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: releng/8.3/sys/netgraph/ng_l2tp.c 206658 2010-04-15 12:40:02Z mav $
   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 /* Whether to use m_copypacket() or m_dup() */
  346 #define L2TP_COPY_MBUF          m_copypacket
  347 
  348 #define ERROUT(x)       do { error = (x); goto done; } while (0)
  349 
  350 /************************************************************************
  351                         NETGRAPH NODE STUFF
  352 ************************************************************************/
  353 
  354 /*
  355  * Node type constructor
  356  */
  357 static int
  358 ng_l2tp_constructor(node_p node)
  359 {
  360         priv_p priv;
  361         int     i;
  362 
  363         /* Allocate private structure */
  364         priv = malloc(sizeof(*priv), M_NETGRAPH_L2TP, M_NOWAIT | M_ZERO);
  365         if (priv == NULL)
  366                 return (ENOMEM);
  367         NG_NODE_SET_PRIVATE(node, priv);
  368         priv->node = node;
  369 
  370         /* Apply a semi-reasonable default configuration */
  371         priv->conf.peer_win = 1;
  372         priv->conf.rexmit_max = L2TP_MAX_REXMIT;
  373         priv->conf.rexmit_max_to = L2TP_MAX_REXMIT_TO;
  374 
  375         /* Initialize sequence number state */
  376         ng_l2tp_seq_init(priv);
  377 
  378         for (i = 0; i < SESSHASHSIZE; i++)
  379             LIST_INIT(&priv->sesshash[i]);
  380 
  381         /* Done */
  382         return (0);
  383 }
  384 
  385 /*
  386  * Give our OK for a hook to be added.
  387  */
  388 static int
  389 ng_l2tp_newhook(node_p node, hook_p hook, const char *name)
  390 {
  391         const priv_p priv = NG_NODE_PRIVATE(node);
  392 
  393         /* Check hook name */
  394         if (strcmp(name, NG_L2TP_HOOK_CTRL) == 0) {
  395                 if (priv->ctrl != NULL)
  396                         return (EISCONN);
  397                 priv->ctrl = hook;
  398                 NG_HOOK_SET_RCVDATA(hook, ng_l2tp_rcvdata_ctrl);
  399         } else if (strcmp(name, NG_L2TP_HOOK_LOWER) == 0) {
  400                 if (priv->lower != NULL)
  401                         return (EISCONN);
  402                 priv->lower = hook;
  403                 NG_HOOK_SET_RCVDATA(hook, ng_l2tp_rcvdata_lower);
  404         } else {
  405                 static const char hexdig[16] = "0123456789abcdef";
  406                 u_int16_t session_id;
  407                 hookpriv_p hpriv;
  408                 uint16_t hash;
  409                 const char *hex;
  410                 int i;
  411                 int j;
  412 
  413                 /* Parse hook name to get session ID */
  414                 if (strncmp(name, NG_L2TP_HOOK_SESSION_P,
  415                     sizeof(NG_L2TP_HOOK_SESSION_P) - 1) != 0)
  416                         return (EINVAL);
  417                 hex = name + sizeof(NG_L2TP_HOOK_SESSION_P) - 1;
  418                 for (session_id = i = 0; i < 4; i++) {
  419                         for (j = 0; j < 16 && hex[i] != hexdig[j]; j++);
  420                         if (j == 16)
  421                                 return (EINVAL);
  422                         session_id = (session_id << 4) | j;
  423                 }
  424                 if (hex[i] != '\0')
  425                         return (EINVAL);
  426 
  427                 /* Create hook private structure */
  428                 hpriv = malloc(sizeof(*hpriv),
  429                     M_NETGRAPH_L2TP, M_NOWAIT | M_ZERO);
  430                 if (hpriv == NULL)
  431                         return (ENOMEM);
  432                 hpriv->conf.session_id = session_id;
  433                 hpriv->conf.control_dseq = L2TP_CONTROL_DSEQ;
  434                 hpriv->conf.enable_dseq = L2TP_ENABLE_DSEQ;
  435                 hpriv->hook = hook;
  436                 NG_HOOK_SET_PRIVATE(hook, hpriv);
  437                 hash = SESSHASH(hpriv->conf.session_id);
  438                 LIST_INSERT_HEAD(&priv->sesshash[hash], hpriv, sessions);
  439         }
  440 
  441         /* Done */
  442         return (0);
  443 }
  444 
  445 /*
  446  * Receive a control message.
  447  */
  448 static int
  449 ng_l2tp_rcvmsg(node_p node, item_p item, hook_p lasthook)
  450 {
  451         const priv_p priv = NG_NODE_PRIVATE(node);
  452         struct ng_mesg *resp = NULL;
  453         struct ng_mesg *msg;
  454         int error = 0;
  455 
  456         NGI_GET_MSG(item, msg);
  457         switch (msg->header.typecookie) {
  458         case NGM_L2TP_COOKIE:
  459                 switch (msg->header.cmd) {
  460                 case NGM_L2TP_SET_CONFIG:
  461                     {
  462                         struct ng_l2tp_config *const conf =
  463                                 (struct ng_l2tp_config *)msg->data;
  464 
  465                         /* Check for invalid or illegal config */
  466                         if (msg->header.arglen != sizeof(*conf)) {
  467                                 error = EINVAL;
  468                                 break;
  469                         }
  470                         conf->enabled = !!conf->enabled;
  471                         conf->match_id = !!conf->match_id;
  472                         if (priv->conf.enabled
  473                             && ((priv->conf.tunnel_id != 0
  474                                && conf->tunnel_id != priv->conf.tunnel_id)
  475                               || ((priv->conf.peer_id != 0
  476                                && conf->peer_id != priv->conf.peer_id)))) {
  477                                 error = EBUSY;
  478                                 break;
  479                         }
  480 
  481                         /* Save calling node as failure target */
  482                         priv->ftarget = NGI_RETADDR(item);
  483 
  484                         /* Adjust sequence number state */
  485                         if ((error = ng_l2tp_seq_adjust(priv, conf)) != 0)
  486                                 break;
  487 
  488                         /* Update node's config */
  489                         priv->conf = *conf;
  490                         break;
  491                     }
  492                 case NGM_L2TP_GET_CONFIG:
  493                     {
  494                         struct ng_l2tp_config *conf;
  495 
  496                         NG_MKRESPONSE(resp, msg, sizeof(*conf), M_NOWAIT);
  497                         if (resp == NULL) {
  498                                 error = ENOMEM;
  499                                 break;
  500                         }
  501                         conf = (struct ng_l2tp_config *)resp->data;
  502                         *conf = priv->conf;
  503                         break;
  504                     }
  505                 case NGM_L2TP_SET_SESS_CONFIG:
  506                     {
  507                         struct ng_l2tp_sess_config *const conf =
  508                             (struct ng_l2tp_sess_config *)msg->data;
  509                         hookpriv_p hpriv;
  510 
  511                         /* Check for invalid or illegal config. */
  512                         if (msg->header.arglen != sizeof(*conf)) {
  513                                 error = EINVAL;
  514                                 break;
  515                         }
  516 
  517                         /* Find matching hook */
  518                         hpriv = ng_l2tp_find_session(priv, conf->session_id);
  519                         if (hpriv == NULL) {
  520                                 error = ENOENT;
  521                                 break;
  522                         }
