diff --git a/sys/dev/xen/netback/netback.c b/sys/dev/xen/netback/netback.c
index 950a68ca74e3..a6111e265f58 100644
--- a/sys/dev/xen/netback/netback.c
+++ b/sys/dev/xen/netback/netback.c
@@ -30,6 +30,7 @@
 
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
+#include "opt_sctp.h"
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -57,6 +58,10 @@ __FBSDID("$FreeBSD$");
 #include <netinet/ip.h>
 #include <netinet/tcp.h>
 #include <netinet/udp.h>
+#ifdef SCTP
+#include <netinet/sctp.h>
+#include <netinet/sctp_crc32.h>
+#endif
 
 #include <vm/vm_extern.h>
 #include <vm/vm_kern.h>
@@ -295,6 +300,11 @@ fixup_checksum(struct mbuf *m)
 			htons(IPPROTO_TCP + (iplen - iphlen)));
 		th->th_sum = in_cksum_skip(m, iplen + sizeof(*eh), sizeof(*eh) + iphlen);
 		m->m_pkthdr.csum_flags &= ~CSUM_TCP;
+#ifdef SCTP
+	} else if (sw_csum & CSUM_SCTP) {
+		sctp_delayed_cksum(m);
+		sw_csum &= ~CSUM_SCTP;
+#endif
 	} else {
 		u_short csum;
 		struct udphdr *uh = (struct udphdr *)((caddr_t)ip + iphlen);
@@ -908,7 +918,8 @@ netif_rx(netif_t *netif)
 #ifdef XEN_NETBACK_FIXUP_CSUM
 		/* Check if we need to compute a checksum.  This happens */
 		/* when bridging from one domain to another. */
-		if ((m->m_pkthdr.csum_flags & CSUM_DELAY_DATA))
+		if ((m->m_pkthdr.csum_flags & CSUM_DELAY_DATA) ||
+			(m->m_pkthdr.csum_flags & CSUM_SCTP))
 			fixup_checksum(m);
 #endif
 
diff --git a/sys/net/if_ethersubr.c b/sys/net/if_ethersubr.c
index 73a08dd51a35..e74bb74c86e6 100644
--- a/sys/net/if_ethersubr.c
+++ b/sys/net/if_ethersubr.c
@@ -299,6 +299,8 @@ ether_output(struct ifnet *ifp, struct mbuf *m,
 			csum_flags |= (CSUM_IP_CHECKED|CSUM_IP_VALID);
 		if (m->m_pkthdr.csum_flags & CSUM_DELAY_DATA)
 			csum_flags |= (CSUM_DATA_VALID|CSUM_PSEUDO_HDR);
+		if (m->m_pkthdr.csum_flags & CSUM_SCTP)
+			csum_flags |= CSUM_SCTP_VALID;
 		m->m_pkthdr.csum_flags |= csum_flags;
 		m->m_pkthdr.csum_data = 0xffff;
 		return (if_simloop(ifp, m, dst->sa_family, 0));
@@ -339,6 +341,8 @@ ether_output(struct ifnet *ifp, struct mbuf *m,
 			csum_flags |= (CSUM_IP_CHECKED|CSUM_IP_VALID);
 		if (m->m_pkthdr.csum_flags & CSUM_DELAY_DATA)
 			csum_flags |= (CSUM_DATA_VALID|CSUM_PSEUDO_HDR);
+		if (m->m_pkthdr.csum_flags & CSUM_SCTP)
+			csum_flags |= CSUM_SCTP_VALID;
 
 		if (m->m_flags & M_BCAST) {
 			struct mbuf *n;
diff --git a/sys/netinet/ip_divert.c b/sys/netinet/ip_divert.c
index d6eb16f833fe..c2e31916c46b 100644
--- a/sys/netinet/ip_divert.c
+++ b/sys/netinet/ip_divert.c
@@ -34,6 +34,7 @@ __FBSDID("$FreeBSD$");
 #include "opt_inet.h"
 #include "opt_ipfw.h"
 #include "opt_mac.h"
+#include "opt_sctp.h"
 #ifndef INET
 #error "IPDIVERT requires INET."
 #endif
@@ -76,6 +77,9 @@ __FBSDID("$FreeBSD$");
 #include <netinet/ip_var.h>
 #include <netinet/ip_fw.h>
 #include <netinet/vinet.h>
+#ifdef SCTP
+#include <netinet/sctp_crc32.h>
+#endif
 
