The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/netgraph/ng_l2tp.c

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    1 /*-
    2  * Copyright (c) 2001-2002 Packet Design, LLC.
    3  * All rights reserved.
    4  * 
    5  * Subject to the following obligations and disclaimer of warranty,
    6  * use and redistribution of this software, in source or object code
    7  * forms, with or without modifications are expressly permitted by
    8  * Packet Design; provided, however, that:
    9  * 
   10  *    (i)  Any and all reproductions of the source or object code
   11  *         must include the copyright notice above and the following
   12  *         disclaimer of warranties; and
   13  *    (ii) No rights are granted, in any manner or form, to use
   14  *         Packet Design trademarks, including the mark "PACKET DESIGN"
   15  *         on advertising, endorsements, or otherwise except as such
   16  *         appears in the above copyright notice or in the software.
   17  * 
   18  * THIS SOFTWARE IS BEING PROVIDED BY PACKET DESIGN "AS IS", AND
   19  * TO THE MAXIMUM EXTENT PERMITTED BY LAW, PACKET DESIGN MAKES NO
   20  * REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING
   21  * THIS SOFTWARE, INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED
   22  * WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE,
   23  * OR NON-INFRINGEMENT.  PACKET DESIGN DOES NOT WARRANT, GUARANTEE,
   24  * OR MAKE ANY REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS
   25  * OF THE USE OF THIS SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY,
   26  * RELIABILITY OR OTHERWISE.  IN NO EVENT SHALL PACKET DESIGN BE
   27  * LIABLE FOR ANY DAMAGES RESULTING FROM OR ARISING OUT OF ANY USE
   28  * OF THIS SOFTWARE, INCLUDING WITHOUT LIMITATION, ANY DIRECT,
   29  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, PUNITIVE, OR CONSEQUENTIAL
   30  * DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES, LOSS OF
   31  * USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER ANY THEORY OF
   32  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   33  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
   34  * THE USE OF THIS SOFTWARE, EVEN IF PACKET DESIGN IS ADVISED OF
   35  * THE POSSIBILITY OF SUCH DAMAGE.
   36  * 
   37  * Author: Archie Cobbs <archie@freebsd.org>
   38  *
   39  * $FreeBSD$
   40  */
   41 
   42 /*
   43  * L2TP netgraph node type.
   44  *
   45  * This node type implements the lower layer of the
   46  * L2TP protocol as specified in RFC 2661.
   47  */
   48 
   49 #include <sys/param.h>
   50 #include <sys/systm.h>
   51 #include <sys/kernel.h>
   52 #include <sys/time.h>
   53 #include <sys/conf.h>
   54 #include <sys/mbuf.h>
   55 #include <sys/malloc.h>
   56 #include <sys/errno.h>
   57 #include <sys/libkern.h>
   58 
   59 #include <netgraph/ng_message.h>
   60 #include <netgraph/netgraph.h>
   61 #include <netgraph/ng_parse.h>
   62 #include <netgraph/ng_l2tp.h>
   63 
   64 #ifdef NG_SEPARATE_MALLOC
   65 MALLOC_DEFINE(M_NETGRAPH_L2TP, "netgraph_l2tp", "netgraph l2tp node");
   66 #else
   67 #define M_NETGRAPH_L2TP M_NETGRAPH
   68 #endif
   69 
   70 /* L2TP header format (first 2 bytes only) */
   71 #define L2TP_HDR_CTRL           0x8000                  /* control packet */
   72 #define L2TP_HDR_LEN            0x4000                  /* has length field */
   73 #define L2TP_HDR_SEQ            0x0800                  /* has ns, nr fields */
   74 #define L2TP_HDR_OFF            0x0200                  /* has offset field */
   75 #define L2TP_HDR_PRIO           0x0100                  /* give priority */
   76 #define L2TP_HDR_VERS_MASK      0x000f                  /* version field mask */
   77 #define L2TP_HDR_VERSION        0x0002                  /* version field */
   78 
   79 /* Bits that must be zero or one in first two bytes of header */
   80 #define L2TP_CTRL_0BITS         0x030d                  /* ctrl: must be 0 */
   81 #define L2TP_CTRL_1BITS         0xc802                  /* ctrl: must be 1 */
   82 #define L2TP_DATA_0BITS         0x800d                  /* data: must be 0 */
   83 #define L2TP_DATA_1BITS         0x0002                  /* data: must be 1 */
   84 
   85 /* Standard xmit ctrl and data header bits */
   86 #define L2TP_CTRL_HDR           (L2TP_HDR_CTRL | L2TP_HDR_LEN \
   87                                     | L2TP_HDR_SEQ | L2TP_HDR_VERSION)
   88 #define L2TP_DATA_HDR           (L2TP_HDR_VERSION)      /* optional: len, seq */
   89 
   90 /* Some hard coded values */
   91 #define L2TP_MAX_XWIN           128                     /* my max xmit window */
   92 #define L2TP_MAX_REXMIT         5                       /* default max rexmit */
   93 #define L2TP_MAX_REXMIT_TO      30                      /* default rexmit to */
   94 #define L2TP_DELAYED_ACK        ((hz + 19) / 20)        /* delayed ack: 50 ms */
   95 
   96 /* Default data sequence number configuration for new sessions */
   97 #define L2TP_CONTROL_DSEQ       1                       /* we are the lns */
   98 #define L2TP_ENABLE_DSEQ        1                       /* enable data seq # */
   99 
  100 /* Compare sequence numbers using circular math */
  101 #define L2TP_SEQ_DIFF(x, y)     ((int)((int16_t)(x) - (int16_t)(y)))
  102 
  103 #define SESSHASHSIZE            0x0020
  104 #define SESSHASH(x)             (((x) ^ ((x) >> 8)) & (SESSHASHSIZE - 1))
  105 
  106 /* Hook private data (data session hooks only) */
  107 struct ng_l2tp_hook_private {
  108         struct ng_l2tp_sess_config      conf;   /* hook/session config */
  109         struct ng_l2tp_session_stats    stats;  /* per sessions statistics */
  110         hook_p                          hook;   /* hook reference */
  111         u_int16_t                       ns;     /* data ns sequence number */
  112         u_int16_t                       nr;     /* data nr sequence number */
  113         LIST_ENTRY(ng_l2tp_hook_private) sessions;
  114 };
  115 typedef struct ng_l2tp_hook_private *hookpriv_p;
  116 
  117 /*
  118  * Sequence number state
  119  *
  120  * Invariants:
  121  *    - If cwnd < ssth, we're doing slow start, otherwise congestion avoidance
  122  *    - The number of unacknowledged xmit packets is (ns - rack) <= seq->wmax
  123  *    - The first (ns - rack) mbuf's in xwin[] array are copies of these
  124  *      unacknowledged packets; the remainder of xwin[] consists first of
  125  *      zero or more further untransmitted packets in the transmit queue
  126  *    - We try to keep the peer's receive window as full as possible.
  127  *      Therefore, (i < cwnd && xwin[i] != NULL) implies (ns - rack) > i.
