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*SOLVED* VE with veth, using MAC address it shouldn't be aware of [message #10004]

Sun, 04 February 2007 10:02

samlt
Messages: 8
Registered: February 2007

Junior Member

hello,

Here is a picture, of what I have: (I don't know how it will look for you, so you can also find it here (EDIT: or as an attachement)

linksys router                  |----------------------------------------- my computer with openvz -------------------------------------------------------------------------|
00:0f:66:83:45:8e               |       eth0                            veth103.0                     |--------------------------------------------------------------------||
10.3.0.13          -------------| 00:30:1B:B6:F2:1C               00:18:51:B4:A6:85  ---------------  |      eth0                 VE: name=debnated(not yet nated actually)||
                                |     10.3.0.50                        10.4.0.50                      | 00:18:51:ce:18:98                                                  ||
                                |                                                                     |   10.4.0.52                                                        ||
                                |                                                                     ---------------------------------------------------------------------||
                                |-------------------------------------------------------------------------------------------------------------------------------------------|

on the VE "debnated" (ip: 10.4.0.52):
ping 10.3.0.13

one tcpdump process running on the eth0 and the other on veth103.0 : (after sorting them (and added the "== interface" at the end of the line), here is what I get)

1) 10:02:24.541939 00:18:51:ce:18:98 (oui Unknown) > Broadcast, ethertype ARP (0x0806), length 42: arp who-has 10.4.0.50 tell debnated == on veth103.0
2) 10:02:24.541968 00:18:51:b4:a6:85 (oui Unknown) > 00:18:51:ce:18:98 (oui Unknown), ethertype ARP (0x0806), length 42: arp reply 10.4.0.50 is-at 00:18:51:b4:a6:85 (oui Unknown) == on veth103.0
3) 10:02:24.541973 00:30:1b:b6:f2:1c (oui Unknown) > 00:0f:66:83:45:8e (oui Unknown), ethertype IPv4 (0x0800), length 98: debnated > linksys: ICMP echo request, id 56597, seq 1, length 64 == on veth103.0
4) 10:02:24.542005 00:30:1b:b6:f2:1c (oui Unknown) > 00:0f:66:83:45:8e (oui Unknown), ethertype IPv4 (0x0800), length 98: debnated > linksys: ICMP echo request, id 56597, seq 1, length 64 == on eth0
5) 10:02:24.542615 00:0f:66:83:45:8e (oui Unknown) > 00:30:1b:b6:f2:1c (oui Unknown), ethertype IPv4 (0x0800), length 98: linksys > debnated: ICMP echo reply, id 56597, seq 1, length 64 == on eth0
6) 10:02:24.542633 00:18:51:b4:a6:85 (oui Unknown) > 00:18:51:ce:18:98 (oui Unknown), ethertype IPv4 (0x0800), length 98: linksys > debnated: ICMP echo reply, id 56597, seq 1, length 64 == on veth103.0
7) 10:02:29.540780 00:18:51:b4:a6:85 (oui Unknown) > 00:18:51:ce:18:98 (oui Unknown), ethertype ARP (0x0806), length 42: arp who-has debnated tell 10.4.0.50 == on veth103.0
8) 10:02:29.540809 00:18:51:ce:18:98 (oui Unknown) > 00:18:51:b4:a6:85 (oui Unknown), ethertype ARP (0x0806), length 42: arp reply debnated is-at 00:18:51:ce:18:98 (oui Unknown) == on veth103.0

take the 3) line for example, look at the MAC address, shouldn't it be 00:18:51:ce:18:98 > 00:18:51:B4:A6:85 instead ? the VE "debnated" should not even know thess MAC address? (unless I misunderstood something)

here is the arp cache on 'debnated", just after the ping:

 debnated:/ #  arp   
  Address                  HWtype  HWaddress           Flags Mask            Iface
  10.4.0.50                ether   00:18:51:B4:A6:85   C                     eth0

I don't know if it's because of how openvz works, or if I made something wrong?

thanks in advance

Attachment: temp.txt
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[Updated on: Sat, 10 February 2007 01:31]

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Re: VE with veth, using MAC address it shouldn't be aware of [message #10016 is a reply to message #10004]

Mon, 05 February 2007 11:08

Andrey Mirkin
Messages: 193
Registered: May 2006

Senior Member

Can you please post here output of commands "ip a ls" and "ip ro ls" in VE and VE0.

