text: /*	$NetBSD: svc_vc.c,v 1.7 2000/08/03 00:01:53 fvdl Exp $	*/
  
  /*-
   * Copyright (c) 2009, Sun Microsystems, Inc.
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without 
   * modification, are permitted provided that the following conditions are met:
   * - Redistributions of source code must retain the above copyright notice, 
   *   this list of conditions and the following disclaimer.
   * - 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.
   * - Neither the name of Sun Microsystems, Inc. nor the names of its 
   *   contributors may be used to endorse or promote products derived 
   *   from this software without specific prior written permission.
   * 
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT HOLDER 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.
   */
  
  #if defined(LIBC_SCCS) && !defined(lint)
  static char *sccsid2 = "@(#)svc_tcp.c 1.21 87/08/11 Copyr 1984 Sun Micro";
  static char *sccsid = "@(#)svc_tcp.c	2.2 88/08/01 4.0 RPCSRC";
  #endif
  #include <sys/cdefs.h>
  __FBSDID("$FreeBSD: releng/9.3/sys/rpc/svc_vc.c 261082 2014-01-23 17:27:16Z mav $");
  
  /*
   * svc_vc.c, Server side for Connection Oriented based RPC. 
   *
   * Actually implements two flavors of transporter -
   * a tcp rendezvouser (a listner and connection establisher)
   * and a record/tcp stream.
   */
  
  #include <sys/param.h>
  #include <sys/limits.h>
  #include <sys/lock.h>
  #include <sys/kernel.h>
  #include <sys/malloc.h>
  #include <sys/mbuf.h>
  #include <sys/mutex.h>
  #include <sys/proc.h>
  #include <sys/protosw.h>
  #include <sys/queue.h>
  #include <sys/socket.h>
  #include <sys/socketvar.h>
  #include <sys/sx.h>
  #include <sys/systm.h>
  #include <sys/uio.h>
  
  #include <net/vnet.h>
  
  #include <netinet/tcp.h>
  
  #include <rpc/rpc.h>
  
  #include <rpc/krpc.h>
  #include <rpc/rpc_com.h>
  
  #include <security/mac/mac_framework.h>
  
  static bool_t svc_vc_rendezvous_recv(SVCXPRT *, struct rpc_msg *,
      struct sockaddr **, struct mbuf **);
  static enum xprt_stat svc_vc_rendezvous_stat(SVCXPRT *);
  static void svc_vc_rendezvous_destroy(SVCXPRT *);
  static bool_t svc_vc_null(void);
  static void svc_vc_destroy(SVCXPRT *);
  static enum xprt_stat svc_vc_stat(SVCXPRT *);
  static bool_t svc_vc_ack(SVCXPRT *, uint32_t *);
  static bool_t svc_vc_recv(SVCXPRT *, struct rpc_msg *,
      struct sockaddr **, struct mbuf **);
  static bool_t svc_vc_reply(SVCXPRT *, struct rpc_msg *,
      struct sockaddr *, struct mbuf *, uint32_t *seq);
  static bool_t svc_vc_control(SVCXPRT *xprt, const u_int rq, void *in);
  static bool_t svc_vc_rendezvous_control (SVCXPRT *xprt, const u_int rq,
      void *in);
  static void svc_vc_backchannel_destroy(SVCXPRT *);
  static enum xprt_stat svc_vc_backchannel_stat(SVCXPRT *);
  static bool_t svc_vc_backchannel_recv(SVCXPRT *, struct rpc_msg *,
      struct sockaddr **, struct mbuf **);
  static bool_t svc_vc_backchannel_reply(SVCXPRT *, struct rpc_msg *,
      struct sockaddr *, struct mbuf *, uint32_t *);
  static bool_t svc_vc_backchannel_control(SVCXPRT *xprt, const u_int rq,
      void *in);
  static SVCXPRT *svc_vc_create_conn(SVCPOOL *pool, struct socket *so,
      struct sockaddr *raddr);
  static int svc_vc_accept(struct socket *head, struct socket **sop);
  static int svc_vc_soupcall(struct socket *so, void *arg, int waitflag);
  