  523 
  524                         /* Update hook's config */
  525                         hpriv->conf = *conf;
  526                         break;
  527                     }
  528                 case NGM_L2TP_GET_SESS_CONFIG:
  529                     {
  530                         struct ng_l2tp_sess_config *conf;
  531                         u_int16_t session_id;
  532                         hookpriv_p hpriv;
  533 
  534                         /* Get session ID */
  535                         if (msg->header.arglen != sizeof(session_id)) {
  536                                 error = EINVAL;
  537                                 break;
  538                         }
  539                         memcpy(&session_id, msg->data, 2);
  540 
  541                         /* Find matching hook */
  542                         hpriv = ng_l2tp_find_session(priv, session_id);
  543                         if (hpriv == NULL) {
  544                                 error = ENOENT;
  545                                 break;
  546                         }
  547 
  548                         /* Send response */
  549                         NG_MKRESPONSE(resp, msg, sizeof(hpriv->conf), M_NOWAIT);
  550                         if (resp == NULL) {
  551                                 error = ENOMEM;
  552                                 break;
  553                         }
  554                         conf = (struct ng_l2tp_sess_config *)resp->data;
  555                         *conf = hpriv->conf;
  556                         break;
  557                     }
  558                 case NGM_L2TP_GET_STATS:
  559                 case NGM_L2TP_CLR_STATS:
  560                 case NGM_L2TP_GETCLR_STATS:
  561                     {
  562                         if (msg->header.cmd != NGM_L2TP_CLR_STATS) {
  563                                 NG_MKRESPONSE(resp, msg,
  564                                     sizeof(priv->stats), M_NOWAIT);
  565                                 if (resp == NULL) {
  566                                         error = ENOMEM;
  567                                         break;
  568                                 }
  569                                 memcpy(resp->data,
  570                                     &priv->stats, sizeof(priv->stats));
  571                         }
  572                         if (msg->header.cmd != NGM_L2TP_GET_STATS)
  573                                 memset(&priv->stats, 0, sizeof(priv->stats));
  574                         break;
  575                     }
  576                 case NGM_L2TP_GET_SESSION_STATS:
  577                 case NGM_L2TP_CLR_SESSION_STATS:
  578                 case NGM_L2TP_GETCLR_SESSION_STATS:
  579                     {
  580                         uint16_t session_id;
  581                         hookpriv_p hpriv;
  582 
  583                         /* Get session ID. */
  584                         if (msg->header.arglen != sizeof(session_id)) {
  585                                 error = EINVAL;
  586                                 break;
  587                         }
  588                         bcopy(msg->data, &session_id, sizeof(uint16_t));
  589 
  590                         /* Find matching hook. */
  591                         hpriv = ng_l2tp_find_session(priv, session_id);
  592                         if (hpriv == NULL) {
  593                                 error = ENOENT;
  594                                 break;
  595                         }
  596 
  597                         if (msg->header.cmd != NGM_L2TP_CLR_SESSION_STATS) {
  598                                 NG_MKRESPONSE(resp, msg,
  599                                     sizeof(hpriv->stats), M_NOWAIT);
  600                                 if (resp == NULL) {
  601                                         error = ENOMEM;
  602                                         break;
  603                                 }
  604                                 bcopy(&hpriv->stats, resp->data,
  605                                         sizeof(hpriv->stats));
  606                         }
  607                         if (msg->header.cmd != NGM_L2TP_GET_SESSION_STATS)
  608                                 bzero(&hpriv->stats, sizeof(hpriv->stats));
  609                         break;
  610                     }
  611                 case NGM_L2TP_SET_SEQ:
  612                     {
  613                         struct ng_l2tp_seq_config *const conf =
  614                                 (struct ng_l2tp_seq_config *)msg->data;
  615 
  616                         /* Check for invalid or illegal seq config. */
  617                         if (msg->header.arglen != sizeof(*conf)) {
  618                                 error = EINVAL;
  619                                 break;
  620                         }
  621                         conf->ns = htons(conf->ns);
  622                         conf->nr = htons(conf->nr);
  623                         conf->rack = htons(conf->rack);
  624                         conf->xack = htons(conf->xack);
  625 
  626                         /* Set sequence numbers. */
  627                         error = ng_l2tp_seq_set(priv, conf);
  628                         break;
  629                     }
  630                 default:
  631                         error = EINVAL;
  632                         break;
  633                 }
  634                 break;
  635         default:
  636                 error = EINVAL;
  637                 break;
  638         }
  639 
  640         /* Done */
  641         NG_RESPOND_MSG(error, node, item, resp);
  642         NG_FREE_MSG(msg);
  643         return (error);
  644 }
  645 
  646 /*
  647  * Destroy node
  648  */
  649 static int
  650 ng_l2tp_shutdown(node_p node)
  651 {
  652         const priv_p priv = NG_NODE_PRIVATE(node);
  653         struct l2tp_seq *const seq = &priv->seq;
  654 
  655         /* Sanity check */
  656         L2TP_SEQ_CHECK(seq);
  657 
  658         /* Reset sequence number state */
  659         ng_l2tp_seq_reset(priv);
  660 
  661         /* Free private data if neither timer is running */
  662         ng_uncallout(&seq->rack_timer, node);
  663         ng_uncallout(&seq->xack_timer, node);
  664 
  665         mtx_destroy(&seq->mtx);
  666 
  667         free(priv, M_NETGRAPH_L2TP);
  668 
  669         /* Unref node */
  670         NG_NODE_UNREF(node);
  671         return (0);
  672 }
  673 
  674 /*
  675  * Hook disconnection
  676  */
  677 static int
  678 ng_l2tp_disconnect(hook_p hook)
  679 {
  680         const node_p node = NG_HOOK_NODE(hook);
  681         const priv_p priv = NG_NODE_PRIVATE(node);
  682 
  683         /* Zero out hook pointer */
  684         if (hook == priv->ctrl)
  685                 priv->ctrl = NULL;
  686         else if (hook == priv->lower)
  687                 priv->lower = NULL;
  688         else {
  689                 const hookpriv_p hpriv = NG_HOOK_PRIVATE(hook);
  690                 LIST_REMOVE(hpriv, sessions);
  691                 free(hpriv, M_NETGRAPH_L2TP);
  692                 NG_HOOK_SET_PRIVATE(hook, NULL);
  693         }
  694 
  695         /* Go away if no longer connected to anything */
  696         if (NG_NODE_NUMHOOKS(node) == 0 && NG_NODE_IS_VALID(node))
  697                 ng_rmnode_self(node);
  698         return (0);
  699 }
  700 
  701 /*************************************************************************
  702                         INTERNAL FUNCTIONS
  703 *************************************************************************/
  704 
  705 /*
  706  * Find the hook with a given session ID.
