ack_limit        3472 net/ipv4/tcp_input.c 		u32 ack_limit = net->ipv4.sysctl_tcp_challenge_ack_limit;
ack_limit        3473 net/ipv4/tcp_input.c 		u32 half = (ack_limit + 1) >> 1;
ack_limit        3476 net/ipv4/tcp_input.c 		WRITE_ONCE(challenge_count, half + prandom_u32_max(ack_limit));