Re: [mpls-linux-general] Problem with tcp connections using MPLS
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Re: [mpls-linux-general] Problem with tcp connections using MPLS
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From: James R. L. <jl...@mi...> - 2005-12-22 04:22:59
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Hello,
I've had others mention something about this as well.
Right now my thinking is HW checksumming is invalid when using MPLS
linux due to a split brain syndrome: IPv4 thinks the hardware will do
the checksumming but by the time the HW gets the packets, the packets are
no longer IPv4 packets and therefore do not get checksummed.
To know if my thinking is correct I need someone to do additional
testing, but no one has stepped forward yet.
If you're willing to help (not just limited to
gui...@ya...), read on:
First off, I'm not sure your tcpdump is valid. There is a known problem
with doing packet captures on a machine with HW checksumming that
is involved in the TCP session.
http://www.ethereal.com/lists/ethereal-users/200507/msg00234.html
Ideally you should do the packet capture on a machine not involved in
the TCP session and with HW checksumming turned off. (you will probably
need a hub or will need to configure a monitor port on a switch). If
neither of these options are available, you could try inserting a LSR into
your network and do the packet capture on the LSR (LSRs do not touch the IP=
v4
header)
Once you have the ability to do valid packet captures then ideally
you should send me the raw pcap files (along with the MAC addresses of
the ethernet interfaces involved).
If you are unable to get valid packet capture then you can still help
me by trying some topologies/configuration options.
Before you do any testing, let me know what tools you have available
and I can help formalize some testing that will help me solve the issue.
On Wed, Dec 21, 2005 at 11:21:32PM +0000, guilhermemtorresbase-lista@yahoo.=
com.br wrote:
> Hello,
>=20
> I`m having some problems with MPLS when making tcp
> connections using MPLS (I`m trying to test with ssh
> and www. ICMP works fine.). I have two FC2 machines
> with rpm installations (I tryed to compile by hand and
> use KNOPPIX too, but I got the same erros).
>=20
> I did a simple testbed like:
>=20
> 1000
> Host A --------------- > Host B
> < ---------------
> 2000
>=20
> I used the following commands to configure:
>=20
> #########
> #Host A:#
> #########
>=20
> ifconfig eth2 192.168.0.1 netmask 255.255.255.0
> mpls nhlfe add key 0=20
> mpls nhlfe change key 0x00000002 instructions push gen
> 1000 nexthop eth2 ipv4 192.168.0.2
> ip route add 192.168.0.2/32 via 192.168.0.1 spec_nh
> 0x8847 0x0000002 advmss 1400
> mpls labelspace add dev eth2 labelspace 0
> mpls ilm add label gen 2000 labelspace 0
>=20
>=20
> #########
> #Host B:#
> #########
>=20
> ifconfig eth0 192.168.0.2 netmask 255.255.255.0
> mpls nhlfe add key 0=20
> mpls nhlfe change key 0x00000002 instructions push gen
> 2000 nexthop eth0 ipv4 192.168.0.1
> ip route add 192.168.0.1/32 via 192.168.0.2 spec_nh
> 0x8847 0x0000002 advmss 1400
> mpls labelspace add dev eth0 labelspace 0
> mpls ilm add label gen 1000 labelspace 0
>=20
> ----
>=20
> The ssh connection only works if I disable the tx/rx
> checksum with ethtool.
> I will copy a tcpdump of a ssh connection to help you
> understand the problem.
>=20
> -----
> 21:06:07.774317 MPLS (label 2000, exp 0, [S], ttl 64)
> IP (tos 0x0, ttl 64, id 35448, offset 0,
> flags [DF], proto 6, length: 60) 192.168.0.2.32779 >
> 192.168.0.1.ssh: S [tcp sum ok]
> 1525719340:1525719340(0) win 5600 <mss
> 1400,sackOK,timestamp 5188436 0,nop,wscale 2>
> 0x0000: 007d 0140 4500 003c 8a78 4000 4006
> 2ef0 .}.@E..<.x@.@...
> 0x0010: c0a8 0002 c0a8 0001 800b 0016 5af0
> a12c ............Z..,
> 0x0020: 0000 0000 a002 15e0 092c 0000 0204
> 0578 .........,.....x
> 0x0030: 0402 080a 004f 2b54 0000 0000 0103
> 0302 .....O+T........
