This seems to have been around for a while. It was reported in Redhat here: 1810727, which was closed for being reported too late in a release cycle.

pjsip wants to read /proc/sys/net to figure out some networking information to configure itself. This seems to be triggering selinux policy violations. As covered in the bug above this local policy will resolve it:

module my-asterisk 1.0;

require {
        type asterisk_t;
        type sysctl_net_t;
        class dir search;
        class file { getattr open read };
}

#============= asterisk_t ==============
allow asterisk_t sysctl_net_t:dir search;
allow asterisk_t sysctl_net_t:file { getattr open read };

Reproducible: Always

Steps to Reproduce:
1. configure asterisk to use pjsip with a "type = transport" section
2. start asterisk
3. check for selinux policy violations for reading from /proc/sys/net/ipv6 and ipv4
Actual Results:  
I think asterisk is actually running ok. I found these issues by reviewing my journalctl setroubleshoot output.

Expected Results:  
No selinux policy voilations