  128  *    - rack_timer is running iff (ns - rack) > 0 (unack'd xmit'd pkts)
  129  *    - If xack != nr, there are unacknowledged recv packet(s) (delayed ack)
  130  *    - xack_timer is running iff xack != nr (unack'd rec'd pkts)
  131  */
  132 struct l2tp_seq {
  133         u_int16_t               ns;             /* next xmit seq we send */
  134         u_int16_t               nr;             /* next recv seq we expect */
  135         u_int16_t               inproc;         /* packet is in processing */
  136         u_int16_t               rack;           /* last 'nr' we rec'd */
  137         u_int16_t               xack;           /* last 'nr' we sent */
  138         u_int16_t               wmax;           /* peer's max recv window */
  139         u_int16_t               cwnd;           /* current congestion window */
  140         u_int16_t               ssth;           /* slow start threshold */
  141         u_int16_t               acks;           /* # consecutive acks rec'd */
  142         u_int16_t               rexmits;        /* # retransmits sent */
  143         struct callout          rack_timer;     /* retransmit timer */
  144         struct callout          xack_timer;     /* delayed ack timer */
  145         struct mbuf             *xwin[L2TP_MAX_XWIN];   /* transmit window */
  146         struct mtx              mtx;                    /* seq mutex */
  147 };
  148 
  149 /* Node private data */
  150 struct ng_l2tp_private {
  151         node_p                  node;           /* back pointer to node */
  152         hook_p                  ctrl;           /* hook to upper layers */
  153         hook_p                  lower;          /* hook to lower layers */
  154         struct ng_l2tp_config   conf;           /* node configuration */
  155         struct ng_l2tp_stats    stats;          /* node statistics */
  156         struct l2tp_seq         seq;            /* ctrl sequence number state */
  157         ng_ID_t                 ftarget;        /* failure message target */
  158         LIST_HEAD(, ng_l2tp_hook_private) sesshash[SESSHASHSIZE];
  159 };
  160 typedef struct ng_l2tp_private *priv_p;
  161 
  162 /* Netgraph node methods */
  163 static ng_constructor_t ng_l2tp_constructor;
  164 static ng_rcvmsg_t      ng_l2tp_rcvmsg;
  165 static ng_shutdown_t    ng_l2tp_shutdown;
  166 static ng_newhook_t     ng_l2tp_newhook;
  167 static ng_rcvdata_t     ng_l2tp_rcvdata;
  168 static ng_rcvdata_t     ng_l2tp_rcvdata_lower;
  169 static ng_rcvdata_t     ng_l2tp_rcvdata_ctrl;
  170 static ng_disconnect_t  ng_l2tp_disconnect;
  171 
  172 /* Internal functions */
  173 static int      ng_l2tp_xmit_ctrl(priv_p priv, struct mbuf *m, u_int16_t ns);
  174 
  175 static void     ng_l2tp_seq_init(priv_p priv);
  176 static int      ng_l2tp_seq_set(priv_p priv,
  177                         const struct ng_l2tp_seq_config *conf);
  178 static int      ng_l2tp_seq_adjust(priv_p priv,
  179                         const struct ng_l2tp_config *conf);
  180 static void     ng_l2tp_seq_reset(priv_p priv);
  181 static void     ng_l2tp_seq_failure(priv_p priv);
  182 static void     ng_l2tp_seq_recv_nr(priv_p priv, u_int16_t nr);
  183 static void     ng_l2tp_seq_xack_timeout(node_p node, hook_p hook,
  184                     void *arg1, int arg2);
  185 static void     ng_l2tp_seq_rack_timeout(node_p node, hook_p hook,
  186                     void *arg1, int arg2);
  187 
  188 static hookpriv_p       ng_l2tp_find_session(priv_p privp, u_int16_t sid);
  189 static ng_fn_eachhook   ng_l2tp_reset_session;
  190 
  191 #ifdef INVARIANTS
  192 static void     ng_l2tp_seq_check(struct l2tp_seq *seq);
  193 #endif
  194 
  195 /* Parse type for struct ng_l2tp_seq_config. */
  196 static const struct ng_parse_struct_field
  197         ng_l2tp_seq_config_fields[] = NG_L2TP_SEQ_CONFIG_TYPE_INFO;
  198 static const struct ng_parse_type ng_l2tp_seq_config_type = {
  199         &ng_parse_struct_type,
  200         &ng_l2tp_seq_config_fields
  201 };
  202 
  203 /* Parse type for struct ng_l2tp_config */
  204 static const struct ng_parse_struct_field
  205         ng_l2tp_config_type_fields[] = NG_L2TP_CONFIG_TYPE_INFO;
  206 static const struct ng_parse_type ng_l2tp_config_type = {
  207         &ng_parse_struct_type,
  208         &ng_l2tp_config_type_fields,
  209 };
  210 
  211 /* Parse type for struct ng_l2tp_sess_config */
  212 static const struct ng_parse_struct_field
  213         ng_l2tp_sess_config_type_fields[] = NG_L2TP_SESS_CONFIG_TYPE_INFO;
  214 static const struct ng_parse_type ng_l2tp_sess_config_type = {
  215         &ng_parse_struct_type,
  216         &ng_l2tp_sess_config_type_fields,
  217 };
  218 
  219 /* Parse type for struct ng_l2tp_stats */
  220 static const struct ng_parse_struct_field
  221         ng_l2tp_stats_type_fields[] = NG_L2TP_STATS_TYPE_INFO;
  222 static const struct ng_parse_type ng_l2tp_stats_type = {
  223         &ng_parse_struct_type,
  224         &ng_l2tp_stats_type_fields
  225 };
  226 
  227 /* Parse type for struct ng_l2tp_session_stats. */
  228 static const struct ng_parse_struct_field
  229         ng_l2tp_session_stats_type_fields[] = NG_L2TP_SESSION_STATS_TYPE_INFO;
  230 static const struct ng_parse_type ng_l2tp_session_stats_type = {
  231         &ng_parse_struct_type,
  232         &ng_l2tp_session_stats_type_fields
  233 };
  234 
  235 /* List of commands and how to convert arguments to/from ASCII */
  236 static const struct ng_cmdlist ng_l2tp_cmdlist[] = {
  237         {
  238           NGM_L2TP_COOKIE,
  239           NGM_L2TP_SET_CONFIG,
  240           "setconfig",
  241           &ng_l2tp_config_type,
  242           NULL
  243         },
  244         {
  245           NGM_L2TP_COOKIE,
  246           NGM_L2TP_GET_CONFIG,
  247           "getconfig",
  248           NULL,
  249           &ng_l2tp_config_type
  250         },
  251         {
  252           NGM_L2TP_COOKIE,
  253           NGM_L2TP_SET_SESS_CONFIG,
  254           "setsessconfig",
  255           &ng_l2tp_sess_config_type,
  256           NULL
  257         },
  258         {
  259           NGM_L2TP_COOKIE,
  260           NGM_L2TP_GET_SESS_CONFIG,
  261           "getsessconfig",
  262           &ng_parse_hint16_type,
  263           &ng_l2tp_sess_config_type
  264         },
  265         {
  266           NGM_L2TP_COOKIE,
  267           NGM_L2TP_GET_STATS,
  268           "getstats",
  269           NULL,
  270           &ng_l2tp_stats_type
  271         },
  272         {
  273           NGM_L2TP_COOKIE,
  274           NGM_L2TP_CLR_STATS,
  275           "clrstats",
  276           NULL,
  277           NULL
  278         },
  279         {
  280           NGM_L2TP_COOKIE,
  281           NGM_L2TP_GETCLR_STATS,
  282           "getclrstats",
  283           NULL,
  284           &ng_l2tp_stats_type
  285         },
  286         {
  287           NGM_L2TP_COOKIE,
  288           NGM_L2TP_GET_SESSION_STATS,
  289           "getsessstats",
  290           &ng_parse_int16_type,
  291           &ng_l2tp_session_stats_type
  292         },
  293         {
  294           NGM_L2TP_COOKIE,
  295           NGM_L2TP_CLR_SESSION_STATS,
  296           "clrsessstats",
  297           &ng_parse_int16_type,
  298           NULL
  299         },
  300         {
  301           NGM_L2TP_COOKIE,
  302           NGM_L2TP_GETCLR_SESSION_STATS,
  303           "getclrsessstats",
  304           &ng_parse_int16_type,
  305           &ng_l2tp_session_stats_type
  306         },
  307         {
  308           NGM_L2TP_COOKIE,
  309           NGM_L2TP_ACK_FAILURE,
  310           "ackfailure",
  311           NULL,
  312           NULL
  313         },
  314         {
  315           NGM_L2TP_COOKIE,
  316           NGM_L2TP_SET_SEQ,
  317           "setsequence",
  318           &ng_l2tp_seq_config_type,
  319           NULL
  320         },
  321         { 0 }
  322 };
  323 
  324 /* Node type descriptor */
  325 static struct ng_type ng_l2tp_typestruct = {
  326         .version =      NG_ABI_VERSION,
  327         .name =         NG_L2TP_NODE_TYPE,
  328         .constructor =  ng_l2tp_constructor,
  329         .rcvmsg =       ng_l2tp_rcvmsg,
  330         .shutdown =     ng_l2tp_shutdown,
  331         .newhook =      ng_l2tp_newhook,
  332         .rcvdata =      ng_l2tp_rcvdata,
  333         .disconnect =   ng_l2tp_disconnect,
  334         .cmdlist =      ng_l2tp_cmdlist,
  335 };
  336 NETGRAPH_INIT(l2tp, &ng_l2tp_typestruct);
  337 
  338 /* Sequence number state sanity checking */
  339 #ifdef INVARIANTS
  340 #define L2TP_SEQ_CHECK(seq)     ng_l2tp_seq_check(seq)
  341 #else
  342 #define L2TP_SEQ_CHECK(x)       do { } while (0)
  343 #endif
  344 
  345 /* memmove macro */
  346 #define memmove(d, s, l)        bcopy(s, d, l)
  347 
  348 /* Whether to use m_copypacket() or m_dup() */
  349 #define L2TP_COPY_MBUF          m_copypacket
  350 
  351 #define ERROUT(x)       do { error = (x); goto done; } while (0)
  352 
  353 /************************************************************************
  354                         NETGRAPH NODE STUFF
  355 ************************************************************************/
  356 
  357 /*
  358  * Node type constructor
  359  */
  360 static int
  361 ng_l2tp_constructor(node_p node)
  362 {
  363         priv_p priv;
  364         int     i;
  365 
  366         /* Allocate private structure */
  367         MALLOC(priv, priv_p, sizeof(*priv), M_NETGRAPH_L2TP, M_NOWAIT | M_ZERO);
  368         if (priv == NULL)
  369                 return (ENOMEM);
  370         NG_NODE_SET_PRIVATE(node, priv);
  371         priv->node = node;
  372 
  373         /* Apply a semi-reasonable default configuration */
  374         priv->conf.peer_win = 1;
  375         priv->conf.rexmit_max = L2TP_MAX_REXMIT;
  376         priv->conf.rexmit_max_to = L2TP_MAX_REXMIT_TO;
  377 
  378         /* Initialize sequence number state */
  379         ng_l2tp_seq_init(priv);
  380 
  381         for (i = 0; i < SESSHASHSIZE; i++)
  382             LIST_INIT(&priv->sesshash[i]);
  383 
  384         /* Done */
  385         return (0);
  386 }
  387 
  388 /*
  389  * Give our OK for a hook to be added.
