kern/46557: ipfw pipe show fails with lots of queues

[Pawel Malachowski]

Hello,

	I've just hit this problem on my 4.10-STABLE dummynet shaper.
Very bad, since `ipfw pipe show N' + net.inet.ip.dummynet.expire=0 is
quite useful for grabbing some per-user statistics. :/


Here are more details what is going on. I hope someone will look at this and
explain why malloc() can fail here and what can be done to prevent this.


% ipfw pipe show
ipfw: getsockopt(IP_DUMMYNET_GET): No buffer space available

This command invokes getsockopt() trying to fetch all pipes data from kernel
to userland.

Kernel part of this is being done in dummynet_get(), which tries to allocate
buf big (previously computed size) enough for all data:

    buf = malloc(size, M_TEMP, M_NOWAIT);
    if (buf == 0) {
	splx(s);
	return ENOBUFS ;
    }

This malloc() call fails sometimes on loaded system (10k-70k of dynamic
pipes + make buildworld;)) causing `ipfw pipe show' command failure.

I've registered temporary MALLOC_DEFINE M_YOYO and changed this malloc/free
from M_TEMP to M_YOYO, ;) so I can easily track this in `vmstat -m' output:

1. Quite early (no problems):
        Type  InUse MemUse HighUse  Limit Requests Limit Limit Size(s)
  IpFw/IpAcct   113    14K     14K 42107K      113    0     0  64,128,256
         yoyo     0     0K    120K 42107K        1    0     0  128K
     dummynet  1612   311K    313K 42107K   139366    0     0  16,128,256,4K
Memory Totals:  In Use       Free    Requests
                 3921K        32K      173824

2. After some time malloc() in dummynet_get() fails and:
        Type  InUse MemUse HighUse  Limit Requests Limit Limit Size(s)
  IpFw/IpAcct   113    14K     14K 42107K      113    0     0  64,128,256
         yoyo     0     0K   2828K 42107K    12913    0     0  128K,512K
     dummynet 21432  2790K   3354K 42107K  9804136    0     0  16,128,256,512,1K,4K
Memory Totals:  In Use       Free    Requests
                 9932K      3029K    14216860

In /sbin/ipfw2, list():
	(do_cmd(ocmd, data, (uintptr_t)&nbytes) < 0)
nbytes were 2188288  // In loop, I +1024 numbytes instead of *2+200, ignore this

In ip_dummynet.c, dummynet_get():
	buf = malloc(size, M_YOYO, M_NOWAIT); // note: M_TEMP => M_YOYO
size was 2390416 and malloc() failed.


-- 
Paweł Małachowski