> 21:06:07.777745 MPLS (label 1000, exp 0, [S], ttl 64)
> IP (tos 0x0, ttl 64, id 0, offset 0, flags
> [DF], proto 6, length: 60) 192.168.0.1.ssh >
> 192.168.0.2.32779: S [tcp sum ok]
> 2714454171:2714454171(0) ack 1525719341 win 5552 <mss
> 1400,sackOK,timestamp 9334616 5188436,nop,wscale 2>
> 0x0000: 003e 8140 4500 003c 0000 4000 4006
> b968 .>.@E..<..@.@..h
> 0x0010: c0a8 0001 c0a8 0002 0016 800b a1cb
> 489b ..............H.
> 0x0020: 5af0 a12d a012 15b0 aefd 0000 0204
> 0578 Z..-...........x
> 0x0030: 0402 080a 008e 6f58 004f 2b54 0103
> 0302 ......oX.O+T....
> 21:06:07.774606 MPLS (label 2000, exp 0, [S], ttl 64)
> IP (tos 0x0, ttl 64, id 35450, offset 0,
> flags [DF], proto 6, length: 52) 192.168.0.2.32779 >
> 192.168.0.1.ssh: . [tcp sum ok] ack 1 win 1400
> <nop,nop,timestamp 5188437 9334616>
> 0x0000: 007d 0140 4500 0034 8a7a 4000 4006
> 2ef6 .}.@E..4.z@.@...
> 0x0010: c0a8 0002 c0a8 0001 800b 0016 5af0
> a12d ............Z..-
> 0x0020: a1cb 489c 8010 0578 edbf 0000 0101
> 080a ..H....x........
> 0x0030: 004f 2b55 008e 6f58 =20
> .O+U..oX
> 21:06:07.776026 MPLS (label 1000, exp 0, [S], ttl 64)
> IP (tos 0x0, ttl 64, id 10181, offset 0,
> flags [DF], proto 6, length: 77) 192.168.0.1.ssh >
> 192.168.0.2.32779: P [bad tcp cksum 8193 (->52a3)!]
> 1:26(25) ack 1 win 1388 <nop,nop,timestamp 9334618
> 5188437>
> 0x0000: 003e 8140 4500 004d 27c5 4000 4006
> 9192 .>.@E..M'.@.@...
> 0x0010: c0a8 0001 c0a8 0002 0016 800b a1cb
> 489c ..............H.
> 0x0020: 5af0 a12d 8018 056c 8193 0000 0101
> 080a Z..-...l........
> 0x0030: 008e 6f5a 004f 2b55 5353 482d 312e
> 3939 ..oZ.O+USSH-1.99
> 0x0040: 2d4f 7065 6e53 5348 5f33 2e36 2e31
> 7032 -OpenSSH_3.6.1p2
> 0x0050: 0a
> 21:06:07.976486 MPLS (label 1000, exp 0, [S], ttl 64)
> IP (tos 0x0, ttl 64, id 10183, offset 0,
> flags [DF], proto 6, length: 77) 192.168.0.1.ssh >
> 192.168.0.2.32779: P [bad tcp cksum 8193 (->51da)!]
> 1:26(25) ack 1 win 1388 <nop,nop,timestamp 9334819
> 5188437>
> 0x0000: 003e 8140 4500 004d 27c7 4000 4006
> 9190 .>.@E..M'.@.@...
> 0x0010: c0a8 0001 c0a8 0002 0016 800b a1cb
> 489c ..............H.
> 0x0020: 5af0 a12d 8018 056c 8193 0000 0101
> 080a Z..-...l........
> 0x0030: 008e 7023 004f 2b55 5353 482d 312e
> 3939 ..p#.O+USSH-1.99
> 0x0040: 2d4f 7065 6e53 5348 5f33 2e36 2e31
> 7032 -OpenSSH_3.6.1p2
> 0x0050: 0a =20
> .
> 21:06:08.378424 MPLS (label 1000, exp 0, [S], ttl 64)
> IP (tos 0x0, ttl 64, id 10185, offset 0,
> flags [DF], proto 6, length: 77) 192.168.0.1.ssh >
> 192.168.0.2.32779: P [bad tcp cksum 8193 (->5048)!]
> 1:26(25) ack 1 win 1388 <nop,nop,timestamp 9335221
> 5188437>
> 0x0000: 003e 8140 4500 004d 27c9 4000 4006
> 918e .>.@E..M'.@.@...
