We did check for null-deref before checking 'a->type', but contol
continues and passes potential null-ptr to the processing function
_mdns_execute_action()
Fixed by asserting action != NULL, since it is an invalid state which
should never happen.
Fixes CID 467739: Use after free in mdns.c, mdns_service_remove_for_host
We should look only for one match in the service list, since if we
assume there could be aliases, we might free one and reference the
other.
Fixes CID 467738: Logically dead code in mdns.c, _copy_mdns_txt_items
Introduced by probably by a merge confilict, as the fix was added in
two separate PRs, merging d4da9cb0 first and 8a690503 later
Adds action semaphore the same way it's done in mdns_hostname_add()
There could still potentially be a minor issue when calling these two APIs
simultanously. Will solve the same ways as in 8a690503 (tracked as
IDF-10913)
Original issue (data race when updating hostname): mdns_service_add()
makes a copy of the local hostname and calls using the local copy
mdns_service_add_for_host().
When mdns's hostname is updated the local copy gets out of sync.
**API race issue**: Most of the current API correctly lock the mdns service,
but sometimes unlocks it before sending an action to the action queue,
so it's possible that the situation changes before the actual action
takes place.
**Fix**: After locking the mdns service, we proceed directly with updating
internal structures and do not post actions into the action queue.
**Fix wrtt hostname**: Use mdns_service_add_for_host(hostname=NULL)
for all self hosted services.
MAJOR CHANGE: Fixed mdns API issues when add/remove/update records from multiple threads
This and the following commits fix the API race issues for these mdns APIs:
* mdns_service_add_for_host
* mdns_service_port_set_for_host
* mdns_service_txt_set_for_host
* mdns_service_txt_item_set_for_host_with_explicit_value_len
* mdns_service_txt_item_remove_for_host
* mdns_service_subtype_add_for_host
* mdns_service_instance_name_set_for_host
* mdns_service_remove_for_host
* mdns_service_remove_all
the lookup_service API calls _copy_mdns_txt_items(), which tries to
allocate new TXT records, but didn't handle the case with no TXT.
Originally the _copy_mdns_txt_items() called calloc() with zero's which
returned NULL (on espressif toolchain), so it's safe, but we could see
an error message:
E (1170) mdns: Cannot allocate memory (line: 6191, free heap: 281368 bytes)
This commit addresses the empty TXT case and gets rid of the error
message.
