Index: sys/modules/Makefile
===================================================================
--- sys/modules/Makefile
+++ sys/modules/Makefile
@@ -319,6 +319,7 @@
 	${_safe} \
 	${_sbni} \
 	scc \
+	${_sctp} \
 	sdhci \
 	${_sdhci_acpi} \
 	sdhci_pci \
@@ -430,6 +431,9 @@
 .if ${KERN_OPTS:MIPSEC_SUPPORT} && !${KERN_OPTS:MIPSEC}
 _ipsec=		ipsec
 .endif
+.if ${KERN_OPTS:MSCTP_SUPPORT} || ${KERN_OPTS:MSCTP}
+_sctp=		sctp
+.endif
 .endif
 
 .if (${MK_INET_SUPPORT} != "no" && ${MK_INET6_SUPPORT} != "no") || \
Index: sys/modules/sctp/Makefile
===================================================================
--- /dev/null
+++ sys/modules/sctp/Makefile
@@ -0,0 +1,30 @@
+# $FreeBSD$
+
+.PATH: ${SRCTOP}/sys/netinet
+.PATH: ${SRCTOP}/sys/netinet6
+
+KMOD=	sctp
+SRCS=	sctp_asconf.c \
+	sctp_auth.c \
+	sctp_bsd_addr.c \
+	sctp_cc_functions.c \
+	sctp_crc32.c \
+	sctp_indata.c \
+	sctp_input.c \
+	sctp_kdtrace.c \
+	sctp_module.c \
+	sctp_output.c \
+	sctp_pcb.c \
+	sctp_peeloff.c \
+	sctp_ss_functions.c \
+	sctp_syscalls.c \
+	sctp_sysctl.c \
+	sctp_timer.c \
+	sctp_usrreq.c \
+	sctp6_usrreq.c \
+	sctputil.c
+
+SRCS+=	device_if.h bus_if.h vnode_if.h
+SRCS+=	opt_capsicum.h opt_ktrace.h opt_inet.h opt_inet6.h opt_sctp.h
+
+.include <bsd.kmod.mk>
Index: sys/netinet/sctp_module.c
===================================================================
--- /dev/null
+++ sys/netinet/sctp_module.c
@@ -0,0 +1,197 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ *
+ * Copyright (c) 2019-2020 The FreeBSD Foundation
+ *
+ * This software was developed by Mark Johnston under sponsorship from
+ * the FreeBSD Foundation.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include "opt_inet.h"
+#include "opt_inet6.h"
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/kernel.h>
+#include <sys/module.h>
+#include <sys/protosw.h>
+#include <sys/socket.h>
+
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <netinet/ip_var.h>
+#include <netinet/sctp.h>
+#include <netinet/sctp_pcb.h>
+#include <netinet/sctp_var.h>
+#include <netinet/sctp_os_bsd.h>
+
+#include <netinet6/ip6_var.h>
+#include <netinet6/sctp6_var.h>
+
+#ifdef INET
+extern struct domain inetdomain;
+
+struct protosw sctp_stream_protosw = {
+	.pr_type =		SOCK_STREAM,
+	.pr_domain =		&inetdomain,
+	.pr_protocol =		IPPROTO_SCTP,
+	.pr_flags =		PR_CONNREQUIRED|PR_WANTRCVD|PR_LASTHDR,
+	.pr_input =		sctp_input,
+	.pr_ctlinput =		sctp_ctlinput,
+	.pr_ctloutput =		sctp_ctloutput,
+	.pr_drain =		sctp_drain,
+	.pr_usrreqs =		&sctp_usrreqs,
+};
+
+struct protosw sctp_seqpacket_protosw = {
+	.pr_type =		SOCK_SEQPACKET,
+	.pr_domain =		&inetdomain,
+	.pr_protocol =		IPPROTO_SCTP,
+	.pr_flags =		PR_WANTRCVD|PR_LASTHDR,
+	.pr_input =		sctp_input,
+	.pr_ctlinput =		sctp_ctlinput,
+	.pr_ctloutput =		sctp_ctloutput,
+	.pr_drain =		sctp_drain,
+	.pr_usrreqs =		&sctp_usrreqs,
+};
+#endif
+
+#ifdef INET6