  390  */
  391 static int
  392 ng_l2tp_newhook(node_p node, hook_p hook, const char *name)
  393 {
  394         const priv_p priv = NG_NODE_PRIVATE(node);
  395 
  396         /* Check hook name */
  397         if (strcmp(name, NG_L2TP_HOOK_CTRL) == 0) {
  398                 if (priv->ctrl != NULL)
  399                         return (EISCONN);
  400                 priv->ctrl = hook;
  401                 NG_HOOK_SET_RCVDATA(hook, ng_l2tp_rcvdata_ctrl);
  402         } else if (strcmp(name, NG_L2TP_HOOK_LOWER) == 0) {
  403                 if (priv->lower != NULL)
  404                         return (EISCONN);
  405                 priv->lower = hook;
  406                 NG_HOOK_SET_RCVDATA(hook, ng_l2tp_rcvdata_lower);
  407         } else {
  408                 static const char hexdig[16] = "0123456789abcdef";
  409                 u_int16_t session_id;
  410                 hookpriv_p hpriv;
  411                 uint16_t hash;
  412                 const char *hex;
  413                 int i;
  414                 int j;
  415 
  416                 /* Parse hook name to get session ID */
  417                 if (strncmp(name, NG_L2TP_HOOK_SESSION_P,
  418                     sizeof(NG_L2TP_HOOK_SESSION_P) - 1) != 0)
  419                         return (EINVAL);
  420                 hex = name + sizeof(NG_L2TP_HOOK_SESSION_P) - 1;
  421                 for (session_id = i = 0; i < 4; i++) {
  422                         for (j = 0; j < 16 && hex[i] != hexdig[j]; j++);
  423                         if (j == 16)
  424                                 return (EINVAL);
  425                         session_id = (session_id << 4) | j;
  426                 }
  427                 if (hex[i] != '\0')
  428                         return (EINVAL);
  429 
  430                 /* Create hook private structure */
  431                 MALLOC(hpriv, hookpriv_p,
  432                     sizeof(*hpriv), M_NETGRAPH_L2TP, M_NOWAIT | M_ZERO);
  433                 if (hpriv == NULL)
  434                         return (ENOMEM);
  435                 hpriv->conf.session_id = session_id;
  436                 hpriv->conf.control_dseq = L2TP_CONTROL_DSEQ;
  437                 hpriv->conf.enable_dseq = L2TP_ENABLE_DSEQ;
  438                 hpriv->hook = hook;
  439                 NG_HOOK_SET_PRIVATE(hook, hpriv);
  440                 hash = SESSHASH(hpriv->conf.session_id);
  441                 LIST_INSERT_HEAD(&priv->sesshash[hash], hpriv, sessions);
  442         }
  443 
  444         /* Done */
  445         return (0);
  446 }
  447 
  448 /*
  449  * Receive a control message.
  450  */
  451 static int
  452 ng_l2tp_rcvmsg(node_p node, item_p item, hook_p lasthook)
  453 {
  454         const priv_p priv = NG_NODE_PRIVATE(node);
  455         struct ng_mesg *resp = NULL;
  456         struct ng_mesg *msg;
  457         int error = 0;
  458 
  459         NGI_GET_MSG(item, msg);
  460         switch (msg->header.typecookie) {
  461         case NGM_L2TP_COOKIE:
  462                 switch (msg->header.cmd) {
  463                 case NGM_L2TP_SET_CONFIG:
  464                     {
  465                         struct ng_l2tp_config *const conf =
  466                                 (struct ng_l2tp_config *)msg->data;
  467 
  468                         /* Check for invalid or illegal config */
  469                         if (msg->header.arglen != sizeof(*conf)) {
  470                                 error = EINVAL;
  471                                 break;
  472                         }
  473                         conf->enabled = !!conf->enabled;
  474                         conf->match_id = !!conf->match_id;
  475                         if (priv->conf.enabled
  476                             && ((priv->conf.tunnel_id != 0
  477                                && conf->tunnel_id != priv->conf.tunnel_id)
  478                               || ((priv->conf.peer_id != 0
  479                                && conf->peer_id != priv->conf.peer_id)))) {
  480                                 error = EBUSY;
  481                                 break;
  482                         }
  483 
  484                         /* Save calling node as failure target */
  485                         priv->ftarget = NGI_RETADDR(item);
  486 
  487                         /* Adjust sequence number state */
  488                         if ((error = ng_l2tp_seq_adjust(priv, conf)) != 0)
  489                                 break;
  490 
  491                         /* Update node's config */
  492                         priv->conf = *conf;
  493                         break;
  494                     }
  495                 case NGM_L2TP_GET_CONFIG:
  496                     {
  497                         struct ng_l2tp_config *conf;
  498 
  499                         NG_MKRESPONSE(resp, msg, sizeof(*conf), M_NOWAIT);
  500                         if (resp == NULL) {
  501                                 error = ENOMEM;
  502                                 break;
  503                         }
  504                         conf = (struct ng_l2tp_config *)resp->data;
  505                         *conf = priv->conf;
  506                         break;
  507                     }
  508                 case NGM_L2TP_SET_SESS_CONFIG:
  509                     {
  510                         struct ng_l2tp_sess_config *const conf =
  511                             (struct ng_l2tp_sess_config *)msg->data;
  512                         hookpriv_p hpriv;
  513 
  514                         /* Check for invalid or illegal config. */
  515                         if (msg->header.arglen != sizeof(*conf)) {
  516                                 error = EINVAL;
  517                                 break;
  518                         }
  519 
  520                         /* Find matching hook */
  521                         hpriv = ng_l2tp_find_session(priv, conf->session_id);
  522                         if (hpriv == NULL) {
  523                                 error = ENOENT;
  524                                 break;
  525                         }
  526 
  527                         /* Update hook's config */
  528                         hpriv->conf = *conf;
  529                         break;
  530                     }
  531                 case NGM_L2TP_GET_SESS_CONFIG:
  532                     {
  533                         struct ng_l2tp_sess_config *conf;
  534                         u_int16_t session_id;
  535                         hookpriv_p hpriv;
  536 
  537                         /* Get session ID */
  538                         if (msg->header.arglen != sizeof(session_id)) {
  539                                 error = EINVAL;
  540                                 break;
  541                         }
  542                         memcpy(&session_id, msg->data, 2);
  543 
  544                         /* Find matching hook */
  545                         hpriv = ng_l2tp_find_session(priv, session_id);
  546                         if (hpriv == NULL) {
  547                                 error = ENOENT;
  548                                 break;
  549                         }
  550 
  551                         /* Send response */
  552                         NG_MKRESPONSE(resp, msg, sizeof(hpriv->conf), M_NOWAIT);
  553                         if (resp == NULL) {
  554                                 error = ENOMEM;