  707  */
  708 static hookpriv_p
  709 ng_l2tp_find_session(priv_p privp, u_int16_t sid)
  710 {
  711         uint16_t        hash = SESSHASH(sid);
  712         hookpriv_p      hpriv = NULL;
  713 
  714         LIST_FOREACH(hpriv, &privp->sesshash[hash], sessions) {
  715                 if (hpriv->conf.session_id == sid)
  716                         break;
  717         }
  718 
  719         return (hpriv);
  720 }
  721 
  722 /*
  723  * Reset a hook's session state.
  724  */
  725 static int
  726 ng_l2tp_reset_session(hook_p hook, void *arg)
  727 {
  728         const hookpriv_p hpriv = NG_HOOK_PRIVATE(hook);
  729 
  730         if (hpriv != NULL) {
  731                 hpriv->conf.control_dseq = 0;
  732                 hpriv->conf.enable_dseq = 0;
  733                 bzero(&hpriv->stats, sizeof(struct ng_l2tp_session_stats));
  734                 hpriv->nr = 0;
  735                 hpriv->ns = 0;
  736         }
  737         return (-1);
  738 }
  739 
  740 /*
  741  * Handle an incoming frame from below.
  742  */
  743 static int
  744 ng_l2tp_rcvdata_lower(hook_p h, item_p item)
  745 {
  746         static const u_int16_t req_bits[2][2] = {
  747                 { L2TP_DATA_0BITS, L2TP_DATA_1BITS },
  748                 { L2TP_CTRL_0BITS, L2TP_CTRL_1BITS },
  749         };
  750         const node_p node = NG_HOOK_NODE(h);
  751         const priv_p priv = NG_NODE_PRIVATE(node);
  752         hookpriv_p hpriv = NULL;
  753         hook_p hook = NULL;
  754         struct mbuf *m;
  755         u_int16_t tid, sid;
  756         u_int16_t hdr;
  757         u_int16_t ns, nr;
  758         int is_ctrl;
  759         int error;
  760         int len, plen;
  761 
  762         /* Sanity check */
  763         L2TP_SEQ_CHECK(&priv->seq);
  764 
  765         /* If not configured, reject */
  766         if (!priv->conf.enabled) {
  767                 NG_FREE_ITEM(item);
  768                 ERROUT(ENXIO);
  769         }
  770 
  771         /* Grab mbuf */
  772         NGI_GET_M(item, m);
  773 
  774         /* Remember full packet length; needed for per session accounting. */
  775         plen = m->m_pkthdr.len;
  776 
  777         /* Update stats */
  778         priv->stats.recvPackets++;
  779         priv->stats.recvOctets += plen;
  780 
  781         /* Get initial header */
  782         if (m->m_pkthdr.len < 6) {
  783                 priv->stats.recvRunts++;
  784                 NG_FREE_ITEM(item);
  785                 NG_FREE_M(m);
  786                 ERROUT(EINVAL);
  787         }
  788         if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
  789                 priv->stats.memoryFailures++;
  790                 NG_FREE_ITEM(item);
  791                 ERROUT(EINVAL);
  792         }
  793         hdr = (mtod(m, uint8_t *)[0] << 8) + mtod(m, uint8_t *)[1];
  794         m_adj(m, 2);
  795 
  796         /* Check required header bits and minimum length */
  797         is_ctrl = (hdr & L2TP_HDR_CTRL) != 0;
  798         if ((hdr & req_bits[is_ctrl][0]) != 0
  799             || (~hdr & req_bits[is_ctrl][1]) != 0) {
  800                 priv->stats.recvInvalid++;
  801                 NG_FREE_ITEM(item);
  802                 NG_FREE_M(m);
  803                 ERROUT(EINVAL);
  804         }
  805         if (m->m_pkthdr.len < 4                         /* tunnel, session id */
  806             + (2 * ((hdr & L2TP_HDR_LEN) != 0))         /* length field */
  807             + (4 * ((hdr & L2TP_HDR_SEQ) != 0))         /* seq # fields */
  808             + (2 * ((hdr & L2TP_HDR_OFF) != 0))) {      /* offset field */
  809                 priv->stats.recvRunts++;
  810                 NG_FREE_ITEM(item);
  811                 NG_FREE_M(m);
  812                 ERROUT(EINVAL);
  813         }
  814 
  815         /* Get and validate length field if present */
  816         if ((hdr & L2TP_HDR_LEN) != 0) {
  817                 if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
  818                         priv->stats.memoryFailures++;
  819                         NG_FREE_ITEM(item);
  820                         ERROUT(EINVAL);
  821                 }
  822                 len = (mtod(m, uint8_t *)[0] << 8) + mtod(m, uint8_t *)[1] - 4;
  823                 m_adj(m, 2);
  824                 if (len < 0 || len > m->m_pkthdr.len) {
  825                         priv->stats.recvInvalid++;
  826                         NG_FREE_ITEM(item);
  827                         NG_FREE_M(m);
  828                         ERROUT(EINVAL);
  829                 }
  830                 if (len < m->m_pkthdr.len)              /* trim extra bytes */
  831                         m_adj(m, -(m->m_pkthdr.len - len));
  832         }
  833 
  834         /* Get tunnel ID and session ID */
  835         if (m->m_len < 4 && (m = m_pullup(m, 4)) == NULL) {
  836                 priv->stats.memoryFailures++;
  837                 NG_FREE_ITEM(item);
  838                 ERROUT(EINVAL);
  839         }
  840         tid = (mtod(m, u_int8_t *)[0] << 8) + mtod(m, u_int8_t *)[1];
  841         sid = (mtod(m, u_int8_t *)[2] << 8) + mtod(m, u_int8_t *)[3];
  842         m_adj(m, 4);
  843 
  844         /* Check tunnel ID */
  845         if (tid != priv->conf.tunnel_id &&
  846             (priv->conf.match_id || tid != 0)) {
  847                 priv->stats.recvWrongTunnel++;
  848                 NG_FREE_ITEM(item);
  849                 NG_FREE_M(m);
  850                 ERROUT(EADDRNOTAVAIL);
  851         }
  852 
  853         /* Check session ID (for data packets only) */
  854         if ((hdr & L2TP_HDR_CTRL) == 0) {
  855                 hpriv = ng_l2tp_find_session(priv, sid);
  856                 if (hpriv == NULL) {
  857                         priv->stats.recvUnknownSID++;
  858                         NG_FREE_ITEM(item);
  859                         NG_FREE_M(m);
  860                         ERROUT(ENOTCONN);
  861                 }
  862                 hook = hpriv->hook;
  863         }
  864 
  865         /* Get Ns, Nr fields if present */
  866         if ((hdr & L2TP_HDR_SEQ) != 0) {
