The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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

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    1 /*
    2  * Copyright (c) 2005 Jeffrey M. Hsu.  All rights reserved.
    3  * Copyright (c) 1982, 1986, 1988, 1990, 1993
    4  *      The Regents of the University of California.  All rights reserved.
    5  *
    6  * Redistribution and use in source and binary forms, with or without
    7  * modification, are permitted provided that the following conditions
    8  * are met:
    9  * 1. Redistributions of source code must retain the above copyright
   10  *    notice, this list of conditions and the following disclaimer.
   11  * 2. Redistributions in binary form must reproduce the above copyright
   12  *    notice, this list of conditions and the following disclaimer in the
   13  *    documentation and/or other materials provided with the distribution.
   14  * 3. Neither the name of the University nor the names of its contributors
   15  *    may be used to endorse or promote products derived from this software
   16  *    without specific prior written permission.
   17  *
   18  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   19  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   20  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   21  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   22  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   23  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   24  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   25  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   26  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   27  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   28  * SUCH DAMAGE.
   29  *
   30  *      @(#)uipc_socket2.c      8.1 (Berkeley) 6/10/93
   31  * $FreeBSD: src/sys/kern/uipc_socket2.c,v 1.55.2.17 2002/08/31 19:04:55 dwmalone Exp $
   32  * $DragonFly: src/sys/kern/uipc_socket2.c,v 1.33 2008/09/02 16:17:52 dillon Exp $
   33  */
   34 
   35 #include "opt_param.h"
   36 #include <sys/param.h>
   37 #include <sys/systm.h>
   38 #include <sys/domain.h>
   39 #include <sys/file.h>   /* for maxfiles */
   40 #include <sys/kernel.h>
   41 #include <sys/proc.h>
   42 #include <sys/malloc.h>
   43 #include <sys/mbuf.h>
   44 #include <sys/protosw.h>
   45 #include <sys/resourcevar.h>
   46 #include <sys/stat.h>
   47 #include <sys/socket.h>
   48 #include <sys/socketvar.h>
   49 #include <sys/socketops.h>
   50 #include <sys/signalvar.h>
   51 #include <sys/sysctl.h>
   52 #include <sys/event.h>
   53 
   54 #include <sys/thread2.h>
   55 #include <sys/msgport2.h>
   56 #include <sys/socketvar2.h>
   57 
   58 #include <net/netisr2.h>
   59 
   60 int     maxsockets;
   61 
   62 /*
   63  * Primitive routines for operating on sockets and socket buffers
   64  */
   65 
   66 u_long  sb_max = SB_MAX;
   67 u_long  sb_max_adj =
   68     SB_MAX * MCLBYTES / (MSIZE + MCLBYTES); /* adjusted sb_max */
   69 
   70 static  u_long sb_efficiency = 8;       /* parameter for sbreserve() */
   71 
   72 /************************************************************************
   73  * signalsockbuf procedures                                             *
   74  ************************************************************************/
   75 
   76 /*
   77  * Wait for data to arrive at/drain from a socket buffer.
   78  *
   79  * NOTE: Caller must generally hold the ssb_lock (client side lock) since
   80  *       WAIT/WAKEUP only works for one client at a time.
   81  *
   82  * NOTE: Caller always retries whatever operation it was waiting on.
   83  */
   84 int
   85 ssb_wait(struct signalsockbuf *ssb)
   86 {
   87         uint32_t flags;
   88         int pflags;
   89         int error;
   90 
   91         pflags = (ssb->ssb_flags & SSB_NOINTR) ? 0 : PCATCH;
   92 
   93         for (;;) {
   94                 flags = ssb->ssb_flags;
   95                 cpu_ccfence();
   96 
   97                 /*
   98                  * WAKEUP and WAIT interlock eachother.  We can catch the
   99                  * race by checking to see if WAKEUP has already been set,
  100                  * and only setting WAIT if WAKEUP is clear.
  101                  */
  102                 if (flags & SSB_WAKEUP) {
  103                         if (atomic_cmpset_int(&ssb->ssb_flags, flags,
  104                                               flags & ~SSB_WAKEUP)) {
  105                                 error = 0;
  106                                 break;
  107                         }
  108                         continue;
  109                 }
  110 
  111                 /*
  112                  * Only set WAIT if WAKEUP is clear.