  static struct xp_ops svc_vc_rendezvous_ops = {
  	.xp_recv =	svc_vc_rendezvous_recv,
  	.xp_stat =	svc_vc_rendezvous_stat,
  	.xp_reply =	(bool_t (*)(SVCXPRT *, struct rpc_msg *,
  		struct sockaddr *, struct mbuf *, uint32_t *))svc_vc_null,
  	.xp_destroy =	svc_vc_rendezvous_destroy,
  	.xp_control =	svc_vc_rendezvous_control
  };
  
  static struct xp_ops svc_vc_ops = {
  	.xp_recv =	svc_vc_recv,
  	.xp_stat =	svc_vc_stat,
  	.xp_ack =	svc_vc_ack,
  	.xp_reply =	svc_vc_reply,
  	.xp_destroy =	svc_vc_destroy,
  	.xp_control =	svc_vc_control
  };
  
  static struct xp_ops svc_vc_backchannel_ops = {
  	.xp_recv =	svc_vc_backchannel_recv,
  	.xp_stat =	svc_vc_backchannel_stat,
  	.xp_reply =	svc_vc_backchannel_reply,
  	.xp_destroy =	svc_vc_backchannel_destroy,
  	.xp_control =	svc_vc_backchannel_control
  };
  
  /*
   * Usage:
   *	xprt = svc_vc_create(sock, send_buf_size, recv_buf_size);
   *
   * Creates, registers, and returns a (rpc) tcp based transporter.
   * Once *xprt is initialized, it is registered as a transporter
   * see (svc.h, xprt_register).  This routine returns
   * a NULL if a problem occurred.
   *
   * The filedescriptor passed in is expected to refer to a bound, but
   * not yet connected socket.
   *
   * Since streams do buffered io similar to stdio, the caller can specify
   * how big the send and receive buffers are via the second and third parms;
   * 0 => use the system default.
   */
  SVCXPRT *
  svc_vc_create(SVCPOOL *pool, struct socket *so, size_t sendsize,
      size_t recvsize)
  {
  	SVCXPRT *xprt;
  	struct sockaddr* sa;
  	int error;
  
  	SOCK_LOCK(so);
  	if (so->so_state & (SS_ISCONNECTED|SS_ISDISCONNECTED)) {
  		SOCK_UNLOCK(so);
  		error = so->so_proto->pr_usrreqs->pru_peeraddr(so, &sa);
  		if (error)
  			return (NULL);
  		xprt = svc_vc_create_conn(pool, so, sa);
  		free(sa, M_SONAME);
  		return (xprt);
  	}
  	SOCK_UNLOCK(so);
  
  	xprt = svc_xprt_alloc();
  	sx_init(&xprt->xp_lock, "xprt->xp_lock");
  	xprt->xp_pool = pool;
  	xprt->xp_socket = so;
  	xprt->xp_p1 = NULL;
  	xprt->xp_p2 = NULL;
  	xprt->xp_ops = &svc_vc_rendezvous_ops;
  
  	error = so->so_proto->pr_usrreqs->pru_sockaddr(so, &sa);
  	if (error) {
  		goto cleanup_svc_vc_create;
  	}
  
  	memcpy(&xprt->xp_ltaddr, sa, sa->sa_len);
  	free(sa, M_SONAME);
  
  	xprt_register(xprt);
  
  	solisten(so, SOMAXCONN, curthread);
  
  	SOCKBUF_LOCK(&so->so_rcv);
  	xprt->xp_upcallset = 1;
  	soupcall_set(so, SO_RCV, svc_vc_soupcall, xprt);
  	SOCKBUF_UNLOCK(&so->so_rcv);
  
  	return (xprt);
  cleanup_svc_vc_create:
  	if (xprt) {
  		sx_destroy(&xprt->xp_lock);
  		svc_xprt_free(xprt);
  	}
  	return (NULL);
  }
  