  867                 if (m->m_len < 4 && (m = m_pullup(m, 4)) == NULL) {
  868                         priv->stats.memoryFailures++;
  869                         NG_FREE_ITEM(item);
  870                         ERROUT(EINVAL);
  871                 }
  872                 ns = (mtod(m, u_int8_t *)[0] << 8) + mtod(m, u_int8_t *)[1];
  873                 nr = (mtod(m, u_int8_t *)[2] << 8) + mtod(m, u_int8_t *)[3];
  874                 m_adj(m, 4);
  875         } else
  876                 ns = nr = 0;
  877 
  878         /* Strip offset padding if present */
  879         if ((hdr & L2TP_HDR_OFF) != 0) {
  880                 u_int16_t offset;
  881 
  882                 /* Get length of offset padding */
  883                 if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
  884                         priv->stats.memoryFailures++;
  885                         NG_FREE_ITEM(item);
  886                         ERROUT(EINVAL);
  887                 }
  888                 offset = (mtod(m, u_int8_t *)[0] << 8) + mtod(m, u_int8_t *)[1];
  889 
  890                 /* Trim offset padding */
  891                 if ((2+offset) > m->m_pkthdr.len) {
  892                         priv->stats.recvInvalid++;
  893                         NG_FREE_ITEM(item);
  894                         NG_FREE_M(m);
  895                         ERROUT(EINVAL);
  896                 }
  897                 m_adj(m, 2+offset);
  898         }
  899 
  900         /* Handle control packets */
  901         if ((hdr & L2TP_HDR_CTRL) != 0) {
  902                 struct l2tp_seq *const seq = &priv->seq;
  903 
  904                 /* Handle receive ack sequence number Nr */
  905                 ng_l2tp_seq_recv_nr(priv, nr);
  906 
  907                 /* Discard ZLB packets */
  908                 if (m->m_pkthdr.len == 0) {
  909                         priv->stats.recvZLBs++;
  910                         NG_FREE_ITEM(item);
  911                         NG_FREE_M(m);
  912                         ERROUT(0);
  913                 }
  914 
  915                 mtx_lock(&seq->mtx);
  916                 /*
  917                  * If not what we expect or we are busy, drop packet and
  918                  * send an immediate ZLB ack.
  919                  */
  920                 if (ns != seq->nr || seq->inproc) {
  921                         if (L2TP_SEQ_DIFF(ns, seq->nr) <= 0)
  922                                 priv->stats.recvDuplicates++;
  923                         else
  924                                 priv->stats.recvOutOfOrder++;
  925                         mtx_unlock(&seq->mtx);
  926                         ng_l2tp_xmit_ctrl(priv, NULL, seq->ns);
  927                         NG_FREE_ITEM(item);
  928                         NG_FREE_M(m);
  929                         ERROUT(0);
  930                 }
  931                 /*
  932                  * Until we deliver this packet we can't receive next one as
  933                  * we have no information for sending ack.
  934                  */
  935                 seq->inproc = 1;
  936                 mtx_unlock(&seq->mtx);
  937 
  938                 /* Prepend session ID to packet. */
  939                 M_PREPEND(m, 2, M_DONTWAIT);
  940                 if (m == NULL) {
  941                         seq->inproc = 0;
  942                         priv->stats.memoryFailures++;
  943                         NG_FREE_ITEM(item);
  944                         ERROUT(ENOBUFS);
  945                 }
  946                 mtod(m, u_int8_t *)[0] = sid >> 8;
  947                 mtod(m, u_int8_t *)[1] = sid & 0xff;
  948 
  949                 /* Deliver packet to upper layers */
  950                 NG_FWD_NEW_DATA(error, item, priv->ctrl, m);
  951                 
  952                 mtx_lock(&seq->mtx);
  953                 /* Ready to process next packet. */
  954                 seq->inproc = 0;
  955 
  956                 /* If packet was successfully delivered send ack. */
  957                 if (error == 0) {
  958                         /* Update recv sequence number */
  959                         seq->nr++;
  960                         /* Start receive ack timer, if not already running */
  961                         if (!callout_active(&seq->xack_timer)) {
  962                                 ng_callout(&seq->xack_timer, priv->node, NULL,
  963                                     L2TP_DELAYED_ACK, ng_l2tp_seq_xack_timeout,
  964                                     NULL, 0);
  965                         }
  966                 }
  967                 mtx_unlock(&seq->mtx);
  968 
  969                 ERROUT(error);
  970         }
  971 
  972         /* Per session packet, account it. */
  973         hpriv->stats.recvPackets++;
  974         hpriv->stats.recvOctets += plen;
  975 
  976         /* Follow peer's lead in data sequencing, if configured to do so */
  977         if (!hpriv->conf.control_dseq)
  978                 hpriv->conf.enable_dseq = ((hdr & L2TP_HDR_SEQ) != 0);
  979 
  980         /* Handle data sequence numbers if present and enabled */
  981         if ((hdr & L2TP_HDR_SEQ) != 0) {
  982                 if (hpriv->conf.enable_dseq
  983                     && L2TP_SEQ_DIFF(ns, hpriv->nr) < 0) {
  984                         NG_FREE_ITEM(item);     /* duplicate or out of order */
  985                         NG_FREE_M(m);
  986                         priv->stats.recvDataDrops++;
  987                         ERROUT(0);
  988                 }
  989                 hpriv->nr = ns + 1;
  990         }
  991 
  992         /* Drop empty data packets */
  993         if (m->m_pkthdr.len == 0) {
  994                 NG_FREE_ITEM(item);
  995                 NG_FREE_M(m);
  996                 ERROUT(0);
  997         }
  998 
  999         /* Deliver data */
 1000         NG_FWD_NEW_DATA(error, item, hook, m);
 1001 done:
 1002         /* Done */
 1003         L2TP_SEQ_CHECK(&priv->seq);
 1004         return (error);
 1005 }
 1006 
 1007 /*
 1008  * Handle an outgoing control frame.