  113                  */
  114                 tsleep_interlock(&ssb->ssb_cc, pflags);
  115                 if (atomic_cmpset_int(&ssb->ssb_flags, flags,
  116                                       flags | SSB_WAIT)) {
  117                         error = tsleep(&ssb->ssb_cc, pflags | PINTERLOCKED,
  118                                        "sbwait", ssb->ssb_timeo);
  119                         break;
  120                 }
  121         }
  122         return (error);
  123 }
  124 
  125 /*
  126  * Lock a sockbuf already known to be locked;
  127  * return any error returned from sleep (EINTR).
  128  */
  129 int
  130 _ssb_lock(struct signalsockbuf *ssb)
  131 {
  132         uint32_t flags;
  133         int pflags;
  134         int error;
  135 
  136         pflags = (ssb->ssb_flags & SSB_NOINTR) ? 0 : PCATCH;
  137 
  138         for (;;) {
  139                 flags = ssb->ssb_flags;
  140                 cpu_ccfence();
  141                 if (flags & SSB_LOCK) {
  142                         tsleep_interlock(&ssb->ssb_flags, pflags);
  143                         if (atomic_cmpset_int(&ssb->ssb_flags, flags,
  144                                               flags | SSB_WANT)) {
  145                                 error = tsleep(&ssb->ssb_flags,
  146                                                pflags | PINTERLOCKED,
  147                                                "sblock", 0);
  148                                 if (error)
  149                                         break;
  150                         }
  151                 } else {
  152                         if (atomic_cmpset_int(&ssb->ssb_flags, flags,
  153                                               flags | SSB_LOCK)) {
  154                                 lwkt_gettoken(&ssb->ssb_token);
  155                                 error = 0;
  156                                 break;
  157                         }
  158                 }
  159         }
  160         return (error);
  161 }
  162 
  163 /*
  164  * This does the same for sockbufs.  Note that the xsockbuf structure,
  165  * since it is always embedded in a socket, does not include a self
  166  * pointer nor a length.  We make this entry point public in case
  167  * some other mechanism needs it.
  168  */
  169 void
  170 ssbtoxsockbuf(struct signalsockbuf *ssb, struct xsockbuf *xsb)
  171 {
  172         xsb->sb_cc = ssb->ssb_cc;
  173         xsb->sb_hiwat = ssb->ssb_hiwat;
  174         xsb->sb_mbcnt = ssb->ssb_mbcnt;
  175         xsb->sb_mbmax = ssb->ssb_mbmax;
  176         xsb->sb_lowat = ssb->ssb_lowat;
  177         xsb->sb_flags = ssb->ssb_flags;
  178         xsb->sb_timeo = ssb->ssb_timeo;
  179 }
  180 
  181 
  182 /************************************************************************
  183  * Procedures which manipulate socket state flags, wakeups, etc.        *
  184  ************************************************************************
  185  *
  186  * Normal sequence from the active (originating) side is that
  187  * soisconnecting() is called during processing of connect() call, resulting
  188  * in an eventual call to soisconnected() if/when the connection is
  189  * established.  When the connection is torn down soisdisconnecting() is
  190  * called during processing of disconnect() call, and soisdisconnected() is
  191  * called when the connection to the peer is totally severed.
  192  *
  193  * The semantics of these routines are such that connectionless protocols
  194  * can call soisconnected() and soisdisconnected() only, bypassing the
  195  * in-progress calls when setting up a ``connection'' takes no time.
  196  *
  197  * From the passive side, a socket is created with two queues of sockets:
  198  * so_incomp for connections in progress and so_comp for connections
  199  * already made and awaiting user acceptance.  As a protocol is preparing
  200  * incoming connections, it creates a socket structure queued on so_incomp
  201  * by calling sonewconn().  When the connection is established,
  202  * soisconnected() is called, and transfers the socket structure to so_comp,
  203  * making it available to accept().
  204  *
  205  * If a socket is closed with sockets on either so_incomp or so_comp, these
  206  * sockets are dropped.
  207  *
  208  * If higher level protocols are implemented in the kernel, the wakeups
  209  * done here will sometimes cause software-interrupt process scheduling.
