Details of /proc/net/ip_conntrack and /proc/net/nf_conntrack

The format of a line from /proc/net/ip_conntrack is the same as for /proc/net/nf_conntrack, except the first two columns are missing. I'll try to summarize the format of the latter file, as I understand it from the net/netfilter/nf_conntrack_standalone.c, net/netfilter/nf_conntrack_acct.c and the net/netfilter/nf_conntrack_proto_*.c kernel source files. The term layer refers to the OSI protocol la