Xen networking problems in -current with xn driver?

I upgraded my VPS machine to today's current, and on reboot I couldn't 
get into it by network.

A quick switch to the VNC console showed that it was up but that it 
couldn't get out.


The xn interfaces said they were UP but attempts to get out were met 
with "network is down".

if I did 'tcpdump -n -i xn0' (and xn1) hten all was fine again.

tcpdump saw packets, and in fact ipfw saw some packets coming in even 
before that but it was not possible to send.


Has anyone seen similar?

some relevant parts of the dmesg output.:


T(vga): text 80x25
XEN: Hypervisor version 3.4 detected.
CPU: Intel(R) Xeon(R) CPU           E5620  _at_ 2.40GHz (2400.05-MHz 
686-class CPU)
   Origin="GenuineIntel"  Id=0x206c2  Family=0x6  Model=0x2c Stepping=2
Features=0x1781fbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,MMX,FXSR,SSE,SSE2,HTT>
Features2=0x80982201<SSE3,SSSE3,CX16,SSE4.1,SSE4.2,POPCNT,HV>
   AMD Features=0x20100000<NX,LM>
   AMD Features2=0x1<LAHF>
Hypervisor: Origin = "XenVMMXenVMM"
real memory  = 536870912 (512 MB)
avail memory = 503783424 (480 MB)
Event timer "LAPIC" quality 400
ACPI APIC Table: <Xen HVM>
WARNING: L1 data cache covers less APIC IDs than a core
0 < 1
WARNING: L2 data cache covers less APIC IDs than a core
0 < 1
WARNING: L3 data cache covers less APIC IDs than a core
0 < 1

ipfw2 (+ipv6) initialized, divert loadable, nat enabled, default to 
deny, logging disabled
xs_dev0: <Xenstore user-space device> on xenstore0
xenbusb_front0: <Xen Frontend Devices> on xenstore0
xn0: <Virtual Network Interface> at device/vif/0 on xenbusb_front0
xn0: Ethernet address: 00:16:3e:01:99:54
xn1: <Virtual Network Interface> at device/vif/1 on xenbusb_front0
xn1: Ethernet address: 00:16:3e:01:9a:54
xenbusb_back0: <Xen Backend Devices> on xenstore0
xenballoon0: <Xen Balloon Device> on xenstore0
xctrl0: <Xen Control Device> on xenstore0
xn0: backend features: feature-sg feature-gso-tcp4
xn1: backend features: feature-sg feature-gso-tcp4
xbd0: 20480MB <Virtual Block Device> at device/vbd/768 on xenbusb_front0
xbd0: attaching as ada0
xbd0: features: write_barrier
xbd0: synchronize cache commands enabled.