Index: sys/netipsec/xform.h
===================================================================
--- sys/netipsec/xform.h
+++ sys/netipsec/xform.h
@@ -110,7 +110,7 @@
 struct cryptoini;
 /* XF_AH */
 int xform_ah_authsize(const struct auth_hash *);
-extern int ah_init0(struct secasvar *, struct xformsw *, struct cryptoini *);
+extern int ah_init0(struct secasvar *, struct xformsw *, struct cryptoini *, struct cryptoini *);
 extern int ah_zeroize(struct secasvar *sav);
 extern size_t ah_hdrsiz(struct secasvar *);
 
Index: sys/netipsec/xform_ah.c
===================================================================
--- sys/netipsec/xform_ah.c
+++ sys/netipsec/xform_ah.c
@@ -174,7 +174,7 @@
  * NB: public for use by esp_init.
  */
 int
-ah_init0(struct secasvar *sav, struct xformsw *xsp, struct cryptoini *cria)
+ah_init0(struct secasvar *sav, struct xformsw *xsp, struct cryptoini *cria, struct cryptoini *crin)
 {
 	const struct auth_hash *thash;
 	int keylen;
@@ -241,6 +241,13 @@
 	cria->cri_key = sav->key_auth->key_data;
 	cria->cri_mlen = AUTHSIZE(sav);
 
+	if (sav->flags & SADB_X_SAFLAGS_ESN &&
+	    sav->replay != NULL && sav->replay->wsize != 0) {
+		bzero(crin, sizeof(*crin));
+		crin->cri_alg = CRYPTO_ESN;
+		cria->cri_next = crin;
+	}
+
 	return 0;
 }
 
@@ -250,10 +257,10 @@
 static int
 ah_init(struct secasvar *sav, struct xformsw *xsp)
 {
-	struct cryptoini cria;
+	struct cryptoini cria, crin;
 	int error;
 
-	error = ah_init0(sav, xsp, &cria);
+	error = ah_init0(sav, xsp, &cria, &crin);
 	return error ? error :
 		 crypto_newsession(&sav->tdb_cryptoid, &cria, V_crypto_support);
 }
@@ -648,6 +655,13 @@
 	crda->crd_klen = _KEYBITS(sav->key_auth);
 	crda->crd_key = sav->key_auth->key_data;
 
+	if (sav->flags & SADB_X_SAFLAGS_ESN &&
+	    sav->replay != NULL && sav->replay->wsize != 0) {
+		seqh = htonl(seqh);
+		memcpy(crda->crd_esn, &seqh, 4);
+		crda->crd_flags |= CRD_F_ESN;
+	}
+
 	/* Allocate IPsec-specific opaque crypto info. */
 	xd = malloc(sizeof(*xd) + skip + rplen + authsize, M_XDATA,
 	    M_NOWAIT | M_ZERO);
@@ -874,6 +888,7 @@
 	uint16_t iplen;
 	int error, rplen, authsize, ahsize, maxpacketsize, roff;
 	uint8_t prot;
+	uint32_t seqh;
 
 	IPSEC_ASSERT(sav != NULL, ("null SA"));
 	ahx = sav->tdb_authalgxform;
@@ -1008,6 +1023,12 @@
 	crda->crd_key = sav->key_auth->key_data;
 	crda->crd_klen = _KEYBITS(sav->key_auth);
 
+	if (sav->flags & SADB_X_SAFLAGS_ESN && sav->replay != NULL) {
+		seqh = htonl((uint32_t)(sav->replay->count >> 32));
+		memcpy(crda->crd_esn, &seqh, 4);
+		crda->crd_flags |= CRD_F_ESN;
+	}
+
 	/* Allocate IPsec-specific opaque crypto info. */
 	xd =  malloc(sizeof(struct xform_data) + skip, M_XDATA,
 	    M_NOWAIT | M_ZERO);
Index: sys/netipsec/xform_esp.c
===================================================================
--- sys/netipsec/xform_esp.c
+++ sys/netipsec/xform_esp.c
@@ -137,7 +137,7 @@
 esp_init(struct secasvar *sav, struct xformsw *xsp)
 {
 	const struct enc_xform *txform;
-	struct cryptoini cria, crie;
+	struct cryptoini cria, crie, crin;
 	int keylen;
 	int error;
 
@@ -197,7 +197,7 @@
 	 * Setup AH-related state.
 	 */
 	if (sav->alg_auth != 0) {
-		error = ah_init0(sav, xsp, &cria);
+		error = ah_init0(sav, xsp, &cria, &crin);
 		if (error)
 			return error;
 	}
@@ -395,6 +395,13 @@
 
 		crda->crd_alg = esph->type;
 
+		if (sav->flags & SADB_X_SAFLAGS_ESN &&
+		    sav->replay != NULL && sav->replay->wsize != 0) {
+			seqh = htonl(seqh);
+			memcpy(crda->crd_esn, &seqh, 4);
+			crda->crd_flags |= CRD_F_ESN;
+		}
+
 		/* Copy the authenticator */
 		m_copydata(m, m->m_pkthdr.len - alen, alen,
 		    (caddr_t) (xd + 1));
@@ -665,6 +672,7 @@
 	int hlen, rlen, padding, blks, alen, i, roff;
 	int error, maxpacketsize;
 	uint8_t prot;
+	uint32_t seqh;
 
 	IPSEC_ASSERT(sav != NULL, ("null SA"));
 	esph = sav->tdb_authalgxform;
@@ -887,6 +895,12 @@
 		else
 			crda->crd_len = m->m_pkthdr.len - (skip + alen);
 		crda->crd_inject = m->m_pkthdr.len - alen;
+
+		if (sav->flags & SADB_X_SAFLAGS_ESN && sav->replay != NULL) {
+			seqh = htonl((uint32_t)(sav->replay->count >> 32));
+			memcpy(crda->crd_esn, &seqh, 4);
+			crda->crd_flags |= CRD_F_ESN;
+		}
 	}
 
 	return crypto_dispatch(crp);