@alex1452 This is not an answer to your question, I'm sorry. But I have a question for you, if you don't mind.
You said you compiled libcap with the executables. I did the same, checking (Y) in both libcap and the executables in make menuconfig (SDK).
However, the make only resulted in libcap_2.25-2_x86_64.ipk and when I installed it in my router, no setcap command was found.
What file(s) did you transfer to the OpenWrt machine so you could have setcap capabilities? Was it just the libpcap .ipk or another one too?