FreeBSD/Linux Kernel Cross Reference
sys/kern/uipc_socket2.c

     /*
      * Copyright (c) 1982, 1986, 1988, 1990, 1993
      *      The Regents of the University of California.  All rights reserved.
      *
      * 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.
     * 3. All advertising materials mentioning features or use of this software
     *    must display the following acknowledgement:
     *      This product includes software developed by the University of
     *      California, Berkeley and its contributors.
     * 4. Neither the name of the University 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 REGENTS 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 REGENTS 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.
     *
     *      @(#)uipc_socket2.c      8.1 (Berkeley) 6/10/93
     * $FreeBSD$
     */
    
    #include "opt_param.h"
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/domain.h>
    #include <sys/file.h>   /* for maxfiles */
    #include <sys/kernel.h>
    #include <sys/proc.h>
    #include <sys/malloc.h>
    #include <sys/mbuf.h>
    #include <sys/protosw.h>
    #include <sys/resourcevar.h>
    #include <sys/stat.h>
    #include <sys/socket.h>
    #include <sys/socketvar.h>
    #include <sys/signalvar.h>
    #include <sys/sysctl.h>
    #include <sys/aio.h> /* for aio_swake proto */
    #include <sys/event.h>
    
    int     maxsockets;
    
    /*
     * Primitive routines for operating on sockets and socket buffers
     */
    
    u_long  sb_max = SB_MAX;
    u_long  sb_max_adj =
        SB_MAX * MCLBYTES / (MSIZE + MCLBYTES); /* adjusted sb_max */
    
    static  u_long sb_efficiency = 8;       /* parameter for sbreserve() */
    
    /*
     * Procedures to manipulate state flags of socket
     * and do appropriate wakeups.  Normal sequence from the
     * active (originating) side is that soisconnecting() is
     * called during processing of connect() call,
     * resulting in an eventual call to soisconnected() if/when the
     * connection is established.  When the connection is torn down
     * soisdisconnecting() is called during processing of disconnect() call,
     * and soisdisconnected() is called when the connection to the peer
     * is totally severed.  The semantics of these routines are such that
     * connectionless protocols can call soisconnected() and soisdisconnected()
     * only, bypassing the in-progress calls when setting up a ``connection''
     * takes no time.
     *
     * From the passive side, a socket is created with
     * two queues of sockets: so_incomp for connections in progress
     * and so_comp for connections already made and awaiting user acceptance.
     * As a protocol is preparing incoming connections, it creates a socket
     * structure queued on so_incomp by calling sonewconn().  When the connection
     * is established, soisconnected() is called, and transfers the
     * socket structure to so_comp, making it available to accept().
     *
     * If a socket is closed with sockets on either
     * so_incomp or so_comp, these sockets are dropped.
     *
     * If higher level protocols are implemented in
     * the kernel, the wakeups done here will sometimes
     * cause software-interrupt process scheduling.
     */
    
    void
    soisconnecting(so)
           register struct socket *so;
   {
   
           so->so_state &= ~(SS_ISCONNECTED|SS_ISDISCONNECTING);
           so->so_state |= SS_ISCONNECTING;
   }
   
   void
   soisconnected(so)
           struct socket *so;
   {
           struct socket *head = so->so_head;
   
           so->so_state &= ~(SS_ISCONNECTING|SS_ISDISCONNECTING|SS_ISCONFIRMING);
           so->so_state |= SS_ISCONNECTED;
           if (head && (so->so_state & SS_INCOMP)) {
                   if ((so->so_options & SO_ACCEPTFILTER) != 0) {
                           so->so_upcall = head->so_accf->so_accept_filter->accf_callback;
                           so->so_upcallarg = head->so_accf->so_accept_filter_arg;
                           so->so_rcv.sb_flags |= SB_UPCALL;
                           so->so_options &= ~SO_ACCEPTFILTER;
                           so->so_upcall(so, so->so_upcallarg, 0);
                           return;
                   }
                   TAILQ_REMOVE(&head->so_incomp, so, so_list);
                   head->so_incqlen--;
                   so->so_state &= ~SS_INCOMP;
                   TAILQ_INSERT_TAIL(&head->so_comp, so, so_list);
                   head->so_qlen++;
                   so->so_state |= SS_COMP;
                   sorwakeup(head);
                   wakeup_one(&head->so_timeo);
           } else {
                   wakeup(&so->so_timeo);
                   sorwakeup(so);
                   sowwakeup(so);
           }
   }
   
   void
   soisdisconnecting(so)
           register struct socket *so;
   {
   
           so->so_state &= ~SS_ISCONNECTING;
           so->so_state |= (SS_ISDISCONNECTING|SS_CANTRCVMORE|SS_CANTSENDMORE);
           wakeup((caddr_t)&so->so_timeo);
           sowwakeup(so);
           sorwakeup(so);
   }
   
   void
   soisdisconnected(so)
           register struct socket *so;
   {
   
           so->so_state &= ~(SS_ISCONNECTING|SS_ISCONNECTED|SS_ISDISCONNECTING);
           so->so_state |= (SS_CANTRCVMORE|SS_CANTSENDMORE|SS_ISDISCONNECTED);
           wakeup((caddr_t)&so->so_timeo);
           sbdrop(&so->so_snd, so->so_snd.sb_cc);
           sowwakeup(so);
           sorwakeup(so);
   }
   