  /*
   * Create a new transport for a socket optained via soaccept().
   */
  SVCXPRT *
  svc_vc_create_conn(SVCPOOL *pool, struct socket *so, struct sockaddr *raddr)
  {
  	SVCXPRT *xprt = NULL;
  	struct cf_conn *cd = NULL;
  	struct sockaddr* sa = NULL;
  	struct sockopt opt;
  	int one = 1;
  	int error;
  
  	bzero(&opt, sizeof(struct sockopt));
  	opt.sopt_dir = SOPT_SET;
  	opt.sopt_level = SOL_SOCKET;
  	opt.sopt_name = SO_KEEPALIVE;
  	opt.sopt_val = &one;
  	opt.sopt_valsize = sizeof(one);
  	error = sosetopt(so, &opt);
  	if (error) {
  		return (NULL);
  	}
  
  	if (so->so_proto->pr_protocol == IPPROTO_TCP) {
  		bzero(&opt, sizeof(struct sockopt));
  		opt.sopt_dir = SOPT_SET;
  		opt.sopt_level = IPPROTO_TCP;
  		opt.sopt_name = TCP_NODELAY;
  		opt.sopt_val = &one;
  		opt.sopt_valsize = sizeof(one);
  		error = sosetopt(so, &opt);
  		if (error) {
  			return (NULL);
  		}
  	}
  
  	cd = mem_alloc(sizeof(*cd));
  	cd->strm_stat = XPRT_IDLE;
  
  	xprt = svc_xprt_alloc();
  	sx_init(&xprt->xp_lock, "xprt->xp_lock");
  	xprt->xp_pool = pool;
  	xprt->xp_socket = so;
  	xprt->xp_p1 = cd;
  	xprt->xp_p2 = NULL;
  	xprt->xp_ops = &svc_vc_ops;
  
  	/*
  	 * See http://www.connectathon.org/talks96/nfstcp.pdf - client
  	 * has a 5 minute timer, server has a 6 minute timer.
  	 */
  	xprt->xp_idletimeout = 6 * 60;
  
  	memcpy(&xprt->xp_rtaddr, raddr, raddr->sa_len);
  
  	error = so->so_proto->pr_usrreqs->pru_sockaddr(so, &sa);
  	if (error)
  		goto cleanup_svc_vc_create;
  
  	memcpy(&xprt->xp_ltaddr, sa, sa->sa_len);
  	free(sa, M_SONAME);
  
  	xprt_register(xprt);
  
  	SOCKBUF_LOCK(&so->so_rcv);
  	xprt->xp_upcallset = 1;
  	soupcall_set(so, SO_RCV, svc_vc_soupcall, xprt);
  	SOCKBUF_UNLOCK(&so->so_rcv);
  
  	/*
  	 * Throw the transport into the active list in case it already
  	 * has some data buffered.
  	 */
  	sx_xlock(&xprt->xp_lock);
  	xprt_active(xprt);
  	sx_xunlock(&xprt->xp_lock);
  
  	return (xprt);
  cleanup_svc_vc_create:
  	if (xprt) {
  		sx_destroy(&xprt->xp_lock);
  		svc_xprt_free(xprt);
  	}
  	if (cd)
  		mem_free(cd, sizeof(*cd));
  	return (NULL);
  }
  
  /*
   * Create a new transport for a backchannel on a clnt_vc socket.
   */
  SVCXPRT *
  svc_vc_create_backchannel(SVCPOOL *pool)
  {
  	SVCXPRT *xprt = NULL;
  	struct cf_conn *cd = NULL;
  
  	cd = mem_alloc(sizeof(*cd));
  	cd->strm_stat = XPRT_IDLE;
  
  	xprt = svc_xprt_alloc();
  	sx_init(&xprt->xp_lock, "xprt->xp_lock");
  	xprt->xp_pool = pool;
  	xprt->xp_socket = NULL;
  	xprt->xp_p1 = cd;
  	xprt->xp_p2 = NULL;
  	xprt->xp_ops = &svc_vc_backchannel_ops;
  	return (xprt);
  }
  
  /*
   * This does all of the accept except the final call to soaccept. The
   * caller will call soaccept after dropping its locks (soaccept may
   * call malloc).
   */
  int
  svc_vc_accept(struct socket *head, struct socket **sop)
  {
  	int error = 0;
  	struct socket *so;
  
  	if ((head->so_options & SO_ACCEPTCONN) == 0) {
  		error = EINVAL;
  		goto done;
  	}
  #ifdef MAC
  	error = mac_socket_check_accept(curthread->td_ucred, head);
  	if (error != 0)
  		goto done;
  #endif
  	ACCEPT_LOCK();
  	if (TAILQ_EMPTY(&head->so_comp)) {
  		ACCEPT_UNLOCK();
  		error = EWOULDBLOCK;
  		goto done;
  	}
  	so = TAILQ_FIRST(&head->so_comp);
  	KASSERT(!(so->so_qstate & SQ_INCOMP), ("svc_vc_accept: so SQ_INCOMP"));
  	KASSERT(so->so_qstate & SQ_COMP, ("svc_vc_accept: so not SQ_COMP"));
  