Andrey Mirkin

http://static.openvz.org/userbars/openvz-developer.png

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Re: VE with veth, using MAC address it shouldn't be aware of [message #10022 is a reply to message #10016]

Mon, 05 February 2007 16:02

samlt
Messages: 8
Registered: February 2007

Junior Member

oh yes I didn't give their routing tables :/

in the VE0
ip addr ls

2: lo: <LOOPBACK,UP,10000> mtu 16436 qdisc noqueue 
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
4: eth0: <BROADCAST,MULTICAST,UP,10000> mtu 1500 qdisc pfifo_fast qlen 1000
    link/ether 00:30:1b:b6:f2:1c brd ff:ff:ff:ff:ff:ff
    inet 10.3.0.50/24 scope global eth0
1: venet0: <BROADCAST,POINTOPOINT,NOARP,UP,10000> mtu 1500 qdisc noqueue 
    link/void 
3: veth103.0: <BROADCAST,MULTICAST,UP,10000> mtu 1500 qdisc noqueue 
    link/ether 00:18:51:b4:a6:85 brd ff:ff:ff:ff:ff:ff
    inet 10.4.0.50/24 scope global veth103.0

and
ip route ls

10.4.0.0/24 dev veth103.0  proto kernel  scope link  src 10.4.0.50 
10.3.0.0/24 dev eth0  proto kernel  scope link  src 10.3.0.50 
127.0.0.0/8 dev lo  scope link 
default via 10.3.0.13 dev eth0

In the VE
ip addr l

1: lo: <LOOPBACK,UP,10000> mtu 16436 qdisc noqueue 
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
3: venet0: <BROADCAST,POINTOPOINT,NOARP> mtu 1500 qdisc noqueue 
    link/void 
    inet 127.0.0.1/32 scope host venet0
5: eth0: <BROADCAST,MULTICAST,UP,10000> mtu 1500 qdisc noqueue 
    link/ether 00:18:51:ce:18:98 brd ff:ff:ff:ff:ff:ff
    inet 10.4.0.52/24 brd 10.4.0.255 scope global eth0

and
ip r l

10.4.0.0/24 dev eth0  proto kernel  scope link  src 10.4.0.52 
default via 10.4.0.50 dev eth0

There is nothing special. Let me know if you need anything else.

Smile

[Updated on: Mon, 05 February 2007 16:02]

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Re: VE with veth, using MAC address it shouldn't be aware of [message #10023 is a reply to message #10022]

Mon, 05 February 2007 16:18

Andrey Mirkin
Messages: 193
Registered: May 2006

Senior Member

Can you please post here output of "ip neigh ls" in VE and VE0.
Also please post here tcpdump output without sorting for veth103.0 and eth0 in VE0.

Andrey Mirkin

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Re: VE with veth, using MAC address it shouldn't be aware of [message #10029 is a reply to message #10023]

Mon, 05 February 2007 17:43

samlt
Messages: 8
Registered: February 2007

Junior Member

sure

in the VE

ping 10.3.0.13
PING 10.3.0.13 (10.3.0.13) 56(84) bytes of data.
64 bytes from 10.3.0.13: icmp_seq=1 ttl=63 time=1.43 ms