+extern struct domain inet6domain;
+
+struct protosw sctp6_stream_protosw = {
+	.pr_type =		SOCK_STREAM,
+	.pr_domain =		&inet6domain,
+	.pr_protocol =		IPPROTO_SCTP,
+	.pr_flags =		PR_CONNREQUIRED|PR_WANTRCVD|PR_LASTHDR,
+	.pr_input =		sctp6_input,
+	.pr_ctlinput =		sctp6_ctlinput,
+	.pr_ctloutput =		sctp_ctloutput,
+	.pr_init =		sctp_init,
+	.pr_drain =		sctp_drain,
+	.pr_usrreqs =		&sctp6_usrreqs,
+};
+
+struct protosw sctp6_seqpacket_protosw = {
+	.pr_type =		SOCK_SEQPACKET,
+	.pr_domain =		&inet6domain,
+	.pr_protocol =		IPPROTO_SCTP,
+	.pr_flags =		PR_WANTRCVD|PR_LASTHDR,
+	.pr_input =		sctp6_input,
+	.pr_ctlinput =		sctp6_ctlinput,
+	.pr_ctloutput =		sctp_ctloutput,
+#ifndef INET	/* Do not call initialization and drain routines twice. */
+	.pr_init =		sctp_init,
+	.pr_drain =		sctp_drain,
+#endif
+	.pr_usrreqs =		&sctp6_usrreqs,
+};
+#endif
+
+static int
+sctp_module_load(void)
+{
+	int error;
+
+#ifdef INET
+	error = pf_proto_register(PF_INET, &sctp_stream_protosw);
+	if (error != 0)
+		return (error);
+	error = pf_proto_register(PF_INET, &sctp_seqpacket_protosw);
+	if (error != 0)
+		return (error);
+	error = ipproto_register(IPPROTO_SCTP);
+	if (error != 0)
+		return (error);
+#endif
+#ifdef INET6
+	error = pf_proto_register(PF_INET6, &sctp6_stream_protosw);
+	if (error != 0)
+		return (error);
+	error = pf_proto_register(PF_INET6, &sctp6_seqpacket_protosw);
+	if (error != 0)
+		return (error);
+	error = ip6proto_register(IPPROTO_SCTP);
+	if (error != 0)
+		return (error);
+#endif
+	error = sctp_syscalls_init();
+	if (error != 0)
+		return (error);
+	return (0);
+}
+
+static int __unused
+sctp_module_unload(void)
+{
+
+	(void)sctp_syscalls_uninit();
+
+#ifdef INET
+	(void)ipproto_unregister(IPPROTO_SCTP);
+	(void)pf_proto_unregister(PF_INET, IPPROTO_SCTP, SOCK_STREAM);
+	(void)pf_proto_unregister(PF_INET, IPPROTO_SCTP, SOCK_SEQPACKET);
+#endif
+#ifdef INET6
+	(void)ip6proto_unregister(IPPROTO_SCTP);
+	(void)pf_proto_unregister(PF_INET6, IPPROTO_SCTP, SOCK_STREAM);
+	(void)pf_proto_unregister(PF_INET6, IPPROTO_SCTP, SOCK_SEQPACKET);
+#endif
+	return (0);
+}
+
+static int
+sctp_modload(struct module *module, int cmd, void *arg)
+{
+	int error;
+
+	switch (cmd) {
+	case MOD_LOAD:
+		error = sctp_module_load();
+		break;
+	case MOD_UNLOAD:
+		/*
+		 * Unloading SCTP is currently unsupported.  Currently, SCTP
+		 * iterator threads are not stopped during unload.
+		 */
+		error = EOPNOTSUPP;
+		break;
+	default:
+		error = 0;
+		break;
+	}
+	return (error);
+}
+
+static moduledata_t sctp_mod = {
+	"sctp",
+	&sctp_modload,
+	NULL,
+};
+
+DECLARE_MODULE(sctp, sctp_mod, SI_SUB_PROTO_IFATTACHDOMAIN, SI_ORDER_ANY);
+MODULE_VERSION(sctp, 1);
Index: sys/netinet/sctp_os_bsd.h
===================================================================
--- sys/netinet/sctp_os_bsd.h
+++ sys/netinet/sctp_os_bsd.h
@@ -45,9 +45,12 @@
 #include "opt_sctp.h"
 
