Man pages matching name pcap_fopen_offline in section 3pcap:

pcap_fopen_offline.3pcap.en	debian 10 / libpcap0.8-dev
pcap_fopen_offline.3pcap.en	debian 11 / libpcap0.8-dev
pcap_fopen_offline.3pcap.en	debian 12 / libpcap0.8-dev