GRE_ACK           210 drivers/net/ppp/pptp.c 		hdr->gre_hd.flags |= GRE_ACK;
GRE_ACK            41 include/uapi/linux/if_tunnel.h #define GRE_IS_ACK(f)		((f) & GRE_ACK)
GRE_ACK           595 net/core/flow_dissector.c 		if (hdr->flags & GRE_ACK)