  555                                 break;
  556                         }
  557                         conf = (struct ng_l2tp_sess_config *)resp->data;
  558                         *conf = hpriv->conf;
  559                         break;
  560                     }
  561                 case NGM_L2TP_GET_STATS:
  562                 case NGM_L2TP_CLR_STATS:
  563                 case NGM_L2TP_GETCLR_STATS:
  564                     {
  565                         if (msg->header.cmd != NGM_L2TP_CLR_STATS) {
  566                                 NG_MKRESPONSE(resp, msg,
  567                                     sizeof(priv->stats), M_NOWAIT);
  568                                 if (resp == NULL) {
  569                                         error = ENOMEM;
  570                                         break;
  571                                 }
  572                                 memcpy(resp->data,
  573                                     &priv->stats, sizeof(priv->stats));
  574                         }
  575                         if (msg->header.cmd != NGM_L2TP_GET_STATS)
  576                                 memset(&priv->stats, 0, sizeof(priv->stats));
  577                         break;
  578                     }
  579                 case NGM_L2TP_GET_SESSION_STATS:
  580                 case NGM_L2TP_CLR_SESSION_STATS:
  581                 case NGM_L2TP_GETCLR_SESSION_STATS:
  582                     {
  583                         uint16_t session_id;
  584                         hookpriv_p hpriv;
  585 
  586                         /* Get session ID. */
  587                         if (msg->header.arglen != sizeof(session_id)) {
  588                                 error = EINVAL;
  589                                 break;
  590                         }
  591                         bcopy(msg->data, &session_id, sizeof(uint16_t));
  592 
  593                         /* Find matching hook. */
  594                         hpriv = ng_l2tp_find_session(priv, session_id);
  595                         if (hpriv == NULL) {
  596                                 error = ENOENT;
  597                                 break;
  598                         }
  599 
  600                         if (msg->header.cmd != NGM_L2TP_CLR_SESSION_STATS) {
  601                                 NG_MKRESPONSE(resp, msg,
  602                                     sizeof(hpriv->stats), M_NOWAIT);
  603                                 if (resp == NULL) {
  604                                         error = ENOMEM;
  605                                         break;
  606                                 }
  607                                 bcopy(&hpriv->stats, resp->data,
  608                                         sizeof(hpriv->stats));
  609                         }
  610                         if (msg->header.cmd != NGM_L2TP_GET_SESSION_STATS)
  611                                 bzero(&hpriv->stats, sizeof(hpriv->stats));
  612                         break;
  613                     }
  614                 case NGM_L2TP_SET_SEQ:
  615                     {
  616                         struct ng_l2tp_seq_config *const conf =
  617                                 (struct ng_l2tp_seq_config *)msg->data;
  618 
  619                         /* Check for invalid or illegal seq config. */
  620                         if (msg->header.arglen != sizeof(*conf)) {
  621                                 error = EINVAL;
  622                                 break;
  623                         }
  624                         conf->ns = htons(conf->ns);
  625                         conf->nr = htons(conf->nr);
  626                         conf->rack = htons(conf->rack);
  627                         conf->xack = htons(conf->xack);
  628 
  629                         /* Set sequence numbers. */
  630                         error = ng_l2tp_seq_set(priv, conf);
  631                         break;
  632                     }
  633                 default:
  634                         error = EINVAL;
  635                         break;
  636                 }
  637                 break;
  638         default:
  639                 error = EINVAL;
  640                 break;
  641         }
  642 
  643         /* Done */
  644         NG_RESPOND_MSG(error, node, item, resp);
  645         NG_FREE_MSG(msg);
  646         return (error);
  647 }
  648 
  649 /*
  650  * Destroy node
  651  */
  652 static int
  653 ng_l2tp_shutdown(node_p node)
  654 {
  655         const priv_p priv = NG_NODE_PRIVATE(node);
  656         struct l2tp_seq *const seq = &priv->seq;
  657 
  658         /* Sanity check */
  659         L2TP_SEQ_CHECK(seq);
  660 
  661         /* Reset sequence number state */
  662         ng_l2tp_seq_reset(priv);
  663 
  664         /* Free private data if neither timer is running */
  665         ng_uncallout(&seq->rack_timer, node);
  666         ng_uncallout(&seq->xack_timer, node);
  667 
  668         mtx_destroy(&seq->mtx);
  669 
  670         FREE(priv, M_NETGRAPH_L2TP);
  671 
  672         /* Unref node */
  673         NG_NODE_UNREF(node);
  674         return (0);
  675 }
  676 
  677 /*
  678  * Hook disconnection
  679  */
  680 static int
  681 ng_l2tp_disconnect(hook_p hook)
  682 {
  683         const node_p node = NG_HOOK_NODE(hook);
  684         const priv_p priv = NG_NODE_PRIVATE(node);
  685 
  686         /* Zero out hook pointer */
  687         if (hook == priv->ctrl)
  688                 priv->ctrl = NULL;
  689         else if (hook == priv->lower)
  690                 priv->lower = NULL;
  691         else {
  692                 const hookpriv_p hpriv = NG_HOOK_PRIVATE(hook);
  693                 LIST_REMOVE(hpriv, sessions);
  694                 FREE(hpriv, M_NETGRAPH_L2TP);
  695                 NG_HOOK_SET_PRIVATE(hook, NULL);
  696         }
  697 
  698         /* Go away if no longer connected to anything */
  699         if (NG_NODE_NUMHOOKS(node) == 0 && NG_NODE_IS_VALID(node))
  700                 ng_rmnode_self(node);
  701         return (0);
  702 }
  703 
  704 /*************************************************************************
  705                         INTERNAL FUNCTIONS
  706 *************************************************************************/
  707 
  708 /*
  709  * Find the hook with a given session ID.
  710  */
  711 static hookpriv_p
  712 ng_l2tp_find_session(priv_p privp, u_int16_t sid)
  713 {
  714         uint16_t        hash = SESSHASH(sid);
  715         hookpriv_p      hpriv = NULL;
  716 
  717         LIST_FOREACH(hpriv, &privp->sesshash[hash], sessions) {
  718                 if (hpriv->conf.session_id == sid)
  719                         break;
  720         }
  721 
  722         return (hpriv);
  723 }
  724 
  725 /*
  726  * Reset a hook's session state.
  727  */
  728 static int
  729 ng_l2tp_reset_session(hook_p hook, void *arg)
  730 {
  731         const hookpriv_p hpriv = NG_HOOK_PRIVATE(hook);
  732 
  733         if (hpriv != NULL) {
  734                 hpriv->conf.control_dseq = 0;
  735                 hpriv->conf.enable_dseq = 0;
  736                 bzero(&hpriv->stats, sizeof(struct ng_l2tp_session_stats));
  737                 hpriv->nr = 0;
  738                 hpriv->ns = 0;
  739         }
  740         return (-1);
  741 }
  742 
  743 /*
  744  * Handle an incoming frame from below.