  	/*
  	 * Before changing the flags on the socket, we have to bump the
  	 * reference count.  Otherwise, if the protocol calls sofree(),
  	 * the socket will be released due to a zero refcount.
  	 * XXX might not need soref() since this is simpler than kern_accept.
  	 */
  	SOCK_LOCK(so);			/* soref() and so_state update */
  	soref(so);			/* file descriptor reference */
  
  	TAILQ_REMOVE(&head->so_comp, so, so_list);
  	head->so_qlen--;
  	so->so_state |= (head->so_state & SS_NBIO);
  	so->so_qstate &= ~SQ_COMP;
  	so->so_head = NULL;
  
  	SOCK_UNLOCK(so);
  	ACCEPT_UNLOCK();
  
  	*sop = so;
  
  	/* connection has been removed from the listen queue */
  	KNOTE_UNLOCKED(&head->so_rcv.sb_sel.si_note, 0);
  done:
  	return (error);
  }
  
  /*ARGSUSED*/
  static bool_t
  svc_vc_rendezvous_recv(SVCXPRT *xprt, struct rpc_msg *msg,
      struct sockaddr **addrp, struct mbuf **mp)
  {
  	struct socket *so = NULL;
  	struct sockaddr *sa = NULL;
  	int error;
  	SVCXPRT *new_xprt;
  
  	/*
  	 * The socket upcall calls xprt_active() which will eventually
  	 * cause the server to call us here. We attempt to accept a
  	 * connection from the socket and turn it into a new
  	 * transport. If the accept fails, we have drained all pending
  	 * connections so we call xprt_inactive().
  	 */
  	sx_xlock(&xprt->xp_lock);
  
  	error = svc_vc_accept(xprt->xp_socket, &so);
  
  	if (error == EWOULDBLOCK) {
  		/*
  		 * We must re-test for new connections after taking
  		 * the lock to protect us in the case where a new
  		 * connection arrives after our call to accept fails
  		 * with EWOULDBLOCK.
  		 */
  		ACCEPT_LOCK();
  		if (TAILQ_EMPTY(&xprt->xp_socket->so_comp))
  			xprt_inactive_self(xprt);
  		ACCEPT_UNLOCK();
  		sx_xunlock(&xprt->xp_lock);
  		return (FALSE);
  	}
  
  	if (error) {
  		SOCKBUF_LOCK(&xprt->xp_socket->so_rcv);
  		if (xprt->xp_upcallset) {
  			xprt->xp_upcallset = 0;
  			soupcall_clear(xprt->xp_socket, SO_RCV);
  		}
  		SOCKBUF_UNLOCK(&xprt->xp_socket->so_rcv);
  		xprt_inactive_self(xprt);
  		sx_xunlock(&xprt->xp_lock);
  		return (FALSE);
  	}
  
  	sx_xunlock(&xprt->xp_lock);
  
  	sa = 0;
  	error = soaccept(so, &sa);
  
  	if (error) {
  		/*
  		 * XXX not sure if I need to call sofree or soclose here.
  		 */
  		if (sa)
  			free(sa, M_SONAME);
  		return (FALSE);
  	}
  
  	/*
  	 * svc_vc_create_conn will call xprt_register - we don't need
  	 * to do anything with the new connection except derefence it.
  	 */
  	new_xprt = svc_vc_create_conn(xprt->xp_pool, so, sa);
  	if (!new_xprt) {
  		soclose(so);
  	} else {
  		SVC_RELEASE(new_xprt);
  	}
  
  	free(sa, M_SONAME);
  
