login: DF2845: [1] allocating 32-byte FIXEDLEN sbuf
DF2845: [2] installing 0-returning drain
DF2845: [3] catting 255 bytes (first drain fires at byte 32)
DF2845:        drain called with len=31 -> returning 0
panic: Bad drain amount 0 for sbuf 0xfffff80117a49380
cpuid = 5
Trace beginning at frame 0xfffff80117e1f608
sbuf_drain() at sbuf_drain+0x98 0xffffffff806a0ac8 
sbuf_drain() at sbuf_drain+0x98 0xffffffff806a0ac8 
sbuf_put_byte() at sbuf_put_byte+0x6f 0xffffffff806a0cff 
sbuf_cat() at sbuf_cat+0x4c 0xffffffff806a11fc 
df2845_sysctl() at df2845_sysctl+0xe6 0xffffffff80a7fde6 
sysctl_root.isra.5() at sysctl_root.isra.5+0x166 0xffffffff80683d06 
Debugger("panic")

CPU5 stopping CPUs: 0x0000001f
 stopped
Stopped at      Debugger+0x7c:  movb    $0,0xbdad79(%rip)
db>