[ixp1200] peth driver question, need help

I use peth driver with ixp1200, and meet this error message. this error will drop some output packet occasionally, who will tell me what is happend, thanks very much this error is below: $ insmod ue.o $ insmod octmac.o $ insmod giga_drv.o $ rs_udebug $ load $ ping 1.2.1.1 then I meet the error message like that: peth_start_xmit called peth_start_xmit: new descriptor = 0 Bad descriptor 0, dropping outgoing packet pethFreeDescriptor: descriptor = 0 pethFreeDescriptor: Bad descriptor 0 Best Regard