diff --git a/sys/fs/nfs/nfs.h b/sys/fs/nfs/nfs.h
index 4e79d3afbd2f..7212a685d902 100644
--- a/sys/fs/nfs/nfs.h
+++ b/sys/fs/nfs/nfs.h
@@ -747,6 +747,7 @@ struct nfsrv_descript {
 #define	ND_ERELOOKUP		0x40000000000
 #define	ND_MACHCRED		0x80000000000
 #define	ND_CANEXTPG		0x100000000000
+#define	ND_RDMA			0x200000000000
 
 /*
  * ND_GSS should be the "or" of all GSS type authentications.
diff --git a/sys/fs/nfsserver/nfs_nfsdkrpc.c b/sys/fs/nfsserver/nfs_nfsdkrpc.c
index 16c21b4e1607..20b76d6152cd 100644
--- a/sys/fs/nfsserver/nfs_nfsdkrpc.c
+++ b/sys/fs/nfsserver/nfs_nfsdkrpc.c
@@ -120,6 +120,10 @@ VNET_DEFINE(struct nfsv4lock, nfsd_suspend_lock);
 
 VNET_DEFINE_STATIC(bool, nfsrvd_inited) = false;
 
+/* Server RDMA listen hook, set by nfsrdma at MOD_LOAD. */
+svc_rdma_listen_ftype *svc_rdma_listen = NULL;
+int nfsrvd_rdma_port = 0;
+
 /*
  * NFS server system calls
  */
@@ -181,7 +185,8 @@ nfssvc_program(struct svc_req *rqst, SVCXPRT *xprt)
 	nd.nd_mreq = NULL;
 	nd.nd_cred = NULL;
 
-	if (VNET(nfs_privport) != 0) {
+	/* xp_socket is NULL for RDMA. */
+	if (VNET(nfs_privport) != 0 && xprt->xp_socket != NULL) {
 		/* Check if source port is privileged */
 		u_short port;
 		struct sockaddr *nam = nd.nd_nam;
@@ -260,6 +265,18 @@ nfssvc_program(struct svc_req *rqst, SVCXPRT *xprt)
 			goto out;
 		}
 
+		/*
+		 * For RDMA, ND_GSSINTEGRITY and ND_GSSPRIVACY are not
+		 * supported.
+		 */
+		if ((nd.nd_flag & (ND_GSSINTEGRITY | ND_GSSPRIVACY)) != 0 &&
+		    xprt->xp_socket == NULL) {
+			svcerr_auth(rqst, AUTH_FAILED);
+			svc_freereq(rqst);
+			m_freem(nd.nd_mrep);
+			goto out;
+		}
+
 		/* Acquire the principal name for the RPCSEC_GSS cases. */
 		if ((nd.nd_flag & (ND_NFSV4 | ND_GSS)) == (ND_NFSV4 | ND_GSS)) {
 			rcredp = NULL;
@@ -332,6 +349,10 @@ nfssvc_program(struct svc_req *rqst, SVCXPRT *xprt)
 		if ((nfsrv_mextpg || xprt->xp_extpg) && nd.nd_nam2 == NULL &&
 		    PMAP_HAS_DMAP != 0)
 			nd.nd_flag |= ND_CANEXTPG;
+
+		/* If the xprt xp_socket == NULL, this is a RDMA call. */
+		if (xprt->xp_socket == NULL)
+			nd.nd_flag |= ND_RDMA;
 #ifdef MAC
 		mac_cred_associate_nfsd(nd.nd_cred);
 #endif
@@ -620,6 +641,21 @@ nfsrvd_nfsd(struct thread *td, struct nfsd_nfsd_args *args)
 		VNET(nfsrv_numnfsd)++;	/* Num for this vnet. */
 