  210  */
  211 
  212 void
  213 soisconnecting(struct socket *so)
  214 {
  215         soclrstate(so, SS_ISCONNECTED | SS_ISDISCONNECTING);
  216         sosetstate(so, SS_ISCONNECTING);
  217 }
  218 
  219 void
  220 soisconnected(struct socket *so)
  221 {
  222         struct socket *head;
  223 
  224         while ((head = so->so_head) != NULL) {
  225                 lwkt_getpooltoken(head);
  226                 if (so->so_head == head)
  227                         break;
  228                 lwkt_relpooltoken(head);
  229         }
  230 
  231         soclrstate(so, SS_ISCONNECTING | SS_ISDISCONNECTING | SS_ISCONFIRMING);
  232         sosetstate(so, SS_ISCONNECTED);
  233         if (head && (so->so_state & SS_INCOMP)) {
  234                 if ((so->so_options & SO_ACCEPTFILTER) != 0) {
  235                         so->so_upcall = head->so_accf->so_accept_filter->accf_callback;
  236                         so->so_upcallarg = head->so_accf->so_accept_filter_arg;
  237                         atomic_set_int(&so->so_rcv.ssb_flags, SSB_UPCALL);
  238                         so->so_options &= ~SO_ACCEPTFILTER;
  239                         so->so_upcall(so, so->so_upcallarg, 0);
  240                         lwkt_relpooltoken(head);
  241                         return;
  242                 }
  243 
  244                 /*
  245                  * Listen socket are not per-cpu.
  246                  */
  247                 TAILQ_REMOVE(&head->so_incomp, so, so_list);
  248                 head->so_incqlen--;
  249                 TAILQ_INSERT_TAIL(&head->so_comp, so, so_list);
  250                 head->so_qlen++;
  251                 sosetstate(so, SS_COMP);
  252                 soclrstate(so, SS_INCOMP);
  253 
  254                 /*
  255                  * XXX head may be on a different protocol thread.
  256                  *     sorwakeup()->sowakeup() is hacked atm.
  257                  */
  258                 sorwakeup(head);
  259                 wakeup_one(&head->so_timeo);
  260         } else {
  261                 wakeup(&so->so_timeo);
  262                 sorwakeup(so);
  263                 sowwakeup(so);
  264         }
  265         if (head)
  266                 lwkt_relpooltoken(head);
  267 }
  268 
  269 void
  270 soisdisconnecting(struct socket *so)
  271 {
  272         soclrstate(so, SS_ISCONNECTING);
  273         sosetstate(so, SS_ISDISCONNECTING | SS_CANTRCVMORE | SS_CANTSENDMORE);
  274         wakeup((caddr_t)&so->so_timeo);
  275         sowwakeup(so);
  276         sorwakeup(so);
  277 }
  278 
  279 void
  280 soisdisconnected(struct socket *so)
  281 {
  282         soclrstate(so, SS_ISCONNECTING | SS_ISCONNECTED | SS_ISDISCONNECTING);
  283         sosetstate(so, SS_CANTRCVMORE | SS_CANTSENDMORE | SS_ISDISCONNECTED);
  284         wakeup((caddr_t)&so->so_timeo);
  285         sbdrop(&so->so_snd.sb, so->so_snd.ssb_cc);
  286         sowwakeup(so);
  287         sorwakeup(so);
  288 }
  289 
  290 void
  291 soisreconnecting(struct socket *so)
  292 {
  293         soclrstate(so, SS_ISDISCONNECTING | SS_ISDISCONNECTED |
  294                        SS_CANTRCVMORE | SS_CANTSENDMORE);
  295         sosetstate(so, SS_ISCONNECTING);
  296 }
  297 
  298 void
  299 soisreconnected(struct socket *so)
  300 {
  301         soclrstate(so, SS_ISDISCONNECTED | SS_CANTRCVMORE | SS_CANTSENDMORE);
  302         soisconnected(so);
  303 }
  304 
  305 /*
  306  * Set or change the message port a socket receives commands on.
  307  *
  308  * XXX
  309  */
  310 void
  311 sosetport(struct socket *so, lwkt_port_t port)
  312 {
  313         so->so_port = port;
  314 }
  315 
  316 /*
  317  * When an attempt at a new connection is noted on a socket
  318  * which accepts connections, sonewconn is called.  If the
  319  * connection is possible (subject to space constraints, etc.)
  320  * then we allocate a new structure, propoerly linked into the
  321  * data structure of the original socket, and return this.
  322  * Connstatus may be 0, or SO_ISCONFIRMING, or SO_ISCONNECTED.
  323  *
  324  * The new socket is returned with one ref and so_pcb assigned.
  325  * The reference is implied by so_pcb.
