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/6.4/sys/netgraph/ng_l2tp.c 177354 2008-03-18 17:33:03Z 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 /* 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 = htons(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                         conf->tunnel_id = htons(conf->tunnel_id);
  476                         conf->peer_id = htons(conf->peer_id);
  477                         if (priv->conf.enabled
  478                             && ((priv->conf.tunnel_id != 0
  479                                && conf->tunnel_id != priv->conf.tunnel_id)
  480                               || ((priv->conf.peer_id != 0
  481                                && conf->peer_id != priv->conf.peer_id)))) {
  482                                 error = EBUSY;
  483                                 break;
  484                         }
  485 
  486                         /* Save calling node as failure target */
  487                         priv->ftarget = NGI_RETADDR(item);
  488 
  489                         /* Adjust sequence number state */
  490                         if ((error = ng_l2tp_seq_adjust(priv, conf)) != 0)
  491                                 break;
  492 
  493                         /* Update node's config */
  494                         priv->conf = *conf;
  495                         break;
  496                     }
  497                 case NGM_L2TP_GET_CONFIG:
  498                     {
  499                         struct ng_l2tp_config *conf;
  500 
  501                         NG_MKRESPONSE(resp, msg, sizeof(*conf), M_NOWAIT);
  502                         if (resp == NULL) {
  503                                 error = ENOMEM;
  504                                 break;
  505                         }
  506                         conf = (struct ng_l2tp_config *)resp->data;
  507                         *conf = priv->conf;
  508 
  509                         /* Put ID's in host order */
  510                         conf->tunnel_id = ntohs(conf->tunnel_id);
  511                         conf->peer_id = ntohs(conf->peer_id);
  512                         break;
  513                     }
  514                 case NGM_L2TP_SET_SESS_CONFIG:
  515                     {
  516                         struct ng_l2tp_sess_config *const conf =
  517                             (struct ng_l2tp_sess_config *)msg->data;
  518                         hookpriv_p hpriv;
  519 
  520                         /* Check for invalid or illegal config. */
  521                         if (msg->header.arglen != sizeof(*conf)) {
  522                                 error = EINVAL;
  523                                 break;
  524                         }
  525 
  526                         /* Put ID's in network order */
  527                         conf->session_id = htons(conf->session_id);
  528                         conf->peer_id = htons(conf->peer_id);
  529 
  530                         /* Find matching hook */
  531                         hpriv = ng_l2tp_find_session(priv, conf->session_id);
  532                         if (hpriv == NULL) {
  533                                 error = ENOENT;
  534                                 break;
  535                         }
  536 
  537                         /* Update hook's config */
  538                         hpriv->conf = *conf;
  539                         break;
  540                     }
  541                 case NGM_L2TP_GET_SESS_CONFIG:
  542                     {
  543                         struct ng_l2tp_sess_config *conf;
  544                         u_int16_t session_id;
  545                         hookpriv_p hpriv;
  546 
  547                         /* Get session ID */
  548                         if (msg->header.arglen != sizeof(session_id)) {
  549                                 error = EINVAL;
  550                                 break;
  551                         }
  552                         memcpy(&session_id, msg->data, 2);
  553                         session_id = htons(session_id);
  554 
  555                         /* Find matching hook */
  556                         hpriv = ng_l2tp_find_session(priv, session_id);
  557                         if (hpriv == NULL) {
  558                                 error = ENOENT;
  559                                 break;
  560                         }
  561 
  562                         /* Send response */
  563                         NG_MKRESPONSE(resp, msg, sizeof(hpriv->conf), M_NOWAIT);
  564                         if (resp == NULL) {
  565                                 error = ENOMEM;
  566                                 break;
  567                         }
  568                         conf = (struct ng_l2tp_sess_config *)resp->data;
  569                         *conf = hpriv->conf;
  570 
  571                         /* Put ID's in host order */
  572                         conf->session_id = ntohs(conf->session_id);
  573                         conf->peer_id = ntohs(conf->peer_id);
  574                         break;
  575                     }
  576                 case NGM_L2TP_GET_STATS:
  577                 case NGM_L2TP_CLR_STATS:
  578                 case NGM_L2TP_GETCLR_STATS:
  579                     {
  580                         if (msg->header.cmd != NGM_L2TP_CLR_STATS) {
  581                                 NG_MKRESPONSE(resp, msg,
  582                                     sizeof(priv->stats), M_NOWAIT);
  583                                 if (resp == NULL) {
  584                                         error = ENOMEM;
  585                                         break;
  586                                 }
  587                                 memcpy(resp->data,
  588                                     &priv->stats, sizeof(priv->stats));
  589                         }
  590                         if (msg->header.cmd != NGM_L2TP_GET_STATS)
  591                                 memset(&priv->stats, 0, sizeof(priv->stats));
  592                         break;
  593                     }
  594                 case NGM_L2TP_GET_SESSION_STATS:
  595                 case NGM_L2TP_CLR_SESSION_STATS:
  596                 case NGM_L2TP_GETCLR_SESSION_STATS:
  597                     {
  598                         uint16_t session_id;
  599                         hookpriv_p hpriv;
  600 
  601                         /* Get session ID. */
  602                         if (msg->header.arglen != sizeof(session_id)) {
  603                                 error = EINVAL;
  604                                 break;
  605                         }
  606                         bcopy(msg->data, &session_id, sizeof(uint16_t));
  607                         session_id = htons(session_id);
  608 
  609                         /* Find matching hook. */
  610                         hpriv = ng_l2tp_find_session(priv, session_id);
  611                         if (hpriv == NULL) {
  612                                 error = ENOENT;
  613                                 break;
  614                         }
  615 
  616                         if (msg->header.cmd != NGM_L2TP_CLR_SESSION_STATS) {
  617                                 NG_MKRESPONSE(resp, msg,
  618                                     sizeof(hpriv->stats), M_NOWAIT);
  619                                 if (resp == NULL) {
  620                                         error = ENOMEM;
  621                                         break;
  622                                 }
  623                                 bcopy(&hpriv->stats, resp->data,
  624                                         sizeof(hpriv->stats));
  625                         }
  626                         if (msg->header.cmd != NGM_L2TP_GET_SESSION_STATS)
  627                                 bzero(&hpriv->stats, sizeof(hpriv->stats));
  628                         break;
  629                     }
  630                 case NGM_L2TP_SET_SEQ:
  631                     {
  632                         struct ng_l2tp_seq_config *const conf =
  633                                 (struct ng_l2tp_seq_config *)msg->data;
  634 
  635                         /* Check for invalid or illegal seq config. */
  636                         if (msg->header.arglen != sizeof(*conf)) {
  637                                 error = EINVAL;
  638                                 break;
  639                         }
  640                         conf->ns = htons(conf->ns);
  641                         conf->nr = htons(conf->nr);
  642                         conf->rack = htons(conf->rack);
  643                         conf->xack = htons(conf->xack);
  644 
  645                         /* Set sequence numbers. */
  646                         error = ng_l2tp_seq_set(priv, conf);
  647                         break;
  648                     }
  649                 default:
  650                         error = EINVAL;
  651                         break;
  652                 }
  653                 break;
  654         default:
  655                 error = EINVAL;
  656                 break;
  657         }
  658 
  659         /* Done */
  660         NG_RESPOND_MSG(error, node, item, resp);
  661         NG_FREE_MSG(msg);
  662         return (error);
  663 }
  664 
  665 /*
  666  * Destroy node
  667  */
  668 static int
  669 ng_l2tp_shutdown(node_p node)
  670 {
  671         const priv_p priv = NG_NODE_PRIVATE(node);
  672         struct l2tp_seq *const seq = &priv->seq;
  673 
  674         /* Sanity check */
  675         L2TP_SEQ_CHECK(seq);
  676 
  677         /* Reset sequence number state */
  678         ng_l2tp_seq_reset(priv);
  679 
  680         /* Free private data if neither timer is running */
  681         ng_uncallout(&seq->rack_timer, node);
  682         ng_uncallout(&seq->xack_timer, node);
  683 
  684         mtx_destroy(&seq->mtx);
  685 
  686         FREE(priv, M_NETGRAPH_L2TP);
  687 
  688         /* Unref node */
  689         NG_NODE_UNREF(node);
  690         return (0);
  691 }
  692 
  693 /*
  694  * Hook disconnection
  695  */
  696 static int
  697 ng_l2tp_disconnect(hook_p hook)
  698 {
  699         const node_p node = NG_HOOK_NODE(hook);
  700         const priv_p priv = NG_NODE_PRIVATE(node);
  701 
  702         /* Zero out hook pointer */
  703         if (hook == priv->ctrl)
  704                 priv->ctrl = NULL;
  705         else if (hook == priv->lower)
  706                 priv->lower = NULL;
  707         else {
  708                 const hookpriv_p hpriv = NG_HOOK_PRIVATE(hook);
  709                 LIST_REMOVE(hpriv, sessions);
  710                 FREE(hpriv, M_NETGRAPH_L2TP);
  711                 NG_HOOK_SET_PRIVATE(hook, NULL);
  712         }
  713 
  714         /* Go away if no longer connected to anything */
  715         if (NG_NODE_NUMHOOKS(node) == 0 && NG_NODE_IS_VALID(node))
  716                 ng_rmnode_self(node);
  717         return (0);
  718 }
  719 
  720 /*************************************************************************
  721                         INTERNAL FUNCTIONS
  722 *************************************************************************/
  723 
  724 /*
  725  * Find the hook with a given session ID (in network order).
  726  */
  727 static hookpriv_p
  728 ng_l2tp_find_session(priv_p privp, u_int16_t sid)
  729 {
  730         uint16_t        hash = SESSHASH(sid);
  731         hookpriv_p      hpriv = NULL;
  732 
  733         LIST_FOREACH(hpriv, &privp->sesshash[hash], sessions) {
  734                 if (hpriv->conf.session_id == sid)
  735                         break;
  736         }
  737 
  738         return (hpriv);
  739 }
  740 
  741 /*
  742  * Reset a hook's session state.
  743  */
  744 static int
  745 ng_l2tp_reset_session(hook_p hook, void *arg)
  746 {
  747         const hookpriv_p hpriv = NG_HOOK_PRIVATE(hook);
  748 
  749         if (hpriv != NULL) {
  750                 hpriv->conf.control_dseq = 0;
  751                 hpriv->conf.enable_dseq = 0;
  752                 bzero(&hpriv->conf, sizeof(struct ng_l2tp_session_stats));
  753                 hpriv->nr = 0;
  754                 hpriv->ns = 0;
  755         }
  756         return (-1);
  757 }
  758 
  759 /*
  760  * Handle an incoming frame from below.