   /*
    * When an attempt at a new connection is noted on a socket
    * which accepts connections, sonewconn is called.  If the
    * connection is possible (subject to space constraints, etc.)
    * then we allocate a new structure, propoerly linked into the
    * data structure of the original socket, and return this.
    * Connstatus may be 0, or SO_ISCONFIRMING, or SO_ISCONNECTED.
    */
   struct socket *
   sonewconn(head, connstatus)
           register struct socket *head;
           int connstatus;
   {
   
           return (sonewconn3(head, connstatus, NULL));
   }
   
   struct socket *
   sonewconn3(head, connstatus, p)
           register struct socket *head;
           int connstatus;
           struct proc *p;
   {
           register struct socket *so;
   
           if (head->so_qlen > 3 * head->so_qlimit / 2)
                   return ((struct socket *)0);
           so = soalloc(0);
           if (so == NULL)
                   return ((struct socket *)0);
           if ((head->so_options & SO_ACCEPTFILTER) != 0)
                   connstatus = 0;
           so->so_head = head;
           so->so_type = head->so_type;
           so->so_options = head->so_options &~ SO_ACCEPTCONN;
           so->so_linger = head->so_linger;
           so->so_state = head->so_state | SS_NOFDREF;
           so->so_proto = head->so_proto;
           so->so_timeo = head->so_timeo;
           so->so_cred = p ? p->p_ucred : head->so_cred;
           crhold(so->so_cred);
           if (soreserve(so, head->so_snd.sb_hiwat, head->so_rcv.sb_hiwat) ||
               (*so->so_proto->pr_usrreqs->pru_attach)(so, 0, NULL)) {
                   sodealloc(so);
                   return ((struct socket *)0);
           }
   
           if (connstatus) {
                   TAILQ_INSERT_TAIL(&head->so_comp, so, so_list);
                   so->so_state |= SS_COMP;
                   head->so_qlen++;
           } else {
                   if (head->so_incqlen > head->so_qlimit) {
                           struct socket *sp;
                           sp = TAILQ_FIRST(&head->so_incomp);
                           (void) soabort(sp);
                   }
                   TAILQ_INSERT_TAIL(&head->so_incomp, so, so_list);
                   so->so_state |= SS_INCOMP;
                   head->so_incqlen++;
           }
           if (connstatus) {
                   sorwakeup(head);
                   wakeup_one(&head->so_timeo);
                   so->so_state |= connstatus;
           }
           return (so);
   }
   
   /*
    * Socantsendmore indicates that no more data will be sent on the
    * socket; it would normally be applied to a socket when the user
    * informs the system that no more data is to be sent, by the protocol
    * code (in case PRU_SHUTDOWN).  Socantrcvmore indicates that no more data
    * will be received, and will normally be applied to the socket by a
    * protocol when it detects that the peer will send no more data.
    * Data queued for reading in the socket may yet be read.
    */
   
   void
   socantsendmore(so)
           struct socket *so;
   {
   
           so->so_state |= SS_CANTSENDMORE;
           sowwakeup(so);
   }
   
   void
   socantrcvmore(so)
           struct socket *so;
   {
   
           so->so_state |= SS_CANTRCVMORE;
           sorwakeup(so);
   }
   
   /*
    * Wait for data to arrive at/drain from a socket buffer.
    */
   int
   sbwait(sb)
           struct sockbuf *sb;
   {
   
           sb->sb_flags |= SB_WAIT;
           return (tsleep((caddr_t)&sb->sb_cc,
               (sb->sb_flags & SB_NOINTR) ? PSOCK : PSOCK | PCATCH, "sbwait",
               sb->sb_timeo));
   }
   
   /*
    * Lock a sockbuf already known to be locked;
    * return any error returned from sleep (EINTR).
    */
   int
   sb_lock(sb)
           register struct sockbuf *sb;
   {
           int error;
   
           while (sb->sb_flags & SB_LOCK) {
                   sb->sb_flags |= SB_WANT;
                   error = tsleep((caddr_t)&sb->sb_flags,
                       (sb->sb_flags & SB_NOINTR) ? PSOCK : PSOCK|PCATCH,
                       "sblock", 0);
                   if (error)
                           return (error);
           }
           sb->sb_flags |= SB_LOCK;
           return (0);
   }
   