 		NFSD_UNLOCK();
+		/*
+		 * If nfsrvd_rdma_port has been set and the nfsrdma.ko module
+		 * has been loaded, start the server side RDMA.
+		 * RDMA does not work within a vnet jail.
+		 */
+		if (!jailed(curthread->td_ucred) && svc_rdma_listen != NULL &&
+		    nfsrvd_rdma_port != 0) {
+			error = svc_rdma_listen(VNET(nfsrvd_pool),
+			    nfsrvd_rdma_port);
+			if (error != 0) {
+				printf("nfsrvd_nfsd: RDMA listen failed=%d\n",
+				    error);
+				nfsrvd_rdma_port = 0;
+			}
+		}
 		error = nfsrv_createdevids(args, td);
 		if (error == 0) {
 			/* An empty string implies AUTH_SYS only. */
@@ -695,6 +731,11 @@ nfsrvd_init(int terminating)
 	if (terminating) {
 		VNET(nfsd_master_proc) = NULL;
 		NFSD_UNLOCK();
+
+		/* Turn off the RDMA listener, if enabled. */
+		if (!jailed(curthread->td_ucred) && svc_rdma_listen != NULL)
+			(void)svc_rdma_listen(VNET(nfsrvd_pool), 0);
+
 		nfsrv_freealllayoutsanddevids();
 		nfsrv_freeallbackchannel_xprts();
 		svcpool_close(VNET(nfsrvd_pool));
diff --git a/sys/fs/nfsserver/nfs_nfsdserv.c b/sys/fs/nfsserver/nfs_nfsdserv.c
index 704667bd27b6..dd6e4805606a 100644
--- a/sys/fs/nfsserver/nfs_nfsdserv.c
+++ b/sys/fs/nfsserver/nfs_nfsdserv.c
@@ -49,6 +49,7 @@
 #include <fs/nfs/nfsport.h>
 #include <sys/extattr.h>
 #include <sys/filio.h>
+#include <rpc/krpc.h>
 
 /* Global vars */
 extern u_int32_t newnfs_false, newnfs_true;
@@ -1076,6 +1077,20 @@ nfsrvd_read(struct nfsrv_descript *nd, __unused int isdgram,
 	}
 	*tl = txdr_unsigned(cnt);
 	if (m3) {
+		/*
+		 * For RDMA, inform the server side rdma the reduction's
+		 * position.
+		 */
+		if ((nd->nd_flag & ND_RDMA) != 0 && nd->nd_xprt != NULL) {
+			KASSERT(cnt > 0,
+			    ("nfsrvd_read: m3 != NULL when cnt == 0"));
+			struct rpcrdma_reduce ddp;
+
+			ddp.xid = nd->nd_retxid;
+			ddp.off = (uint32_t)m_length(nd->nd_mreq, NULL);
+			ddp.len = (uint32_t)cnt;
+			(void)SVC_CONTROL(nd->nd_xprt, SVCSET_READDDP, &ddp);
+		}
 		nd->nd_mb->m_next = m3;
 		nd->nd_mb = m2;
 		if ((m2->m_flags & M_EXTPG) != 0) {
diff --git a/sys/rpc/clnt_bck.c b/sys/rpc/clnt_bck.c
index 9ff85b1fa2c0..65eb95c56fa5 100644
--- a/sys/rpc/clnt_bck.c
+++ b/sys/rpc/clnt_bck.c
@@ -83,6 +83,9 @@
 #include <rpc/krpc.h>
 #include <rpc/rpcsec_tls.h>
 
+/* The RDMA module will set this function pointer non-NULL. */
+clnt_bck_rdma_send_ftype *clnt_bck_rdma_send = NULL;
+
 struct cmessage {
         struct cmsghdr cmsg;
         struct cmsgcred cmcred;
@@ -269,12 +272,15 @@ call_again:
 	}
 	mreq->m_pkthdr.len = m_length(mreq, NULL);
 