 #include <sys/param.h>
+#include <sys/domain.h>
+#include <sys/eventhandler.h>
 #include <sys/ktr.h>
 #include <sys/systm.h>
 #include <sys/malloc.h>
+#include <sys/module.h>
 #include <sys/kernel.h>
 #include <sys/sysctl.h>
 #include <sys/mbuf.h>
@@ -85,7 +88,6 @@
 #include <netinet/icmp_var.h>
 
 #ifdef INET6
-#include <sys/domain.h>
 #include <netinet/ip6.h>
 #include <netinet6/in6_fib.h>
 #include <netinet6/ip6_var.h>
@@ -477,4 +479,7 @@
 
 #define SCTP_IS_LISTENING(inp) ((inp->sctp_flags & SCTP_PCB_FLAGS_ACCEPTING) != 0)
 
+int	sctp_syscalls_init(void);
+int	sctp_syscalls_uninit(void);
+
 #endif
Index: sys/netinet/sctp_syscalls.c
===================================================================
--- sys/netinet/sctp_syscalls.c
+++ sys/netinet/sctp_syscalls.c
@@ -69,6 +69,8 @@
 #include <sys/ktrace.h>
 #endif
 #ifdef COMPAT_FREEBSD32
+#include <compat/freebsd32/freebsd32.h>
+#include <compat/freebsd32/freebsd32_syscall.h>
 #include <compat/freebsd32/freebsd32_util.h>
 #endif
 
@@ -78,6 +80,7 @@
 #include <security/mac/mac_framework.h>
 
 #include <netinet/sctp.h>
+#include <netinet/sctp_os_bsd.h>
 #include <netinet/sctp_peeloff.h>
 
 static struct syscall_helper_data sctp_syscalls[] = {
@@ -88,28 +91,52 @@
 	SYSCALL_INIT_LAST
 };
 
-static void
-sctp_syscalls_init(void *unused __unused)
+#ifdef COMPAT_FREEBSD32
+static struct syscall_helper_data sctp32_syscalls[] = {
+	SYSCALL32_INIT_HELPER_COMPAT(sctp_peeloff),
+	SYSCALL32_INIT_HELPER_COMPAT(sctp_generic_sendmsg),
+	SYSCALL32_INIT_HELPER_COMPAT(sctp_generic_sendmsg_iov),
+	SYSCALL32_INIT_HELPER_COMPAT(sctp_generic_recvmsg),
+	SYSCALL_INIT_LAST
+};
+#endif
+
+int
+sctp_syscalls_init(void)
 {
-	int error __unused;
+	int error;
 