  326  */
  327 struct socket *
  328 sonewconn_faddr(struct socket *head, int connstatus,
  329     const struct sockaddr *faddr)
  330 {
  331         struct socket *so;
  332         struct socket *sp;
  333         struct pru_attach_info ai;
  334 
  335         if (head->so_qlen > 3 * head->so_qlimit / 2)
  336                 return (NULL);
  337         so = soalloc(1, head->so_proto);
  338         if (so == NULL)
  339                 return (NULL);
  340 
  341         /*
  342          * Set the port prior to attaching the inpcb to the current
  343          * cpu's protocol thread (which should be the current thread
  344          * but might not be in all cases).  This serializes any pcb ops
  345          * which occur to our cpu allowing us to complete the attachment
  346          * without racing anything.
  347          */
  348         if (head->so_proto->pr_flags & PR_SYNC_PORT)
  349                 sosetport(so, &netisr_sync_port);
  350         else
  351                 sosetport(so, netisr_cpuport(mycpuid));
  352         if ((head->so_options & SO_ACCEPTFILTER) != 0)
  353                 connstatus = 0;
  354         so->so_head = head;
  355         so->so_type = head->so_type;
  356         so->so_options = head->so_options &~ SO_ACCEPTCONN;
  357         so->so_linger = head->so_linger;
  358 
  359         /*
  360          * NOTE: Clearing NOFDREF implies referencing the so with
  361          *       soreference().
  362          */
  363         so->so_state = head->so_state | SS_NOFDREF | SS_ASSERTINPROG;
  364         so->so_cred = crhold(head->so_cred);
  365         ai.sb_rlimit = NULL;
  366         ai.p_ucred = NULL;
  367         ai.fd_rdir = NULL;              /* jail code cruft XXX JH */
  368 
  369         /*
  370          * Reserve space and call pru_attach.  We can direct-call the
  371          * function since we're already in the protocol thread.
  372          */
  373         if (soreserve(so, head->so_snd.ssb_hiwat,
  374                       head->so_rcv.ssb_hiwat, NULL) ||
  375             so_pru_attach_direct(so, 0, &ai)) {
  376                 so->so_head = NULL;
  377                 soclrstate(so, SS_ASSERTINPROG);
  378                 sofree(so);             /* remove implied pcb ref */
  379                 return (NULL);
  380         }
  381         KKASSERT(((so->so_proto->pr_flags & PR_ASYNC_RCVD) == 0 &&
  382             so->so_refs == 2) ||        /* attach + our base ref */
  383            ((so->so_proto->pr_flags & PR_ASYNC_RCVD) &&
  384             so->so_refs == 3));         /* + async rcvd ref */
  385         sofree(so);
  386         KKASSERT(so->so_port != NULL);
  387         so->so_rcv.ssb_lowat = head->so_rcv.ssb_lowat;
  388         so->so_snd.ssb_lowat = head->so_snd.ssb_lowat;
  389         so->so_rcv.ssb_timeo = head->so_rcv.ssb_timeo;
  390         so->so_snd.ssb_timeo = head->so_snd.ssb_timeo;
  391 
  392         if (head->so_rcv.ssb_flags & SSB_AUTOLOWAT)
  393                 so->so_rcv.ssb_flags |= SSB_AUTOLOWAT;
  394         else
  395                 so->so_rcv.ssb_flags &= ~SSB_AUTOLOWAT;
  396 
  397         if (head->so_snd.ssb_flags & SSB_AUTOLOWAT)
  398                 so->so_snd.ssb_flags |= SSB_AUTOLOWAT;
  399         else
  400                 so->so_snd.ssb_flags &= ~SSB_AUTOLOWAT;
  401 
  402         if (head->so_rcv.ssb_flags & SSB_AUTOSIZE)
  403                 so->so_rcv.ssb_flags |= SSB_AUTOSIZE;
  404         else
  405                 so->so_rcv.ssb_flags &= ~SSB_AUTOSIZE;
  406 
  407         if (head->so_snd.ssb_flags & SSB_AUTOSIZE)
  408                 so->so_snd.ssb_flags |= SSB_AUTOSIZE;
  409         else
  410                 so->so_snd.ssb_flags &= ~SSB_AUTOSIZE;
  411 
  412         /*
  413          * Save the faddr, if the information is provided and
  414          * the protocol can perform the saving opertation.