> 0x0010: c0a8 0001 c0a8 0002 0016 800b a1cb
> 489c ..............H.
> 0x0020: 5af0 a12d 8018 056c 8193 0000 0101
> 080a Z..-...l........
> 0x0030: 008e 71b5 004f 2b55 5353 482d 312e
> 3939 ..q..O+USSH-1.99
> 0x0040: 2d4f 7065 6e53 5348 5f33 2e36 2e31
> 7032 -OpenSSH_3.6.1p2
> 0x0050: 0a =20
> .
> 21:06:09.182300 MPLS (label 1000, exp 0, [S], ttl 64)
> IP (tos 0x0, ttl 64, id 10187, offset 0,
> flags [DF], proto 6, length: 77) 192.168.0.1.ssh >
> 192.168.0.2.32779: P [bad tcp cksum 8193 (->4d24)!]
> 1:26(25) ack 1 win 1388 <nop,nop,timestamp 9336025
> 5188437>
> 0x0000: 003e 8140 4500 004d 27cb 4000 4006
> 918c .>.@E..M'.@.@...
> 0x0010: c0a8 0001 c0a8 0002 0016 800b a1cb
> 489c ..............H.
> 0x0020: 5af0 a12d 8018 056c 8193 0000 0101
> 080a Z..-...l........
> 0x0030: 008e 74d9 004f 2b55 5353 482d 312e
> 3939 ..t..O+USSH-1.99
> 0x0040: 2d4f 7065 6e53 5348 5f33 2e36 2e31
> 7032 -OpenSSH_3.6.1p2
> 0x0050: 0a =20
> .
> 21:06:10.790058 MPLS (label 1000, exp 0, [S], ttl 64)
> IP (tos 0x0, ttl 64, id 10189, offset 0,
> flags [DF], proto 6, length: 77) 192.168.0.1.ssh >
> 192.168.0.2.32779: P [bad tcp cksum 8193 (->46dc)!]
> 1:26(25) ack 1 win 1388 <nop,nop,timestamp 9337633
> 5188437>
> 0x0000: 003e 8140 4500 004d 27cd 4000 4006
> 918a .>.@E..M'.@.@...
> 0x0010: c0a8 0001 c0a8 0002 0016 800b a1cb
> 489c ..............H.
> 0x0020: 5af0 a12d 8018 056c 8193 0000 0101
> 080a Z..-...l........
> 0x0030: 008e 7b21 004f 2b55 5353 482d 312e
> 3939 ..{!.O+USSH-1.99
> 0x0040: 2d4f 7065 6e53 5348 5f33 2e36 2e31
> 7032 -OpenSSH_3.6.1p2
> 0x0050: 0a =20
> .
> 21:06:14.005571 MPLS (label 1000, exp 0, [S], ttl 64)
> IP (tos 0x0, ttl 64, id 10191, offset 0,
> flags [DF], proto 6, length: 77) 192.168.0.1.ssh >
> 192.168.0.2.32779: P [bad tcp cksum 8193 (->3a4c)!]
> 1:26(25) ack 1 win 1388 <nop,nop,timestamp 9340849
> 5188437>
> 0x0000: 003e 8140 4500 004d 27cf 4000 4006
> 9188 .>.@E..M'.@.@...
> 0x0010: c0a8 0001 c0a8 0002 0016 800b a1cb
> 489c ..............H.
> 0x0020: 5af0 a12d 8018 056c 8193 0000 0101
> 080a Z..-...l........
> 0x0030: 008e 87b1 004f 2b55 5353 482d 312e
> 3939 .....O+USSH-1.99
> 0x0040: 2d4f 7065 6e53 5348 5f33 2e36 2e31
> 7032 -OpenSSH_3.6.1p2
> 0x0050: 0a =20
> .
> 21:06:20.436593 MPLS (label 1000, exp 0, [S], ttl 64)
> IP (tos 0x0, ttl 64, id 10193, offset 0,
> flags [DF], proto 6, length: 77) 192.168.0.1.ssh >
> 192.168.0.2.32779: P [bad tcp cksum 8193 (->212c)!]
> 1:26(25) ack 1 win 1388 <nop,nop,timestamp 9347281
> 5188437>
> 0x0000: 003e 8140 4500 004d 27d1 4000 4006
> 9186 .>.@E..M'.@.@...