--- 10.3.0.13 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 1.430/1.430/1.430/0.000 ms

then ip neigh ls

10.4.0.50 dev eth0 lladdr 00:18:51:b4:a6:85 nud reachable

in the VE0
on eth0

tcpdump -i 1  src net 10 and dst net 10 -e
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 68 bytes
18:30:12.066702 00:30:1b:b6:f2:1c (oui Unknown) > 00:0f:66:83:45:8e (oui Unknown), ethertype IPv4 (0x0800), length 98: debnated > linksys: ICMP echo request, id 26134, seq 1, length 64
18:30:12.067175 00:0f:66:83:45:8e (oui Unknown) > 00:30:1b:b6:f2:1c (oui Unknown), ethertype IPv4 (0x0800), length 98: linksys > debnated: ICMP echo reply, id 26134, seq 1, length 64
18:30:17.065558 00:30:1b:b6:f2:1c (oui Unknown) > 00:0f:66:83:45:8e (oui Unknown), ethertype ARP (0x0806), length 42: arp who-has linksys tell 10.3.0.50
18:30:17.065866 00:0f:66:83:45:8e (oui Unknown) > 00:30:1b:b6:f2:1c (oui Unknown), ethertype ARP (0x0806), length 60: arp reply linksys is-at 00:0f:66:83:45:8e (oui Unknown)

on veth103.0

tcpdump -i 3  src net 10 and dst net 10 -e
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on veth103.0, link-type EN10MB (Ethernet), capture size 68 bytes
18:30:12.066645 00:18:51:ce:18:98 (oui Unknown) > Broadcast, ethertype ARP (0x0806), length 42: arp who-has 10.4.0.50 tell debnated
18:30:12.066671 00:18:51:b4:a6:85 (oui Unknown) > 00:18:51:ce:18:98 (oui Unknown), ethertype ARP (0x0806), length 42: arp reply 10.4.0.50 is-at 00:18:51:b4:a6:85 (oui Unknown)
18:30:12.066677 00:30:1b:b6:f2:1c (oui Unknown) > 00:0f:66:83:45:8e (oui Unknown), ethertype IPv4 (0x0800), length 98: debnated > linksys: ICMP echo request, id 26134, seq 1, length 64
18:30:12.067191 00:18:51:b4:a6:85 (oui Unknown) > 00:18:51:ce:18:98 (oui Unknown), ethertype IPv4 (0x0800), length 98: linksys > debnated: ICMP echo reply, id 26134, seq 1, length 64
18:30:17.065571 00:18:51:b4:a6:85 (oui Unknown) > 00:18:51:ce:18:98 (oui Unknown), ethertype ARP (0x0806), length 42: arp who-has debnated tell 10.4.0.50
18:30:17.065599 00:18:51:ce:18:98 (oui Unknown) > 00:18:51:b4:a6:85 (oui Unknown), ethertype ARP (0x0806), length 42: arp reply debnated is-at 00:18:51:ce:18:98 (oui Unknown)

ip neigh ls

10.4.0.52 dev veth103.0 lladdr 00:18:51:ce:18:98 REACHABLE
10.3.0.13 dev eth0 lladdr 00:0f:66:83:45:8e REACHABLE

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Re: VE with veth, using MAC address it shouldn't be aware of [message #10044 is a reply to message #10029]

Tue, 06 February 2007 11:03

Andrey Mirkin
Messages: 193
Registered: May 2006

Senior Member

Do you use NAT in VE0? Or you have route to 10.4.0.x network on linksys?

Andrey Mirkin

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Re: VE with veth, using MAC address it shouldn't be aware of [message #10047 is a reply to message #10004]

Tue, 06 February 2007 11:44

samlt
Messages: 8
Registered: February 2007

Junior Member

No NAT in VE0, but I did set a route to 10.4.0/24 in the linksys.(going through 10.3.0.50)
I fail to see why it would be important (except that I would have any "echo reply" ) The VE is using (at least that's what I understand looking at tcpdump output) the VE0 eth0 MAC address, and the linksys MAC address.