  745  */
  746 static int
  747 ng_l2tp_rcvdata_lower(hook_p h, item_p item)
  748 {
  749         static const u_int16_t req_bits[2][2] = {
  750                 { L2TP_DATA_0BITS, L2TP_DATA_1BITS },
  751                 { L2TP_CTRL_0BITS, L2TP_CTRL_1BITS },
  752         };
  753         const node_p node = NG_HOOK_NODE(h);
  754         const priv_p priv = NG_NODE_PRIVATE(node);
  755         hookpriv_p hpriv = NULL;
  756         hook_p hook = NULL;
  757         struct mbuf *m;
  758         u_int16_t tid, sid;
  759         u_int16_t hdr;
  760         u_int16_t ns, nr;
  761         int is_ctrl;
  762         int error;
  763         int len, plen;
  764 
  765         /* Sanity check */
  766         L2TP_SEQ_CHECK(&priv->seq);
  767 
  768         /* If not configured, reject */
  769         if (!priv->conf.enabled) {
  770                 NG_FREE_ITEM(item);
  771                 ERROUT(ENXIO);
  772         }
  773 
  774         /* Grab mbuf */
  775         NGI_GET_M(item, m);
  776 
  777         /* Remember full packet length; needed for per session accounting. */
  778         plen = m->m_pkthdr.len;
  779 
  780         /* Update stats */
  781         priv->stats.recvPackets++;
  782         priv->stats.recvOctets += plen;
  783 
  784         /* Get initial header */
  785         if (m->m_pkthdr.len < 6) {
  786                 priv->stats.recvRunts++;
  787                 NG_FREE_ITEM(item);
  788                 NG_FREE_M(m);
  789                 ERROUT(EINVAL);
  790         }
  791         if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
  792                 priv->stats.memoryFailures++;
  793                 NG_FREE_ITEM(item);
  794                 ERROUT(EINVAL);
  795         }
  796         hdr = ntohs(*mtod(m, u_int16_t *));
  797         m_adj(m, 2);
  798 
  799         /* Check required header bits and minimum length */
  800         is_ctrl = (hdr & L2TP_HDR_CTRL) != 0;
  801         if ((hdr & req_bits[is_ctrl][0]) != 0
  802             || (~hdr & req_bits[is_ctrl][1]) != 0) {
  803                 priv->stats.recvInvalid++;
  804                 NG_FREE_ITEM(item);
  805                 NG_FREE_M(m);
  806                 ERROUT(EINVAL);
  807         }
  808         if (m->m_pkthdr.len < 4                         /* tunnel, session id */
  809             + (2 * ((hdr & L2TP_HDR_LEN) != 0))         /* length field */
  810             + (4 * ((hdr & L2TP_HDR_SEQ) != 0))         /* seq # fields */
  811             + (2 * ((hdr & L2TP_HDR_OFF) != 0))) {      /* offset field */
  812                 priv->stats.recvRunts++;
  813                 NG_FREE_ITEM(item);
  814                 NG_FREE_M(m);
  815                 ERROUT(EINVAL);
  816         }
  817 
  818         /* Get and validate length field if present */
  819         if ((hdr & L2TP_HDR_LEN) != 0) {
  820                 if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
  821                         priv->stats.memoryFailures++;
  822                         NG_FREE_ITEM(item);
  823                         ERROUT(EINVAL);
  824                 }
  825                 len = (u_int16_t)ntohs(*mtod(m, u_int16_t *)) - 4;
  826                 m_adj(m, 2);
  827                 if (len < 0 || len > m->m_pkthdr.len) {
  828                         priv->stats.recvInvalid++;
  829                         NG_FREE_ITEM(item);
  830                         NG_FREE_M(m);
  831                         ERROUT(EINVAL);
  832                 }
  833                 if (len < m->m_pkthdr.len)              /* trim extra bytes */
  834                         m_adj(m, -(m->m_pkthdr.len - len));
  835         }
  836 
  837         /* Get tunnel ID and session ID */
  838         if (m->m_len < 4 && (m = m_pullup(m, 4)) == NULL) {
  839                 priv->stats.memoryFailures++;
  840                 NG_FREE_ITEM(item);
  841                 ERROUT(EINVAL);
  842         }
  843         tid = (mtod(m, u_int8_t *)[0] << 8) + mtod(m, u_int8_t *)[1];
  844         sid = (mtod(m, u_int8_t *)[2] << 8) + mtod(m, u_int8_t *)[3];
  845         m_adj(m, 4);
  846 
  847         /* Check tunnel ID */
  848         if (tid != priv->conf.tunnel_id &&
  849             (priv->conf.match_id || tid != 0)) {
  850                 priv->stats.recvWrongTunnel++;
  851                 NG_FREE_ITEM(item);
  852                 NG_FREE_M(m);
  853                 ERROUT(EADDRNOTAVAIL);
  854         }
  855 
  856         /* Check session ID (for data packets only) */
  857         if ((hdr & L2TP_HDR_CTRL) == 0) {
  858                 hpriv = ng_l2tp_find_session(priv, sid);
  859                 if (hpriv == NULL) {
  860                         priv->stats.recvUnknownSID++;
  861                         NG_FREE_ITEM(item);
  862                         NG_FREE_M(m);
  863                         ERROUT(ENOTCONN);
  864                 }
  865                 hook = hpriv->hook;
  866         }
  867 
  868         /* Get Ns, Nr fields if present */
  869         if ((hdr & L2TP_HDR_SEQ) != 0) {
  870                 if (m->m_len < 4 && (m = m_pullup(m, 4)) == NULL) {
  871                         priv->stats.memoryFailures++;
  872                         NG_FREE_ITEM(item);
  873                         ERROUT(EINVAL);
  874                 }
  875                 ns = (mtod(m, u_int8_t *)[0] << 8) + mtod(m, u_int8_t *)[1];
  876                 nr = (mtod(m, u_int8_t *)[2] << 8) + mtod(m, u_int8_t *)[3];
  877                 m_adj(m, 4);
  878         } else
  879                 ns = nr = 0;
  880 
  881         /* Strip offset padding if present */
  882         if ((hdr & L2TP_HDR_OFF) != 0) {
  883                 u_int16_t offset;
  884 
  885                 /* Get length of offset padding */
  886                 if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
  887                         priv->stats.memoryFailures++;
  888                         NG_FREE_ITEM(item);
  889                         ERROUT(EINVAL);
  890                 }
  891                 offset = (mtod(m, u_int8_t *)[0] << 8) + mtod(m, u_int8_t *)[1];
  892 
  893                 /* Trim offset padding */
  894                 if ((2+offset) > m->m_pkthdr.len) {
  895                         priv->stats.recvInvalid++;
  896                         NG_FREE_ITEM(item);
  897                         NG_FREE_M(m);
  898                         ERROUT(EINVAL);
  899                 }
  900                 m_adj(m, 2+offset);
  901         }
  902 
  903         /* Handle control packets */
  904         if ((hdr & L2TP_HDR_CTRL) != 0) {
  905                 struct l2tp_seq *const seq = &priv->seq;
  906 
  907                 /* Handle receive ack sequence number Nr */
  908                 ng_l2tp_seq_recv_nr(priv, nr);
  909 
  910                 /* Discard ZLB packets */
  911                 if (m->m_pkthdr.len == 0) {
  912                         priv->stats.recvZLBs++;
  913                         NG_FREE_ITEM(item);
  914                         NG_FREE_M(m);
  915                         ERROUT(0);
  916                 }
  917 
  918                 mtx_lock(&seq->mtx);
  919                 /*
  920                  * If not what we expect or we are busy, drop packet and
  921                  * send an immediate ZLB ack.
  922                  */
  923                 if (ns != seq->nr || seq->inproc) {
  924                         if (L2TP_SEQ_DIFF(ns, seq->nr) <= 0)
  925                                 priv->stats.recvDuplicates++;
  926                         else
  927                                 priv->stats.recvOutOfOrder++;
  928                         mtx_unlock(&seq->mtx);
  929                         ng_l2tp_xmit_ctrl(priv, NULL, seq->ns);
  930                         NG_FREE_ITEM(item);
  931                         NG_FREE_M(m);
  932                         ERROUT(0);
  933                 }
  934                 /*
  935                  * Until we deliver this packet we can't receive next one as
  936                  * we have no information for sending ack.
  937                  */
  938                 seq->inproc = 1;
  939                 mtx_unlock(&seq->mtx);
  940 
  941                 /* Prepend session ID to packet. */
  942                 M_PREPEND(m, 2, M_DONTWAIT);
  943                 if (m == NULL) {
  944                         seq->inproc = 0;
  945                         priv->stats.memoryFailures++;
  946                         NG_FREE_ITEM(item);
  947                         ERROUT(ENOBUFS);
  948                 }
  949                 mtod(m, u_int8_t *)[0] = sid >> 8;
  950                 mtod(m, u_int8_t *)[1] = sid & 0xff;
  951 
  952                 /* Deliver packet to upper layers */
  953                 NG_FWD_NEW_DATA(error, item, priv->ctrl, m);
  954                 
  955                 mtx_lock(&seq->mtx);
  956                 /* Ready to process next packet. */
  957                 seq->inproc = 0;
  958 
  959                 /* If packet was successfully delivered send ack. */
  960                 if (error == 0) {
  961                         /* Update recv sequence number */
  962                         seq->nr++;
  963                         /* Start receive ack timer, if not already running */
  964                         if (!callout_active(&seq->xack_timer)) {
  965                                 ng_callout(&seq->xack_timer, priv->node, NULL,
  966                                     L2TP_DELAYED_ACK, ng_l2tp_seq_xack_timeout,
  967                                     NULL, 0);
  968                         }
  969                 }
  970                 mtx_unlock(&seq->mtx);
  971 
  972                 ERROUT(error);
  973         }
  974 
  975         /* Per session packet, account it. */
  976         hpriv->stats.recvPackets++;
  977         hpriv->stats.recvOctets += plen;
  978 
  979         /* Follow peer's lead in data sequencing, if configured to do so */
  980         if (!hpriv->conf.control_dseq)
  981                 hpriv->conf.enable_dseq = ((hdr & L2TP_HDR_SEQ) != 0);
  982 
  983         /* Handle data sequence numbers if present and enabled */
  984         if ((hdr & L2TP_HDR_SEQ) != 0) {
  985                 if (hpriv->conf.enable_dseq
  986                     && L2TP_SEQ_DIFF(ns, hpriv->nr) < 0) {
  987                         NG_FREE_ITEM(item);     /* duplicate or out of order */
  988                         NG_FREE_M(m);
  989                         priv->stats.recvDataDrops++;
  990                         ERROUT(0);
  991                 }
  992                 hpriv->nr = ns + 1;
  993         }
  994 
  995         /* Drop empty data packets */
  996         if (m->m_pkthdr.len == 0) {
  997                 NG_FREE_ITEM(item);
  998                 NG_FREE_M(m);
  999                 ERROUT(0);
 1000         }
 1001 
 1002         /* Deliver data */
 1003         NG_FWD_NEW_DATA(error, item, hook, m);
 1004 done:
 1005         /* Done */
 1006         L2TP_SEQ_CHECK(&priv->seq);
 1007         return (error);
 1008 }
 1009 
 1010 /*
 1011  * Handle an outgoing control frame.