   /*
    * Wakeup processes waiting on a socket buffer.
    * Do asynchronous notification via SIGIO
    * if the socket has the SS_ASYNC flag set.
    */
   void
   sowakeup(so, sb)
           register struct socket *so;
           register struct sockbuf *sb;
   {
           selwakeup(&sb->sb_sel);
           sb->sb_flags &= ~SB_SEL;
           if (sb->sb_flags & SB_WAIT) {
                   sb->sb_flags &= ~SB_WAIT;
                   wakeup((caddr_t)&sb->sb_cc);
           }
           if ((so->so_state & SS_ASYNC) && so->so_sigio != NULL)
                   pgsigio(so->so_sigio, SIGIO, 0);
           if (sb->sb_flags & SB_UPCALL)
                   (*so->so_upcall)(so, so->so_upcallarg, M_DONTWAIT);
           if (sb->sb_flags & SB_AIO)
                   aio_swake(so, sb);
           KNOTE(&sb->sb_sel.si_note, 0);
   }
   
   /*
    * Socket buffer (struct sockbuf) utility routines.
    *
    * Each socket contains two socket buffers: one for sending data and
    * one for receiving data.  Each buffer contains a queue of mbufs,
    * information about the number of mbufs and amount of data in the
    * queue, and other fields allowing select() statements and notification
    * on data availability to be implemented.
    *
    * Data stored in a socket buffer is maintained as a list of records.
    * Each record is a list of mbufs chained together with the m_next
    * field.  Records are chained together with the m_nextpkt field. The upper
    * level routine soreceive() expects the following conventions to be
    * observed when placing information in the receive buffer:
    *
    * 1. If the protocol requires each message be preceded by the sender's
    *    name, then a record containing that name must be present before
    *    any associated data (mbuf's must be of type MT_SONAME).
    * 2. If the protocol supports the exchange of ``access rights'' (really
    *    just additional data associated with the message), and there are
    *    ``rights'' to be received, then a record containing this data
    *    should be present (mbuf's must be of type MT_RIGHTS).
    * 3. If a name or rights record exists, then it must be followed by
    *    a data record, perhaps of zero length.
    *
    * Before using a new socket structure it is first necessary to reserve
    * buffer space to the socket, by calling sbreserve().  This should commit
    * some of the available buffer space in the system buffer pool for the
    * socket (currently, it does nothing but enforce limits).  The space
    * should be released by calling sbrelease() when the socket is destroyed.
    */
   
   int
   soreserve(so, sndcc, rcvcc)
           register struct socket *so;
           u_long sndcc, rcvcc;
   {
           struct proc *p = curproc;
   
           if (sbreserve(&so->so_snd, sndcc, so, p) == 0)
                   goto bad;
           if (sbreserve(&so->so_rcv, rcvcc, so, p) == 0)
                   goto bad2;
           if (so->so_rcv.sb_lowat == 0)
                   so->so_rcv.sb_lowat = 1;
           if (so->so_snd.sb_lowat == 0)
                   so->so_snd.sb_lowat = MCLBYTES;
           if (so->so_snd.sb_lowat > so->so_snd.sb_hiwat)
                   so->so_snd.sb_lowat = so->so_snd.sb_hiwat;
           return (0);
   bad2:
           sbrelease(&so->so_snd, so);
   bad:
           return (ENOBUFS);
   }
   
   static int
   sysctl_handle_sb_max(SYSCTL_HANDLER_ARGS)
   {
           int error = 0;
           u_long old_sb_max = sb_max;
   
           error = SYSCTL_OUT(req, arg1, sizeof(int));
           if (error || !req->newptr)
                   return (error);
           error = SYSCTL_IN(req, arg1, sizeof(int));
           if (error)
                   return (error);
           if (sb_max < MSIZE + MCLBYTES) {
                   sb_max = old_sb_max;
                   return (EINVAL);
           }
           sb_max_adj = (u_quad_t)sb_max * MCLBYTES / (MSIZE + MCLBYTES);
           return (0);
   }
           
   /*
    * Allot mbufs to a sockbuf.
    * Attempt to scale mbmax so that mbcnt doesn't become limiting
    * if buffering efficiency is near the normal case.
    */
   int
   sbreserve(sb, cc, so, p)
           struct sockbuf *sb;
           u_long cc;
           struct socket *so;
           struct proc *p;
   {
   