  415          */
  416         if (faddr != NULL && so->so_proto->pr_usrreqs->pru_savefaddr != NULL)
  417                 so->so_proto->pr_usrreqs->pru_savefaddr(so, faddr);
  418 
  419         lwkt_getpooltoken(head);
  420         if (connstatus) {
  421                 TAILQ_INSERT_TAIL(&head->so_comp, so, so_list);
  422                 sosetstate(so, SS_COMP);
  423                 head->so_qlen++;
  424         } else {
  425                 if (head->so_incqlen > head->so_qlimit) {
  426                         sp = TAILQ_FIRST(&head->so_incomp);
  427                         TAILQ_REMOVE(&head->so_incomp, sp, so_list);
  428                         head->so_incqlen--;
  429                         soclrstate(sp, SS_INCOMP);
  430                         sp->so_head = NULL;
  431                         soaborta(sp);
  432                 }
  433                 TAILQ_INSERT_TAIL(&head->so_incomp, so, so_list);
  434                 sosetstate(so, SS_INCOMP);
  435                 head->so_incqlen++;
  436         }
  437         lwkt_relpooltoken(head);
  438         if (connstatus) {
  439                 /*
  440                  * XXX head may be on a different protocol thread.
  441                  *     sorwakeup()->sowakeup() is hacked atm.
  442                  */
  443                 sorwakeup(head);
  444                 wakeup((caddr_t)&head->so_timeo);
  445                 sosetstate(so, connstatus);
  446         }
  447         soclrstate(so, SS_ASSERTINPROG);
  448         return (so);
  449 }
  450 
  451 struct socket *
  452 sonewconn(struct socket *head, int connstatus)
  453 {
  454         return sonewconn_faddr(head, connstatus, NULL);
  455 }
  456 
  457 /*
  458  * Socantsendmore indicates that no more data will be sent on the
  459  * socket; it would normally be applied to a socket when the user
  460  * informs the system that no more data is to be sent, by the protocol
  461  * code (in case PRU_SHUTDOWN).  Socantrcvmore indicates that no more data
  462  * will be received, and will normally be applied to the socket by a
  463  * protocol when it detects that the peer will send no more data.
  464  * Data queued for reading in the socket may yet be read.
  465  */
  466 void
  467 socantsendmore(struct socket *so)
  468 {
  469         sosetstate(so, SS_CANTSENDMORE);
  470         sowwakeup(so);
  471 }
  472 
  473 void
  474 socantrcvmore(struct socket *so)
  475 {
  476         sosetstate(so, SS_CANTRCVMORE);
  477         sorwakeup(so);
  478 }
  479 
  480 /*
  481  * Wakeup processes waiting on a socket buffer.  Do asynchronous notification
  482  * via SIGIO if the socket has the SS_ASYNC flag set.
  483  *
  484  * For users waiting on send/recv try to avoid unnecessary context switch
  485  * thrashing.  Particularly for senders of large buffers (needs to be
  486  * extended to sel and aio? XXX)
  487  *
  488  * WARNING!  Can be called on a foreign socket from the wrong protocol
  489  *           thread.  aka is called on the 'head' listen socket when
  490  *           a new connection comes in.
  491  */
  492 void
  493 sowakeup(struct socket *so, struct signalsockbuf *ssb)
  494 {
  495         struct kqinfo *kqinfo = &ssb->ssb_kq;
  496         uint32_t flags;
  497 
  498         /*
  499          * Check conditions, set the WAKEUP flag, and clear and signal if
  500          * the WAIT flag is found to be set.  This interlocks against the
  501          * client side.
  502          */
  503         for (;;) {
  504                 flags = ssb->ssb_flags;
  505                 cpu_ccfence();
  506 
  507                 if ((ssb == &so->so_snd && ssb_space(ssb) >= ssb->ssb_lowat) ||
  508                     (ssb == &so->so_rcv && ssb->ssb_cc >= ssb->ssb_lowat) ||
  509                     (ssb == &so->so_snd && (so->so_state & SS_CANTSENDMORE)) ||
  510                     (ssb == &so->so_rcv && (so->so_state & SS_CANTRCVMORE))
  511                 ) {
  512                         if (atomic_cmpset_int(&ssb->ssb_flags, flags,
  513                                           (flags | SSB_WAKEUP) & ~SSB_WAIT)) {
  514                                 if (flags & SSB_WAIT)
  515                                         wakeup(&ssb->ssb_cc);
  516                                 break;
  517                         }
  518                 } else {
  519                         break;
  520                 }
  521         }
  522 
  523         /*
  524          * Misc other events
  525          */
  526         if ((so->so_state & SS_ASYNC) && so->so_sigio != NULL)
  527                 pgsigio(so->so_sigio, SIGIO, 0);
  528         if (ssb->ssb_flags & SSB_UPCALL)
  529                 (*so->so_upcall)(so, so->so_upcallarg, MB_DONTWAIT);
  530         KNOTE(&kqinfo->ki_note, 0);
  531 
  532         /*
  533          * This is a bit of a hack.  Multiple threads can wind up scanning
  534          * ki_mlist concurrently due to the fact that this function can be
  535          * called on a foreign socket, so we can't afford to block here.