  761  */
  762 static int
  763 ng_l2tp_rcvdata_lower(hook_p h, item_p item)
  764 {
  765         static const u_int16_t req_bits[2][2] = {
  766                 { L2TP_DATA_0BITS, L2TP_DATA_1BITS },
  767                 { L2TP_CTRL_0BITS, L2TP_CTRL_1BITS },
  768         };
  769         const node_p node = NG_HOOK_NODE(h);
  770         const priv_p priv = NG_NODE_PRIVATE(node);
  771         hookpriv_p hpriv = NULL;
  772         hook_p hook = NULL;
  773         u_int16_t ids[2];
  774         struct mbuf *m;
  775         u_int16_t hdr;
  776         u_int16_t ns;
  777         u_int16_t nr;
  778         int is_ctrl;
  779         int error;
  780         int len, plen;
  781 
  782         /* Sanity check */
  783         L2TP_SEQ_CHECK(&priv->seq);
  784 
  785         /* If not configured, reject */
  786         if (!priv->conf.enabled) {
  787                 NG_FREE_ITEM(item);
  788                 ERROUT(ENXIO);
  789         }
  790 
  791         /* Grab mbuf */
  792         NGI_GET_M(item, m);
  793 
  794         /* Remember full packet length; needed for per session accounting. */
  795         plen = m->m_pkthdr.len;
  796 
  797         /* Update stats */
  798         priv->stats.recvPackets++;
  799         priv->stats.recvOctets += plen;
  800 
  801         /* Get initial header */
  802         if (m->m_pkthdr.len < 6) {
  803                 priv->stats.recvRunts++;
  804                 NG_FREE_ITEM(item);
  805                 NG_FREE_M(m);
  806                 ERROUT(EINVAL);
  807         }
  808         if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
  809                 priv->stats.memoryFailures++;
  810                 NG_FREE_ITEM(item);
  811                 ERROUT(EINVAL);
  812         }
  813         hdr = ntohs(*mtod(m, u_int16_t *));
  814         m_adj(m, 2);
  815 
  816         /* Check required header bits and minimum length */
  817         is_ctrl = (hdr & L2TP_HDR_CTRL) != 0;
  818         if ((hdr & req_bits[is_ctrl][0]) != 0
  819             || (~hdr & req_bits[is_ctrl][1]) != 0) {
  820                 priv->stats.recvInvalid++;
  821                 NG_FREE_ITEM(item);
  822                 NG_FREE_M(m);
  823                 ERROUT(EINVAL);
  824         }
  825         if (m->m_pkthdr.len < 4                         /* tunnel, session id */
  826             + (2 * ((hdr & L2TP_HDR_LEN) != 0))         /* length field */
  827             + (4 * ((hdr & L2TP_HDR_SEQ) != 0))         /* seq # fields */
  828             + (2 * ((hdr & L2TP_HDR_OFF) != 0))) {      /* offset field */
  829                 priv->stats.recvRunts++;
  830                 NG_FREE_ITEM(item);
  831                 NG_FREE_M(m);
  832                 ERROUT(EINVAL);
  833         }
  834 
  835         /* Get and validate length field if present */
  836         if ((hdr & L2TP_HDR_LEN) != 0) {
  837                 if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
  838                         priv->stats.memoryFailures++;
  839                         NG_FREE_ITEM(item);
  840                         ERROUT(EINVAL);
  841                 }
  842                 len = (u_int16_t)ntohs(*mtod(m, u_int16_t *)) - 4;
  843                 m_adj(m, 2);
  844                 if (len < 0 || len > m->m_pkthdr.len) {
  845                         priv->stats.recvInvalid++;
  846                         NG_FREE_ITEM(item);
  847                         NG_FREE_M(m);
  848                         ERROUT(EINVAL);
  849                 }
  850                 if (len < m->m_pkthdr.len)              /* trim extra bytes */
  851                         m_adj(m, -(m->m_pkthdr.len - len));
  852         }
  853 
  854         /* Get tunnel ID and session ID */
  855         if (m->m_len < 4 && (m = m_pullup(m, 4)) == NULL) {
  856                 priv->stats.memoryFailures++;
  857                 NG_FREE_ITEM(item);
  858                 ERROUT(EINVAL);
  859         }
  860         memcpy(ids, mtod(m, u_int16_t *), 4);
  861         m_adj(m, 4);
  862 
  863         /* Check tunnel ID */
  864         if (ids[0] != priv->conf.tunnel_id
  865             && (priv->conf.match_id || ids[0] != 0)) {
  866                 priv->stats.recvWrongTunnel++;
  867                 NG_FREE_ITEM(item);
  868                 NG_FREE_M(m);
  869                 ERROUT(EADDRNOTAVAIL);
  870         }
  871 
  872         /* Check session ID (for data packets only) */
  873         if ((hdr & L2TP_HDR_CTRL) == 0) {
  874                 hpriv = ng_l2tp_find_session(priv, ids[1]);
  875                 if (hpriv == NULL) {
  876                         priv->stats.recvUnknownSID++;
  877                         NG_FREE_ITEM(item);
  878                         NG_FREE_M(m);
  879                         ERROUT(ENOTCONN);
  880                 }
  881                 hook = hpriv->hook;
  882         }
  883 
  884         /* Get Ns, Nr fields if present */
  885         if ((hdr & L2TP_HDR_SEQ) != 0) {
  886                 if (m->m_len < 4 && (m = m_pullup(m, 4)) == NULL) {
  887                         priv->stats.memoryFailures++;
  888                         NG_FREE_ITEM(item);
  889                         ERROUT(EINVAL);
  890                 }
  891                 memcpy(&ns, &mtod(m, u_int16_t *)[0], 2);
  892                 ns = ntohs(ns);
  893                 memcpy(&nr, &mtod(m, u_int16_t *)[1], 2);
  894                 nr = ntohs(nr);
  895                 m_adj(m, 4);
  896         }
  897 
