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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sys/netgraph/ng_tty.c

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    1 /*
    2  * ng_tty.c
    3  */
    4 
    5 /*-
    6  * Copyright (c) 1996-1999 Whistle Communications, Inc.
    7  * All rights reserved.
    8  * 
    9  * Subject to the following obligations and disclaimer of warranty, use and
   10  * redistribution of this software, in source or object code forms, with or
   11  * without modifications are expressly permitted by Whistle Communications;
   12  * provided, however, that:
   13  * 1. Any and all reproductions of the source or object code must include the
   14  *    copyright notice above and the following disclaimer of warranties; and
   15  * 2. No rights are granted, in any manner or form, to use Whistle
   16  *    Communications, Inc. trademarks, including the mark "WHISTLE
   17  *    COMMUNICATIONS" on advertising, endorsements, or otherwise except as
   18  *    such appears in the above copyright notice or in the software.
   19  * 
   20  * THIS SOFTWARE IS BEING PROVIDED BY WHISTLE COMMUNICATIONS "AS IS", AND
   21  * TO THE MAXIMUM EXTENT PERMITTED BY LAW, WHISTLE COMMUNICATIONS MAKES NO
   22  * REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING THIS SOFTWARE,
   23  * INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED WARRANTIES OF
   24  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT.
   25  * WHISTLE COMMUNICATIONS DOES NOT WARRANT, GUARANTEE, OR MAKE ANY
   26  * REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS OF THE USE OF THIS
   27  * SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY, RELIABILITY OR OTHERWISE.
   28  * IN NO EVENT SHALL WHISTLE COMMUNICATIONS BE LIABLE FOR ANY DAMAGES
   29  * RESULTING FROM OR ARISING OUT OF ANY USE OF THIS SOFTWARE, INCLUDING
   30  * WITHOUT LIMITATION, ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
   31  * PUNITIVE, OR CONSEQUENTIAL DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR
   32  * SERVICES, LOSS OF USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER ANY
   33  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   34  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   35  * THIS SOFTWARE, EVEN IF WHISTLE COMMUNICATIONS IS ADVISED OF THE POSSIBILITY
   36  * OF SUCH DAMAGE.
   37  *
   38  * Author: Archie Cobbs <archie@freebsd.org>
   39  *
   40  * Updated by Andrew Thompson <thompsa@FreeBSD.org> for MPSAFE TTY.
   41  *
   42  * $FreeBSD: stable/12/sys/netgraph/ng_tty.c 360258 2020-04-24 13:31:22Z kevans $
   43  * $Whistle: ng_tty.c,v 1.21 1999/11/01 09:24:52 julian Exp $
   44  */
   45 
   46 /*
   47  * This file implements TTY hooks to link in to the netgraph system.  The node
   48  * is created and then passed the callers opened TTY file descriptor number to
   49  * NGM_TTY_SET_TTY, this will hook the tty via ttyhook_register().
   50  *
   51  * Incoming data is delivered directly to ng_tty via the TTY bypass hook as a
   52  * buffer pointer and length, this is converted to a mbuf and passed to the
   53  * peer.
   54  *
   55  * If the TTY device does not support bypass then incoming characters are
   56  * delivered to the hook one at a time, each in its own mbuf. You may
   57  * optionally define a ``hotchar,'' which causes incoming characters to be
   58  * buffered up until either the hotchar is seen or the mbuf is full (MHLEN
   59  * bytes). Then all buffered characters are immediately delivered.
