fa 1f8c       
E..4Y.@.0.......
0x0010   4052 74fc 176f 0406 ec54 53e2 3bff b604       
@Rt..o...TS.;...
0x0020   8010 4218 413a 0000 0101 080a 01d2 1f74       
..B.A:.........t
0x0030   0000 2da0                                      ..-.
20:04:53.843880 64.82.116.252 > 64.82.116.252: icmp: 64.82.116.252
unreachable - need to frag (mtu 1450) (ttl 255, id 1381)
0x0000   4500 0038 0565 0000 ff01 4bc3 4052 74fc       
E..8.e....K.@Rt.
0x0010   4052 74fc 0304 a94c 0000 05aa 4500 05dc       
@Rt....L....E...
0x0020   0564 4000 4006 0000 4052 74fc 4052 74fc       
.d@.@...@Rt.@Rt.
0x0030   0406 176f 3bff bbac                            ...o;...
20:04:53.843982 64.82.116.252 > 64.82.116.252: icmp: 64.82.116.252
unreachable - need to frag (mtu 1450) (ttl 255, id 1381)
0x0000   4500 0038 0565 0000 ff01 4bc3 4052 74fc       
E..8.e....K.@Rt.
0x0010   4052 74fc 0304 a94c 0000 05aa 4500 05dc       
@Rt....L....E...
0x0020   0564 4000 4006 0000 4052 74fc 4052 74fc       
.d@.@...@Rt.@Rt.
0x0030   0406 176f 3bff bbac                            ...o;...

What's going on here?  Why is the MTU 12 bytes less than what I've
configured it for and what ifconfig shows?  And why did it stop
working all of a sudden?  Is it a conspiracy that the NSA doesn't
want me to get 4.1.1 with RSA in it?  Any help appreciated.  I've
tried everything I could think of including rebuilding cvsup.  A
little more info is at the end in case anyone finds it helpful.

Thanks,
- -Tim

su-2.03# ifconfig -a
fxp0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1462
        inet 192.168.1.1 netmask 0xffffff00 broadcast 192.168.1.255
        inet6 fe80::202:b3ff:fe03:aae1%fxp0 prefixlen 64 scopeid 0x1
        ether 00:02:b3:03:aa:e1
        media: autoselect (100baseTX) status: active
        supported media: autoselect 100baseTX <full-duplex> 100baseTX
10baseT/UTP <full-duplex> 10baseT/UTP
xl0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1462
        inet 10.0.0.2 netmask 0xffffff00 broadcast 10.0.0.255
        inet6 fe80::201:2ff:fe48:ad91%xl0 prefixlen 64 scopeid 0x2
        ether 00:01:02:48:ad:91
        media: 10baseT/UTP (10baseT/UTP <half-duplex>)
        supported media: 10baseT/UTP <full-duplex> 10baseT/UTP
<half-duplex> 10baseT/UTP
lp0: flags=8810<POINTOPOINT,SIMPLEX,MULTICAST> mtu 1500
ppp0: flags=8010<POINTOPOINT,MULTICAST> mtu 1500
sl0: flags=c010<POINTOPOINT,LINK2,MULTICAST> mtu 552
faith0: flags=8000<MULTICAST> mtu 1500
gif0: flags=8010<POINTOPOINT,MULTICAST> mtu 1280
gif1: flags=8010<POINTOPOINT,MULTICAST> mtu 1280
gif2: flags=8010<POINTOPOINT,MULTICAST> mtu 1280
gif3: flags=8010<POINTOPOINT,MULTICAST> mtu 1280
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
        inet6 fe80::1%lo0 prefixlen 64 scopeid 0xb
        inet6 ::1 prefixlen 128
        inet 127.0.0.1 netmask 0xff000000
tun0: flags=8151<UP,POINTOPOINT,RUNNING,PROMISC,MULTICAST> mtu 1462
        inet6 fe80::202:b3ff:fe03:aae1%tun0 --> :: prefixlen 64
scopeid 0xc
        inet 216.175.93.55 --> 216.175.93.1 netmask 0xffffffff
        Opened by PID 107
su-2.03# netstat -rn
Routing tables

Internet:
Destination        Gateway            Flags      Netif Expire
default            216.175.93.1       UGSc       17      686     tun0
10/24              link#2             UC          0        0      xl0
=>
10.0.0.255         ff:ff:ff:ff:ff:ff  UHLWb       2        8      xl0
127.0.0.1          127.0.0.1          UH          2      140      lo0
192.168.1          link#1             UC          0        0     fxp0
=>
192.168.1.4        0:0:86:15:ab:f6    UHLW        2      134     fxp0
   962
192.168.1.5        0:0:86:5b:9d:d6    UHLW        4      541     fxp0
  1163
192.168.1.255      ff:ff:ff:ff:ff:ff  UHLWb       2       23     fxp0
216.175.93.1       216.175.93.55      UH         17        0     tun0

Internet6:
Destination                       Gateway                       Flags
     Netif Expire
::1                               ::1                           UH   
      lo0
fe80::%fxp0/64                    link#1                        UC   
     fxp0
fe80::%xl0/64                     link#2                        UC   
      xl0
fe80::%lo0/64                     fe80::1%lo0                   Uc   
      lo0
fe80::%tun0/64                    link#12                       UC   
     tun0
fe80::202:b3ff:fe03:aae1%tun0     ::1                           UH   
      lo0
ff01::/32                         ::1                           U    
      lo0
ff02::%fxp0/32                    link#1                        UC   
     fxp0
ff02::%xl0/32                     link#2                        UC   
      xl0
ff02::%lo0/32                     fe80::1%lo0                   UC   
      lo0
ff02::%tun0/32                    link#12                       UC   
     tun0

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