It isn't the syslogd's responsibility to do a lookup of the pid, it is the application and the application is the one specifying the pid anyway.
Based on the example given, it sounds like what is desired is for the firewall to log the pid of the application that generated the request. This is the kernel's responsibility via netfilter, and netfilter is controlled via iptables (and up above maybe another tool like ufw). However, iptables does not support this (see 'man iptables' for more information). It used to have the '--cmd-owner' option, but this was removed long ago because it was deemed unfixably broken.
It isn't the syslogd's responsibility to do a lookup of the pid, it is the application and the application is the one specifying the pid anyway.
Based on the example given, it sounds like what is desired is for the firewall to log the pid of the application that generated the request. This is the kernel's responsibility via netfilter, and netfilter is controlled via iptables (and up above maybe another tool like ufw). However, iptables does not support this (see 'man iptables' for more information). It used to have the '--cmd-owner' option, but this was removed long ago because it was deemed unfixably broken.