  	return (FALSE); /* there is never an rpc msg to be processed */
  }
  
  /*ARGSUSED*/
  static enum xprt_stat
  svc_vc_rendezvous_stat(SVCXPRT *xprt)
  {
  
  	return (XPRT_IDLE);
  }
  
  static void
  svc_vc_destroy_common(SVCXPRT *xprt)
  {
  	SOCKBUF_LOCK(&xprt->xp_socket->so_rcv);
  	if (xprt->xp_upcallset) {
  		xprt->xp_upcallset = 0;
  		soupcall_clear(xprt->xp_socket, SO_RCV);
  	}
  	SOCKBUF_UNLOCK(&xprt->xp_socket->so_rcv);
  
  	if (xprt->xp_socket)
  		(void)soclose(xprt->xp_socket);
  
  	if (xprt->xp_netid)
  		(void) mem_free(xprt->xp_netid, strlen(xprt->xp_netid) + 1);
  	svc_xprt_free(xprt);
  }
  
  static void
  svc_vc_rendezvous_destroy(SVCXPRT *xprt)
  {
  
  	svc_vc_destroy_common(xprt);
  }
  
  static void
  svc_vc_destroy(SVCXPRT *xprt)
  {
  	struct cf_conn *cd = (struct cf_conn *)xprt->xp_p1;
  
  	svc_vc_destroy_common(xprt);
  
  	if (cd->mreq)
  		m_freem(cd->mreq);
  	if (cd->mpending)
  		m_freem(cd->mpending);
  	mem_free(cd, sizeof(*cd));
  }
  
  static void
  svc_vc_backchannel_destroy(SVCXPRT *xprt)
  {
  	struct cf_conn *cd = (struct cf_conn *)xprt->xp_p1;
  	struct mbuf *m, *m2;
  
  	svc_xprt_free(xprt);
  	m = cd->mreq;
  	while (m != NULL) {
  		m2 = m;
  		m = m->m_nextpkt;
  		m_freem(m2);
  	}
  	mem_free(cd, sizeof(*cd));
  }
  
  /*ARGSUSED*/
  static bool_t
  svc_vc_control(SVCXPRT *xprt, const u_int rq, void *in)
  {
  	return (FALSE);
  }
  
  static bool_t
  svc_vc_rendezvous_control(SVCXPRT *xprt, const u_int rq, void *in)
  {
  
  	return (FALSE);
  }
  
  static bool_t
  svc_vc_backchannel_control(SVCXPRT *xprt, const u_int rq, void *in)
  {
  
  	return (FALSE);
  }
  
  static enum xprt_stat
  svc_vc_stat(SVCXPRT *xprt)
  {
  	struct cf_conn *cd;
  
  	cd = (struct cf_conn *)(xprt->xp_p1);
  
  	if (cd->strm_stat == XPRT_DIED)
  		return (XPRT_DIED);
  
  	if (cd->mreq != NULL && cd->resid == 0 && cd->eor)
  		return (XPRT_MOREREQS);
  
  	if (soreadable(xprt->xp_socket))
  		return (XPRT_MOREREQS);
  
  	return (XPRT_IDLE);
  }
  
  static bool_t
  svc_vc_ack(SVCXPRT *xprt, uint32_t *ack)
  {
  
  	*ack = atomic_load_acq_32(&xprt->xp_snt_cnt);
  	*ack -= xprt->xp_socket->so_snd.sb_cc;
  	return (TRUE);
  }
  
  static enum xprt_stat
  svc_vc_backchannel_stat(SVCXPRT *xprt)
  {
  	struct cf_conn *cd;
  
  	cd = (struct cf_conn *)(xprt->xp_p1);
  
  	if (cd->mreq != NULL)
  		return (XPRT_MOREREQS);
  
  	return (XPRT_IDLE);
  }
  
  /*
   * If we have an mbuf chain in cd->mpending, try to parse a record from it,
   * leaving the result in cd->mreq. If we don't have a complete record, leave
   * the partial result in cd->mreq and try to read more from the socket.
   */
  static int
  svc_vc_process_pending(SVCXPRT *xprt)
  {
  	struct cf_conn *cd = (struct cf_conn *) xprt->xp_p1;
  	struct socket *so = xprt->xp_socket;
  	struct mbuf *m;
  