   60  */
   61 
   62 #include <sys/param.h>
   63 #include <sys/systm.h>
   64 #include <sys/conf.h>
   65 #include <sys/errno.h>
   66 #include <sys/fcntl.h>
   67 #include <sys/ioccom.h>
   68 #include <sys/kernel.h>
   69 #include <sys/malloc.h>
   70 #include <sys/mbuf.h>
   71 #include <sys/priv.h>
   72 #include <sys/socket.h>
   73 #include <sys/syslog.h>
   74 #include <sys/tty.h>
   75 #include <sys/ttycom.h>
   76 #include <sys/proc.h>
   77 
   78 #include <net/if.h>
   79 #include <net/if_var.h>
   80 
   81 #include <netgraph/ng_message.h>
   82 #include <netgraph/netgraph.h>
   83 #include <netgraph/ng_tty.h>
   84 
   85 /* Per-node private info */
   86 struct ngt_softc {
   87         struct tty      *tp;            /* Terminal device */
   88         node_p          node;           /* Netgraph node */
   89         hook_p          hook;           /* Netgraph hook */
   90         struct ifqueue  outq;           /* Queue of outgoing data */
   91         size_t          outqlen;        /* Number of bytes in outq */
   92         struct mbuf     *m;             /* Incoming non-bypass data buffer */
   93         short           hotchar;        /* Hotchar, or -1 if none */
   94         u_int           flags;          /* Flags */
   95 };
   96 typedef struct ngt_softc *sc_p;
   97 
   98 /* Flags */
   99 #define FLG_DEBUG               0x0002
  100 
  101 /* Netgraph methods */
  102 static ng_constructor_t         ngt_constructor;
  103 static ng_rcvmsg_t              ngt_rcvmsg;
  104 static ng_shutdown_t            ngt_shutdown;
  105 static ng_newhook_t             ngt_newhook;
  106 static ng_connect_t             ngt_connect;
  107 static ng_rcvdata_t             ngt_rcvdata;
  108 static ng_disconnect_t          ngt_disconnect;
  109 
  110 #define ERROUT(x)               do { error = (x); goto done; } while (0)
  111 
  112 static th_getc_inject_t         ngt_getc_inject;
  113 static th_getc_poll_t           ngt_getc_poll;
  114 static th_rint_t                ngt_rint;
  115 static th_rint_bypass_t         ngt_rint_bypass;
  116 static th_rint_poll_t           ngt_rint_poll;
  117 
  118 static struct ttyhook ngt_hook = {
  119         .th_getc_inject = ngt_getc_inject,
  120         .th_getc_poll = ngt_getc_poll,
  121         .th_rint = ngt_rint,
  122         .th_rint_bypass = ngt_rint_bypass,
  123         .th_rint_poll = ngt_rint_poll,
  124 };
  125 
  126 /* Netgraph node type descriptor */
  127 static struct ng_type typestruct = {
  128         .version =      NG_ABI_VERSION,
  129         .name =         NG_TTY_NODE_TYPE,
  130         .constructor =  ngt_constructor,
  131         .rcvmsg =       ngt_rcvmsg,
  132         .shutdown =     ngt_shutdown,
  133         .newhook =      ngt_newhook,
  134         .connect =      ngt_connect,
  135         .rcvdata =      ngt_rcvdata,
  136         .disconnect =   ngt_disconnect,
  137 };
  138 NETGRAPH_INIT(tty, &typestruct);
  139 
  140 #define NGTLOCK(sc)     IF_LOCK(&sc->outq)
  141 #define NGTUNLOCK(sc)   IF_UNLOCK(&sc->outq)
  142 
  143 /******************************************************************
  144                     NETGRAPH NODE METHODS
  145 ******************************************************************/
  146 
  147 /*
  148  * Initialize a new node of this type.
  149  *
  150  * We only allow nodes to be created as a result of setting
  151  * the line discipline on a tty, so always return an error if not.
  152  */
  153 static int
  154 ngt_constructor(node_p node)
  155 {
  156         sc_p sc;
  157 
  158         /* Allocate private structure */
  159         sc = malloc(sizeof(*sc), M_NETGRAPH, M_WAITOK | M_ZERO);
  160 
  161         NG_NODE_SET_PRIVATE(node, sc);
  162         sc->node = node;
  163 
  164         mtx_init(&sc->outq.ifq_mtx, "ng_tty node+queue", NULL, MTX_DEF);
  165         IFQ_SET_MAXLEN(&sc->outq, ifqmaxlen);
  166 
  167         return (0);
  168 }
  169 
  170 /*
  171  * Add a new hook. There can only be one.
