This is xnu-10002.1.13. See this file in:
Directory listing for xnu-10002.1.13//bsd/skywalk/packet
Makefile
os_packet.h
os_packet_private.h
packet_common.h
packet_copy.c
packet_kern.c
packet_queue.h
packet_var.h
pbufpool.c
pbufpool_kern.c
pbufpool_var.h