pcap isnt working as expected

[slaesh]

Describe the bug

Starting wpanctl to capture packets.

To Reproduce

sudo ./wpanctl pcap ~/test.pcap
pcap: Capture started!
got 24 bytes <-- my modifications, just to see if something is coming in..

Expected behavior

incoming packets should be written into the pcap-file.
but there are only 24 bytes written into that file, and then nothing else.
even if there are packets incoming, see logs..

Console/log output

wpantund logs:
wpantund[428023]: Inbound DBus message for INTERFACE "PcapToFd" from ":1.3081"
wpantund[428023]: Tickle...
wpantund[428023]: [->NCP] CMD_NOOP tid:13
wpantund[428023]: ↳ 8D00
wpantund[428023]: [NCP->] CMD_PROP_VALUE_IS(PROP_LAST_STATUS) tid:13
wpantund[428023]: [-NCP-]: Last status (STATUS_OK, 0)
wpantund[428023]: [NCP->] CMD_PROP_VALUE_IS(PROP_STREAM_NET) tid:0
wpantund[428023]: [NCP->] IPv6 len:80 type:17(cksum 0x0736) [SECURE]
wpantund[428023]: to(local):[ff03::1]:5683
wpantund[428023]: from(remote):[fdde:ad00:beef:0:309c:6d25:722c:e23a]:5683
wpantund[428023]: [NCP->] CMD_PROP_VALUE_IS(PROP_STREAM_NET) tid:0
wpantund[428023]: [NCP->] IPv6 len:80 type:17(cksum 0x7e92) [SECURE]
wpantund[428023]: to(local):[ff03::1]:5683
wpantund[428023]: from(remote):[fdde:ad00:beef:0:309c:6d25:722c:e23a]:5683
wpantund[428023]: [NCP->] CMD_PROP_VALUE_IS(PROP_STREAM_NET) tid:0
wpantund[428023]: [NCP->] IPv6 len:80 type:17(cksum 0xa4be) [SECURE]
wpantund[428023]: to(local):[ff03::1]:5683
wpantund[428023]: from(remote):[fdde:ad00:beef:0:309c:6d25:722c:e23a]:5683

Additional context

see attached file.
test.txt