 1012  */
 1013 static int
 1014 ng_l2tp_rcvdata_ctrl(hook_p hook, item_p item)
 1015 {
 1016         const node_p node = NG_HOOK_NODE(hook);
 1017         const priv_p priv = NG_NODE_PRIVATE(node);
 1018         struct l2tp_seq *const seq = &priv->seq;
 1019         struct mbuf *m;
 1020         int error;
 1021         int i;
 1022         u_int16_t       ns;
 1023 
 1024         /* Sanity check */
 1025         L2TP_SEQ_CHECK(&priv->seq);
 1026 
 1027         /* If not configured, reject */
 1028         if (!priv->conf.enabled) {
 1029                 NG_FREE_ITEM(item);
 1030                 ERROUT(ENXIO);
 1031         }
 1032 
 1033         /* Grab mbuf and discard other stuff XXX */
 1034         NGI_GET_M(item, m);
 1035         NG_FREE_ITEM(item);
 1036 
 1037         /* Packet should have session ID prepended */
 1038         if (m->m_pkthdr.len < 2) {
 1039                 priv->stats.xmitInvalid++;
 1040                 m_freem(m);
 1041                 ERROUT(EINVAL);
 1042         }
 1043 
 1044         /* Check max length */
 1045         if (m->m_pkthdr.len >= 0x10000 - 14) {
 1046                 priv->stats.xmitTooBig++;
 1047                 m_freem(m);
 1048                 ERROUT(EOVERFLOW);
 1049         }
 1050 
 1051         mtx_lock(&seq->mtx);
 1052 
 1053         /* Find next empty slot in transmit queue */
 1054         for (i = 0; i < L2TP_MAX_XWIN && seq->xwin[i] != NULL; i++);
 1055         if (i == L2TP_MAX_XWIN) {
 1056                 mtx_unlock(&seq->mtx);
 1057                 priv->stats.xmitDrops++;
 1058                 m_freem(m);
 1059                 ERROUT(ENOBUFS);
 1060         }
 1061         seq->xwin[i] = m;
 1062 
 1063         /* If peer's receive window is already full, nothing else to do */
 1064         if (i >= seq->cwnd) {
 1065                 mtx_unlock(&seq->mtx);
 1066                 ERROUT(0);
 1067         }
 1068 
 1069         /* Start retransmit timer if not already running */
 1070         if (!callout_active(&seq->rack_timer))
 1071                 ng_callout(&seq->rack_timer, node, NULL,
 1072                     hz, ng_l2tp_seq_rack_timeout, NULL, 0);
 1073         
 1074         ns = seq->ns++;
 1075         
 1076         mtx_unlock(&seq->mtx);
 1077 
 1078         /* Copy packet */
 1079         if ((m = L2TP_COPY_MBUF(m, M_DONTWAIT)) == NULL) {
 1080                 priv->stats.memoryFailures++;
 1081                 ERROUT(ENOBUFS);
 1082         }
 1083 
 1084         /* Send packet and increment xmit sequence number */
 1085         error = ng_l2tp_xmit_ctrl(priv, m, ns);
 1086 done:
 1087         /* Done */
 1088         L2TP_SEQ_CHECK(&priv->seq);
 1089         return (error);
 1090 }
 1091 
 1092 /*
 1093  * Handle an outgoing data frame.
 1094  */
 1095 static int
 1096 ng_l2tp_rcvdata(hook_p hook, item_p item)
 1097 {
 1098         const priv_p priv = NG_NODE_PRIVATE(NG_HOOK_NODE(hook));
 1099         const hookpriv_p hpriv = NG_HOOK_PRIVATE(hook);
 1100         struct mbuf *m;
 1101         u_int16_t hdr;
 1102         int error;
 1103         int i = 1;
 1104 
 1105         /* Sanity check */
 1106         L2TP_SEQ_CHECK(&priv->seq);
 1107 
 1108         /* If not configured, reject */
 1109         if (!priv->conf.enabled) {
 1110                 NG_FREE_ITEM(item);
 1111                 ERROUT(ENXIO);
 1112         }
 1113 
 1114         /* Get mbuf */
 1115         NGI_GET_M(item, m);
 1116 
 1117         /* Check max length */
 1118         if (m->m_pkthdr.len >= 0x10000 - 12) {
 1119                 priv->stats.xmitDataTooBig++;
 1120                 NG_FREE_ITEM(item);
 1121                 NG_FREE_M(m);
 1122                 ERROUT(EOVERFLOW);
 1123         }
 1124 
 1125         /* Prepend L2TP header */
 1126         M_PREPEND(m, 6
 1127             + (2 * (hpriv->conf.include_length != 0))
 1128             + (4 * (hpriv->conf.enable_dseq != 0)),
 1129             M_DONTWAIT);
 1130         if (m == NULL) {
 1131                 priv->stats.memoryFailures++;
 1132                 NG_FREE_ITEM(item);
 1133                 ERROUT(ENOBUFS);
 1134         }
 1135         hdr = L2TP_DATA_HDR;
 1136         if (hpriv->conf.include_length) {
 1137                 hdr |= L2TP_HDR_LEN;
 1138                 mtod(m, u_int16_t *)[i++] = htons(m->m_pkthdr.len);
 1139         }
 1140         mtod(m, u_int16_t *)[i++] = htons(priv->conf.peer_id);
 1141         mtod(m, u_int16_t *)[i++] = htons(hpriv->conf.peer_id);
 1142         if (hpriv->conf.enable_dseq) {
 1143                 hdr |= L2TP_HDR_SEQ;
 1144                 mtod(m, u_int16_t *)[i++] = htons(hpriv->ns);
 1145                 mtod(m, u_int16_t *)[i++] = htons(hpriv->nr);
 1146                 hpriv->ns++;
 1147         }
 1148         mtod(m, u_int16_t *)[0] = htons(hdr);
 1149 
 1150         /* Update per session stats. */
 1151         hpriv->stats.xmitPackets++;
 1152         hpriv->stats.xmitOctets += m->m_pkthdr.len;
 1153 
 1154         /* And the global one. */
 1155         priv->stats.xmitPackets++;
 1156         priv->stats.xmitOctets += m->m_pkthdr.len;
 1157 
 1158         /* Send packet */
 1159         NG_FWD_NEW_DATA(error, item, priv->lower, m);
 1160 done:
 1161         /* Done */
 1162         L2TP_SEQ_CHECK(&priv->seq);
 1163         return (error);
 1164 }
 1165 
 1166 /*
 1167  * Send a message to our controlling node that we've failed.
 1168  */
 1169 static void
 1170 ng_l2tp_seq_failure(priv_p priv)
 1171 {
 1172         struct ng_mesg *msg;
 1173         int error;
 1174 
 1175         NG_MKMESSAGE(msg, NGM_L2TP_COOKIE, NGM_L2TP_ACK_FAILURE, 0, M_NOWAIT);
 1176         if (msg == NULL)
 1177                 return;
 1178         NG_SEND_MSG_ID(error, priv->node, msg, priv->ftarget, 0);
 1179 }
 1180 
 1181 /************************************************************************
 1182                         SEQUENCE NUMBER HANDLING
 1183 ************************************************************************/
 1184 
 1185 /*
 1186  * Initialize sequence number state.
 1187  */
 1188 static void
 1189 ng_l2tp_seq_init(priv_p priv)
 1190 {
 1191         struct l2tp_seq *const seq = &priv->seq;
 1192 
 1193         KASSERT(priv->conf.peer_win >= 1,
 1194             ("%s: peer_win is zero", __func__));
 1195         memset(seq, 0, sizeof(*seq));
 1196         seq->cwnd = 1;
 1197         seq->wmax = priv->conf.peer_win;
 1198         if (seq->wmax > L2TP_MAX_XWIN)
 1199                 seq->wmax = L2TP_MAX_XWIN;
 1200         seq->ssth = seq->wmax;
 1201         ng_callout_init(&seq->rack_timer);
 1202         ng_callout_init(&seq->xack_timer);
 1203         mtx_init(&seq->mtx, "ng_l2tp", NULL, MTX_DEF);
 1204         L2TP_SEQ_CHECK(seq);
 1205 }
 1206 
 1207 /*
 1208  * Set sequence number state as given from user.