           /*
            * p will only be NULL when we're in an interrupt
            * (e.g. in tcp_input())
            */
           if (cc > sb_max_adj)
                   return (0);
           if (!chgsbsize(so->so_cred->cr_uidinfo, &sb->sb_hiwat, cc,
               p ? p->p_rlimit[RLIMIT_SBSIZE].rlim_cur : RLIM_INFINITY)) {
                   return (0);
           }
           sb->sb_mbmax = min(cc * sb_efficiency, sb_max);
           if (sb->sb_lowat > sb->sb_hiwat)
                   sb->sb_lowat = sb->sb_hiwat;
           return (1);
   }
   
   /*
    * Free mbufs held by a socket, and reserved mbuf space.
    */
   void
   sbrelease(sb, so)
           struct sockbuf *sb;
           struct socket *so;
   {
   
           sbflush(sb);
           (void)chgsbsize(so->so_cred->cr_uidinfo, &sb->sb_hiwat, 0,
               RLIM_INFINITY);
           sb->sb_mbmax = 0;
   }
   
   /*
    * Routines to add and remove
    * data from an mbuf queue.
    *
    * The routines sbappend() or sbappendrecord() are normally called to
    * append new mbufs to a socket buffer, after checking that adequate
    * space is available, comparing the function sbspace() with the amount
    * of data to be added.  sbappendrecord() differs from sbappend() in
    * that data supplied is treated as the beginning of a new record.
    * To place a sender's address, optional access rights, and data in a
    * socket receive buffer, sbappendaddr() should be used.  To place
    * access rights and data in a socket receive buffer, sbappendrights()
    * should be used.  In either case, the new data begins a new record.
    * Note that unlike sbappend() and sbappendrecord(), these routines check
    * for the caller that there will be enough space to store the data.
    * Each fails if there is not enough space, or if it cannot find mbufs
    * to store additional information in.
    *
    * Reliable protocols may use the socket send buffer to hold data
    * awaiting acknowledgement.  Data is normally copied from a socket
    * send buffer in a protocol with m_copy for output to a peer,
    * and then removing the data from the socket buffer with sbdrop()
    * or sbdroprecord() when the data is acknowledged by the peer.
    */
   
   #ifdef SOCKBUF_DEBUG
   void
   sblastrecordchk(struct sockbuf *sb, const char *file, int line)
   {
           struct mbuf *m = sb->sb_mb;
   
           while (m && m->m_nextpkt)
                   m = m->m_nextpkt;
   
           if (m != sb->sb_lastrecord) {
                   printf("%s: sb_mb %p sb_lastrecord %p last %p\n",
                           __func__, sb->sb_mb, sb->sb_lastrecord, m);
                   printf("packet chain:\n");
                   for (m = sb->sb_mb; m != NULL; m = m->m_nextpkt)
                           printf("\t%p\n", m);
                   panic("%s from %s:%u", __func__, file, line);
           }
   }
   
   void
   sblastmbufchk(struct sockbuf *sb, const char *file, int line)
   {
           struct mbuf *m = sb->sb_mb;
           struct mbuf *n;
   
           while (m && m->m_nextpkt)
                   m = m->m_nextpkt;
   
           while (m && m->m_next)
                   m = m->m_next;
   
           if (m != sb->sb_mbtail) {
                   printf("%s: sb_mb %p sb_mbtail %p last %p\n",
                           __func__, sb->sb_mb, sb->sb_mbtail, m);
                   printf("packet tree:\n");
                   for (m = sb->sb_mb; m != NULL; m = m->m_nextpkt) {
                           printf("\t");
                           for (n = m; n != NULL; n = n->m_next)
                                   printf("%p ", n);
                           printf("\n");
                   }
                   panic("%s from %s:%u", __func__, file, line);
           }
   }
   #endif /* SOCKBUF_DEBUG */
   
   #define SBLINKRECORD(sb, m0) do {                                       \
           if ((sb)->sb_lastrecord != NULL)                                \
                   (sb)->sb_lastrecord->m_nextpkt = (m0);                  \
           else                                                            \
                   (sb)->sb_mb = (m0);                                     \
           (sb)->sb_lastrecord = (m0);                                     \
   } while (/*CONSTCOND*/0)
   
   /*
    * Append mbuf chain m to the last record in the
    * socket buffer sb.  The additional space associated
    * the mbuf chain is recorded in sb.  Empty mbufs are
    * discarded and mbufs are compacted where possible.
    */
   void
   sbappend(sb, m)
           struct sockbuf *sb;
           struct mbuf *m;
   {
           register struct mbuf *n;
   