  536          *
  537          * We need the pool token for (so) (likely the listne socket if
  538          * SSB_MEVENT is set) because the predicate function may have
  539          * to access the accept queue.
  540          */
  541         if (ssb->ssb_flags & SSB_MEVENT) {
  542                 struct netmsg_so_notify *msg, *nmsg;
  543 
  544                 lwkt_getpooltoken(so);
  545                 TAILQ_FOREACH_MUTABLE(msg, &kqinfo->ki_mlist, nm_list, nmsg) {
  546                         if (msg->nm_predicate(msg)) {
  547                                 TAILQ_REMOVE(&kqinfo->ki_mlist, msg, nm_list);
  548                                 lwkt_replymsg(&msg->base.lmsg,
  549                                               msg->base.lmsg.ms_error);
  550                         }
  551                 }
  552                 if (TAILQ_EMPTY(&ssb->ssb_kq.ki_mlist))
  553                         atomic_clear_int(&ssb->ssb_flags, SSB_MEVENT);
  554                 lwkt_relpooltoken(so);
  555         }
  556 }
  557 
  558 /*
  559  * Socket buffer (struct signalsockbuf) utility routines.
  560  *
  561  * Each socket contains two socket buffers: one for sending data and
  562  * one for receiving data.  Each buffer contains a queue of mbufs,
  563  * information about the number of mbufs and amount of data in the
  564  * queue, and other fields allowing kevent()/select()/poll() statements
  565  * and notification on data availability to be implemented.
  566  *
  567  * Data stored in a socket buffer is maintained as a list of records.
  568  * Each record is a list of mbufs chained together with the m_next
  569  * field.  Records are chained together with the m_nextpkt field. The upper
  570  * level routine soreceive() expects the following conventions to be
  571  * observed when placing information in the receive buffer:
  572  *
  573  * 1. If the protocol requires each message be preceded by the sender's
  574  *    name, then a record containing that name must be present before
  575  *    any associated data (mbuf's must be of type MT_SONAME).
  576  * 2. If the protocol supports the exchange of ``access rights'' (really
  577  *    just additional data associated with the message), and there are
  578  *    ``rights'' to be received, then a record containing this data
  579  *    should be present (mbuf's must be of type MT_RIGHTS).
  580  * 3. If a name or rights record exists, then it must be followed by
  581  *    a data record, perhaps of zero length.
  582  *
  583  * Before using a new socket structure it is first necessary to reserve
  584  * buffer space to the socket, by calling sbreserve().  This should commit
  585  * some of the available buffer space in the system buffer pool for the
  586  * socket (currently, it does nothing but enforce limits).  The space
  587  * should be released by calling ssb_release() when the socket is destroyed.
  588  */
  589 int
  590 soreserve(struct socket *so, u_long sndcc, u_long rcvcc, struct rlimit *rl)
  591 {
  592         if (so->so_snd.ssb_lowat == 0)
  593                 atomic_set_int(&so->so_snd.ssb_flags, SSB_AUTOLOWAT);
  594         if (ssb_reserve(&so->so_snd, sndcc, so, rl) == 0)
  595                 goto bad;
  596         if (ssb_reserve(&so->so_rcv, rcvcc, so, rl) == 0)
  597                 goto bad2;
  598         if (so->so_rcv.ssb_lowat == 0)
  599                 so->so_rcv.ssb_lowat = 1;
  600         if (so->so_snd.ssb_lowat == 0)
  601                 so->so_snd.ssb_lowat = MCLBYTES;
  602         if (so->so_snd.ssb_lowat > so->so_snd.ssb_hiwat)
  603                 so->so_snd.ssb_lowat = so->so_snd.ssb_hiwat;
  604         return (0);
  605 bad2:
  606         ssb_release(&so->so_snd, so);
  607 bad:
  608         return (ENOBUFS);
  609 }
  610 
  611 static int
  612 sysctl_handle_sb_max(SYSCTL_HANDLER_ARGS)
  613 {
  614         int error = 0;
  615         u_long old_sb_max = sb_max;
  616 
  617         error = SYSCTL_OUT(req, arg1, sizeof(int));
  618         if (error || !req->newptr)
  619                 return (error);
  620         error = SYSCTL_IN(req, arg1, sizeof(int));
  621         if (error)
  622                 return (error);
  623         if (sb_max < MSIZE + MCLBYTES) {
  624                 sb_max = old_sb_max;
  625                 return (EINVAL);
  626         }
  627         sb_max_adj = (u_quad_t)sb_max * MCLBYTES / (MSIZE + MCLBYTES);
  628         return (0);
  629 }
  630         
  631 /*
  632  * Allot mbufs to a signalsockbuf.