  	/*
  	 * If cd->resid is non-zero, we have part of the
  	 * record already, otherwise we are expecting a record
  	 * marker.
  	 */
  	if (!cd->resid && cd->mpending) {
  		/*
  		 * See if there is enough data buffered to
  		 * make up a record marker. Make sure we can
  		 * handle the case where the record marker is
  		 * split across more than one mbuf.
  		 */
  		size_t n = 0;
  		uint32_t header;
  
  		m = cd->mpending;
  		while (n < sizeof(uint32_t) && m) {
  			n += m->m_len;
  			m = m->m_next;
  		}
  		if (n < sizeof(uint32_t)) {
  			so->so_rcv.sb_lowat = sizeof(uint32_t) - n;
  			return (FALSE);
  		}
  		m_copydata(cd->mpending, 0, sizeof(header),
  		    (char *)&header);
  		header = ntohl(header);
  		cd->eor = (header & 0x80000000) != 0;
  		cd->resid = header & 0x7fffffff;
  		m_adj(cd->mpending, sizeof(uint32_t));
  	}
  
  	/*
  	 * Start pulling off mbufs from cd->mpending
  	 * until we either have a complete record or
  	 * we run out of data. We use m_split to pull
  	 * data - it will pull as much as possible and
  	 * split the last mbuf if necessary.
  	 */
  	while (cd->mpending && cd->resid) {
  		m = cd->mpending;
  		if (cd->mpending->m_next
  		    || cd->mpending->m_len > cd->resid)
  			cd->mpending = m_split(cd->mpending,
  			    cd->resid, M_WAITOK);
  		else
  			cd->mpending = NULL;
  		if (cd->mreq)
  			m_last(cd->mreq)->m_next = m;
  		else
  			cd->mreq = m;
  		while (m) {
  			cd->resid -= m->m_len;
  			m = m->m_next;
  		}
  	}
  
  	/*
  	 * Block receive upcalls if we have more data pending,
  	 * otherwise report our need.
  	 */
  	if (cd->mpending)
  		so->so_rcv.sb_lowat = INT_MAX;
  	else
  		so->so_rcv.sb_lowat =
  		    imax(1, imin(cd->resid, so->so_rcv.sb_hiwat / 2));
  	return (TRUE);
  }
  
  static bool_t
  svc_vc_recv(SVCXPRT *xprt, struct rpc_msg *msg,
      struct sockaddr **addrp, struct mbuf **mp)
  {
  	struct cf_conn *cd = (struct cf_conn *) xprt->xp_p1;
  	struct uio uio;
  	struct mbuf *m;
  	struct socket* so = xprt->xp_socket;
  	XDR xdrs;
  	int error, rcvflag;
  
  	/*
  	 * Serialise access to the socket and our own record parsing
  	 * state.
  	 */
  	sx_xlock(&xprt->xp_lock);
  
  	for (;;) {
  		/* If we have no request ready, check pending queue. */
  		while (cd->mpending &&
  		    (cd->mreq == NULL || cd->resid != 0 || !cd->eor)) {
  			if (!svc_vc_process_pending(xprt))
  				break;
  		}
  
  		/* Process and return complete request in cd->mreq. */
  		if (cd->mreq != NULL && cd->resid == 0 && cd->eor) {
  
  			xdrmbuf_create(&xdrs, cd->mreq, XDR_DECODE);
  			cd->mreq = NULL;
  
  			/* Check for next request in a pending queue. */
  			svc_vc_process_pending(xprt);
  			if (cd->mreq == NULL || cd->resid != 0) {
  				SOCKBUF_LOCK(&so->so_rcv);
  				if (!soreadable(so))
  					xprt_inactive_self(xprt);
  				SOCKBUF_UNLOCK(&so->so_rcv);
  			}
  
  			sx_xunlock(&xprt->xp_lock);
  
  			if (! xdr_callmsg(&xdrs, msg)) {
  				XDR_DESTROY(&xdrs);
  				return (FALSE);
  			}
  