I know the VE is "sharing/using" (?) the same kernel as VE0, so this is probably normal, but if it is, why, in the VE, does ip n l only give veth103.0 MAC address? In short what would be the use of this "neighbour table" if it isn't used Confused

The fact is, that, on the other way (line 6 in the sorted tcpdump output, first post), the mac addresses are "correct" :

6) 10:02:24.542633 00:18:51:b4:a6:85 (oui Unknown) > 00:18:51:ce:18:98 (oui Unknown), ethertype IPv4 (0x0800), length 98: linksys > debnated: ICMP echo reply, id 56597, seq 1, length 64 == on veth103.0

where 00:18:51:b4:a6:85 is veth103.0 MAC address, and 00:18:51:ce:18:98 is the VE eth0 MAC address.

I going to test the last openvz kernel asap, tonight if I can.

[Updated on: Wed, 07 February 2007 12:32]

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Re: VE with veth, using MAC address it shouldn't be aware of [message #10127 is a reply to message #10047]

Thu, 08 February 2007 18:33

samlt
Messages: 8
Registered: February 2007

Junior Member

well I did try with the latest openvz available : 2.6.18-openvz-028.015
( For what it's worth I'm using gentoo, and I'm using the kernel provided in the gentoo repository)

but I have an other problem with this kernel, I don't know if I did something wrong with the .config ? I can't enter any VE with this kernel:

vzctl enter 103
entered into VE 103
exited from VE 103

I can still exec in the VE though

I don't see anything in /var/log/vzctl.log, vzctl --verbose didn't help. The following is what I've been asked on #openvz:

vzctl exec 103 mount
simfs on / type simfs (rw)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw)
tmpfs on /dev/shm type tmpfs (rw)

and

vzctl exec 103 ls -lh /dev/ptmx
crw-rw-rw-  1 root tty 5, 2 Apr 29  2006 /dev/ptmx

and when connecting through ssh:

ssh 10.4.0.52
Password: 
Last login: Thu Feb  8 19:59:08 2007 from 10.4.0.50
Connection to 10.4.0.52 closed.

(as you can see, the session is closed as soon as I log in :/

So for now I'm back with 2.6.18-openvz-028.010

For the initial problem, is this normal then? or can this be a bug? Should I bug report?

[Updated on: Fri, 09 February 2007 07:30]

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Re: VE with veth, using MAC address it shouldn't be aware of [message #10143 is a reply to message #10047]

Fri, 09 February 2007 12:07

Andrey Mirkin
Messages: 193
Registered: May 2006

Senior Member

I'm sorry for not answering so long.
Right now I have only one explanation of this bug - the problem actually in tcpdump:
1. tcpdump gets information that veth received packet.
2. packet passes through route table and source MAC address in this packet is changed to eth0 MAC address.
3. tcpdump shows packet with changed MAC address.

tcpdump doesn't copy packet when receive it, that is why it shows changed packet.

Usually packets are copied before routing, but this doesn't performed for veth and venet devices due to optimization (reduce overhead).

Actually I was not able to reproduce this bug on the same configuration. What version of tcpdump do you use?

Andrey Mirkin

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Re: VE with veth, using MAC address it shouldn't be aware of [message #10145 is a reply to message #10143]

Fri, 09 February 2007 16:20

samlt
Messages: 8
Registered: February 2007

Junior Member

I'm using tcdump-3.9.5

Quote:

Usually packets are copied before routing, but this doesn't performed for veth and venet devices due to optimization (reduce overhead).

I'm not sure I've understood, "usually packets are copied", does this mean, usually, tcpdump display the copied packet?

This is wierd you cannot reproduce it:/ I have an other VE (precreated slackware template if that matters..) with the same configuration (with veth) and I can reproduce it.