 1009  */
 1010 static int
 1011 ng_l2tp_rcvdata_ctrl(hook_p hook, item_p item)
 1012 {
 1013         const node_p node = NG_HOOK_NODE(hook);
 1014         const priv_p priv = NG_NODE_PRIVATE(node);
 1015         struct l2tp_seq *const seq = &priv->seq;
 1016         struct mbuf *m;
 1017         int error;
 1018         int i;
 1019         u_int16_t       ns;
 1020 
 1021         /* Sanity check */
 1022         L2TP_SEQ_CHECK(&priv->seq);
 1023 
 1024         /* If not configured, reject */
 1025         if (!priv->conf.enabled) {
 1026                 NG_FREE_ITEM(item);
 1027                 ERROUT(ENXIO);
 1028         }
 1029 
 1030         /* Grab mbuf and discard other stuff XXX */
 1031         NGI_GET_M(item, m);
 1032         NG_FREE_ITEM(item);
 1033 
 1034         /* Packet should have session ID prepended */
 1035         if (m->m_pkthdr.len < 2) {
 1036                 priv->stats.xmitInvalid++;
 1037                 m_freem(m);
 1038                 ERROUT(EINVAL);
 1039         }
 1040 
 1041         /* Check max length */
 1042         if (m->m_pkthdr.len >= 0x10000 - 14) {
 1043                 priv->stats.xmitTooBig++;
 1044                 m_freem(m);
 1045                 ERROUT(EOVERFLOW);
 1046         }
 1047 
 1048         mtx_lock(&seq->mtx);
 1049 
 1050         /* Find next empty slot in transmit queue */
 1051         for (i = 0; i < L2TP_MAX_XWIN && seq->xwin[i] != NULL; i++);
 1052         if (i == L2TP_MAX_XWIN) {
 1053                 mtx_unlock(&seq->mtx);
 1054                 priv->stats.xmitDrops++;
 1055                 m_freem(m);
 1056                 ERROUT(ENOBUFS);
 1057         }
 1058         seq->xwin[i] = m;
 1059 
 1060         /* If peer's receive window is already full, nothing else to do */
 1061         if (i >= seq->cwnd) {
 1062                 mtx_unlock(&seq->mtx);
 1063                 ERROUT(0);
 1064         }
 1065 
 1066         /* Start retransmit timer if not already running */
 1067         if (!callout_active(&seq->rack_timer))
 1068                 ng_callout(&seq->rack_timer, node, NULL,
 1069                     hz, ng_l2tp_seq_rack_timeout, NULL, 0);
 1070         
 1071         ns = seq->ns++;
 1072         
 1073         mtx_unlock(&seq->mtx);
 1074 
 1075         /* Copy packet */
 1076         if ((m = L2TP_COPY_MBUF(m, M_DONTWAIT)) == NULL) {
 1077                 priv->stats.memoryFailures++;
 1078                 ERROUT(ENOBUFS);
 1079         }
 1080 
 1081         /* Send packet and increment xmit sequence number */
 1082         error = ng_l2tp_xmit_ctrl(priv, m, ns);
 1083 done:
 1084         /* Done */
 1085         L2TP_SEQ_CHECK(&priv->seq);
 1086         return (error);
 1087 }
 1088 
 1089 /*
 1090  * Handle an outgoing data frame.
 1091  */
 1092 static int
 1093 ng_l2tp_rcvdata(hook_p hook, item_p item)
 1094 {
 1095         const priv_p priv = NG_NODE_PRIVATE(NG_HOOK_NODE(hook));
 1096         const hookpriv_p hpriv = NG_HOOK_PRIVATE(hook);
 1097         struct mbuf *m;
 1098         uint8_t *p;
 1099         u_int16_t hdr;
 1100         int error;
 1101         int i = 2;
 1102 
 1103         /* Sanity check */
 1104         L2TP_SEQ_CHECK(&priv->seq);
 1105 
 1106         /* If not configured, reject */
 1107         if (!priv->conf.enabled) {
 1108                 NG_FREE_ITEM(item);
 1109                 ERROUT(ENXIO);
 1110         }
 1111 
 1112         /* Get mbuf */
 1113         NGI_GET_M(item, m);
 1114 
 1115         /* Check max length */
 1116         if (m->m_pkthdr.len >= 0x10000 - 12) {
 1117                 priv->stats.xmitDataTooBig++;
 1118                 NG_FREE_ITEM(item);
 1119                 NG_FREE_M(m);
 1120                 ERROUT(EOVERFLOW);
 1121         }
 1122 
 1123         /* Prepend L2TP header */
 1124         M_PREPEND(m, 6
 1125             + (2 * (hpriv->conf.include_length != 0))
 1126             + (4 * (hpriv->conf.enable_dseq != 0)),
 1127             M_DONTWAIT);
 1128         if (m == NULL) {
 1129                 priv->stats.memoryFailures++;
 1130                 NG_FREE_ITEM(item);
 1131                 ERROUT(ENOBUFS);
 1132         }
 1133         p = mtod(m, uint8_t *);
 1134         hdr = L2TP_DATA_HDR;
 1135         if (hpriv->conf.include_length) {
 1136                 hdr |= L2TP_HDR_LEN;
 1137                 p[i++] = m->m_pkthdr.len >> 8;
 1138                 p[i++] = m->m_pkthdr.len & 0xff;
 1139         }
 1140         p[i++] = priv->conf.peer_id >> 8;
 1141         p[i++] = priv->conf.peer_id & 0xff;
 1142         p[i++] = hpriv->conf.peer_id >> 8;
 1143         p[i++] = hpriv->conf.peer_id & 0xff;
 1144         if (hpriv->conf.enable_dseq) {
 1145                 hdr |= L2TP_HDR_SEQ;
 1146                 p[i++] = hpriv->ns >> 8;
 1147                 p[i++] = hpriv->ns & 0xff;
 1148                 p[i++] = hpriv->nr >> 8;
 1149                 p[i++] = hpriv->nr & 0xff;
 1150                 hpriv->ns++;
 1151         }
 1152         p[0] = hdr >> 8;
 1153         p[1] = hdr & 0xff;
 1154 
 1155         /* Update per session stats. */
 1156         hpriv->stats.xmitPackets++;
 1157         hpriv->stats.xmitOctets += m->m_pkthdr.len;
 1158 
 1159         /* And the global one. */
 1160         priv->stats.xmitPackets++;
 1161         priv->stats.xmitOctets += m->m_pkthdr.len;
 1162 
 1163         /* Send packet */
 1164         NG_FWD_NEW_DATA(error, item, priv->lower, m);
 1165 done:
 1166         /* Done */
 1167         L2TP_SEQ_CHECK(&priv->seq);
 1168         return (error);
 1169 }
 1170 
 1171 /*
 1172  * Send a message to our controlling node that we've failed.
