pcap = pcap_open_offline(pcap_filename, errbuf);
	pcap_loop(pcap, 0, (pcap_handler)glb_pcap_handler, (u_char *)conf);
I have attempted using pcap_fopen_offline and pcap_file which result in seemingly the same segfault.
pcap_open_offline:
Program terminated with signal SIGSEGV, Segmentation fault.
#0  pcap_loop (p=0x0, cnt=0, callback=0x56229664f2f0 <glb_pcap_handler>, user=0x7fff7c3f2550 "\001") at ./pcap.c:848
848	./pcap.c: No such file or directory.
pcap_file:
Program terminated with signal SIGSEGV, Segmentation fault.
#0  pcap_file (p=0x0) at ./pcap.c:1353
1353	./pcap.c: No such file or directory.
I assume this means that p->rfile is a bad value. Is it possible to detect this bad file before it gets to the point to where things fail?
System details:
root@jessie:/vagrant# tcpdump --version
tcpdump version 4.9.2
libpcap version 1.6.2
OpenSSL 1.0.1t  3 May 2016
root@jessie:/vagrant# uname -a
Linux jessie 3.16.0-4-amd64 #1 SMP Debian 3.16.43-2+deb8u2 (2017-06-26) x86_64 GNU/Linux
root@jessie:/vagrant# cat /etc/issue
Debian GNU/Linux 8 \n \l
I checked the fp like in the case of pcap_fopen_offline
For pcap_fopen_offline(), you have a FILE * that you hand to it, and you've presumably checked whether it's null after assigning the result of fopen() to it (if not, you should, as there's no guarantee that a file open will succeed).
For pcap_open_offline(), you hand it a file name, and it does the fopen() for you and returns a null pointer if the open() fails.  If NULL is returned, there is no FILE *, as a null pointer doesn't point to anything - in particular, it doesn't point to a pcap_t that has an rfile member, so p->rfile doesn't exist - there is no *p that contains an rfile member.