  172  */
  173 static int
  174 ngt_newhook(node_p node, hook_p hook, const char *name)
  175 {
  176         const sc_p sc = NG_NODE_PRIVATE(node);
  177 
  178         if (strcmp(name, NG_TTY_HOOK))
  179                 return (EINVAL);
  180 
  181         if (sc->hook)
  182                 return (EISCONN);
  183 
  184         NGTLOCK(sc);
  185         sc->hook = hook;
  186         NGTUNLOCK(sc);
  187 
  188         return (0);
  189 }
  190 
  191 /*
  192  * Set the hook into queueing mode (for outgoing packets),
  193  * so that we wont deliver mbuf through the whole graph holding
  194  * tty locks.
  195  */
  196 static int
  197 ngt_connect(hook_p hook)
  198 {
  199         NG_HOOK_FORCE_QUEUE(hook);
  200         return (0);
  201 }
  202 
  203 /*
  204  * Disconnect the hook
  205  */
  206 static int
  207 ngt_disconnect(hook_p hook)
  208 {
  209         const sc_p sc = NG_NODE_PRIVATE(NG_HOOK_NODE(hook));
  210 
  211         if (hook != sc->hook)
  212                 panic("%s", __func__);
  213 
  214         NGTLOCK(sc);
  215         sc->hook = NULL;
  216         NGTUNLOCK(sc);
  217 
  218         return (0);
  219 }
  220 
  221 /*
  222  * Remove this node. The does the netgraph portion of the shutdown.
  223  */
  224 static int
  225 ngt_shutdown(node_p node)
  226 {
  227         const sc_p sc = NG_NODE_PRIVATE(node);
  228         struct tty *tp;
  229 
  230         tp = sc->tp;
  231         if (tp != NULL) {
  232                 tty_lock(tp);
  233                 ttyhook_unregister(tp);
  234         }
  235         /* Free resources */
  236         IF_DRAIN(&sc->outq);
  237         mtx_destroy(&(sc)->outq.ifq_mtx);
  238         NG_NODE_UNREF(sc->node);
  239         free(sc, M_NETGRAPH);
  240 
  241         return (0);
  242 }
  243 
  244 /*
  245  * Receive control message
  246  */
  247 static int
  248 ngt_rcvmsg(node_p node, item_p item, hook_p lasthook)
  249 {
  250         struct proc *p;
  251         const sc_p sc = NG_NODE_PRIVATE(node);
  252         struct ng_mesg *msg, *resp = NULL;
  253         int error = 0;
  254 
  255         NGI_GET_MSG(item, msg);
  256         switch (msg->header.typecookie) {
  257         case NGM_TTY_COOKIE:
  258                 switch (msg->header.cmd) {
  259                 case NGM_TTY_SET_TTY:
  260                         if (sc->tp != NULL)
  261                                 return (EBUSY);
  262                         
  263                         p = pfind(((int *)msg->data)[0]);
  264                         if (p == NULL || (p->p_flag & P_WEXIT))
  265                                 return (ESRCH);
  266                         _PHOLD(p);
  267                         PROC_UNLOCK(p);
  268                         error = ttyhook_register(&sc->tp, p, ((int *)msg->data)[1],
  269                             &ngt_hook, sc);
  270                         PRELE(p);
  271                         if (error != 0)
  272                                 return (error);
  273                         break;
  274                 case NGM_TTY_SET_HOTCHAR:
  275                     {
  276                         int     hotchar;
  277 
  278                         if (msg->header.arglen != sizeof(int))
  279                                 ERROUT(EINVAL);
  280                         hotchar = *((int *) msg->data);
  281                         if (hotchar != (u_char) hotchar && hotchar != -1)
  282                                 ERROUT(EINVAL);
  283                         sc->hotchar = hotchar;  /* race condition is OK */
  284                         break;
  285                     }
  286                 case NGM_TTY_GET_HOTCHAR:
  287                         NG_MKRESPONSE(resp, msg, sizeof(int), M_NOWAIT);
  288                         if (!resp)
  289                                 ERROUT(ENOMEM);
  290                         /* Race condition here is OK */
  291                         *((int *) resp->data) = sc->hotchar;
  292                         break;
  293                 default:
  294                         ERROUT(EINVAL);
  295                 }
  296                 break;
  297         default:
  298                 ERROUT(EINVAL);
  299         }
  300 done:
  301         NG_RESPOND_MSG(error, node, item, resp);
  302         NG_FREE_MSG(msg);
  303         return (error);
  304 }
  305 
  306 /*
  307  * Receive incoming data from netgraph system. Put it on our
  308  * output queue and start output if necessary.