           if (m == 0)
                   return;
           SBLASTRECORDCHK(sb);
           n = sb->sb_mb;
           if (n) {
                   while (n->m_nextpkt)
                           n = n->m_nextpkt;
                   do {
                           if (n->m_flags & M_EOR) {
                                   sbappendrecord(sb, m); /* XXXXXX!!!! */
                                   return;
                           }
                   } while (n->m_next && (n = n->m_next));
           } else {
                   /*
                    * XXX Would like to simply use sb_mbtail here, but
                    * XXX I need to verify that I won't miss an EOR that
                    * XXX way.
                    */
                   if ((n = sb->sb_lastrecord) != NULL) {
                           do {
                                   if (n->m_flags & M_EOR) {
                                           sbappendrecord(sb, m); /* XXXXXX!!!! */
                                           return;
                                   }
                           } while (n->m_next && (n = n->m_next));
                   } else {
                           /*
                            * If this is the first record in the socket buffer,
                            * it's also the last record.
                            */
                           sb->sb_lastrecord = m;
                   }
           }
           sbcompress(sb, m, n);
           SBLASTRECORDCHK(sb);
   }
   
   /*
    * This version of sbappend() should only be used when the caller
    * absolutely knows that there will never be more than one record
    * in the socket buffer, that is, a stream protocol (such as TCP).
    */
   void
   sbappendstream(struct sockbuf *sb, struct mbuf *m)
   {
   
           KASSERT(m->m_nextpkt == NULL,("sbappendstream 0"));
           KASSERT(sb->sb_mb == sb->sb_lastrecord,("sbappendstream 1"));
   
           SBLASTMBUFCHK(sb);
   
           sbcompress(sb, m, sb->sb_mbtail);
   
           sb->sb_lastrecord = sb->sb_mb;
           SBLASTRECORDCHK(sb);
   }
   
   #ifdef SOCKBUF_DEBUG
   void
   sbcheck(sb)
           register struct sockbuf *sb;
   {
           register struct mbuf *m;
           register struct mbuf *n = 0;
           register u_long len = 0, mbcnt = 0;
   
           for (m = sb->sb_mb; m; m = n) {
               n = m->m_nextpkt;
               for (; m; m = m->m_next) {
                   len += m->m_len;
                   mbcnt += MSIZE;
                   if (m->m_flags & M_EXT) /*XXX*/ /* pretty sure this is bogus */
                           mbcnt += m->m_ext.ext_size;
               }
           }
           if (len != sb->sb_cc || mbcnt != sb->sb_mbcnt) {
                   printf("cc %ld != %u || mbcnt %ld != %u\n", len, sb->sb_cc,
                       mbcnt, sb->sb_mbcnt);
                   panic("sbcheck");
           }
   }
   #endif
   
   /*
    * As above, except the mbuf chain
    * begins a new record.
    */
   void
   sbappendrecord(sb, m0)
           register struct sockbuf *sb;
           register struct mbuf *m0;
   {
           register struct mbuf *m;
   
           if (m0 == 0)
                   return;
           m = sb->sb_mb;
           if (m)
                   while (m->m_nextpkt)
                           m = m->m_nextpkt;
           /*
            * Put the first mbuf on the queue.
            * Note this permits zero length records.
            */
           sballoc(sb, m0);
           SBLASTRECORDCHK(sb);
           SBLINKRECORD(sb, m0);
           if (m)
                   m->m_nextpkt = m0;
           else
                   sb->sb_mb = m0;
           m = m0->m_next;
           m0->m_next = 0;
           if (m && (m0->m_flags & M_EOR)) {
                   m0->m_flags &= ~M_EOR;
                   m->m_flags |= M_EOR;
           }
           sbcompress(sb, m, m0);
   }
   
   /*
    * As above except that OOB data
    * is inserted at the beginning of the sockbuf,
    * but after any other OOB data.
    */
   void
   sbinsertoob(sb, m0)
           register struct sockbuf *sb;
           register struct mbuf *m0;
   {
           register struct mbuf *m;
           register struct mbuf **mp;
   
           if (m0 == 0)
                   return;
           for (mp = &sb->sb_mb; *mp ; mp = &((*mp)->m_nextpkt)) {
               m = *mp;
               again:
                   switch (m->m_type) {
   
                   case MT_OOBDATA:
                           continue;               /* WANT next train */
   
                   case MT_CONTROL:
                           m = m->m_next;
                           if (m)
                                   goto again;     /* inspect THIS train further */
                   }
                   break;
           }
           /*
            * Put the first mbuf on the queue.
            * Note this permits zero length records.
            */
           sballoc(sb, m0);
           m0->m_nextpkt = *mp;
           *mp = m0;
           m = m0->m_next;
           m0->m_next = 0;
           if (m && (m0->m_flags & M_EOR)) {
                   m0->m_flags &= ~M_EOR;
                   m->m_flags |= M_EOR;
           }
           sbcompress(sb, m, m0);
   }
   