Thanks you for your help

(given that I had no response before, I did a bug report: #466 :/ , the bug is probably invalid then)

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Re: VE with veth, using MAC address it shouldn't be aware of [message #10148 is a reply to message #10145]

Fri, 09 February 2007 17:17

Andrey Mirkin
Messages: 193
Registered: May 2006

Senior Member

I'm using tcpdump-3.8.2-10.RHEL4.
Maybe I just can't reproduce this bug because of race:
Packet should be changed before printing.

Quote:

I'm not sure I've understood, "usually packets are copied", does this mean, usually, tcpdump display the copied packet?

For not virtualized interfaces (e.g. when packets go from eth0 to eth1) packets are copied before changing MAC address. And tcpdump shows a copy of packet, which was not changed.

Andrey Mirkin

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Re: VE with veth, using MAC address it shouldn't be aware of [message #10150 is a reply to message #10148]

Fri, 09 February 2007 18:41

samlt
Messages: 8
Registered: February 2007

Junior Member

And now the million dollar (or euro..) question, why does it work if I make a bridge with only this interface (well this also work if I bridge several interfaces..) ?

brctl show
bridge name     bridge id               STP enabled     interfaces
br0             8000.001851b4a685       no              veth103.0

and

ip a l 
4: eth0: <BROADCAST,MULTICAST,UP,10000> mtu 1500 qdisc pfifo_fast qlen 1000
    link/ether 00:30:1b:b6:f2:1c brd ff:ff:ff:ff:ff:ff
    inet 10.3.0.50/24 scope global eth0
...
9: veth103.0: <BROADCAST,MULTICAST,UP,10000> mtu 1500 qdisc noqueue 
    link/ether 00:18:51:29:5c:12 brd ff:ff:ff:ff:ff:ff
6: br0: <BROADCAST,MULTICAST,UP,10000> mtu 1500 qdisc noqueue 
    link/ether 00:18:51:b4:a6:85 brd ff:ff:ff:ff:ff:ff
    inet 10.4.0.50/24 scope global br0

on the VE0

tcpdump  -i 3 -e
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on br0, link-type EN10MB (Ethernet), capture size 68 bytes
(...)
19:33:34.851958 00:18:51:ce:18:98 (oui Unknown) > 00:18:51:b4:a6:85 (oui Unknown), ethertype IPv4 (0x0800), length 98: debnated > linksys: ICMP echo request, id 15397, seq 1, length 64
19:33:34.852498 00:18:51:b4:a6:85 (oui Unknown) > 00:18:51:ce:18:98 (oui Unknown), ethertype IPv4 (0x0800), length 98: linksys > debnated: ICMP echo reply, id 15397, seq 1, length 64

This means the packet are copied when the interface is a bridge(or at least when it's not a veth nor a venet interface)?

By the way, when you said, the packet are copied, it's the kernel which makes the copy, right?

Thank you

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Re: VE with veth, using MAC address it shouldn't be aware of [message #10152 is a reply to message #10150]

Fri, 09 February 2007 23:00

Andrey Mirkin
Messages: 193
Registered: May 2006

Senior Member

samlt wrote on Fri, 09 February 2007 13:41

And now the million dollar (or euro..) question, why does it work if I make a bridge with only this interface (well this also work if I bridge several interfaces..) ?
This means the packet are copied when the interface is a bridge(or at least when it's not a veth nor a venet interface)?

If you will create a bridge with veth device you will have following situation: all outgoing packets from veth will be delivered to VE0 from bridge interface and these packets will be copied before routing as bridge is not virtual interface. Thus tcpdump will show not changed packets.

Quote:

By the way, when you said, the packet are copied, it's the kernel which makes the copy, right?

Right.

Andrey Mirkin

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Re: VE with veth, using MAC address it shouldn't be aware of [message #10154 is a reply to message #10152]

Sat, 10 February 2007 01:31

samlt
Messages: 8
Registered: February 2007

Junior Member

well, so, answer to my question is, yes this is normal, but what you see is not what's really happenning!

Thank you Andrey Mirkin, I tag this thread as solved

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