dhclient taking up all CPU

[Lodewijk Vöge]

hello,

a while ago someone reported the same problem I had been seeing, that  
dhclient starts taking up 100% CPU. it's probably something comcast  
is doing.

I couldn't get the requested coredump then, if I set kern.corefile  
to /tmp/%N.core and kill -QUIT it, it doesn't seem to produce a  
coredump. but it happened again just now, and I was able to attach  
gdb. this is where it's spinning, in receive_packet() in bpf.c:

(gdb)
285                     if (interface->rbuf_offset == interface- 
 >rbuf_len) {
(gdb)
299                     if (interface->rbuf_len - interface- 
 >rbuf_offset <
(gdb)
306                     memcpy(&hdr, &interface->rbuf[interface- 
 >rbuf_offset],
(gdb)
313                     if (interface->rbuf_offset + hdr.bh_hdrlen +  
hdr.bh_caplen >
(gdb)
320                     interface->rbuf_offset += hdr.bh_hdrlen;
(gdb)
327                     if (hdr.bh_caplen != hdr.bh_datalen) {
(gdb)
328                             interface->rbuf_offset =
(gdb)
331                             continue;
(gdb)
385             } while (!length);

and then it goes back to line 285. interesting variables are:

(gdb) p *interface
$1 = {next = 0x0, hw_address = {htype = 1 '\001', hlen = 6 '\006',
     haddr = "\000\021ؠ\223?\000\000\000\000\000\000\000\000\000"},  
primary_address = {s_addr = 0},
   name = "vr0", '\0' <repeats 12 times>, rfdesc = 7, wfdesc = 7,  
rbuf = 0x807d000 "\022?\\Dk\214", rbuf_max = 4096,
   rbuf_offset = 416, rbuf_len = 415, ifp = 0x806f160, client =  
0x8075000, noifmedia = 0, errors = 0, dead = 0, index = 2}
(gdb) p length
$2 = 0
(gdb) p hdr
$3 = {bh_tstamp = {tv_sec = 0, tv_usec = 0}, bh_caplen = 4294901760,  
bh_datalen = 4294901778, bh_hdrlen = 65535}

this is FreeBSD/i386 6.1-RC as of about two weeks ago.

Lodewijk