 1173  */
 1174 static void
 1175 ng_l2tp_seq_failure(priv_p priv)
 1176 {
 1177         struct ng_mesg *msg;
 1178         int error;
 1179 
 1180         NG_MKMESSAGE(msg, NGM_L2TP_COOKIE, NGM_L2TP_ACK_FAILURE, 0, M_NOWAIT);
 1181         if (msg == NULL)
 1182                 return;
 1183         NG_SEND_MSG_ID(error, priv->node, msg, priv->ftarget, 0);
 1184 }
 1185 
 1186 /************************************************************************
 1187                         SEQUENCE NUMBER HANDLING
 1188 ************************************************************************/
 1189 
 1190 /*
 1191  * Initialize sequence number state.
 1192  */
 1193 static void
 1194 ng_l2tp_seq_init(priv_p priv)
 1195 {
 1196         struct l2tp_seq *const seq = &priv->seq;
 1197 
 1198         KASSERT(priv->conf.peer_win >= 1,
 1199             ("%s: peer_win is zero", __func__));
 1200         memset(seq, 0, sizeof(*seq));
 1201         seq->cwnd = 1;
 1202         seq->wmax = priv->conf.peer_win;
 1203         if (seq->wmax > L2TP_MAX_XWIN)
 1204                 seq->wmax = L2TP_MAX_XWIN;
 1205         seq->ssth = seq->wmax;
 1206         ng_callout_init(&seq->rack_timer);
 1207         ng_callout_init(&seq->xack_timer);
 1208         mtx_init(&seq->mtx, "ng_l2tp", NULL, MTX_DEF);
 1209         L2TP_SEQ_CHECK(seq);
 1210 }
 1211 
 1212 /*
 1213  * Set sequence number state as given from user.
 1214  */
 1215 static int
 1216 ng_l2tp_seq_set(priv_p priv, const struct ng_l2tp_seq_config *conf)
 1217 {
 1218         struct l2tp_seq *const seq = &priv->seq;
 1219 
 1220         /* If node is enabled, deny update to sequence numbers. */
 1221         if (priv->conf.enabled)
 1222                 return (EBUSY);
 1223 
 1224         /* We only can handle the simple cases. */
 1225         if (conf->xack != conf->nr || conf->ns != conf->rack)
 1226                 return (EINVAL);
 1227 
 1228         /* Set ns,nr,rack,xack parameters. */
 1229         seq->ns = conf->ns;
 1230         seq->nr = conf->nr;
 1231         seq->rack = conf->rack;
 1232         seq->xack = conf->xack;
 1233 
 1234         return (0);
 1235 }
 1236 
 1237 /*
 1238  * Adjust sequence number state accordingly after reconfiguration.
 1239  */
 1240 static int
 1241 ng_l2tp_seq_adjust(priv_p priv, const struct ng_l2tp_config *conf)
 1242 {
 1243         struct l2tp_seq *const seq = &priv->seq;
 1244         u_int16_t new_wmax;
 1245 
 1246         /* If disabling node, reset state sequence number */
 1247         if (!conf->enabled) {
 1248                 ng_l2tp_seq_reset(priv);
 1249                 return (0);
 1250         }
 1251 
 1252         /* Adjust peer's max recv window; it can only increase */
 1253         new_wmax = conf->peer_win;
 1254         if (new_wmax > L2TP_MAX_XWIN)
 1255                 new_wmax = L2TP_MAX_XWIN;
 1256         if (new_wmax == 0)
 1257                 return (EINVAL);
 1258         if (new_wmax < seq->wmax)
 1259                 return (EBUSY);
 1260         seq->wmax = new_wmax;
 1261 
 1262         /* Done */
 1263         return (0);
 1264 }
 1265 
 1266 /*
 1267  * Reset sequence number state.
 1268  */
 1269 static void
 1270 ng_l2tp_seq_reset(priv_p priv)
 1271 {
 1272         struct l2tp_seq *const seq = &priv->seq;
 1273         hook_p hook;
 1274         int i;
 1275 
 1276         /* Sanity check */
 1277         L2TP_SEQ_CHECK(seq);
 1278 
 1279         /* Stop timers */
 1280         ng_uncallout(&seq->rack_timer, priv->node);
 1281         ng_uncallout(&seq->xack_timer, priv->node);
 1282 
 1283         /* Free retransmit queue */
 1284         for (i = 0; i < L2TP_MAX_XWIN; i++) {
 1285                 if (seq->xwin[i] == NULL)
 1286                         break;
 1287                 m_freem(seq->xwin[i]);
 1288         }
 1289 
 1290         /* Reset session hooks' sequence number states */
 1291         NG_NODE_FOREACH_HOOK(priv->node, ng_l2tp_reset_session, NULL, hook);
 1292 
 1293         /* Reset node's sequence number state */
 1294         seq->ns = 0;
 1295         seq->nr = 0;
 1296         seq->rack = 0;
 1297         seq->xack = 0;
 1298         seq->wmax = L2TP_MAX_XWIN;
 1299         seq->cwnd = 1;
 1300         seq->ssth = seq->wmax;
 1301         seq->acks = 0;
 1302         seq->rexmits = 0;
 1303         bzero(seq->xwin, sizeof(seq->xwin));
 1304 
 1305         /* Done */
 1306         L2TP_SEQ_CHECK(seq);
 1307 }
 1308 
 1309 /*
 1310  * Handle receipt of an acknowledgement value (Nr) from peer.