  898         /* Strip offset padding if present */
  899         if ((hdr & L2TP_HDR_OFF) != 0) {
  900                 u_int16_t offset;
  901 
  902                 /* Get length of offset padding */
  903                 if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
  904                         priv->stats.memoryFailures++;
  905                         NG_FREE_ITEM(item);
  906                         ERROUT(EINVAL);
  907                 }
  908                 memcpy(&offset, mtod(m, u_int16_t *), 2);
  909                 offset = ntohs(offset);
  910 
  911                 /* Trim offset padding */
  912                 if ((2+offset) > m->m_pkthdr.len) {
  913                         priv->stats.recvInvalid++;
  914                         NG_FREE_ITEM(item);
  915                         NG_FREE_M(m);
  916                         ERROUT(EINVAL);
  917                 }
  918                 m_adj(m, 2+offset);
  919         }
  920 
  921         /* Handle control packets */
  922         if ((hdr & L2TP_HDR_CTRL) != 0) {
  923                 struct l2tp_seq *const seq = &priv->seq;
  924 
  925                 /* Handle receive ack sequence number Nr */
  926                 ng_l2tp_seq_recv_nr(priv, nr);
  927 
  928                 /* Discard ZLB packets */
  929                 if (m->m_pkthdr.len == 0) {
  930                         priv->stats.recvZLBs++;
  931                         NG_FREE_ITEM(item);
  932                         NG_FREE_M(m);
  933                         ERROUT(0);
  934                 }
  935 
  936                 mtx_lock(&seq->mtx);
  937                 /*
  938                  * If not what we expect or we are busy, drop packet and
  939                  * send an immediate ZLB ack.
  940                  */
  941                 if (ns != seq->nr || seq->inproc) {
  942                         if (L2TP_SEQ_DIFF(ns, seq->nr) <= 0)
  943                                 priv->stats.recvDuplicates++;
  944                         else
  945                                 priv->stats.recvOutOfOrder++;
  946                         mtx_unlock(&seq->mtx);
  947                         ng_l2tp_xmit_ctrl(priv, NULL, seq->ns);
  948                         NG_FREE_ITEM(item);
  949                         NG_FREE_M(m);
  950                         ERROUT(0);
  951                 }
  952                 /*
  953                  * Until we deliver this packet we can't receive next one as
  954                  * we have no information for sending ack.
  955                  */
  956                 seq->inproc = 1;
  957                 mtx_unlock(&seq->mtx);
  958 
  959                 /* Prepend session ID to packet. */
  960                 M_PREPEND(m, 2, M_DONTWAIT);
  961                 if (m == NULL) {
  962                         seq->inproc = 0;
  963                         priv->stats.memoryFailures++;
  964                         NG_FREE_ITEM(item);
  965                         ERROUT(ENOBUFS);
  966                 }
  967                 memcpy(mtod(m, u_int16_t *), &ids[1], 2);
  968 
  969                 /* Deliver packet to upper layers */
  970                 NG_FWD_NEW_DATA(error, item, priv->ctrl, m);
  971                 
  972                 mtx_lock(&seq->mtx);
  973                 /* Ready to process next packet. */
  974                 seq->inproc = 0;
  975 
  976                 /* If packet was successfully delivered send ack. */
  977                 if (error == 0) {
  978                         /* Update recv sequence number */
  979                         seq->nr++;
  980                         /* Start receive ack timer, if not already running */
  981                         if (!callout_active(&seq->xack_timer)) {
  982                                 ng_callout(&seq->xack_timer, priv->node, NULL,
  983                                     L2TP_DELAYED_ACK, ng_l2tp_seq_xack_timeout,
  984                                     NULL, 0);
  985                         }
  986                 }
  987                 mtx_unlock(&seq->mtx);
  988 
  989                 ERROUT(error);
  990         }
  991 
  992         /* Per session packet, account it. */
  993         hpriv->stats.recvPackets++;
  994         hpriv->stats.recvOctets += plen;
  995 
  996         /* Follow peer's lead in data sequencing, if configured to do so */
  997         if (!hpriv->conf.control_dseq)
  998                 hpriv->conf.enable_dseq = ((hdr & L2TP_HDR_SEQ) != 0);
  999 
 1000         /* Handle data sequence numbers if present and enabled */
 1001         if ((hdr & L2TP_HDR_SEQ) != 0) {
 1002                 if (hpriv->conf.enable_dseq
 1003                     && L2TP_SEQ_DIFF(ns, hpriv->nr) < 0) {
 1004                         NG_FREE_ITEM(item);     /* duplicate or out of order */
 1005                         NG_FREE_M(m);
 1006                         priv->stats.recvDataDrops++;
 1007                         ERROUT(0);
 1008                 }
 1009                 hpriv->nr = ns + 1;
 1010         }
 1011 
 1012         /* Drop empty data packets */
 1013         if (m->m_pkthdr.len == 0) {
 1014                 NG_FREE_ITEM(item);
 1015                 NG_FREE_M(m);
 1016                 ERROUT(0);
 1017         }
 1018 
 1019         /* Deliver data */
 1020         NG_FWD_NEW_DATA(error, item, hook, m);
 1021 done:
 1022         /* Done */
 1023         L2TP_SEQ_CHECK(&priv->seq);
 1024         return (error);
 1025 }
 1026 
 1027 /*
 1028  * Handle an outgoing control frame.