-	/*
-	 * Prepend a record marker containing the packet length.
-	 */
-	M_PREPEND(mreq, sizeof(uint32_t), M_WAITOK);
-	*mtod(mreq, uint32_t *) =
-	    htonl(0x80000000 | (mreq->m_pkthdr.len - sizeof(uint32_t)));
+	/* RDMA doesn't need a record marker. */
+	if (xprt->xp_socket != NULL) {
+		/*
+		 * Prepend a record marker containing the packet length.
+		 */
+		M_PREPEND(mreq, sizeof(uint32_t), M_WAITOK);
+		*mtod(mreq, uint32_t *) =
+		    htonl(0x80000000 | (mreq->m_pkthdr.len - sizeof(uint32_t)));
+	}
 
 	cr->cr_xid = xid;
 	mtx_lock(&ct->ct_lock);
@@ -297,36 +303,47 @@ call_again:
 	TAILQ_INSERT_TAIL(&ct->ct_pending, cr, cr_link);
 	mtx_unlock(&ct->ct_lock);
 
-	/* For RPC-over-TLS, copy mrep to a chain of ext_pgs. */
-	if ((xprt->xp_tls & RPCTLS_FLAGS_HANDSHAKE) != 0) {
-		/*
-		 * Copy the mbuf chain to a chain of
-		 * ext_pgs mbuf(s) as required by KERN_TLS.
-		 */
-		maxextsiz = TLS_MAX_MSG_SIZE_V10_2;
+	if (xprt->xp_socket != NULL) {
+		/* Handle TCP sockets. */
+		/* For RPC-over-TLS, copy mrep to a chain of ext_pgs. */
+		if ((xprt->xp_tls & RPCTLS_FLAGS_HANDSHAKE) != 0) {
+			/*
+			 * Copy the mbuf chain to a chain of
+			 * ext_pgs mbuf(s) as required by KERN_TLS.
+			 */
+			maxextsiz = TLS_MAX_MSG_SIZE_V10_2;
 #ifdef KERN_TLS
-		if (rpctls_getinfo(&maxlen, false, false))
-			maxextsiz = min(maxextsiz, maxlen);
+			if (rpctls_getinfo(&maxlen, false, false))
+				maxextsiz = min(maxextsiz, maxlen);
 #endif
-		mreq = _rpc_copym_into_ext_pgs(mreq, maxextsiz);
-	}
-	/*
-	 * sosend consumes mreq.
-	 */
-	sx_xlock(&xprt->xp_lock);
-	error = sosend(xprt->xp_socket, NULL, NULL, mreq, NULL, 0, curthread);
-	mreq = NULL;
-	if (error == EMSGSIZE) {
-		SOCK_SENDBUF_LOCK(xprt->xp_socket);
-		sbwait(xprt->xp_socket, SO_SND);
-		SOCK_SENDBUF_UNLOCK(xprt->xp_socket);
+			mreq = _rpc_copym_into_ext_pgs(mreq, maxextsiz);
+		}
+		/*
+		 * sosend consumes mreq.
+		 */
+		sx_xlock(&xprt->xp_lock);
+		error = sosend(xprt->xp_socket, NULL, NULL, mreq, NULL, 0,
+		    curthread);
+		mreq = NULL;
+		if (error == EMSGSIZE) {
+			SOCK_SENDBUF_LOCK(xprt->xp_socket);
+			sbwait(xprt->xp_socket, SO_SND);
+			SOCK_SENDBUF_UNLOCK(xprt->xp_socket);
+			sx_xunlock(&xprt->xp_lock);
+			AUTH_VALIDATE(auth, xid, NULL, NULL);
+			mtx_lock(&ct->ct_lock);
+			TAILQ_REMOVE(&ct->ct_pending, cr, cr_link);
+			goto call_again;
+		}
 		sx_xunlock(&xprt->xp_lock);
-		AUTH_VALIDATE(auth, xid, NULL, NULL);
-		mtx_lock(&ct->ct_lock);
-		TAILQ_REMOVE(&ct->ct_pending, cr, cr_link);
-		goto call_again;
+	} else {
+		/* Handle RDMA. */
+		if (clnt_bck_rdma_send != NULL) {
+			clnt_bck_rdma_send(xprt, mreq);
+			mreq = NULL;
+		} else
+			error = ENOTCONN;
 	}
-	sx_xunlock(&xprt->xp_lock);
 