> 0x0010: c0a8 0001 c0a8 0002 0016 800b a1cb
> 489c ..............H.
> 0x0020: 5af0 a12d 8018 056c 8193 0000 0101
> 080a Z..-...l........
> 0x0030: 008e a0d1 004f 2b55 5353 482d 312e
> 3939 .....O+USSH-1.99
> 0x0040: 2d4f 7065 6e53 5348 5f33 2e36 2e31
> 7032 -OpenSSH_3.6.1p2
> 0x0050: 0a =20
> .
> 21:06:29.122144 arp who-has 192.168.0.2 tell
> 192.168.0.1
> 0x0000: 0001 0800 0604 0001 000c f16e e562
> c0a8 ...........n.b..
> 0x0010: 0001 0000 0000 0000 c0a8 0002 =20
> ............
> 21:06:29.122395 arp reply 192.168.0.2 is-at
> 00:12:3f:fc:ab:e9
> 0x0000: 0001 0800 0604 0002 0012 3ffc abe9
> c0a8 ..........?.....
> 0x0010: 0002 000c f16e e562 c0a8 0001 0000
> 0000 .....n.b........
> 0x0020: 0000 0000 0000 0000 0000 0000 0000 =20
> ..............
> 21:06:33.298637 MPLS (label 1000, exp 0, [S], ttl 64)
> IP (tos 0x0, ttl 64, id 10195, offset 0,
> flags [DF], proto 6, length: 77) 192.168.0.1.ssh >
> 192.168.0.2.32779: P [bad tcp cksum 8193 (->eeeb)!]
> 1:26(25) ack 1 win 1388 <nop,nop,timestamp 9360145
> 5188437>
> 0x0000: 003e 8140 4500 004d 27d3 4000 4006
> 9184 .>.@E..M'.@.@...
> 0x0010: c0a8 0001 c0a8 0002 0016 800b a1cb
> 489c ..............H.
> 0x0020: 5af0 a12d 8018 056c 8193 0000 0101
> 080a Z..-...l........
> 0x0030: 008e d311 004f 2b55 5353 482d 312e
> 3939 .....O+USSH-1.99
> 0x0040: 2d4f 7065 6e53 5348 5f33 2e36 2e31
> 7032 -OpenSSH_3.6.1p2
> 0x0050: 0a =20
> .
> 21:06:42.916901 MPLS (label 2000, exp 0, [S], ttl 64)
> IP (tos 0x0, ttl 64, id 35452, offset 0,
> flags [DF], proto 6, length: 52) 192.168.0.2.32779 >
> 192.168.0.1.ssh: F [tcp sum ok] 1:1(0) ack 1 win 1400
> <nop,nop,timestamp 5223582 9334616>
> 0x0000: 007d 0140 4500 0034 8a7c 4000 4006
> 2ef4 .}.@E..4.|@.@...
> 0x0010: c0a8 0002 c0a8 0001 800b 0016 5af0
> a12d ............Z..-
> 0x0020: a1cb 489c 8011 0578 6475 0000 0101
> 080a ..H....xdu......
> 0x0030: 004f b49e 008e 6f58 =20
> .O....oX
> 21:06:42.917406 MPLS (label 1000, exp 0, [S], ttl 64)
> IP (tos 0x0, ttl 64, id 10197, offset 0,
> flags [DF], proto 6, length: 52) 192.168.0.1.ssh >
> 192.168.0.2.32779: F [tcp sum ok] 26:26(0) ack 2 win
> 1388 <nop,nop,timestamp 9369765 5223582>
> 0x0000: 003e 8140 4500 0034 27d5 4000 4006
> 919b .>.@E..4'.@.@...
> 0x0010: c0a8 0001 c0a8 0002 0016 800b a1cb
> 48b5 ..............H.
> 0x0020: 5af0 a12e 8011 056c db19 0000 0101
> 080a Z......l........
> 0x0030: 008e f8a5 004f b49e =20
> .....O..
> --------------
>=20
> Best regards.
>=20
>=20
> =09
>=20
>=20
>=20
> =09
> =09
> _______________________________________________________=20
> Yahoo! doce lar. Fa?a do Yahoo! sua homepage.=20
> http://br.yahoo.com/homepageset.html=20
>=20
>=20
>=20
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--=20
James R. Leu
jl...@mi...
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