 1311  */
 1312 static void
 1313 ng_l2tp_seq_recv_nr(priv_p priv, u_int16_t nr)
 1314 {
 1315         struct l2tp_seq *const seq = &priv->seq;
 1316         struct mbuf     *xwin[L2TP_MAX_XWIN];   /* partial local copy */
 1317         int             nack;
 1318         int             i, j;
 1319         uint16_t        ns;
 1320 
 1321         mtx_lock(&seq->mtx);
 1322 
 1323         /* Verify peer's ACK is in range */
 1324         if ((nack = L2TP_SEQ_DIFF(nr, seq->rack)) <= 0) {
 1325                 mtx_unlock(&seq->mtx);
 1326                 return;                         /* duplicate ack */
 1327         }
 1328         if (L2TP_SEQ_DIFF(nr, seq->ns) > 0) {
 1329                 mtx_unlock(&seq->mtx);
 1330                 priv->stats.recvBadAcks++;      /* ack for packet not sent */
 1331                 return;
 1332         }
 1333         KASSERT(nack <= L2TP_MAX_XWIN,
 1334             ("%s: nack=%d > %d", __func__, nack, L2TP_MAX_XWIN));
 1335 
 1336         /* Update receive ack stats */
 1337         seq->rack = nr;
 1338         seq->rexmits = 0;
 1339 
 1340         /* Free acknowledged packets and shift up packets in the xmit queue */
 1341         for (i = 0; i < nack; i++)
 1342                 m_freem(seq->xwin[i]);
 1343         memmove(seq->xwin, seq->xwin + nack,
 1344             (L2TP_MAX_XWIN - nack) * sizeof(*seq->xwin));
 1345         memset(seq->xwin + (L2TP_MAX_XWIN - nack), 0,
 1346             nack * sizeof(*seq->xwin));
 1347 
 1348         /*
 1349          * Do slow-start/congestion avoidance windowing algorithm described
 1350          * in RFC 2661, Appendix A. Here we handle a multiple ACK as if each
 1351          * ACK had arrived separately.
 1352          */
 1353         if (seq->cwnd < seq->wmax) {
 1354 
 1355                 /* Handle slow start phase */
 1356                 if (seq->cwnd < seq->ssth) {
 1357                         seq->cwnd += nack;
 1358                         nack = 0;
 1359                         if (seq->cwnd > seq->ssth) {    /* into cg.av. phase */
 1360                                 nack = seq->cwnd - seq->ssth;
 1361                                 seq->cwnd = seq->ssth;
 1362                         }
 1363                 }
 1364 
 1365                 /* Handle congestion avoidance phase */
 1366                 if (seq->cwnd >= seq->ssth) {
 1367                         seq->acks += nack;
 1368                         while (seq->acks >= seq->cwnd) {
 1369                                 seq->acks -= seq->cwnd;
 1370                                 if (seq->cwnd < seq->wmax)
 1371                                         seq->cwnd++;
 1372                         }
 1373                 }
 1374         }
 1375 
 1376         /* Stop xmit timer */
 1377         if (callout_active(&seq->rack_timer))
 1378                 ng_uncallout(&seq->rack_timer, priv->node);
 1379 
 1380         /* If transmit queue is empty, we're done for now */
 1381         if (seq->xwin[0] == NULL) {
 1382                 mtx_unlock(&seq->mtx);
 1383                 return;
 1384         }
 1385 
 1386         /* Start restransmit timer again */
 1387         ng_callout(&seq->rack_timer, priv->node, NULL,
 1388             hz, ng_l2tp_seq_rack_timeout, NULL, 0);
 1389 
 1390         /*
 1391          * Send more packets, trying to keep peer's receive window full.
 1392          * Make copy of everything we need before lock release.
 1393          */
 1394         ns = seq->ns;
 1395         j = 0;
 1396         while ((i = L2TP_SEQ_DIFF(seq->ns, seq->rack)) < seq->cwnd
 1397             && seq->xwin[i] != NULL) {
 1398                 xwin[j++] = seq->xwin[i];
 1399                 seq->ns++;
 1400         }
 1401 
 1402         mtx_unlock(&seq->mtx);
 1403 
 1404         /*
 1405          * Send prepared.
 1406          * If there is a memory error, pretend packet was sent, as it
 1407          * will get retransmitted later anyway.
 1408          */
 1409         for (i = 0; i < j; i++) {
 1410                 struct mbuf     *m;
 1411                 if ((m = L2TP_COPY_MBUF(xwin[i], M_DONTWAIT)) == NULL)
 1412                         priv->stats.memoryFailures++;
 1413                 else
 1414                         ng_l2tp_xmit_ctrl(priv, m, ns);
 1415                 ns++;
 1416         }
 1417 }
 1418 
 1419 /*
 1420  * Handle an ack timeout. We have an outstanding ack that we
 1421  * were hoping to piggy-back, but haven't, so send a ZLB.
 1422  */
 1423 static void
 1424 ng_l2tp_seq_xack_timeout(node_p node, hook_p hook, void *arg1, int arg2)
 1425 {
 1426         const priv_p priv = NG_NODE_PRIVATE(node);
 1427         struct l2tp_seq *const seq = &priv->seq;
 1428 
 1429         /* Make sure callout is still active before doing anything */
 1430         if (callout_pending(&seq->xack_timer) ||
 1431             (!callout_active(&seq->xack_timer)))
 1432                 return;
 1433 
 1434         /* Sanity check */
 1435         L2TP_SEQ_CHECK(seq);
 1436 
 1437         /* Send a ZLB */
 1438         ng_l2tp_xmit_ctrl(priv, NULL, seq->ns);
 1439 
 1440         /* callout_deactivate() is not needed here 
 1441             as ng_uncallout() was called by ng_l2tp_xmit_ctrl() */
 1442 
 1443         /* Sanity check */
 1444         L2TP_SEQ_CHECK(seq);
 1445 }
 1446 
 1447 /* 
 1448  * Handle a transmit timeout. The peer has failed to respond
 1449  * with an ack for our packet, so retransmit it.
