Function tcp_init

freebsd/netinet/tcp_subr.c:1091–1242

}

void
tcp_init(void)
{
	const char *tcbhash_tuneable;
	int hashsize;

	tcbhash_tuneable = "net.inet.tcp.tcbhashsize";

#ifdef TCP_HHOOK
	if (hhook_head_register(HHOOK_TYPE_TCP, HHOOK_TCP_EST_IN,
	    &V_tcp_hhh[HHOOK_TCP_EST_IN], HHOOK_NOWAIT|HHOOK_HEADISINVNET) != 0)
		printf("%s: WARNING: unable to register helper hook\n", __func__);
	if (hhook_head_register(HHOOK_TYPE_TCP, HHOOK_TCP_EST_OUT,
	    &V_tcp_hhh[HHOOK_TCP_EST_OUT], HHOOK_NOWAIT|HHOOK_HEADISINVNET) != 0)
		printf("%s: WARNING: unable to register helper hook\n", __func__);
#endif
#ifdef STATS
	if (tcp_stats_init())
		printf("%s: WARNING: unable to initialise TCP stats\n",
		    __func__);
#endif
	hashsize = TCBHASHSIZE;
	TUNABLE_INT_FETCH(tcbhash_tuneable, &hashsize);
	if (hashsize == 0) {
		/*
		 * Auto tune the hash size based on maxsockets.
		 * A perfect hash would have a 1:1 mapping
		 * (hashsize = maxsockets) however it's been
		 * suggested that O(2) average is better.
		 */
		hashsize = maketcp_hashsize(maxsockets / 4);
		/*
		 * Our historical default is 512,
		 * do not autotune lower than this.
		 */
		if (hashsize < 512)
			hashsize = 512;
		if (bootverbose && IS_DEFAULT_VNET(curvnet))
			printf("%s: %s auto tuned to %d\n", __func__,
			    tcbhash_tuneable, hashsize);
	}
	/*
	 * We require a hashsize to be a power of two.
	 * Previously if it was not a power of two we would just reset it
	 * back to 512, which could be a nasty surprise if you did not notice
	 * the error message.
	 * Instead what we do is clip it to the closest power of two lower
	 * than the specified hash value.
	 */
	if (!powerof2(hashsize)) {
		int oldhashsize = hashsize;

		hashsize = maketcp_hashsize(hashsize);
		/* prevent absurdly low value */
		if (hashsize < 16)
			hashsize = 16;
		printf("%s: WARNING: TCB hash size not a power of 2, "
		    "clipped from %d to %d.\n", __func__, oldhashsize,