 1029  */
 1030 static int
 1031 ng_l2tp_rcvdata_ctrl(hook_p hook, item_p item)
 1032 {
 1033         const node_p node = NG_HOOK_NODE(hook);
 1034         const priv_p priv = NG_NODE_PRIVATE(node);
 1035         struct l2tp_seq *const seq = &priv->seq;
 1036         struct mbuf *m;
 1037         int error;
 1038         int i;
 1039         u_int16_t       ns;
 1040 
 1041         /* Sanity check */
 1042         L2TP_SEQ_CHECK(&priv->seq);
 1043 
 1044         /* If not configured, reject */
 1045         if (!priv->conf.enabled) {
 1046                 NG_FREE_ITEM(item);
 1047                 ERROUT(ENXIO);
 1048         }
 1049 
 1050         /* Grab mbuf and discard other stuff XXX */
 1051         NGI_GET_M(item, m);
 1052         NG_FREE_ITEM(item);
 1053 
 1054         /* Packet should have session ID prepended */
 1055         if (m->m_pkthdr.len < 2) {
 1056                 priv->stats.xmitInvalid++;
 1057                 m_freem(m);
 1058                 ERROUT(EINVAL);
 1059         }
 1060 
 1061         /* Check max length */
 1062         if (m->m_pkthdr.len >= 0x10000 - 14) {
 1063                 priv->stats.xmitTooBig++;
 1064                 m_freem(m);
 1065                 ERROUT(EOVERFLOW);
 1066         }
 1067 
 1068         mtx_lock(&seq->mtx);
 1069 
 1070         /* Find next empty slot in transmit queue */
 1071         for (i = 0; i < L2TP_MAX_XWIN && seq->xwin[i] != NULL; i++);
 1072         if (i == L2TP_MAX_XWIN) {
 1073                 mtx_unlock(&seq->mtx);
 1074                 priv->stats.xmitDrops++;
 1075                 m_freem(m);
 1076                 ERROUT(ENOBUFS);
 1077         }
 1078         seq->xwin[i] = m;
 1079 
 1080         /* If peer's receive window is already full, nothing else to do */
 1081         if (i >= seq->cwnd) {
 1082                 mtx_unlock(&seq->mtx);
 1083                 ERROUT(0);
 1084         }
 1085 
 1086         /* Start retransmit timer if not already running */
 1087         if (!callout_active(&seq->rack_timer))
 1088                 ng_callout(&seq->rack_timer, node, NULL,
 1089                     hz, ng_l2tp_seq_rack_timeout, NULL, 0);
 1090         
 1091         ns = seq->ns++;
 1092         
 1093         mtx_unlock(&seq->mtx);
 1094 
 1095         /* Copy packet */
 1096         if ((m = L2TP_COPY_MBUF(m, M_DONTWAIT)) == NULL) {
 1097                 priv->stats.memoryFailures++;
 1098                 ERROUT(ENOBUFS);
 1099         }
 1100 
 1101         /* Send packet and increment xmit sequence number */
 1102         error = ng_l2tp_xmit_ctrl(priv, m, ns);
 1103 done:
 1104         /* Done */
 1105         L2TP_SEQ_CHECK(&priv->seq);
 1106         return (error);
 1107 }
 1108 
 1109 /*
 1110  * Handle an outgoing data frame.
 1111  */
 1112 static int
 1113 ng_l2tp_rcvdata(hook_p hook, item_p item)
 1114 {
 1115         const priv_p priv = NG_NODE_PRIVATE(NG_HOOK_NODE(hook));
 1116         const hookpriv_p hpriv = NG_HOOK_PRIVATE(hook);
 1117         struct mbuf *m;
 1118         u_int16_t hdr;
 1119         int error;
 1120         int i = 1;
 1121 
 1122         /* Sanity check */
 1123         L2TP_SEQ_CHECK(&priv->seq);
 1124 
 1125         /* If not configured, reject */
 1126         if (!priv->conf.enabled) {
 1127                 NG_FREE_ITEM(item);
 1128                 ERROUT(ENXIO);
 1129         }
 1130 
 1131         /* Get mbuf */
 1132         NGI_GET_M(item, m);
 1133 
 1134         /* Check max length */
 1135         if (m->m_pkthdr.len >= 0x10000 - 12) {
 1136                 priv->stats.xmitDataTooBig++;
 1137                 NG_FREE_ITEM(item);
 1138                 NG_FREE_M(m);
 1139                 ERROUT(EOVERFLOW);
 1140         }
 1141 
 1142         /* Prepend L2TP header */
 1143         M_PREPEND(m, 6
 1144             + (2 * (hpriv->conf.include_length != 0))
 1145             + (4 * (hpriv->conf.enable_dseq != 0)),
 1146             M_DONTWAIT);
 1147         if (m == NULL) {
 1148                 priv->stats.memoryFailures++;
 1149                 NG_FREE_ITEM(item);
 1150                 ERROUT(ENOBUFS);
 1151         }
 1152         hdr = L2TP_DATA_HDR;
 1153         if (hpriv->conf.include_length) {
 1154                 hdr |= L2TP_HDR_LEN;
 1155                 mtod(m, u_int16_t *)[i++] = htons(m->m_pkthdr.len);
 1156         }
 1157         mtod(m, u_int16_t *)[i++] = priv->conf.peer_id;
 1158         mtod(m, u_int16_t *)[i++] = hpriv->conf.peer_id;
 1159         if (hpriv->conf.enable_dseq) {
 1160                 hdr |= L2TP_HDR_SEQ;
 1161                 mtod(m, u_int16_t *)[i++] = htons(hpriv->ns);
 1162                 mtod(m, u_int16_t *)[i++] = htons(hpriv->nr);
 1163                 hpriv->ns++;
 1164         }
 1165         mtod(m, u_int16_t *)[0] = htons(hdr);
 1166 
 1167         /* Update per session stats. */
 1168         hpriv->stats.xmitPackets++;
 1169         hpriv->stats.xmitOctets += m->m_pkthdr.len;
 1170 
 1171         /* And the global one. */
 1172         priv->stats.xmitPackets++;
 1173         priv->stats.xmitOctets += m->m_pkthdr.len;
 1174 
 1175         /* Send packet */
 1176         NG_FWD_NEW_DATA(error, item, priv->lower, m);
 1177 done:
 1178         /* Done */
 1179         L2TP_SEQ_CHECK(&priv->seq);
 1180         return (error);
 1181 }
 1182 
 1183 /*
 1184  * Send a message to our controlling node that we've failed.