  309  */
  310 static int
  311 ngt_rcvdata(hook_p hook, item_p item)
  312 {
  313         const sc_p sc = NG_NODE_PRIVATE(NG_HOOK_NODE(hook));
  314         struct tty *tp = sc->tp;
  315         struct mbuf *m;
  316 
  317         if (hook != sc->hook)
  318                 panic("%s", __func__);
  319 
  320         NGI_GET_M(item, m);
  321         NG_FREE_ITEM(item);
  322 
  323         if (tp == NULL) {
  324                 NG_FREE_M(m);
  325                 return (ENXIO);
  326         }
  327 
  328         IF_LOCK(&sc->outq);
  329         if (_IF_QFULL(&sc->outq)) {
  330                 IF_UNLOCK(&sc->outq);
  331                 NG_FREE_M(m);
  332                 return (ENOBUFS);
  333         }
  334 
  335         _IF_ENQUEUE(&sc->outq, m);
  336         sc->outqlen += m->m_pkthdr.len;
  337         IF_UNLOCK(&sc->outq);
  338 
  339         /* notify the TTY that data is ready */
  340         tty_lock(tp);
  341         if (!tty_gone(tp))
  342                 ttydevsw_outwakeup(tp);
  343         tty_unlock(tp);
  344 
  345         return (0);
  346 }
  347 
  348 static size_t
  349 ngt_getc_inject(struct tty *tp, void *buf, size_t len)
  350 {
  351         sc_p sc = ttyhook_softc(tp);
  352         size_t total = 0;
  353         int length;
  354 
  355         while (len) {
  356                 struct mbuf *m;
  357 
  358                 /* Remove first mbuf from queue */
  359                 IF_DEQUEUE(&sc->outq, m);
  360                 if (m == NULL)
  361                         break;
  362 
  363                 /* Send as much of it as possible */
  364                 while (m != NULL) {
  365                         length = min(m->m_len, len);
  366                         memcpy((char *)buf + total, mtod(m, char *), length);
  367 
  368                         m->m_data += length;
  369                         m->m_len -= length;
  370                         total += length;
  371                         len -= length;
  372 
  373                         if (m->m_len > 0)
  374                                 break;  /* device can't take any more */
  375                         m = m_free(m);
  376                 }
  377 
  378                 /* Put remainder of mbuf chain (if any) back on queue */
  379                 if (m != NULL) {
  380                         IF_PREPEND(&sc->outq, m);
  381                         break;
  382                 }
  383         }
  384         IF_LOCK(&sc->outq);
  385         sc->outqlen -= total;
  386         IF_UNLOCK(&sc->outq);
  387         MPASS(sc->outqlen >= 0);
  388 
  389         return (total);
  390 }
  391 
  392 static size_t
  393 ngt_getc_poll(struct tty *tp)
  394 {
  395         sc_p sc = ttyhook_softc(tp);
  396 
  397         return (sc->outqlen);
  398 }
  399 
  400 /*
  401  * Optimised TTY input.
  402  *
  403  * We get a buffer pointer to hopefully a complete data frame. Do not check for
  404  * the hotchar, just pass it on.
