natd panics are back

This was fixed a while ago and now it has made its way back into
current:

server# uname -a
FreeBSD server.mcneil.com 6.0-CURRENT FreeBSD 6.0-CURRENT #58: Mon Nov 15 08:40:01 PST 2004     root_at_server.mcneil.com:/usr/obj/usr/src/sys/AMD64  amd64

Nov 15 13:56:16 server kernel: Fatal trap 12: page fault while in kernel mode
Nov 15 13:56:16 server kernel: fault virtual address    = 0x18
Nov 15 13:56:16 server kernel: fault code               = supervisor read, page
not present
Nov 15 13:56:16 server kernel: instruction pointer      = 0x8:0xffffffff80354810Nov 15 13:56:16 server kernel: stack pointer            = 0x10:0xffffffffb1c71620
Nov 15 13:56:16 server kernel: frame pointer            = 0x10:0xffffffffb1c71680
Nov 15 13:56:16 server kernel: code segment             = base 0x0, limit 0xfffff, type 0x1b
Nov 15 13:56:16 server kernel: = DPL 0, pres 1, long 1, def32 0, gran 1
Nov 15 13:56:16 server kernel: processor eflags = interrupt enabled, resume, IOPL = 0
Nov 15 13:56:16 server kernel: current process          = 212 (natd)
Nov 15 13:56:16 server kernel: trap number              = 12
Nov 15 13:56:16 server kernel: panic: page fault
Nov 15 13:56:16 server kernel: KDB: enter: panic


(gdb) l *0xffffffff80354810
0xffffffff80354810 is in m_copym (/usr/src/sys/kern/uipc_mbuf.c:373).
368             MBUF_CHECKSLEEP(wait);
369             if (off == 0 && m->m_flags & M_PKTHDR)
370                     copyhdr = 1;
371             while (off > 0) {
372                     KASSERT(m != NULL, ("m_copym, offset > size of mbuf chain"));
373                     if (off < m->m_len)
374                             break;
375                     off -= m->m_len;
376                     m = m->m_next;
377             }