duplicate network packets in bridged mode => Fixed in SVN

[kamensky]

I am running a guest dibbler on a host carrot. The network mode is set to bridged. The home network includes another computer, gaspode. When I ping the guest from gaspode or conversely, I get duplicates:

moshe@dibbler:~(244)-> ping -c 3 gaspode
PING gaspode (192.168.1.69) 56(84) bytes of data.
64 bytes from gaspode (192.168.1.69): icmp_req=1 ttl=64 time=50.4 ms
64 bytes from carrot (192.168.1.66): icmp_req=1 ttl=63 time=50.4 ms (DUP!)
64 bytes from gaspode (192.168.1.69): icmp_req=2 ttl=64 time=4.65 ms
64 bytes from carrot (192.168.1.66): icmp_req=2 ttl=63 time=4.74 ms (DUP!)
64 bytes from gaspode (192.168.1.69): icmp_req=3 ttl=64 time=10.5 ms

--- gaspode ping statistics ---
3 packets transmitted, 3 received, +2 duplicates, 0% packet loss, time 2003ms
rtt min/avg/max/mdev = 4.659/24.153/50.447/21.560 ms

moshe@gaspode:~(1894)-> ping -c 3 dibbler
PING dibbler.gateway.2wire.net (192.168.1.65) 56(84) bytes of data.
From carrot (192.168.1.66): icmp_seq=1 Redirect Host(New nexthop: dibbler (192.168.1.65))
64 bytes from dibbler (192.168.1.65): icmp_req=1 ttl=64 time=38.6 ms
64 bytes from dibbler (192.168.1.65): icmp_req=1 ttl=63 time=38.6 ms (DUP!)
From carrot (192.168.1.66): icmp_seq=2 Redirect Host(New nexthop: dibbler (192.168.1.65))
64 bytes from dibbler (192.168.1.65): icmp_req=2 ttl=64 time=60.1 ms
64 bytes from dibbler (192.168.1.65): icmp_req=2 ttl=63 time=60.1 ms (DUP!)
From carrot (192.168.1.66): icmp_seq=3 Redirect Host(New nexthop: dibbler (192.168.1.65))
64 bytes from dibbler (192.168.1.65): icmp_req=3 ttl=64 time=83.5 ms

--- dibbler.gateway.2wire.net ping statistics ---
3 packets transmitted, 3 received, +2 duplicates, 0% packet loss, time 2002ms
rtt min/avg/max/mdev = 38.643/56.245/83.575/16.719 ms

There is no problem when pinging to or from the host. I am also getting duplicates when pinging external addresses from the guest. However, other external internet services seem to work properly with the guest, whereas I cannot use ssh between the guest and gaspode (in either direction).

Here is a link to a thread on the mailing list where I tried to solve the problem:

 http://sourceforge.net/mailarchive/message.php?msg_id=28100263

I attach the vbox log file, and a Wireshark capture of a ping command (Wireshark running on the host). More information below.

IP addresses and OSes:

dibbler (guest), Gentoo Linux,          192.168.1.65
carrot (host), MacOsX (Darwin) 10.8.0,  192.168.1.66
gaspode        Gentoo Linux,            192.168.1.69
router                                  192.168.1.254

The host is connected by wireless (airport) to the router. gaspode is connected by cable to the router.

Routing table on dibbler (guest):

moshe@dibbler:~(248)-> netstat -nr
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
0.0.0.0         192.168.1.254   0.0.0.0         UG        0 0          0 eth1
127.0.0.0       127.0.0.1       255.0.0.0       UG        0 0          0 lo
192.168.1.0     0.0.0.0         255.255.255.0   U         0 0          0 eth1

Routing table on carrot (host):

moshe@carrot:~(248)-> netstat -nr
Routing tables

Internet:
Destination        Gateway            Flags        Refs      Use   Netif Expire
default            192.168.1.254      UGSc           26       38     en1
127                127.0.0.1          UCS             0        0     lo0
127.0.0.1          127.0.0.1          UH             11   976428     lo0
169.254            link#5             UCS             0        0     en1
192.168.1          link#5             UCS             3        0     en1
192.168.1.65       8:0:27:3a:49:3a    UHLWI           1      460     en1    844
192.168.1.66       127.0.0.1          UHS             2     3158     lo0
192.168.1.69       58:b0:35:ee:a5:5f  UHLWI           4      842     en1    837
192.168.1.254      0:25:3c:c0:f3:49   UHLWI          46     2440     en1   1200

Routing table on gaspode:

moshe@gaspode:~(1909)-> netstat -nr
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
0.0.0.0         192.168.1.254   0.0.0.0         UG        0 0          0 eth0
127.0.0.0       127.0.0.1       255.0.0.0       UG        0 0          0 lo
192.168.1.0     0.0.0.0         255.255.255.0   U         0 0          0 eth0

[kamensky]

vbox log file

[kamensky]

wireshark capture on the host

[aleksey]

Duplicate packets are most likely being introduced by the host because it has IP forwarding enabled. You can turn it off with:

sudo sysctl -w net.inet.ip.forwarding=1

If this is not an option I suggest you use host-only instead of bridged mode and configure routing on the hosts accordingly.

[kamensky]

Replying to aleksey:

Duplicate packets are most likely being introduced by the host because it has IP forwarding enabled. You can turn it off with:

sudo sysctl -w net.inet.ip.forwarding=1

If this is not an option I suggest you use host-only instead of bridged mode and configure routing on the hosts accordingly.

Yes, that helped (should be =0 above). Thanks!

[frank]

There will be a fix available in the next maintenance release.

[frank]

Fix is part of 4.1.6.

[_madworm_]

I feel like I have to warm this up again.

I'm on 5.1.8 (linux host) & pretty much see the same thing.

The host is attached to a router (Android AP) via WiFi, the guest is bridged to the host's wlan interface.

[vushakov]

What do you mean exactly by "pretty much the same thing"?

[_madworm_]

Duplicate replies to a ping from the guest that go away when ip forwarding is turned off on the host for the wifi interface that the guest is bridged to.