  405  */
  406 static size_t
  407 ngt_rint_bypass(struct tty *tp, const void *buf, size_t len)
  408 {
  409         sc_p sc = ttyhook_softc(tp);
  410         node_p node = sc->node;
  411         struct mbuf *m, *mb;
  412         size_t total = 0;
  413         int error = 0, length;
  414 
  415         tty_assert_locked(tp);
  416 
  417         if (sc->hook == NULL)
  418                 return (0);
  419 
  420         m = m_getm2(NULL, len, M_NOWAIT, MT_DATA, M_PKTHDR);
  421         if (m == NULL) {
  422                 if (sc->flags & FLG_DEBUG)
  423                         log(LOG_ERR,
  424                             "%s: can't get mbuf\n", NG_NODE_NAME(node));
  425                 return (0);
  426         }
  427         m->m_pkthdr.rcvif = NULL;
  428 
  429         for (mb = m; mb != NULL; mb = mb->m_next) {
  430                 length = min(M_TRAILINGSPACE(mb), len - total);
  431 
  432                 memcpy(mtod(m, char *), (const char *)buf + total, length);
  433                 mb->m_len = length;
  434                 total += length;
  435                 m->m_pkthdr.len += length;
  436         }
  437         if (sc->m != NULL) {
  438                 /*
  439                  * Odd, we have changed from non-bypass to bypass. It is
  440                  * unlikely but not impossible, flush the data first.
  441                  */
  442                 sc->m->m_data = sc->m->m_pktdat;
  443                 NG_SEND_DATA_ONLY(error, sc->hook, sc->m);
  444                 sc->m = NULL;
  445         }
  446         NG_SEND_DATA_ONLY(error, sc->hook, m);
  447 
  448         return (total);
  449 }
  450 
  451 /*
  452  * Receive data coming from the device one char at a time, when it is not in
  453  * bypass mode.
  454  */
  455 static int
  456 ngt_rint(struct tty *tp, char c, int flags)
  457 {
  458         sc_p sc = ttyhook_softc(tp);
  459         node_p node = sc->node;
  460         struct mbuf *m;
  461         int error = 0;
  462 
  463         tty_assert_locked(tp);
  464 
  465         if (sc->hook == NULL)
  466                 return (0);
  467 
  468         if (flags != 0) {
  469                 /* framing error or overrun on this char */
  470                 if (sc->flags & FLG_DEBUG)
  471                         log(LOG_DEBUG, "%s: line error %x\n",
  472                             NG_NODE_NAME(node), flags);
  473                 return (0);
  474         }
  475 
  476         /* Get a new header mbuf if we need one */
  477         if (!(m = sc->m)) {
  478                 MGETHDR(m, M_NOWAIT, MT_DATA);
  479                 if (!m) {
  480                         if (sc->flags & FLG_DEBUG)
  481                                 log(LOG_ERR,
  482                                     "%s: can't get mbuf\n", NG_NODE_NAME(node));
  483                         return (ENOBUFS);
  484                 }
  485                 m->m_len = m->m_pkthdr.len = 0;
  486                 m->m_pkthdr.rcvif = NULL;
  487                 sc->m = m;
  488         }
  489 
  490         /* Add char to mbuf */
  491         *mtod(m, u_char *) = c;
  492         m->m_data++;
  493         m->m_len++;
  494         m->m_pkthdr.len++;
  495 
  496         /* Ship off mbuf if it's time */
  497         if (sc->hotchar == -1 || c == sc->hotchar || m->m_len >= MHLEN) {
  498                 m->m_data = m->m_pktdat;
  499                 sc->m = NULL;
  500                 NG_SEND_DATA_ONLY(error, sc->hook, m);  /* Will queue */
  501         }
  502 
  503         return (error);
  504 }
  505 
  506 static size_t
  507 ngt_rint_poll(struct tty *tp)
  508 {
  509         /* We can always accept input */
  510         return (1);
  511 }
  512 

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