  			*addrp = NULL;
  			*mp = xdrmbuf_getall(&xdrs);
  			XDR_DESTROY(&xdrs);
  
  			return (TRUE);
  		}
  
  		/*
  		 * The socket upcall calls xprt_active() which will eventually
  		 * cause the server to call us here. We attempt to
  		 * read as much as possible from the socket and put
  		 * the result in cd->mpending. If the read fails,
  		 * we have drained both cd->mpending and the socket so
  		 * we can call xprt_inactive().
  		 */
  		uio.uio_resid = 1000000000;
  		uio.uio_td = curthread;
  		m = NULL;
  		rcvflag = MSG_DONTWAIT;
  		error = soreceive(so, NULL, &uio, &m, NULL, &rcvflag);
  
  		if (error == EWOULDBLOCK) {
  			/*
  			 * We must re-test for readability after
  			 * taking the lock to protect us in the case
  			 * where a new packet arrives on the socket
  			 * after our call to soreceive fails with
  			 * EWOULDBLOCK.
  			 */
  			SOCKBUF_LOCK(&so->so_rcv);
  			if (!soreadable(so))
  				xprt_inactive_self(xprt);
  			SOCKBUF_UNLOCK(&so->so_rcv);
  			sx_xunlock(&xprt->xp_lock);
  			return (FALSE);
  		}
  
  		if (error) {
  			SOCKBUF_LOCK(&so->so_rcv);
  			if (xprt->xp_upcallset) {
  				xprt->xp_upcallset = 0;
  				soupcall_clear(so, SO_RCV);
  			}
  			SOCKBUF_UNLOCK(&so->so_rcv);
  			xprt_inactive_self(xprt);
  			cd->strm_stat = XPRT_DIED;
  			sx_xunlock(&xprt->xp_lock);
  			return (FALSE);
  		}
  
  		if (!m) {
  			/*
  			 * EOF - the other end has closed the socket.
  			 */
  			xprt_inactive_self(xprt);
  			cd->strm_stat = XPRT_DIED;
  			sx_xunlock(&xprt->xp_lock);
  			return (FALSE);
  		}
  
  		if (cd->mpending)
  			m_last(cd->mpending)->m_next = m;
  		else
  			cd->mpending = m;
  	}
  }
  
  static bool_t
  svc_vc_backchannel_recv(SVCXPRT *xprt, struct rpc_msg *msg,
      struct sockaddr **addrp, struct mbuf **mp)
  {
  	struct cf_conn *cd = (struct cf_conn *) xprt->xp_p1;
  	struct ct_data *ct;
  	struct mbuf *m;
  	XDR xdrs;
  
  	sx_xlock(&xprt->xp_lock);
  	ct = (struct ct_data *)xprt->xp_p2;
  	if (ct == NULL) {
  		sx_xunlock(&xprt->xp_lock);
  		return (FALSE);
  	}
  	mtx_lock(&ct->ct_lock);
  	m = cd->mreq;
  	if (m == NULL) {
  		xprt_inactive_self(xprt);
  		mtx_unlock(&ct->ct_lock);
  		sx_xunlock(&xprt->xp_lock);
  		return (FALSE);
  	}
  	cd->mreq = m->m_nextpkt;
  	mtx_unlock(&ct->ct_lock);
  	sx_xunlock(&xprt->xp_lock);
  
  	xdrmbuf_create(&xdrs, m, XDR_DECODE);
  	if (! xdr_callmsg(&xdrs, msg)) {
  		XDR_DESTROY(&xdrs);
  		return (FALSE);
  	}
  	*addrp = NULL;
  	*mp = xdrmbuf_getall(&xdrs);
  	XDR_DESTROY(&xdrs);
  	return (TRUE);
  }
  
  static bool_t
  svc_vc_reply(SVCXPRT *xprt, struct rpc_msg *msg,
      struct sockaddr *addr, struct mbuf *m, uint32_t *seq)
  {
  	XDR xdrs;
  	struct mbuf *mrep;
  	bool_t stat = TRUE;
  	int error, len;
  
  	/*
  	 * Leave space for record mark.
  	 */
  	MGETHDR(mrep, M_WAIT, MT_DATA);
  	mrep->m_len = 0;
  	mrep->m_data += sizeof(uint32_t);
  
  	xdrmbuf_create(&xdrs, mrep, XDR_ENCODE);
  
  	if (msg->rm_reply.rp_stat == MSG_ACCEPTED &&
  	    msg->rm_reply.rp_acpt.ar_stat == SUCCESS) {
  		if (!xdr_replymsg(&xdrs, msg))
  			stat = FALSE;
  		else
  			xdrmbuf_append(&xdrs, m);
  	} else {
  		stat = xdr_replymsg(&xdrs, msg);
  	}
  
  	if (stat) {
  		m_fixhdr(mrep);
  
