[Ovmsdev] mDNS crash

Stephen Casner casner at acm.org
Sat Feb 24 11:10:12 HKT 2018

I updated esp-idf and OVMS to get the new MDNS API.  I started OVMS
and my startup script brought up wifi, then all I did was type a '?'
command to get a command list.  Shortly thereafter the system crashed
with a context as shown below (edited).  This looks like an action the
mDNS server took in response to receiving a packet that may have come
from one of my Mac computers or from the DEVKIT-C.  That is, it's not
a crash resulting from a call to the kernel from ovms_mdns.

Unwisely I did not dig further into this crash and it has not repeated
so far.  So I guess I'm just recording this for posterity at this

                                                        -- Steve

OVMS > Guru Meditation Error: Core  0 panic'ed (LoadProhibited)
. Exception was unhandled.
Core 0 register dump:
PC      : 0x401e690f  PS      : 0x00060f30  A0      : 0x801e8c6c  A1      : 0x3fff2e30
A2      : 0x3ffb9260  A3      : 0x3fff2e60  A4      : 0xbaad5678  A5      : 0x00000001
A6      : 0x00060f23  A7      : 0x00000000  A8      : 0x00060023  A9      : 0x3ffe623c
A10     : 0x00000000  A11     : 0x00000000  A12     : 0x8008b35b  A13     : 0x3ffaf8c0
A14     : 0x00000003  A15     : 0x00060023  SAR     : 0x00000019  EXCCAUSE: 0x0000001c
EXCVADDR: 0xbaad5680  LBEG    : 0x4000c2e0  LEND    : 0x4000c2f6  LCOUNT  : 0xffffffff

Entering gdb stub now.
Remote debugging using /dev/cu.SLAB_USBtoUART38
_mdns_append_question (packet=0x3ffb9260 <packet> "", index=0x3fff2e60, q=0xbaad5678)
    at /Users/casner/src/github/my-esp-idf/components/mdns/./mdns.c:988
988         if (q->host) {
(gdb) bt
#0  _mdns_append_question (packet=0x3ffb9260 <packet> "", index=0x3fff2e60, q=0xbaad5678)
    at /Users/casner/src/github/my-esp-idf/components/mdns/./mdns.c:988
#1  0x401e8c6c in _mdns_dispatch_tx_packet (p=0x3ffe6524)
    at /Users/casner/src/github/my-esp-idf/components/mdns/./mdns.c:1156
#2  0x401e91ac in _mdns_tx_handle_packet (p=0x3ffe6524)
    at /Users/casner/src/github/my-esp-idf/components/mdns/./mdns.c:3627
#3  0x401ea3f1 in _mdns_execute_action (action=0x3ffe6a90)
    at /Users/casner/src/github/my-esp-idf/components/mdns/./mdns.c:3889
#4  0x401ea45a in _mdns_service_task (pvParameters=<optimized out>)
    at /Users/casner/src/github/my-esp-idf/components/mdns/./mdns.c:3994

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