 1450  */
 1451 static void
 1452 ng_l2tp_seq_rack_timeout(node_p node, hook_p hook, void *arg1, int arg2)
 1453 {
 1454         const priv_p priv = NG_NODE_PRIVATE(node);
 1455         struct l2tp_seq *const seq = &priv->seq;
 1456         struct mbuf *m;
 1457         u_int delay;
 1458 
 1459         /* Make sure callout is still active before doing anything */
 1460         if (callout_pending(&seq->rack_timer) ||
 1461             (!callout_active(&seq->rack_timer)))
 1462                 return;
 1463 
 1464         /* Sanity check */
 1465         L2TP_SEQ_CHECK(seq);
 1466 
 1467         priv->stats.xmitRetransmits++;
 1468 
 1469         /* Have we reached the retransmit limit? If so, notify owner. */
 1470         if (seq->rexmits++ >= priv->conf.rexmit_max)
 1471                 ng_l2tp_seq_failure(priv);
 1472 
 1473         /* Restart timer, this time with an increased delay */
 1474         delay = (seq->rexmits > 12) ? (1 << 12) : (1 << seq->rexmits);
 1475         if (delay > priv->conf.rexmit_max_to)
 1476                 delay = priv->conf.rexmit_max_to;
 1477         ng_callout(&seq->rack_timer, node, NULL,
 1478             hz * delay, ng_l2tp_seq_rack_timeout, NULL, 0);
 1479 
 1480         /* Do slow-start/congestion algorithm windowing algorithm */
 1481         seq->ns = seq->rack;
 1482         seq->ssth = (seq->cwnd + 1) / 2;
 1483         seq->cwnd = 1;
 1484         seq->acks = 0;
 1485 
 1486         /* Retransmit oldest unack'd packet */
 1487         if ((m = L2TP_COPY_MBUF(seq->xwin[0], M_DONTWAIT)) == NULL)
 1488                 priv->stats.memoryFailures++;
 1489         else
 1490                 ng_l2tp_xmit_ctrl(priv, m, seq->ns++);
 1491 
 1492         /* callout_deactivate() is not needed here 
 1493             as ng_callout() is getting called each time */
 1494 
 1495         /* Sanity check */
 1496         L2TP_SEQ_CHECK(seq);
 1497 }
 1498 
 1499 /*
 1500  * Transmit a control stream packet, payload optional.
 1501  * The transmit sequence number is not incremented.
 1502  */
 1503 static int
 1504 ng_l2tp_xmit_ctrl(priv_p priv, struct mbuf *m, u_int16_t ns)
 1505 {
 1506         struct l2tp_seq *const seq = &priv->seq;
 1507         uint8_t *p;
 1508         u_int16_t session_id = 0;
 1509         int error;
 1510 
 1511         mtx_lock(&seq->mtx);
 1512 
 1513         /* Stop ack timer: we're sending an ack with this packet.
 1514            Doing this before to keep state predictable after error. */
 1515         if (callout_active(&seq->xack_timer))
 1516                 ng_uncallout(&seq->xack_timer, priv->node);
 1517 
 1518         seq->xack = seq->nr;
 1519 
 1520         mtx_unlock(&seq->mtx);
 1521 
 1522         /* If no mbuf passed, send an empty packet (ZLB) */
 1523         if (m == NULL) {
 1524 
 1525                 /* Create a new mbuf for ZLB packet */
 1526                 MGETHDR(m, M_DONTWAIT, MT_DATA);
 1527                 if (m == NULL) {
 1528                         priv->stats.memoryFailures++;
 1529                         return (ENOBUFS);
 1530                 }
 1531                 m->m_len = m->m_pkthdr.len = 12;
 1532                 m->m_pkthdr.rcvif = NULL;
 1533                 priv->stats.xmitZLBs++;
 1534         } else {
 1535 
 1536                 /* Strip off session ID */
 1537                 if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
 1538                         priv->stats.memoryFailures++;
 1539                         return (ENOBUFS);
 1540                 }
 1541                 session_id = (mtod(m, u_int8_t *)[0] << 8) + mtod(m, u_int8_t *)[1];
 1542 
 1543                 /* Make room for L2TP header */
 1544                 M_PREPEND(m, 10, M_DONTWAIT);   /* - 2 + 12 = 10 */
 1545                 if (m == NULL) {
 1546                         priv->stats.memoryFailures++;
 1547                         return (ENOBUFS);
 1548                 }
 1549         }
 1550 
 1551         /* Fill in L2TP header */
 1552         p = mtod(m, u_int8_t *);
 1553         p[0] = L2TP_CTRL_HDR >> 8;
 1554         p[1] = L2TP_CTRL_HDR & 0xff;
 1555         p[2] = m->m_pkthdr.len >> 8;
 1556         p[3] = m->m_pkthdr.len & 0xff;
 1557         p[4] = priv->conf.peer_id >> 8;
 1558         p[5] = priv->conf.peer_id & 0xff;
 1559         p[6] = session_id >> 8;
 1560         p[7] = session_id & 0xff;
 1561         p[8] = ns >> 8;
 1562         p[9] = ns & 0xff;
 1563         p[10] = seq->nr >> 8;
 1564         p[11] = seq->nr & 0xff;
 1565 
 1566         /* Update sequence number info and stats */
 1567         priv->stats.xmitPackets++;
 1568         priv->stats.xmitOctets += m->m_pkthdr.len;
 1569 
 1570         /* Send packet */
 1571         NG_SEND_DATA_ONLY(error, priv->lower, m);
 1572         return (error);
 1573 }
 1574 
 1575 #ifdef INVARIANTS
 1576 /*
 1577  * Sanity check sequence number state.
 1578  */
 1579 static void
 1580 ng_l2tp_seq_check(struct l2tp_seq *seq)
 1581 {
 1582         int self_unack, peer_unack;
 1583         int i;
 1584 
 1585 #define CHECK(p)        KASSERT((p), ("%s: not: %s", __func__, #p))
 1586 
 1587         mtx_lock(&seq->mtx);
 1588 
 1589         self_unack = L2TP_SEQ_DIFF(seq->nr, seq->xack);
 1590         peer_unack = L2TP_SEQ_DIFF(seq->ns, seq->rack);
 1591         CHECK(seq->wmax <= L2TP_MAX_XWIN);
 1592         CHECK(seq->cwnd >= 1);
 1593         CHECK(seq->cwnd <= seq->wmax);
 1594         CHECK(seq->ssth >= 1);
 1595         CHECK(seq->ssth <= seq->wmax);
 1596         if (seq->cwnd < seq->ssth)
 1597                 CHECK(seq->acks == 0);
 1598         else
 1599                 CHECK(seq->acks <= seq->cwnd);
 1600         CHECK(self_unack >= 0);
 1601         CHECK(peer_unack >= 0);
 1602         CHECK(peer_unack <= seq->wmax);
 1603         CHECK((self_unack == 0) ^ callout_active(&seq->xack_timer));
 1604         CHECK((peer_unack == 0) ^ callout_active(&seq->rack_timer));
 1605         for (i = 0; i < peer_unack; i++)
 1606                 CHECK(seq->xwin[i] != NULL);
 1607         for ( ; i < seq->cwnd; i++)         /* verify peer's recv window full */
 1608                 CHECK(seq->xwin[i] == NULL);
 1609 
 1610         mtx_unlock(&seq->mtx);
 1611 
 1612 #undef CHECK
 1613 }
 1614 #endif  /* INVARIANTS */

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