   /*
    * Append address and data, and optionally, control (ancillary) data
    * to the receive queue of a socket.  If present,
    * m0 must include a packet header with total length.
    * Returns 0 if no space in sockbuf or insufficient mbufs.
    */
   int
   sbappendaddr(sb, asa, m0, control)
           register struct sockbuf *sb;
           struct sockaddr *asa;
           struct mbuf *m0, *control;
   {
           register struct mbuf *m, *n, *nlast;
           int space = asa->sa_len;
   
   if (m0 && (m0->m_flags & M_PKTHDR) == 0)
   panic("sbappendaddr");
           if (m0)
                   space += m0->m_pkthdr.len;
           for (n = control; n; n = n->m_next) {
                   space += n->m_len;
                   if (n->m_next == 0)     /* keep pointer to last control buf */
                           break;
           }
           if (space > sbspace(sb))
                   return (0);
           if (asa->sa_len > MLEN)
                   return (0);
           MGET(m, M_DONTWAIT, MT_SONAME);
           if (m == 0)
                   return (0);
           m->m_len = asa->sa_len;
           bcopy((caddr_t)asa, mtod(m, caddr_t), asa->sa_len);
           if (n)
                   n->m_next = m0;         /* concatenate data to control */
           else
                   control = m0;
           m->m_next = control;
           for (n = m; n->m_next != NULL; n = n->m_next)
                   sballoc(sb, n);
           sballoc(sb, n);
           nlast = n;
           SBLINKRECORD(sb, m);
   
           sb->sb_mbtail = nlast;
           SBLASTMBUFCHK(sb);
   
           SBLASTRECORDCHK(sb);
           return (1);
   }
   
   int
   sbappendcontrol(sb, m0, control)
           struct sockbuf *sb;
           struct mbuf *control, *m0;
   {
           register struct mbuf *m, *n, *mlast;
           int space = 0;
   
           if (control == 0)
                   panic("sbappendcontrol");
           for (m = control; ; m = m->m_next) {
                   space += m->m_len;
                   if (m->m_next == 0)
                           break;
           }
           n = m;                  /* save pointer to last control buffer */
           for (m = m0; m; m = m->m_next)
                   space += m->m_len;
           if (space > sbspace(sb))
                   return (0);
           n->m_next = m0;                 /* concatenate data to control */
   
           SBLASTRECORDCHK(sb);
   
           for (m = control; m->m_next; m = m->m_next)
                   sballoc(sb, m);
           sballoc(sb, m);
           mlast = m;
           SBLINKRECORD(sb, control);
   
           sb->sb_mbtail = mlast;
           SBLASTMBUFCHK(sb);
   
           SBLASTRECORDCHK(sb);
           return (1);
   }
   
   /*
    * Compress mbuf chain m into the socket
    * buffer sb following mbuf n.  If n
    * is null, the buffer is presumed empty.
    */
   void
   sbcompress(sb, m, n)
           register struct sockbuf *sb;
           register struct mbuf *m, *n;
   {
           register int eor = 0;
           register struct mbuf *o;
   
           while (m) {
                   eor |= m->m_flags & M_EOR;
                   if (m->m_len == 0 &&
                       (eor == 0 ||
                        (((o = m->m_next) || (o = n)) &&
                         o->m_type == m->m_type))) {
                           if (sb->sb_lastrecord == m)
                                   sb->sb_lastrecord = m->m_next;
                           m = m_free(m);
                           continue;
                   }
                   if (n && (n->m_flags & M_EOR) == 0 &&
                       M_WRITABLE(n) &&
                       m->m_len <= MCLBYTES / 4 && /* XXX: Don't copy too much */
                       m->m_len <= M_TRAILINGSPACE(n) &&
                       n->m_type == m->m_type) {
                           bcopy(mtod(m, caddr_t), mtod(n, caddr_t) + n->m_len,
                               (unsigned)m->m_len);
                           n->m_len += m->m_len;
                           sb->sb_cc += m->m_len;
                           m = m_free(m);
                           continue;
                   }
                   if (n)
                           n->m_next = m;
                   else
                           sb->sb_mb = m;
                   sb->sb_mbtail = m;
                   sballoc(sb, m);
                   n = m;
                   m->m_flags &= ~M_EOR;
                   m = m->m_next;
                   n->m_next = 0;
           }
           if (eor) {
                   if (n)
                           n->m_flags |= eor;
                   else
                           printf("semi-panic: sbcompress\n");
           }
           SBLASTMBUFCHK(sb);
   }
   