 1209  */
 1210 static int
 1211 ng_l2tp_seq_set(priv_p priv, const struct ng_l2tp_seq_config *conf)
 1212 {
 1213         struct l2tp_seq *const seq = &priv->seq;
 1214 
 1215         /* If node is enabled, deny update to sequence numbers. */
 1216         if (priv->conf.enabled)
 1217                 return (EBUSY);
 1218 
 1219         /* We only can handle the simple cases. */
 1220         if (conf->xack != conf->nr || conf->ns != conf->rack)
 1221                 return (EINVAL);
 1222 
 1223         /* Set ns,nr,rack,xack parameters. */
 1224         seq->ns = conf->ns;
 1225         seq->nr = conf->nr;
 1226         seq->rack = conf->rack;
 1227         seq->xack = conf->xack;
 1228 
 1229         return (0);
 1230 }
 1231 
 1232 /*
 1233  * Adjust sequence number state accordingly after reconfiguration.
 1234  */
 1235 static int
 1236 ng_l2tp_seq_adjust(priv_p priv, const struct ng_l2tp_config *conf)
 1237 {
 1238         struct l2tp_seq *const seq = &priv->seq;
 1239         u_int16_t new_wmax;
 1240 
 1241         /* If disabling node, reset state sequence number */
 1242         if (!conf->enabled) {
 1243                 ng_l2tp_seq_reset(priv);
 1244                 return (0);
 1245         }
 1246 
 1247         /* Adjust peer's max recv window; it can only increase */
 1248         new_wmax = conf->peer_win;
 1249         if (new_wmax > L2TP_MAX_XWIN)
 1250                 new_wmax = L2TP_MAX_XWIN;
 1251         if (new_wmax == 0)
 1252                 return (EINVAL);
 1253         if (new_wmax < seq->wmax)
 1254                 return (EBUSY);
 1255         seq->wmax = new_wmax;
 1256 
 1257         /* Done */
 1258         return (0);
 1259 }
 1260 
 1261 /*
 1262  * Reset sequence number state.
 1263  */
 1264 static void
 1265 ng_l2tp_seq_reset(priv_p priv)
 1266 {
 1267         struct l2tp_seq *const seq = &priv->seq;
 1268         hook_p hook;
 1269         int i;
 1270 
 1271         /* Sanity check */
 1272         L2TP_SEQ_CHECK(seq);
 1273 
 1274         /* Stop timers */
 1275         ng_uncallout(&seq->rack_timer, priv->node);
 1276         ng_uncallout(&seq->xack_timer, priv->node);
 1277 
 1278         /* Free retransmit queue */
 1279         for (i = 0; i < L2TP_MAX_XWIN; i++) {
 1280                 if (seq->xwin[i] == NULL)
 1281                         break;
 1282                 m_freem(seq->xwin[i]);
 1283         }
 1284 
 1285         /* Reset session hooks' sequence number states */
 1286         NG_NODE_FOREACH_HOOK(priv->node, ng_l2tp_reset_session, NULL, hook);
 1287 
 1288         /* Reset node's sequence number state */
 1289         seq->ns = 0;
 1290         seq->nr = 0;
 1291         seq->rack = 0;
 1292         seq->xack = 0;
 1293         seq->wmax = L2TP_MAX_XWIN;
 1294         seq->cwnd = 1;
 1295         seq->ssth = seq->wmax;
 1296         seq->acks = 0;
 1297         seq->rexmits = 0;
 1298         bzero(seq->xwin, sizeof(seq->xwin));
 1299 
 1300         /* Done */
 1301         L2TP_SEQ_CHECK(seq);
 1302 }
 1303 
 1304 /*
 1305  * Handle receipt of an acknowledgement value (Nr) from peer.
 1306  */
 1307 static void
 1308 ng_l2tp_seq_recv_nr(priv_p priv, u_int16_t nr)
 1309 {
 1310         struct l2tp_seq *const seq = &priv->seq;
 1311         struct mbuf     *xwin[L2TP_MAX_XWIN];   /* partial local copy */
 1312         int             nack;
 1313         int             i, j;
 1314         uint16_t        ns;
 1315 
 1316         mtx_lock(&seq->mtx);
 1317 
 1318         /* Verify peer's ACK is in range */
 1319         if ((nack = L2TP_SEQ_DIFF(nr, seq->rack)) <= 0) {
 1320                 mtx_unlock(&seq->mtx);
 1321                 return;                         /* duplicate ack */
 1322         }
 1323         if (L2TP_SEQ_DIFF(nr, seq->ns) > 0) {
 1324                 mtx_unlock(&seq->mtx);
 1325                 priv->stats.recvBadAcks++;      /* ack for packet not sent */
 1326                 return;
 1327         }
 1328         KASSERT(nack <= L2TP_MAX_XWIN,
 1329             ("%s: nack=%d > %d", __func__, nack, L2TP_MAX_XWIN));
 1330 
 1331         /* Update receive ack stats */
 1332         seq->rack = nr;
 1333         seq->rexmits = 0;
 1334 
 1335         /* Free acknowledged packets and shift up packets in the xmit queue */
 1336         for (i = 0; i < nack; i++)
 1337                 m_freem(seq->xwin[i]);
 1338         memmove(seq->xwin, seq->xwin + nack,
 1339             (L2TP_MAX_XWIN - nack) * sizeof(*seq->xwin));
 1340         memset(seq->xwin + (L2TP_MAX_XWIN - nack), 0,
 1341             nack * sizeof(*seq->xwin));
 1342 
 1343         /*
 1344          * Do slow-start/congestion avoidance windowing algorithm described
 1345          * in RFC 2661, Appendix A. Here we handle a multiple ACK as if each
 1346          * ACK had arrived separately.
 1347          */
 1348         if (seq->cwnd < seq->wmax) {
 1349 
 1350                 /* Handle slow start phase */
 1351                 if (seq->cwnd < seq->ssth) {
 1352                         seq->cwnd += nack;
 1353                         nack = 0;
 1354                         if (seq->cwnd > seq->ssth) {    /* into cg.av. phase */
 1355                                 nack = seq->cwnd - seq->ssth;
 1356                                 seq->cwnd = seq->ssth;
 1357                         }
 1358                 }
 1359 
 1360                 /* Handle congestion avoidance phase */
 1361                 if (seq->cwnd >= seq->ssth) {
 1362                         seq->acks += nack;
 1363                         while (seq->acks >= seq->cwnd) {
 1364                                 seq->acks -= seq->cwnd;
 1365                                 if (seq->cwnd < seq->wmax)
 1366                                         seq->cwnd++;
 1367                         }
 1368                 }
 1369         }
 1370 
 1371         /* Stop xmit timer */
 1372         if (callout_active(&seq->rack_timer))
 1373                 ng_uncallout(&seq->rack_timer, priv->node);
 1374 
 1375         /* If transmit queue is empty, we're done for now */
 1376         if (seq->xwin[0] == NULL) {
 1377                 mtx_unlock(&seq->mtx);
 1378                 return;
 1379         }
 1380 
 1381         /* Start restransmit timer again */
 1382         ng_callout(&seq->rack_timer, priv->node, NULL,
 1383             hz, ng_l2tp_seq_rack_timeout, NULL, 0);
 1384 
 1385         /*
 1386          * Send more packets, trying to keep peer's receive window full.
 1387          * Make copy of everything we need before lock release.
 1388          */
 1389         ns = seq->ns;
 1390         j = 0;
 1391         while ((i = L2TP_SEQ_DIFF(seq->ns, seq->rack)) < seq->cwnd
 1392             && seq->xwin[i] != NULL) {
 1393                 xwin[j++] = seq->xwin[i];
 1394                 seq->ns++;
 1395         }
 1396 
 1397         mtx_unlock(&seq->mtx);
 1398 
 1399         /*
 1400          * Send prepared.
 1401          * If there is a memory error, pretend packet was sent, as it
 1402          * will get retransmitted later anyway.
 1403          */
 1404         for (i = 0; i < j; i++) {
 1405                 struct mbuf     *m;
 1406                 if ((m = L2TP_COPY_MBUF(xwin[i], M_DONTWAIT)) == NULL)
 1407                         priv->stats.memoryFailures++;
 1408                 else
 1409                         ng_l2tp_xmit_ctrl(priv, m, ns);
 1410                 ns++;
 1411         }
 1412 }
 1413 
 1414 /*
 1415  * Handle an ack timeout. We have an outstanding ack that we
 1416  * were hoping to piggy-back, but haven't, so send a ZLB.