 1185  */
 1186 static void
 1187 ng_l2tp_seq_failure(priv_p priv)
 1188 {
 1189         struct ng_mesg *msg;
 1190         int error;
 1191 
 1192         NG_MKMESSAGE(msg, NGM_L2TP_COOKIE, NGM_L2TP_ACK_FAILURE, 0, M_NOWAIT);
 1193         if (msg == NULL)
 1194                 return;
 1195         NG_SEND_MSG_ID(error, priv->node, msg, priv->ftarget, 0);
 1196 }
 1197 
 1198 /************************************************************************
 1199                         SEQUENCE NUMBER HANDLING
 1200 ************************************************************************/
 1201 
 1202 /*
 1203  * Initialize sequence number state.
 1204  */
 1205 static void
 1206 ng_l2tp_seq_init(priv_p priv)
 1207 {
 1208         struct l2tp_seq *const seq = &priv->seq;
 1209 
 1210         KASSERT(priv->conf.peer_win >= 1,
 1211             ("%s: peer_win is zero", __func__));
 1212         memset(seq, 0, sizeof(*seq));
 1213         seq->cwnd = 1;
 1214         seq->wmax = priv->conf.peer_win;
 1215         if (seq->wmax > L2TP_MAX_XWIN)
 1216                 seq->wmax = L2TP_MAX_XWIN;
 1217         seq->ssth = seq->wmax;
 1218         ng_callout_init(&seq->rack_timer);
 1219         ng_callout_init(&seq->xack_timer);
 1220         mtx_init(&seq->mtx, "ng_l2tp", NULL, MTX_DEF);
 1221         L2TP_SEQ_CHECK(seq);
 1222 }
 1223 
 1224 /*
 1225  * Set sequence number state as given from user.
 1226  */
 1227 static int
 1228 ng_l2tp_seq_set(priv_p priv, const struct ng_l2tp_seq_config *conf)
 1229 {
 1230         struct l2tp_seq *const seq = &priv->seq;
 1231 
 1232         /* If node is enabled, deny update to sequence numbers. */
 1233         if (priv->conf.enabled)
 1234                 return (EBUSY);
 1235 
 1236         /* We only can handle the simple cases. */
 1237         if (conf->xack != conf->nr || conf->ns != conf->rack)
 1238                 return (EINVAL);
 1239 
 1240         /* Set ns,nr,rack,xack parameters. */
 1241         seq->ns = conf->ns;
 1242         seq->nr = conf->nr;
 1243         seq->rack = conf->rack;
 1244         seq->xack = conf->xack;
 1245 
 1246         return (0);
 1247 }
 1248 
 1249 /*
 1250  * Adjust sequence number state accordingly after reconfiguration.
 1251  */
 1252 static int
 1253 ng_l2tp_seq_adjust(priv_p priv, const struct ng_l2tp_config *conf)
 1254 {
 1255         struct l2tp_seq *const seq = &priv->seq;
 1256         u_int16_t new_wmax;
 1257 
 1258         /* If disabling node, reset state sequence number */
 1259         if (!conf->enabled) {
 1260                 ng_l2tp_seq_reset(priv);
 1261                 return (0);
 1262         }
 1263 
 1264         /* Adjust peer's max recv window; it can only increase */
 1265         new_wmax = conf->peer_win;
 1266         if (new_wmax > L2TP_MAX_XWIN)
 1267                 new_wmax = L2TP_MAX_XWIN;
 1268         if (new_wmax == 0)
 1269                 return (EINVAL);
 1270         if (new_wmax < seq->wmax)
 1271                 return (EBUSY);
 1272         seq->wmax = new_wmax;
 1273 
 1274         /* Done */
 1275         return (0);
 1276 }
 1277 
 1278 /*
 1279  * Reset sequence number state.
 1280  */
 1281 static void
 1282 ng_l2tp_seq_reset(priv_p priv)
 1283 {
 1284         struct l2tp_seq *const seq = &priv->seq;
 1285         hook_p hook;
 1286         int i;
 1287 
 1288         /* Sanity check */
 1289         L2TP_SEQ_CHECK(seq);
 1290 
 1291         /* Stop timers */
 1292         ng_uncallout(&seq->rack_timer, priv->node);
 1293         ng_uncallout(&seq->xack_timer, priv->node);
 1294 
 1295         /* Free retransmit queue */
 1296         for (i = 0; i < L2TP_MAX_XWIN; i++) {
 1297                 if (seq->xwin[i] == NULL)
 1298                         break;
 1299                 m_freem(seq->xwin[i]);
 1300         }
 1301 
 1302         /* Reset session hooks' sequence number states */
 1303         NG_NODE_FOREACH_HOOK(priv->node, ng_l2tp_reset_session, NULL, hook);
 1304 
 1305         /* Reset node's sequence number state */
 1306         seq->ns = 0;
 1307         seq->nr = 0;
 1308         seq->rack = 0;
 1309         seq->xack = 0;
 1310         seq->wmax = L2TP_MAX_XWIN;
 1311         seq->cwnd = 1;
 1312         seq->ssth = seq->wmax;
 1313         seq->acks = 0;
 1314         seq->rexmits = 0;
 1315         bzero(seq->xwin, sizeof(seq->xwin));
 1316 
 1317         /* Done */
 1318         L2TP_SEQ_CHECK(seq);
 1319 }
 1320 
 1321 /*
 1322  * Handle receipt of an acknowledgement value (Nr) from peer.
