Function tcp_ctloutput

freebsd/netinet/tcp_usrreq.c:1824–1997

#define INP_WLOCK_RECHECK(inp) INP_WLOCK_RECHECK_CLEANUP((inp), /* noop */)

int
tcp_ctloutput(struct socket *so, struct sockopt *sopt)
{
	int	error;
	struct	inpcb *inp;
	struct	tcpcb *tp;
	struct tcp_function_block *blk;
	struct tcp_function_set fsn;

	error = 0;
	inp = sotoinpcb(so);
	KASSERT(inp != NULL, ("tcp_ctloutput: inp == NULL"));
	if (sopt->sopt_level != IPPROTO_TCP) {
#ifdef INET6
		if (inp->inp_vflag & INP_IPV6PROTO) {
			error = ip6_ctloutput(so, sopt);
			/*
			 * In case of the IPV6_USE_MIN_MTU socket option,
			 * the INC_IPV6MINMTU flag to announce a corresponding
			 * MSS during the initial handshake.
			 * If the TCP connection is not in the front states,
			 * just reduce the MSS being used.
			 * This avoids the sending of TCP segments which will
			 * be fragmented at the IPv6 layer.
			 */
			if ((error == 0) &&
			    (sopt->sopt_dir == SOPT_SET) &&
			    (sopt->sopt_level == IPPROTO_IPV6) &&
			    (sopt->sopt_name == IPV6_USE_MIN_MTU)) {
				INP_WLOCK(inp);
				if ((inp->inp_flags &
				    (INP_TIMEWAIT | INP_DROPPED))) {
					INP_WUNLOCK(inp);
					return (ECONNRESET);
				}
				inp->inp_inc.inc_flags |= INC_IPV6MINMTU;
				tp = intotcpcb(inp);
				if ((tp->t_state >= TCPS_SYN_SENT) &&
				    (inp->inp_inc.inc_flags & INC_ISIPV6)) {
					struct ip6_pktopts *opt;

					opt = inp->in6p_outputopts;
					if ((opt != NULL) &&
					    (opt->ip6po_minmtu ==
					    IP6PO_MINMTU_ALL)) {
						if (tp->t_maxseg > TCP6_MSS) {
							tp->t_maxseg = TCP6_MSS;
						}
					}
				}
				INP_WUNLOCK(inp);
			}
		}
#endif /* INET6 */
#if defined(INET6) && defined(INET)
		else
#endif
#ifdef INET