 1417  */
 1418 static void
 1419 ng_l2tp_seq_xack_timeout(node_p node, hook_p hook, void *arg1, int arg2)
 1420 {
 1421         const priv_p priv = NG_NODE_PRIVATE(node);
 1422         struct l2tp_seq *const seq = &priv->seq;
 1423 
 1424         /* Make sure callout is still active before doing anything */
 1425         if (callout_pending(&seq->xack_timer) ||
 1426             (!callout_active(&seq->xack_timer)))
 1427                 return;
 1428 
 1429         /* Sanity check */
 1430         L2TP_SEQ_CHECK(seq);
 1431 
 1432         /* Send a ZLB */
 1433         ng_l2tp_xmit_ctrl(priv, NULL, seq->ns);
 1434 
 1435         /* callout_deactivate() is not needed here 
 1436             as ng_uncallout() was called by ng_l2tp_xmit_ctrl() */
 1437 
 1438         /* Sanity check */
 1439         L2TP_SEQ_CHECK(seq);
 1440 }
 1441 
 1442 /* 
 1443  * Handle a transmit timeout. The peer has failed to respond
 1444  * with an ack for our packet, so retransmit it.
 1445  */
 1446 static void
 1447 ng_l2tp_seq_rack_timeout(node_p node, hook_p hook, void *arg1, int arg2)
 1448 {
 1449         const priv_p priv = NG_NODE_PRIVATE(node);
 1450         struct l2tp_seq *const seq = &priv->seq;
 1451         struct mbuf *m;
 1452         u_int delay;
 1453 
 1454         /* Make sure callout is still active before doing anything */
 1455         if (callout_pending(&seq->rack_timer) ||
 1456             (!callout_active(&seq->rack_timer)))
 1457                 return;
 1458 
 1459         /* Sanity check */
 1460         L2TP_SEQ_CHECK(seq);
 1461 
 1462         priv->stats.xmitRetransmits++;
 1463 
 1464         /* Have we reached the retransmit limit? If so, notify owner. */
 1465         if (seq->rexmits++ >= priv->conf.rexmit_max)
 1466                 ng_l2tp_seq_failure(priv);
 1467 
 1468         /* Restart timer, this time with an increased delay */
 1469         delay = (seq->rexmits > 12) ? (1 << 12) : (1 << seq->rexmits);
 1470         if (delay > priv->conf.rexmit_max_to)
 1471                 delay = priv->conf.rexmit_max_to;
 1472         ng_callout(&seq->rack_timer, node, NULL,
 1473             hz * delay, ng_l2tp_seq_rack_timeout, NULL, 0);
 1474 
 1475         /* Do slow-start/congestion algorithm windowing algorithm */
 1476         seq->ns = seq->rack;
 1477         seq->ssth = (seq->cwnd + 1) / 2;
 1478         seq->cwnd = 1;
 1479         seq->acks = 0;
 1480 
 1481         /* Retransmit oldest unack'd packet */
 1482         if ((m = L2TP_COPY_MBUF(seq->xwin[0], M_DONTWAIT)) == NULL)
 1483                 priv->stats.memoryFailures++;
 1484         else
 1485                 ng_l2tp_xmit_ctrl(priv, m, seq->ns++);
 1486 
 1487         /* callout_deactivate() is not needed here 
 1488             as ng_callout() is getting called each time */
 1489 
 1490         /* Sanity check */
 1491         L2TP_SEQ_CHECK(seq);
 1492 }
 1493 
 1494 /*
 1495  * Transmit a control stream packet, payload optional.
 1496  * The transmit sequence number is not incremented.
 1497  */
 1498 static int
 1499 ng_l2tp_xmit_ctrl(priv_p priv, struct mbuf *m, u_int16_t ns)
 1500 {
 1501         struct l2tp_seq *const seq = &priv->seq;
 1502         u_int16_t session_id = 0;
 1503         int error;
 1504 
 1505         mtx_lock(&seq->mtx);
 1506 
 1507         /* Stop ack timer: we're sending an ack with this packet.
 1508            Doing this before to keep state predictable after error. */
 1509         if (callout_active(&seq->xack_timer))
 1510                 ng_uncallout(&seq->xack_timer, priv->node);
 1511 
 1512         seq->xack = seq->nr;
 1513 
 1514         mtx_unlock(&seq->mtx);
 1515 
 1516         /* If no mbuf passed, send an empty packet (ZLB) */
 1517         if (m == NULL) {
 1518 
 1519                 /* Create a new mbuf for ZLB packet */
 1520                 MGETHDR(m, M_DONTWAIT, MT_DATA);
 1521                 if (m == NULL) {
 1522                         priv->stats.memoryFailures++;
 1523                         return (ENOBUFS);
 1524                 }
 1525                 m->m_len = m->m_pkthdr.len = 12;
 1526                 m->m_pkthdr.rcvif = NULL;
 1527                 priv->stats.xmitZLBs++;
 1528         } else {
 1529 
 1530                 /* Strip off session ID */
 1531                 if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
 1532                         priv->stats.memoryFailures++;
 1533                         return (ENOBUFS);
 1534                 }
 1535                 session_id = (mtod(m, u_int8_t *)[0] << 8) + mtod(m, u_int8_t *)[1];
 1536 
 1537                 /* Make room for L2TP header */
 1538                 M_PREPEND(m, 10, M_DONTWAIT);   /* - 2 + 12 = 10 */
 1539                 if (m == NULL) {
 1540                         priv->stats.memoryFailures++;
 1541                         return (ENOBUFS);
 1542                 }
 1543         }
 1544 
 1545         /* Fill in L2TP header */
 1546         mtod(m, u_int16_t *)[0] = htons(L2TP_CTRL_HDR);
 1547         mtod(m, u_int16_t *)[1] = htons(m->m_pkthdr.len);
 1548         mtod(m, u_int16_t *)[2] = htons(priv->conf.peer_id);
 1549         mtod(m, u_int16_t *)[3] = htons(session_id);
 1550         mtod(m, u_int16_t *)[4] = htons(ns);
 1551         mtod(m, u_int16_t *)[5] = htons(seq->nr);
 1552 
 1553         /* Update sequence number info and stats */
 1554         priv->stats.xmitPackets++;
 1555         priv->stats.xmitOctets += m->m_pkthdr.len;
 1556 
 1557         /* Send packet */
 1558         NG_SEND_DATA_ONLY(error, priv->lower, m);
 1559         return (error);
 1560 }
 1561 
 1562 #ifdef INVARIANTS
 1563 /*
 1564  * Sanity check sequence number state.
 1565  */
 1566 static void
 1567 ng_l2tp_seq_check(struct l2tp_seq *seq)
 1568 {
 1569         int self_unack, peer_unack;
 1570         int i;
 1571 
 1572 #define CHECK(p)        KASSERT((p), ("%s: not: %s", __func__, #p))
 1573 
 1574         mtx_lock(&seq->mtx);
 1575 
 1576         self_unack = L2TP_SEQ_DIFF(seq->nr, seq->xack);
 1577         peer_unack = L2TP_SEQ_DIFF(seq->ns, seq->rack);
 1578         CHECK(seq->wmax <= L2TP_MAX_XWIN);
 1579         CHECK(seq->cwnd >= 1);
 1580         CHECK(seq->cwnd <= seq->wmax);
 1581         CHECK(seq->ssth >= 1);
 1582         CHECK(seq->ssth <= seq->wmax);
 1583         if (seq->cwnd < seq->ssth)
 1584                 CHECK(seq->acks == 0);
 1585         else
 1586                 CHECK(seq->acks <= seq->cwnd);
 1587         CHECK(self_unack >= 0);
 1588         CHECK(peer_unack >= 0);
 1589         CHECK(peer_unack <= seq->wmax);
 1590         CHECK((self_unack == 0) ^ callout_active(&seq->xack_timer));
 1591         CHECK((peer_unack == 0) ^ callout_active(&seq->rack_timer));
 1592         for (i = 0; i < peer_unack; i++)
 1593                 CHECK(seq->xwin[i] != NULL);
 1594         for ( ; i < seq->cwnd; i++)         /* verify peer's recv window full */
 1595                 CHECK(seq->xwin[i] == NULL);
 1596 
 1597         mtx_unlock(&seq->mtx);
 1598 
 1599 #undef CHECK
 1600 }
 1601 #endif  /* INVARIANTS */

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