 1323  */
 1324 static void
 1325 ng_l2tp_seq_recv_nr(priv_p priv, u_int16_t nr)
 1326 {
 1327         struct l2tp_seq *const seq = &priv->seq;
 1328         struct mbuf     *xwin[L2TP_MAX_XWIN];   /* partial local copy */
 1329         int             nack;
 1330         int             i, j;
 1331         uint16_t        ns;
 1332 
 1333         mtx_lock(&seq->mtx);
 1334 
 1335         /* Verify peer's ACK is in range */
 1336         if ((nack = L2TP_SEQ_DIFF(nr, seq->rack)) <= 0) {
 1337                 mtx_unlock(&seq->mtx);
 1338                 return;                         /* duplicate ack */
 1339         }
 1340         if (L2TP_SEQ_DIFF(nr, seq->ns) > 0) {
 1341                 mtx_unlock(&seq->mtx);
 1342                 priv->stats.recvBadAcks++;      /* ack for packet not sent */
 1343                 return;
 1344         }
 1345         KASSERT(nack <= L2TP_MAX_XWIN,
 1346             ("%s: nack=%d > %d", __func__, nack, L2TP_MAX_XWIN));
 1347 
 1348         /* Update receive ack stats */
 1349         seq->rack = nr;
 1350         seq->rexmits = 0;
 1351 
 1352         /* Free acknowledged packets and shift up packets in the xmit queue */
 1353         for (i = 0; i < nack; i++)
 1354                 m_freem(seq->xwin[i]);
 1355         memmove(seq->xwin, seq->xwin + nack,
 1356             (L2TP_MAX_XWIN - nack) * sizeof(*seq->xwin));
 1357         memset(seq->xwin + (L2TP_MAX_XWIN - nack), 0,
 1358             nack * sizeof(*seq->xwin));
 1359 
 1360         /*
 1361          * Do slow-start/congestion avoidance windowing algorithm described
 1362          * in RFC 2661, Appendix A. Here we handle a multiple ACK as if each
 1363          * ACK had arrived separately.
 1364          */
 1365         if (seq->cwnd < seq->wmax) {
 1366 
 1367                 /* Handle slow start phase */
 1368                 if (seq->cwnd < seq->ssth) {
 1369                         seq->cwnd += nack;
 1370                         nack = 0;
 1371                         if (seq->cwnd > seq->ssth) {    /* into cg.av. phase */
 1372                                 nack = seq->cwnd - seq->ssth;
 1373                                 seq->cwnd = seq->ssth;
 1374                         }
 1375                 }
 1376 
 1377                 /* Handle congestion avoidance phase */
 1378                 if (seq->cwnd >= seq->ssth) {
 1379                         seq->acks += nack;
 1380                         while (seq->acks >= seq->cwnd) {
 1381                                 seq->acks -= seq->cwnd;
 1382                                 if (seq->cwnd < seq->wmax)
 1383                                         seq->cwnd++;
 1384                         }
 1385                 }
 1386         }
 1387 
 1388         /* Stop xmit timer */
 1389         if (callout_active(&seq->rack_timer))
 1390                 ng_uncallout(&seq->rack_timer, priv->node);
 1391 
 1392         /* If transmit queue is empty, we're done for now */
 1393         if (seq->xwin[0] == NULL) {
 1394                 mtx_unlock(&seq->mtx);
 1395                 return;
 1396         }
 1397 
 1398         /* Start restransmit timer again */
 1399         ng_callout(&seq->rack_timer, priv->node, NULL,
 1400             hz, ng_l2tp_seq_rack_timeout, NULL, 0);
 1401 
 1402         /*
 1403          * Send more packets, trying to keep peer's receive window full.
 1404          * Make copy of everything we need before lock release.
 1405          */
 1406         ns = seq->ns;
 1407         j = 0;
 1408         while ((i = L2TP_SEQ_DIFF(seq->ns, seq->rack)) < seq->cwnd
 1409             && seq->xwin[i] != NULL) {
 1410                 xwin[j++] = seq->xwin[i];
 1411                 seq->ns++;
 1412         }
 1413 
 1414         mtx_unlock(&seq->mtx);
 1415 
 1416         /*
 1417          * Send prepared.
 1418          * If there is a memory error, pretend packet was sent, as it
 1419          * will get retransmitted later anyway.
 1420          */
 1421         for (i = 0; i < j; i++) {
 1422                 struct mbuf     *m;
 1423                 if ((m = L2TP_COPY_MBUF(xwin[i], M_DONTWAIT)) == NULL)
 1424                         priv->stats.memoryFailures++;
 1425                 else
 1426                         ng_l2tp_xmit_ctrl(priv, m, ns);
 1427                 ns++;
 1428         }
 1429 }
 1430 
 1431 /*
 1432  * Handle an ack timeout. We have an outstanding ack that we
 1433  * were hoping to piggy-back, but haven't, so send a ZLB.