  633  *
  634  * Attempt to scale mbmax so that mbcnt doesn't become limiting
  635  * if buffering efficiency is near the normal case.
  636  *
  637  * sb_max only applies to user-sockets (where rl != NULL).  It does
  638  * not apply to kernel sockets or kernel-controlled sockets.  Note
  639  * that NFS overrides the sockbuf limits created when nfsd creates
  640  * a socket.
  641  */
  642 int
  643 ssb_reserve(struct signalsockbuf *ssb, u_long cc, struct socket *so,
  644             struct rlimit *rl)
  645 {
  646         /*
  647          * rl will only be NULL when we're in an interrupt (eg, in tcp_input)
  648          * or when called from netgraph (ie, ngd_attach)
  649          */
  650         if (rl && cc > sb_max_adj)
  651                 cc = sb_max_adj;
  652         if (!chgsbsize(so->so_cred->cr_uidinfo, &ssb->ssb_hiwat, cc,
  653                        rl ? rl->rlim_cur : RLIM_INFINITY)) {
  654                 return (0);
  655         }
  656         if (rl)
  657                 ssb->ssb_mbmax = min(cc * sb_efficiency, sb_max);
  658         else
  659                 ssb->ssb_mbmax = cc * sb_efficiency;
  660 
  661         /*
  662          * AUTOLOWAT is set on send buffers and prevents large writes
  663          * from generating a huge number of context switches.
  664          */
  665         if (ssb->ssb_flags & SSB_AUTOLOWAT) {
  666                 ssb->ssb_lowat = ssb->ssb_hiwat / 2;
  667                 if (ssb->ssb_lowat < MCLBYTES)
  668                         ssb->ssb_lowat = MCLBYTES;
  669         }
  670         if (ssb->ssb_lowat > ssb->ssb_hiwat)
  671                 ssb->ssb_lowat = ssb->ssb_hiwat;
  672         return (1);
  673 }
  674 
  675 /*
  676  * Free mbufs held by a socket, and reserved mbuf space.
  677  */
  678 void
  679 ssb_release(struct signalsockbuf *ssb, struct socket *so)
  680 {
  681         sbflush(&ssb->sb);
  682         (void)chgsbsize(so->so_cred->cr_uidinfo, &ssb->ssb_hiwat, 0,
  683             RLIM_INFINITY);
  684         ssb->ssb_mbmax = 0;
  685 }
  686 
  687 /*
  688  * Some routines that return EOPNOTSUPP for entry points that are not
  689  * supported by a protocol.  Fill in as needed.
  690  */
  691 void
  692 pr_generic_notsupp(netmsg_t msg)
  693 {
  694         lwkt_replymsg(&msg->lmsg, EOPNOTSUPP);
  695 }
  696 
  697 int
  698 pru_sosend_notsupp(struct socket *so, struct sockaddr *addr, struct uio *uio,
  699            struct mbuf *top, struct mbuf *control, int flags,
  700            struct thread *td)
  701 {
  702         if (top)
  703                 m_freem(top);
  704         if (control)
  705                 m_freem(control);
  706         return (EOPNOTSUPP);
  707 }
  708 
  709 int
  710 pru_soreceive_notsupp(struct socket *so, struct sockaddr **paddr,
  711                       struct uio *uio, struct sockbuf *sio,
  712                       struct mbuf **controlp, int *flagsp)
  713 {
  714         return (EOPNOTSUPP);
  715 }
  716 
  717 /*
  718  * This isn't really a ``null'' operation, but it's the default one
  719  * and doesn't do anything destructive.
