Tested on HEADr355854

re0: <RealTek 8168/8111 B/C/CP/D/DP/E/F/G PCIe Gigabit Ethernet> port 0xe000-0xe0ff mem 0xf0404000-0xf0404fff,0xf0400000-0xf0403fff irq 17 at device 0.0 on pci3
re0: Using 1 MSI-X message
re0: Chip rev. 0x2c800000
re0: MAC rev. 0x00100000
miibus0: <MII bus> on re0
re0: Using defaults for TSO: 65518/35/2048
re0: Ethernet address: 00:13:3b:11:5e:b4
re0: netmap queues/slots: TX 1/256, RX 1/256
axe0: <SMC SMC2209USB/ETH, class 2/0, rev 2.00/0.01, addr 5> on usbus0
miibus0: <MII bus> on axe0
ue0: <USB Ethernet> on axe0


BEFORE:
# devinfo -v | grep re0
            re0 pnpinfo vendor=0x10ec device=0x8168 subvendor=0x10ec subdevice=0x0123 class=0x020000 at slot=0 function=0 dbsf=pci0:3:0:0 handle=\_SB_.PCI0.RP02.PXSX
# devinfo -v | grep axe
              axe0 pnpinfo vendor=0x0b95 product=0x1720 devclass=0x02 devsubclass=0x00 devproto=0x00 sernum="" release=0x0001 mode=host intclass=0x00 intsubclass=0x00 intprotocol=0x00 at bus=0 hubaddr=1 port=1 devaddr=2 interface=0 ugen=ugen0.2
# 
# devctl detach pci0:3:0:0
#
# vmstat -m | grep devbuf
       devbuf 34770 70136K       -    35686  16,32,64,128,256,512,1024,2048,4096,8192,65536
# devctl attach pci0:3:0:0 
# vmstat -m | grep devbuf
       devbuf 35307 70188K       -    36223  16,32,64,128,256,512,1024,2048,4096,8192,65536
# devctl detach pci0:3:0:0
# vmstat -m | grep devbuf
       devbuf 34779 70122K       -    36223  16,32,64,128,256,512,1024,2048,4096,8192,65536
# 
# 
## re LEAKED 9 times of type 'devbuf' (M_DEVBUF)

# devinfo -v | grep axe
              axe0 pnpinfo vendor=0x0b95 product=0x1720 devclass=0x02 devsubclass=0x00 devproto=0x00 sernum="" release=0x0001 mode=host intclass=0x00 intsubclass=0x00 intprotocol=0x00 at bus=0 hubaddr=1 port=1 devaddr=2 interface=0 ugen=ugen0.2
# 
# vmstat -m | grep devbuf
       devbuf 35298 70089K       -    36874  16,32,64,128,256,512,1024,2048,4096,8192,65536
## INSERT axe device
# vmstat -m | grep devbuf
       devbuf 35361 70146K       -    36952  16,32,64,128,256,512,1024,2048,4096,8192,65536
## REMOVE axe device
# vmstat -m | grep devbuf
       devbuf 35300 70055K       -    36952  16,32,64,128,256,512,1024,2048,4096,8192,65536
# 
## axe LEAKED 2 times of type 'devbuf' (M_DEVBUF)

AFTER:
# devinfo -v | grep re0
            re0 pnpinfo vendor=0x10ec device=0x8168 subvendor=0x10ec subdevice=0x0123 class=0x020000 at slot=0 function=0 dbsf=pci0:3:0:0 handle=\_SB_.PCI0.RP02.PXSX
# devinfo -v | grep axe
              axe0 pnpinfo vendor=0x0b95 product=0x1720 devclass=0x02 devsubclass=0x00 devproto=0x00 sernum="" release=0x0001 mode=host intclass=0x00 intsubclass=0x00 intprotocol=0x00 at bus=0 hubaddr=1 port=1 devaddr=5 interface=0 ugen=ugen0.5
# 
# devctl detach pci0:3:0:0
# 
# vmstat -m | grep devbuf
       devbuf 34763 70063K       -    35643  16,32,64,128,256,512,1024,2048,4096,8192,65536
# devctl attach pci0:3:0:0 
#  vmstat -m | grep devbuf
       devbuf 35300 70115K       -    36180  16,32,64,128,256,512,1024,2048,4096,8192,65536
#  devctl detach pci0:3:0:0
# vmstat -m | grep devbuf
       devbuf 34770 70048K       -    36180  16,32,64,128,256,512,1024,2048,4096,8192,65536
# 
# 
## re LEAKED 7 times of type 'devbuf' (M_DEVBUF) 2 leaks plugged

# 
# vmstat -m | grep devbuf
       devbuf 34770 70048K       -    36180  16,32,64,128,256,512,1024,2048,4096,8192,65536
## INSERT axe device
# vmstat -m | grep devbuf
       devbuf 34833 70105K       -    36258  16,32,64,128,256,512,1024,2048,4096,8192,65536
## REMOVE axe device
# vmstat -m | grep devbuf
       devbuf 34770 70013K       -    36258  16,32,64,128,256,512,1024,2048,4096,8192,65536
# 

## axe LEAKED 0 times of type 'devbuf' (M_DEVBUF) 2 leaks plugged