 	reply_msg.acpted_rply.ar_verf.oa_flavor = AUTH_NULL;
 	reply_msg.acpted_rply.ar_verf.oa_base = cr->cr_verf;
diff --git a/sys/rpc/krpc.h b/sys/rpc/krpc.h
index f77e2d2d7428..f53b07ed86b6 100644
--- a/sys/rpc/krpc.h
+++ b/sys/rpc/krpc.h
@@ -42,6 +42,10 @@ enum clnt_stat clnt_bck_call(CLIENT *, struct rpc_callextra *, rpcproc_t,
     struct mbuf *, struct mbuf **, struct timeval, SVCXPRT *);
 struct mbuf *_rpc_copym_into_ext_pgs(struct mbuf *, int);
 
+/* Callback function for server side RDMA. */
+typedef int	clnt_bck_rdma_send_ftype(SVCXPRT *xprt, struct mbuf *m);
+extern clnt_bck_rdma_send_ftype *clnt_bck_rdma_send;
+
 /*
  * A pending RPC request which awaits a reply. Requests which have
  * received their reply will have cr_xid set to zero and cr_mrep to
@@ -136,6 +140,29 @@ struct cf_conn {  /* kept in xprt->xp_p1 for actual connection */
 
 void rpcnl_init(void);
 
+/* RDMA procedures. */
+enum rdma_proc {
+	RDMA_MSG = 0,
+	RDMA_NOMSG = 1,
+	RDMA_MSGP = 2,	/* Not used. */
+	RDMA_DONE = 3,	/* Not used. */
+	RDMA_ERROR = 4
+};
+
+enum rdma_errcode {
+	RDMA_ERR_VERS = 1,
+	RDMA_ERR_CHUNK = 2
+};
+
+/* Structure use by both client and server RDMA for reductions (RFC8166). */
+struct rpcrdma_reduce {
+	struct iovec	*iov;
+	uint32_t	xid;
+	uint32_t	off;
+	uint32_t	len;
+	uint8_t		into_mem;
+};
+
 #endif	/* _KERNEL */
 
 #endif	/* _RPC_KRPC_H_ */
diff --git a/sys/rpc/svc.h b/sys/rpc/svc.h
index e73e61e5ac93..a7cbb639f48e 100644
--- a/sys/rpc/svc.h
+++ b/sys/rpc/svc.h
@@ -76,6 +76,7 @@
 #define SVCSET_VERSQUIET	2
 #define SVCGET_CONNMAXREC	3
 #define SVCSET_CONNMAXREC	4
+#define SVCSET_READDDP		5
 
 /*
  * Operations for rpc_control().
@@ -342,6 +343,16 @@ typedef struct __rpc_svcpool {
 	SVCGROUP	sp_groups[SVC_MAXGROUPS]; /* Thread/port groups. */
 } SVCPOOL;
 
+/*
+ * svc_rdma_listen is the function in the nfsrdma.ko module called to
+ * enable the RDMA server side listener.
+ * nfsrvd_rdma_port - The port# that RDMA should listen on for the NFS server.
+ */
+typedef int	svc_rdma_listen_ftype(SVCPOOL *pool, int port);
+extern svc_rdma_listen_ftype *svc_rdma_listen;
+extern int	nfsrvd_rdma_port;
+extern int	newnfs_numnfsd;
+
 /*
  * Operations defined on an SVCXPRT handle
  *
diff --git a/sys/rpc/svc_auth.c b/sys/rpc/svc_auth.c
index acbb1112e270..030f55e44a97 100644
--- a/sys/rpc/svc_auth.c
+++ b/sys/rpc/svc_auth.c
@@ -107,6 +107,9 @@ _authenticate(struct svc_req *rqst, struct rpc_msg *msg)
 		dummy = _svcauth_rpcsec_gss(rqst, msg);
 		return (dummy);
 	case AUTH_TLS:
+		/* Not supported for RDMA. */
+		if (rqst->rq_xprt->xp_socket == NULL)
+			return (AUTH_REJECTEDCRED);
 		dummy = _svcauth_rpcsec_tls(rqst, msg);
 		return (dummy);
 	default: