xen and networking problems

[brook%biology.nmsu.edu@localhost (Brook Milligan)]

Now that I have gotten a xen kernel to boot (thanks!)[1], I am having
trouble with the network interface under xen.  In short, the kernel
boots and apparently configures the interface, but no packets can be
transmitted.  The identical configuration works fine with a MONOLITHIC
kernel compiled from current source as of 2009-08-01 (which is the
same as for the xen kernel and the entire system).

When booted with 64Mb (of a total 16Gb) of RAM for dom0, the
XEN3PAE_DOM0 kernel probes the network interfaces as follows:

     fxp0 at pci7 dev 2 function 0: i82550 Ethernet, rev 13
     ioapic0: int17 
0x1a9c0<vector=0xc0,delmode=0x1,logical,actlo,level,masked,dest=0x0> 
0xf000000<target=0xf>
     fxp0: interrupting at ioapic0 pin 17, event channel 6
     fxp0: Ethernet address 00:30:48:23:3a:81
     inphy0 at fxp0 phy 1: i82555 10/100 media interface, rev. 4
     inphy0: 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto
     fxp1 at pci7 dev 3 function 0: i82550 Ethernet, rev 13
     fxp1: interrupting at ioapic0 pin 18, event channel 5
     xen_alloc_contig: XENMEM_decrease_reservation failed!
     fxp1: unable to allocate control data, error = 12

Note the error with the second interface.  When booted with either
256Mb or 1024Mb of RAM the same error shows up, but for both network
interfaces.

The one physical interface is configured as follows:

     # ifconfig.fxp0
     media autoselect
     inet 172.16.0.2/24

and a bridge is configured as follows for later use by domUs:

     # ifconfig.bridge0
     create
     !brconfig $int add fxp0
     !brconfig $int stp fxp0
     !brconfig $int up

'ifconfig -a' reports the following (which is essentially identical,
barring the missing fxp1 interface, to the report when running
successfully under the MONOLITHIC kernel):

     fxp0: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu 1500
             
capabilities=3f00<IP4CSUM_Rx,IP4CSUM_Tx,TCP4CSUM_Rx,TCP4CSUM_Tx,UDP4CSUM_Rx,UDP4CSUM_Tx>
             enabled=0
             address: 00:30:48:23:3a:81
             media: Ethernet autoselect (100baseTX full-duplex)
             status: active
             inet 172.16.0.2 netmask 0xffffff00 broadcast 172.16.0.255
             inet6 fe80::230:48ff:fe23:3a81%fxp0 prefixlen 64 scopeid 0x1
     lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 33184
             inet 127.0.0.1 netmask 0xff000000
             inet6 ::1 prefixlen 128
             inet6 fe80::1%lo0 prefixlen 64 scopeid 0x2
     bridge0: flags=41<UP,RUNNING> mtu 1500

However, no packets can be transmitted.  For example, ping reports
'host is down' errors.

Where shall I be looking for solutions to this?  Are there known
networking problems with xen?  Is this something special with the fxp
driver?  with my hardware?  Any suggestions on where to start are
welcome.  I very much appreciate the help.

Thanks alot.

Cheers,
Brook

[1] See the thread starting with
    http://mail-index.netbsd.org/port-xen/2009/10/29/msg005516.html