  		/*
  		 * Prepend a record marker containing the reply length.
  		 */
  		M_PREPEND(mrep, sizeof(uint32_t), M_WAIT);
  		len = mrep->m_pkthdr.len;
  		*mtod(mrep, uint32_t *) =
  			htonl(0x80000000 | (len - sizeof(uint32_t)));
  		atomic_add_acq_32(&xprt->xp_snd_cnt, len);
  		error = sosend(xprt->xp_socket, NULL, NULL, mrep, NULL,
  		    0, curthread);
  		if (!error) {
  			atomic_add_rel_32(&xprt->xp_snt_cnt, len);
  			if (seq)
  				*seq = xprt->xp_snd_cnt;
  			stat = TRUE;
  		} else
  			atomic_subtract_32(&xprt->xp_snd_cnt, len);
  	} else {
  		m_freem(mrep);
  	}
  
  	XDR_DESTROY(&xdrs);
  	xprt->xp_p2 = NULL;
  
  	return (stat);
  }
  
  static bool_t
  svc_vc_backchannel_reply(SVCXPRT *xprt, struct rpc_msg *msg,
      struct sockaddr *addr, struct mbuf *m, uint32_t *seq)
  {
  	struct ct_data *ct;
  	XDR xdrs;
  	struct mbuf *mrep;
  	bool_t stat = TRUE;
  	int error;
  
  	/*
  	 * Leave space for record mark.
  	 */
  	MGETHDR(mrep, M_WAITOK, MT_DATA);
  	mrep->m_len = 0;
  	mrep->m_data += sizeof(uint32_t);
  
  	xdrmbuf_create(&xdrs, mrep, XDR_ENCODE);
  
  	if (msg->rm_reply.rp_stat == MSG_ACCEPTED &&
  	    msg->rm_reply.rp_acpt.ar_stat == SUCCESS) {
  		if (!xdr_replymsg(&xdrs, msg))
  			stat = FALSE;
  		else
  			xdrmbuf_append(&xdrs, m);
  	} else {
  		stat = xdr_replymsg(&xdrs, msg);
  	}
  
  	if (stat) {
  		m_fixhdr(mrep);
  
  		/*
  		 * Prepend a record marker containing the reply length.
  		 */
  		M_PREPEND(mrep, sizeof(uint32_t), M_WAITOK);
  		*mtod(mrep, uint32_t *) =
  			htonl(0x80000000 | (mrep->m_pkthdr.len
  				- sizeof(uint32_t)));
  		sx_xlock(&xprt->xp_lock);
  		ct = (struct ct_data *)xprt->xp_p2;
  		if (ct != NULL)
  			error = sosend(ct->ct_socket, NULL, NULL, mrep, NULL,
  			    0, curthread);
  		else
  			error = EPIPE;
  		sx_xunlock(&xprt->xp_lock);
  		if (!error) {
  			stat = TRUE;
  		}
  	} else {
  		m_freem(mrep);
  	}
  
  	XDR_DESTROY(&xdrs);
  
  	return (stat);
  }
  
  static bool_t
  svc_vc_null()
  {
  
  	return (FALSE);
  }
  
  static int
  svc_vc_soupcall(struct socket *so, void *arg, int waitflag)
  {
  	SVCXPRT *xprt = (SVCXPRT *) arg;
  
  	if (soreadable(xprt->xp_socket))
  		xprt_active(xprt);
  	return (SU_OK);
  }
  
  #if 0
  /*
   * Get the effective UID of the sending process. Used by rpcbind, keyserv
   * and rpc.yppasswdd on AF_LOCAL.
   */
  int
  __rpc_get_local_uid(SVCXPRT *transp, uid_t *uid) {
  	int sock, ret;
  	gid_t egid;
  	uid_t euid;
  	struct sockaddr *sa;
  
  	sock = transp->xp_fd;
  	sa = (struct sockaddr *)transp->xp_rtaddr;
  	if (sa->sa_family == AF_LOCAL) {
  		ret = getpeereid(sock, &euid, &egid);
  		if (ret == 0)
  			*uid = euid;
  		return (ret);
  	} else
  		return (-1);
  }
  #endif
  