   /*
    * Free all mbufs in a sockbuf.
    * Check that all resources are reclaimed.
    */
   void
   sbflush(sb)
           register struct sockbuf *sb;
   {
   
           if (sb->sb_flags & SB_LOCK)
                   panic("sbflush: locked");
           while (sb->sb_mbcnt) {
                   /*
                    * Don't call sbdrop(sb, 0) if the leading mbuf is non-empty:
                    * we would loop forever. Panic instead.
                    */
                   if (!sb->sb_cc && (sb->sb_mb == NULL || sb->sb_mb->m_len))
                           break;
                   sbdrop(sb, (int)sb->sb_cc);
           }
           if (sb->sb_cc || sb->sb_mb || sb->sb_mbcnt)
                   panic("sbflush: cc %ld || mb %p || mbcnt %ld", sb->sb_cc, (void *)sb->sb_mb, sb->sb_mbcnt);
   }
   
   /*
    * Drop data from (the front of) a sockbuf.
    */
   void
   sbdrop(sb, len)
           register struct sockbuf *sb;
           register int len;
   {
           register struct mbuf *m;
           struct mbuf *next;
   
           next = (m = sb->sb_mb) ? m->m_nextpkt : 0;
           while (len > 0) {
                   if (m == 0) {
                           if (next == 0)
                                   panic("sbdrop");
                           m = next;
                           next = m->m_nextpkt;
                           continue;
                   }
                   if (m->m_len > len) {
                           m->m_len -= len;
                           m->m_data += len;
                           sb->sb_cc -= len;
                           break;
                   }
                   len -= m->m_len;
                   sbfree(sb, m);
                   m = m_free(m);
           }
           while (m && m->m_len == 0) {
                   sbfree(sb, m);
                   m = m_free(m);
           }
           if (m) {
                   sb->sb_mb = m;
                   m->m_nextpkt = next;
           } else
                   sb->sb_mb = next;
           /*
            * First part is an inline SB_EMPTY_FIXUP().  Second part
            * makes sure sb_lastrecord is up-to-date if we dropped
            * part of the last record.
            */
           m = sb->sb_mb;
           if (m == NULL) {
                   sb->sb_mbtail = NULL;
                   sb->sb_lastrecord = NULL;
           } else if (m->m_nextpkt == NULL) {
                   sb->sb_lastrecord = m;
           }
   }
   
   /*
    * Drop a record off the front of a sockbuf
    * and move the next record to the front.
    */
   void
   sbdroprecord(sb)
           register struct sockbuf *sb;
   {
           register struct mbuf *m;
   
           m = sb->sb_mb;
           if (m) {
                   sb->sb_mb = m->m_nextpkt;
                   do {
                           sbfree(sb, m);
                           m = m_free(m);
                   } while (m);
           }
           SB_EMPTY_FIXUP(sb);
   }
   
   /*
    * Create a "control" mbuf containing the specified data
    * with the specified type for presentation on a socket buffer.
    */
   struct mbuf *
   sbcreatecontrol(p, size, type, level)
           caddr_t p;
           register int size;
           int type, level;
   {
           register struct cmsghdr *cp;
           struct mbuf *m;
   
           if (CMSG_SPACE((u_int)size) > MCLBYTES)
                   return ((struct mbuf *) NULL);
           if ((m = m_get(M_DONTWAIT, MT_CONTROL)) == NULL)
                   return ((struct mbuf *) NULL);
           if (CMSG_SPACE((u_int)size) > MLEN) {
                   MCLGET(m, M_DONTWAIT);
                   if ((m->m_flags & M_EXT) == 0) {
                           m_free(m);
                           return ((struct mbuf *) NULL);
                   }
           }
           cp = mtod(m, struct cmsghdr *);
           m->m_len = 0;
           KASSERT(CMSG_SPACE((u_int)size) <= M_TRAILINGSPACE(m),
               ("sbcreatecontrol: short mbuf"));
           if (p != NULL)
                   (void)memcpy(CMSG_DATA(cp), p, size);
           m->m_len = CMSG_SPACE(size);
           cp->cmsg_len = CMSG_LEN(size);
           cp->cmsg_level = level;
           cp->cmsg_type = type;
           return (m);
   }
   
   /*
    * Some routines that return EOPNOTSUPP for entry points that are not
    * supported by a protocol.  Fill in as needed.
    */
   int
   pru_accept_notsupp(struct socket *so, struct sockaddr **nam)
   {
           return EOPNOTSUPP;
   }
   
   int
   pru_connect_notsupp(struct socket *so, struct sockaddr *nam, struct proc *p)
   {
           return EOPNOTSUPP;
   }
   
   int
   pru_connect2_notsupp(struct socket *so1, struct socket *so2)
   {
           return EOPNOTSUPP;
  }
  
  int
  pru_control_notsupp(struct socket *so, u_long cmd, caddr_t data,
                      struct ifnet *ifp, struct proc *p)
  {
          return EOPNOTSUPP;
  }
  
  int
  pru_listen_notsupp(struct socket *so, struct proc *p)
  {
          return EOPNOTSUPP;
  }
  
  int
  pru_rcvd_notsupp(struct socket *so, int flags)
  {
          return EOPNOTSUPP;
  }
  
  int
  pru_rcvoob_notsupp(struct socket *so, struct mbuf *m, int flags)
  {
          return EOPNOTSUPP;
  }
  
