Linux-bridge, uml, and harware-hub

Hello,

I use bridge to give user-mode-linux boxs an Internet access

When the uml-host is connected to the gateway via a cross-wired cable, everything works fine.

If I put a hub (I've also make tests with another hub and a switch) between the host and the gateway, uml-guests no more see the gateway (and therefore no more see the Internet)

In both case the uml-host can ping the gateway and the uml-guests, the gateway can always ping the uml-host, and the uml-guests can always ping the uml-host:

* direct cross wired cable between umlhost and gateway:

[umlhost:br2:192.168.1.2/24] -------- [gateway:eth4:192.168.1.1/24]

           |
           |

[uml1:eth0:192.168.1.3/24]

umlhost# ping 192.168.1.1 is OK
umlhost# ping 192.168.1.3 is OK
uml1# ping 192.168.1.1 is OK

* a hub (or a switch) between umlhost and gateway

[umlhost:br2:192.168.1.2/24] --[hub]-- [gateway:eth4:192.168.1.1/24]

           |
           |

[uml1:eth0:192.168.1.3/24]

umlhost# ping 192.168.1.1 is OK
umlhost# ping 192.168.1.3 is OK
uml1# ping 192.168.1.1 no response
gateway# ping 192.168.1.3 no response

I've noticed that dmesg gives me lot of lines like theses:
eth2: received packet with own address as source address
eth2: received packet with own address as source address
...

I first think about a MAC adress sort of conflict, so I take care of assigning specifics ones to the uml-guests, but no changes.

What did I miss ?

Thanks,
Olivier.

PS: my current configuration look like this:

host kernel is a 2.4.22 (with almost all security patchs, skas3, and cryptoloop) SMP enabled on a dual PIII/400
(cannot try latest 2.4 kernel now, it's planned)

umlhost# brctl show

bridge name     bridge id               STP enabled     interfaces
br2             8000.0080c8e8ac3f       no              eth2

tap0

umlhost# brctl showmacs br2
port no mac addr is local? ageing timer
1 00:00:e8:3d:be:81 no 202.29 (this is the
gateway)

 1     00:80:c8:e8:ac:3f       yes                0.00   (this is eth2)
 2     00:ff:c0:6a:b1:46       yes                0.00   (this is tap0)
 2     fe:fd:0a:00:00:01       no               218.27   (this is eth0 

inside uml)

umlhost# ifconfig eth2
eth2 Link encap:Ethernet HWaddr 00:80:C8:E8:AC:3F

         UP BROADCAST RUNNING PROMISC MULTICAST  MTU:1500  Metric:1
         RX packets:1029587 errors:0 dropped:5 overruns:0 frame:104
         TX packets:2307201 errors:3 dropped:0 overruns:3 carrier:0
         collisions:0 txqueuelen:100
         RX bytes:152173060 (145.1 MiB)  TX bytes:3011077736 (2.8 GiB)
         Interrupt:18 Base address:0x9000

umlhost# ifconfig tap0
tap0 Link encap:Ethernet HWaddr 00:FF:C0:6A:B1:46
UP BROADCAST RUNNING PROMISC MULTICAST MTU:1500 Metric:1 RX packets:7595 errors:0 dropped:0 overruns:0 frame:0 TX packets:7641 errors:0 dropped:2 overruns:0 carrier:0 collisions:0 txqueuelen:100
RX bytes:6853964 (6.5 MiB) TX bytes:732177 (715.0 KiB)

umlhost# ifconfig br2
br2 Link encap:Ethernet HWaddr 00:80:C8:E8:AC:3F
inet addr:192.168.1.2 Bcast:192.168.1.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:4019 errors:0 dropped:0 overruns:0 frame:0 TX packets:1342 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0
RX bytes:394739 (385.4 KiB) TX bytes:184260 (179.9 KiB)

uml1:~# ifconfig eth0
eth0      Link encap:Ethernet  HWaddr FE:FD:0A:00:00:01
         inet addr:192.168.1.3  Bcast:192.168.1.255  Mask:255.255.255.0
         inet6 addr: fe80::fcfd:aff:fe00:1/64 Scope:Link
         UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
         RX packets:7641 errors:0 dropped:0 overruns:0 frame:0
         TX packets:7595 errors:0 dropped:0 overruns:0 carrier:0
         collisions:0 txqueuelen:100
         RX bytes:625203 (610.5 KiB)  TX bytes:6853964 (6.5 MiB)
         Interrupt:5

gateway# ifconfig eth4
eth4 Link encap:10Mbps Ethernet HWaddr 00:00:E8:3D:BE:81
inet addr:192.168.1.1 Bcast:192.168.1.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:6188 errors:0 dropped:0 overruns:0
TX packets:5398 errors:0 dropped:0 overruns:0 Interrupt:12 Base address:0xc400