If the header file is included test_utils_interactive_sync() will
be defined as an empty function when the module is not used, e.g.
added to DISABLE_MODULES in tests/*
sock_util used ot check RIOT_VERSION for selecting fmt functions.
RIOT's Makefile.dep sets fmt as a dependency for sock_util,
so the usual MODULE_FMT can be used.
One special case less.
This updates (or adds) a compression context whenever a new prefix
arrives at the border router. This allows 6LoWPAN to compress said
prefix in the network.
Sadly, there is now way to just remove the context when the prefix is
overwritten, so I do not do it. If an administrator chooses to reset the
prefix they can use `6ctx del` which timeouts the prefix appropriately,
but IMHO it doesn't hurt to keep the old contexts.
Saving RAM is more important than saving a few cycles
used by re-creating the request buffer in the error case.
Also reduce the size of the buffer to 128 bytes.
If we are just requesting the AAAA record it is unlikely
for the reply to take up the maximum size of 512 bytes.
We were already placing restrictions on the domain name length,
those are now actually a bit more relaxed (112 bytes instead of 64)
This way, the sock-types can use the sock_async_ctx_t type in their
definition without including `sock_async_ctx.h` (potentially creating
further cyclic includes).
If a new event is fired during the execution of the event callback,
`event->type` might change. However as `event->type` is set to 0 after
the execution of the callback, that leads to it being 0 on the next
round of the event handler's execution, leading in the event getting
lost.
If there is more than one interface, print the id of the receiving
interface for convenience.
```
ping6 ff02::1
2020-02-20 18:19:38,644 # 12 bytes from fe80::d0ae:c1b:2054:58e%7: icmp_seq=0 ttl=64 rssi=-45 dBm time=4.801 ms
2020-02-20 18:19:38,652 # 12 bytes from fe80::d0ae:c1b:2054:58c%8: icmp_seq=0 ttl=64 rssi=-63 dBm time=13.422 ms (DUP!)
2020-02-20 18:19:38,661 # 12 bytes from fe80::c78:16d9:8aca:ba9a%8: icmp_seq=0 ttl=64 rssi=-44 dBm time=21.819 ms (DUP!)
2020-02-20 18:19:39,648 # 12 bytes from fe80::d0ae:c1b:2054:58e%7: icmp_seq=1 ttl=64 rssi=-44 dBm time=4.797 ms
2020-02-20 18:19:39,657 # 12 bytes from fe80::d0ae:c1b:2054:58c%8: icmp_seq=1 ttl=64 rssi=-61 dBm time=12.917 ms (DUP!)
2020-02-20 18:19:39,666 # 12 bytes from fe80::c78:16d9:8aca:ba9a%8: icmp_seq=1 ttl=64 rssi=-43 dBm time=21.679 ms (DUP!)
2020-02-20 18:19:40,657 # 12 bytes from fe80::d0ae:c1b:2054:58e%7: icmp_seq=2 ttl=64 rssi=-41 dBm time=4.795 ms
```