  /*
   * This isn't really a ``null'' operation, but it's the default one
   * and doesn't do anything destructive.
   */
  int
  pru_sense_null(struct socket *so, struct stat *sb)
  {
          sb->st_blksize = so->so_snd.sb_hiwat;
          return 0;
  }
  
  /*
   * Make a copy of a sockaddr in a malloced buffer of type M_SONAME.
   */
  struct sockaddr *
  dup_sockaddr(sa, canwait)
          struct sockaddr *sa;
          int canwait;
  {
          struct sockaddr *sa2;
  
          MALLOC(sa2, struct sockaddr *, sa->sa_len, M_SONAME, 
                 canwait ? M_WAITOK : M_NOWAIT);
          if (sa2)
                  bcopy(sa, sa2, sa->sa_len);
          return sa2;
  }
  
  /*
   * Create an external-format (``xsocket'') structure using the information
   * in the kernel-format socket structure pointed to by so.  This is done
   * to reduce the spew of irrelevant information over this interface,
   * to isolate user code from changes in the kernel structure, and
   * potentially to provide information-hiding if we decide that
   * some of this information should be hidden from users.
   */
  void
  sotoxsocket(struct socket *so, struct xsocket *xso)
  {
          xso->xso_len = sizeof *xso;
          xso->xso_so = so;
          xso->so_type = so->so_type;
          xso->so_options = so->so_options;
          xso->so_linger = so->so_linger;
          xso->so_state = so->so_state;
          xso->so_pcb = so->so_pcb;
          xso->xso_protocol = so->so_proto->pr_protocol;
          xso->xso_family = so->so_proto->pr_domain->dom_family;
          xso->so_qlen = so->so_qlen;
          xso->so_incqlen = so->so_incqlen;
          xso->so_qlimit = so->so_qlimit;
          xso->so_timeo = so->so_timeo;
          xso->so_error = so->so_error;
          xso->so_pgid = so->so_sigio ? so->so_sigio->sio_pgid : 0;
          xso->so_oobmark = so->so_oobmark;
          sbtoxsockbuf(&so->so_snd, &xso->so_snd);
          sbtoxsockbuf(&so->so_rcv, &xso->so_rcv);
          xso->so_uid = so->so_cred->cr_uid;
  }
  
  /*
   * This does the same for sockbufs.  Note that the xsockbuf structure,
   * since it is always embedded in a socket, does not include a self
   * pointer nor a length.  We make this entry point public in case
   * some other mechanism needs it.
   */
  void
  sbtoxsockbuf(struct sockbuf *sb, struct xsockbuf *xsb)
  {
          xsb->sb_cc = sb->sb_cc;
          xsb->sb_hiwat = sb->sb_hiwat;
          xsb->sb_mbcnt = sb->sb_mbcnt;
          xsb->sb_mbmax = sb->sb_mbmax;
          xsb->sb_lowat = sb->sb_lowat;
          xsb->sb_flags = sb->sb_flags;
          xsb->sb_timeo = sb->sb_timeo;
  }
  
  /*
   * Here is the definition of some of the basic objects in the kern.ipc
   * branch of the MIB.
   */
  SYSCTL_NODE(_kern, KERN_IPC, ipc, CTLFLAG_RW, 0, "IPC");
  
  /* This takes the place of kern.maxsockbuf, which moved to kern.ipc. */
  static int dummy;
  SYSCTL_INT(_kern, KERN_DUMMY, dummy, CTLFLAG_RW, &dummy, 0, "");
  SYSCTL_OID(_kern_ipc, KIPC_MAXSOCKBUF, maxsockbuf, CTLTYPE_INT|CTLFLAG_RW, 
      &sb_max, 0, sysctl_handle_sb_max, "I", "Maximum socket buffer size");
  SYSCTL_INT(_kern_ipc, OID_AUTO, maxsockets, CTLFLAG_RD, 
      &maxsockets, 0, "Maximum number of sockets avaliable");
  SYSCTL_INT(_kern_ipc, KIPC_SOCKBUF_WASTE, sockbuf_waste_factor, CTLFLAG_RW,
      &sb_efficiency, 0, "");
  
  /*
   * Initialise maxsockets 
   */
  static void init_maxsockets(void *ignored)
  {
      TUNABLE_INT_FETCH("kern.ipc.maxsockets", &maxsockets);
      maxsockets = imax(maxsockets, imax(maxfiles, nmbclusters));
  }
  SYSINIT(param, SI_SUB_TUNABLES, SI_ORDER_ANY, init_maxsockets, NULL);

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