multicast panic in -current?

When running sources cvsupped on Monday on amd64,
I hit the following panic when attempting to add
a multicast address.  I don't have a stack trace,
but I do have a ddb trace.

Fatal trap 12: page fault while in kernel mode
fault virtual address   = 0x68
fault code              = supervisor read, page not present
instruction pointer     = 0x8:0xffffffff80343402
stack pointer           = 0x10:0xffffffff9399b830
frame pointer           = 0x10:0xffffffff9399b8e0
code segment            = base 0x0, limit 0xfffff, type 0x1b
                        = DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags        = interrupt enabled, resume, IOPL = 0
current process         = 1615 (multicast)
[thread pid 1615 tid 100073 ]
Stopped at      ip_output+0x352:        testb   $0x5,0x68(%rdx)
db> tr
Tracing pid 1615 tid 100073 td 0xffffff0013d09000
ip_output() at ip_output+0x352
igmp_sendpkt() at igmp_sendpkt+0x123
igmp_joingroup() at igmp_joingroup+0xa1
in_addmulti() at in_addmulti+0x19f
ip_ctloutput() at ip_ctloutput+0xfc6
sosetopt() at sosetopt+0x178
kern_setsockopt() at kern_setsockopt+0x111
setsockopt() at setsockopt+0x22
syscall() at syscall+0x272
Xfast_syscall() at Xfast_syscall+0xa8
--- syscall (105, FreeBSD ELF64, setsockopt), rip = 0x8006c0e8c, rsp =
0x7fffffffe668, rbp = 0x3 ---
db> 

>From gdb after the reboot:

(gdb) l *ip_output+0x352 
0xffffffff80343402 is in ip_output (../../../netinet/ip_output.c:249).
244             }
245             /*
246              * Calculate MTU.  If we have a route that is up, use that,
247              * otherwise use the interface's MTU.
248              */
249             if (ro->ro_rt->rt_flags & (RTF_UP | RTF_HOST)) {
250                     /*
251                      * This case can happen if the user changed the MTU
252                      * of an interface after enabling IP on it.  Because
253                      * most netifs don't keep track of routes pointing to

0xffffffff80337613 is in igmp_sendpkt (../../../netinet/igmp.c:510).
505              * XXX
506              * Do we have to worry about reentrancy here?  Don't think so.
507              */
508             ip_output(m, router_alert, &igmprt, 0, &imo, NULL);
509
510             ++igmpstat.igps_snd_reports;
511     }


Drew