  720  */
  721 void
  722 pru_sense_null(netmsg_t msg)
  723 {
  724         msg->sense.nm_stat->st_blksize = msg->base.nm_so->so_snd.ssb_hiwat;
  725         lwkt_replymsg(&msg->lmsg, 0);
  726 }
  727 
  728 /*
  729  * Make a copy of a sockaddr in a malloced buffer of type M_SONAME.  Callers
  730  * of this routine assume that it always succeeds, so we have to use a 
  731  * blockable allocation even though we might be called from a critical thread.
  732  */
  733 struct sockaddr *
  734 dup_sockaddr(const struct sockaddr *sa)
  735 {
  736         struct sockaddr *sa2;
  737 
  738         sa2 = kmalloc(sa->sa_len, M_SONAME, M_INTWAIT);
  739         bcopy(sa, sa2, sa->sa_len);
  740         return (sa2);
  741 }
  742 
  743 /*
  744  * Create an external-format (``xsocket'') structure using the information
  745  * in the kernel-format socket structure pointed to by so.  This is done
  746  * to reduce the spew of irrelevant information over this interface,
  747  * to isolate user code from changes in the kernel structure, and
  748  * potentially to provide information-hiding if we decide that
  749  * some of this information should be hidden from users.
  750  */
  751 void
  752 sotoxsocket(struct socket *so, struct xsocket *xso)
  753 {
  754         xso->xso_len = sizeof *xso;
  755         xso->xso_so = so;
  756         xso->so_type = so->so_type;
  757         xso->so_options = so->so_options;
  758         xso->so_linger = so->so_linger;
  759         xso->so_state = so->so_state;
  760         xso->so_pcb = so->so_pcb;
  761         xso->xso_protocol = so->so_proto->pr_protocol;
  762         xso->xso_family = so->so_proto->pr_domain->dom_family;
  763         xso->so_qlen = so->so_qlen;
  764         xso->so_incqlen = so->so_incqlen;
  765         xso->so_qlimit = so->so_qlimit;
  766         xso->so_timeo = so->so_timeo;
  767         xso->so_error = so->so_error;
  768         xso->so_pgid = so->so_sigio ? so->so_sigio->sio_pgid : 0;
  769         xso->so_oobmark = so->so_oobmark;
  770         ssbtoxsockbuf(&so->so_snd, &xso->so_snd);
  771         ssbtoxsockbuf(&so->so_rcv, &xso->so_rcv);
  772         xso->so_uid = so->so_cred->cr_uid;
  773 }
  774 
  775 /*
  776  * Here is the definition of some of the basic objects in the kern.ipc
  777  * branch of the MIB.
  778  */
  779 SYSCTL_NODE(_kern, KERN_IPC, ipc, CTLFLAG_RW, 0, "IPC");
  780 
  781 /*
  782  * This takes the place of kern.maxsockbuf, which moved to kern.ipc.
  783  *
  784  * NOTE! sb_max only applies to user-created socket buffers.
  785  */
  786 static int dummy;
  787 SYSCTL_INT(_kern, KERN_DUMMY, dummy, CTLFLAG_RW, &dummy, 0, "");
  788 SYSCTL_OID(_kern_ipc, KIPC_MAXSOCKBUF, maxsockbuf, CTLTYPE_INT|CTLFLAG_RW, 
  789     &sb_max, 0, sysctl_handle_sb_max, "I", "Maximum socket buffer size");
  790 SYSCTL_INT(_kern_ipc, OID_AUTO, maxsockets, CTLFLAG_RD, 
  791     &maxsockets, 0, "Maximum number of sockets available");
  792 SYSCTL_INT(_kern_ipc, KIPC_SOCKBUF_WASTE, sockbuf_waste_factor, CTLFLAG_RW,
  793     &sb_efficiency, 0,
  794     "Socket buffer limit scaler");
  795 
  796 /*
  797  * Initialize maxsockets 
  798  */
  799 static void
  800 init_maxsockets(void *ignored)
  801 {
  802     TUNABLE_INT_FETCH("kern.ipc.maxsockets", &maxsockets);
  803     maxsockets = imax(maxsockets, imax(maxfiles, nmbclusters));
  804 }
  805 SYSINIT(param, SI_BOOT1_TUNABLES, SI_ORDER_ANY,
  806         init_maxsockets, NULL);
  807 

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