-	error = syscall_helper_register(sctp_syscalls, SY_THR_STATIC);
-	KASSERT((error == 0),
-	    ("%s: syscall_helper_register failed for sctp syscalls", __func__));
+	error = syscall_helper_register(sctp_syscalls, SY_THR_STATIC_KLD);
+	if (error != 0)
+		return (error);
 #ifdef COMPAT_FREEBSD32
-	error = syscall32_helper_register(sctp_syscalls, SY_THR_STATIC);
-	KASSERT((error == 0),
-	    ("%s: syscall32_helper_register failed for sctp syscalls",
-	    __func__));
+	error = syscall32_helper_register(sctp32_syscalls, SY_THR_STATIC_KLD);
+	if (error != 0)
+		return (error);
 #endif
+	return (0);
+}
+
+int
+sctp_syscalls_uninit(void)
+{
+	int error;
+
+#ifdef COMPAT_FREEBSD32
+	error = syscall32_helper_unregister(sctp32_syscalls);
+	if (error != 0)
+		return (error);
+#endif
+	error = syscall_helper_unregister(sctp_syscalls);
+	if (error != 0)
+		return (error);
+	return (0);
 }
-SYSINIT(sctp_syscalls, SI_SUB_SYSCALLS, SI_ORDER_ANY, sctp_syscalls_init, NULL);
 
 /*
  * SCTP syscalls.
  * Functionality only compiled in if SCTP is defined in the kernel Makefile,
  * otherwise all return EOPNOTSUPP.
- * XXX: We should make this loadable one day.
  */
 int
 sys_sctp_peeloff(td, uap)
@@ -119,7 +146,7 @@
 		caddr_t	name;
 	} */ *uap;
 {
-#if (defined(INET) || defined(INET6)) && defined(SCTP)
+#if defined(INET) || defined(INET6)
 	struct file *headfp, *nfp = NULL;
 	struct socket *head, *so;
 	cap_rights_t rights;
@@ -181,9 +208,7 @@
 	fdrop(headfp, td);
 done2:
 	return (error);
-#else  /* SCTP */
-	return (EOPNOTSUPP);
-#endif /* SCTP */
+#endif
 }
 
 int
@@ -199,7 +224,7 @@
 		int flags
 	} */ *uap;
 {
-#if (defined(INET) || defined(INET6)) && defined(SCTP)
+#if defined(INET) || defined(INET6)
 	struct sctp_sndrcvinfo sinfo, *u_sinfo = NULL;
 	struct socket *so;
 	struct file *fp = NULL;
@@ -294,9 +319,7 @@
 sctp_bad2:
 	free(to, M_SONAME);
 	return (error);
-#else  /* SCTP */
-	return (EOPNOTSUPP);
-#endif /* SCTP */
+#endif
 }
 
 int
@@ -312,7 +335,7 @@
 		int flags
 	} */ *uap;
 {
-#if (defined(INET) || defined(INET6)) && defined(SCTP)
+#if defined(INET) || defined(INET6)
 	struct sctp_sndrcvinfo sinfo, *u_sinfo = NULL;
 	struct socket *so;
 	struct file *fp = NULL;
@@ -424,9 +447,7 @@
 sctp_bad2:
 	free(to, M_SONAME);
 	return (error);
-#else  /* SCTP */
-	return (EOPNOTSUPP);
-#endif /* SCTP */
+#endif
 }
 
 int
@@ -442,7 +463,7 @@
 		int *msg_flags
 	} */ *uap;
 {
-#if (defined(INET) || defined(INET6)) && defined(SCTP)
+#if defined(INET) || defined(INET6)
 	uint8_t sockbufstore[256];
 	struct uio auio;
 	struct iovec *iov, *tiov;
@@ -572,7 +593,5 @@
 		fdrop(fp, td);
 
 	return (error);
-#else  /* SCTP */
-	return (EOPNOTSUPP);
-#endif /* SCTP */
+#endif
 }
Index: sys/netinet/sctp_usrreq.c
===================================================================
--- sys/netinet/sctp_usrreq.c
+++ sys/netinet/sctp_usrreq.c
@@ -97,9 +97,9 @@
 static void
 sctp_finish(void *unused __unused)
 {
+	EVENTHANDLER_DEREGISTER(rt_addrmsg, SCTP_BASE_VAR(eh_tag));
 	sctp_pcb_finish();
 }
-
 VNET_SYSUNINIT(sctp, SI_SUB_PROTO_DOMAIN, SI_ORDER_FOURTH, sctp_finish, NULL);
 #endif