 #include <security/mac/mac_framework.h>
 
@@ -222,7 +226,14 @@ divert_packet(struct mbuf *m, int incoming)
 		m->m_pkthdr.csum_flags &= ~CSUM_DELAY_DATA;
 		ip->ip_len = htons(ip->ip_len);
 	}
-
+#ifdef SCTP
+	if (m->m_pkthdr.csum_flags & CSUM_SCTP) {
+		ip->ip_len = ntohs(ip->ip_len);
+		sctp_delayed_cksum(m);
+		m->m_pkthdr.csum_flags &= ~CSUM_SCTP;
+		ip->ip_len = htons(ip->ip_len);
+	}
+#endif
 	/*
 	 * Record receive interface address, if any.
 	 * But only for incoming packets.
diff --git a/sys/netinet/ip_ipsec.c b/sys/netinet/ip_ipsec.c
index a1e082bafa88..77e9aa74e60c 100644
--- a/sys/netinet/ip_ipsec.c
+++ b/sys/netinet/ip_ipsec.c
@@ -31,6 +31,7 @@
 __FBSDID("$FreeBSD$");
 
 #include "opt_ipsec.h"
+#include "opt_sctp.h"
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -56,6 +57,9 @@ __FBSDID("$FreeBSD$");
 #include <netinet/ip_options.h>
 #include <netinet/ip_ipsec.h>
 #include <netinet/vinet.h>
+#ifdef SCTP
+#include <netinet/sctp_crc32.h>
+#endif
 
 #include <machine/in_cksum.h>
 
@@ -328,7 +332,12 @@ ip_ipsec_output(struct mbuf **m, struct inpcb *inp, int *flags, int *error,
 			in_delayed_cksum(*m);
 			(*m)->m_pkthdr.csum_flags &= ~CSUM_DELAY_DATA;
 		}
-
+#ifdef SCTP
+		if ((*m)->m_pkthdr.csum_flags & CSUM_SCTP) {
+			sctp_delayed_cksum(*m);
+			(*m)->m_pkthdr.csum_flags &= ~CSUM_SCTP;
+		}
+#endif
 		ip->ip_len = htons(ip->ip_len);
 		ip->ip_off = htons(ip->ip_off);
 
diff --git a/sys/netinet/ip_output.c b/sys/netinet/ip_output.c
index 2717d6ec25c8..feacb5169f2c 100644
--- a/sys/netinet/ip_output.c
+++ b/sys/netinet/ip_output.c
@@ -38,6 +38,7 @@ __FBSDID("$FreeBSD$");
 #include "opt_mac.h"
 #include "opt_mbuf_stress_test.h"
 #include "opt_mpath.h"
+#include "opt_sctp.h"
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -70,6 +71,10 @@ __FBSDID("$FreeBSD$");
 #include <netinet/ip_var.h>
 #include <netinet/ip_options.h>
 #include <netinet/vinet.h>
+#ifdef SCTP
+#include <netinet/sctp.h>
+#include <netinet/sctp_crc32.h>
+#endif
 
 #ifdef IPSEC
 #include <netinet/ip_ipsec.h>
@@ -485,7 +490,10 @@ ip_output(struct mbuf *m, struct mbuf *opt, struct route *ro, int flags,
 			}
 			m->m_pkthdr.csum_flags |=
 			    CSUM_IP_CHECKED | CSUM_IP_VALID;
-
+#ifdef SCTP
+			if (m->m_pkthdr.csum_flags & CSUM_SCTP)
+				m->m_pkthdr.csum_flags |= CSUM_SCTP_VALID;
+#endif
 			error = netisr_queue(NETISR_IP, m);
 			goto done;
 		} else
@@ -502,6 +510,10 @@ ip_output(struct mbuf *m, struct mbuf *opt, struct route *ro, int flags,
 			    CSUM_DATA_VALID | CSUM_PSEUDO_HDR;
 			m->m_pkthdr.csum_data = 0xffff;
 		}
+#ifdef SCTP
+		if (m->m_pkthdr.csum_flags & CSUM_SCTP)
+			m->m_pkthdr.csum_flags |= CSUM_SCTP_VALID;
+#endif
 		m->m_pkthdr.csum_flags |=
 			    CSUM_IP_CHECKED | CSUM_IP_VALID;
 
@@ -536,6 +548,12 @@ ip_output(struct mbuf *m, struct mbuf *opt, struct route *ro, int flags,
 		in_delayed_cksum(m);
 		sw_csum &= ~CSUM_DELAY_DATA;
 	}
+#ifdef SCTP
+	if (sw_csum & CSUM_SCTP) {
+		sctp_delayed_cksum(m);
+		sw_csum &= ~CSUM_SCTP;
+	}
+#endif
 	m->m_pkthdr.csum_flags &= ifp->if_hwassist;
 
 	/*
@@ -670,7 +688,13 @@ ip_fragment(struct ip *ip, struct mbuf **m_frag, int mtu,
 		in_delayed_cksum(m0);
 		m0->m_pkthdr.csum_flags &= ~CSUM_DELAY_DATA;
 	}
-
+#ifdef SCTP
+	if (m0->m_pkthdr.csum_flags & CSUM_SCTP &&
+	    (if_hwassist_flags & CSUM_IP_FRAGS) == 0) {
+		sctp_delayed_cksum(m0);
+		m0->m_pkthdr.csum_flags &= ~CSUM_SCTP;
+	}
+#endif
 	if (len > PAGE_SIZE) {
 		/* 
 		 * Fragment large datagrams such that each segment