 1434  */
 1435 static void
 1436 ng_l2tp_seq_xack_timeout(node_p node, hook_p hook, void *arg1, int arg2)
 1437 {
 1438         const priv_p priv = NG_NODE_PRIVATE(node);
 1439         struct l2tp_seq *const seq = &priv->seq;
 1440 
 1441         /* Make sure callout is still active before doing anything */
 1442         if (callout_pending(&seq->xack_timer) ||
 1443             (!callout_active(&seq->xack_timer)))
 1444                 return;
 1445 
 1446         /* Sanity check */
 1447         L2TP_SEQ_CHECK(seq);
 1448 
 1449         /* Send a ZLB */
 1450         ng_l2tp_xmit_ctrl(priv, NULL, seq->ns);
 1451 
 1452         /* callout_deactivate() is not needed here 
 1453             as ng_uncallout() was called by ng_l2tp_xmit_ctrl() */
 1454 
 1455         /* Sanity check */
 1456         L2TP_SEQ_CHECK(seq);
 1457 }
 1458 
 1459 /* 
 1460  * Handle a transmit timeout. The peer has failed to respond
 1461  * with an ack for our packet, so retransmit it.
 1462  */
 1463 static void
 1464 ng_l2tp_seq_rack_timeout(node_p node, hook_p hook, void *arg1, int arg2)
 1465 {
 1466         const priv_p priv = NG_NODE_PRIVATE(node);
 1467         struct l2tp_seq *const seq = &priv->seq;
 1468         struct mbuf *m;
 1469         u_int delay;
 1470 
 1471         /* Make sure callout is still active before doing anything */
 1472         if (callout_pending(&seq->rack_timer) ||
 1473             (!callout_active(&seq->rack_timer)))
 1474                 return;
 1475 
 1476         /* Sanity check */
 1477         L2TP_SEQ_CHECK(seq);
 1478 
 1479         priv->stats.xmitRetransmits++;
 1480 
 1481         /* Have we reached the retransmit limit? If so, notify owner. */
 1482         if (seq->rexmits++ >= priv->conf.rexmit_max)
 1483                 ng_l2tp_seq_failure(priv);
 1484 
 1485         /* Restart timer, this time with an increased delay */
 1486         delay = (seq->rexmits > 12) ? (1 << 12) : (1 << seq->rexmits);
 1487         if (delay > priv->conf.rexmit_max_to)
 1488                 delay = priv->conf.rexmit_max_to;
 1489         ng_callout(&seq->rack_timer, node, NULL,
 1490             hz * delay, ng_l2tp_seq_rack_timeout, NULL, 0);
 1491 
 1492         /* Do slow-start/congestion algorithm windowing algorithm */
 1493         seq->ns = seq->rack;
 1494         seq->ssth = (seq->cwnd + 1) / 2;
 1495         seq->cwnd = 1;
 1496         seq->acks = 0;
 1497 
 1498         /* Retransmit oldest unack'd packet */
 1499         if ((m = L2TP_COPY_MBUF(seq->xwin[0], M_DONTWAIT)) == NULL)
 1500                 priv->stats.memoryFailures++;
 1501         else
 1502                 ng_l2tp_xmit_ctrl(priv, m, seq->ns++);
 1503 
 1504         /* callout_deactivate() is not needed here 
 1505             as ng_callout() is getting called each time */
 1506 
 1507         /* Sanity check */
 1508         L2TP_SEQ_CHECK(seq);
 1509 }
 1510 
 1511 /*
 1512  * Transmit a control stream packet, payload optional.
 1513  * The transmit sequence number is not incremented.
 1514  */
 1515 static int
 1516 ng_l2tp_xmit_ctrl(priv_p priv, struct mbuf *m, u_int16_t ns)
 1517 {
 1518         struct l2tp_seq *const seq = &priv->seq;
 1519         u_int16_t session_id = 0;
 1520         int error;
 1521 
 1522         mtx_lock(&seq->mtx);
 1523 
 1524         /* Stop ack timer: we're sending an ack with this packet.
 1525            Doing this before to keep state predictable after error. */
 1526         if (callout_active(&seq->xack_timer))
 1527                 ng_uncallout(&seq->xack_timer, priv->node);
 1528 
 1529         seq->xack = seq->nr;
 1530 
 1531         mtx_unlock(&seq->mtx);
 1532 
 1533         /* If no mbuf passed, send an empty packet (ZLB) */
 1534         if (m == NULL) {
 1535 
 1536                 /* Create a new mbuf for ZLB packet */
 1537                 MGETHDR(m, M_DONTWAIT, MT_DATA);
 1538                 if (m == NULL) {
 1539                         priv->stats.memoryFailures++;
 1540                         return (ENOBUFS);
 1541                 }
 1542                 m->m_len = m->m_pkthdr.len = 12;
 1543                 m->m_pkthdr.rcvif = NULL;
 1544                 priv->stats.xmitZLBs++;
 1545         } else {
 1546 
 1547                 /* Strip off session ID */
 1548                 if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
 1549                         priv->stats.memoryFailures++;
 1550                         return (ENOBUFS);
 1551                 }
 1552                 memcpy(&session_id, mtod(m, u_int16_t *), 2);
 1553                 m_adj(m, 2);
 1554 
 1555                 /* Make room for L2TP header */
 1556                 M_PREPEND(m, 12, M_DONTWAIT);
 1557                 if (m == NULL) {
 1558                         priv->stats.memoryFailures++;
 1559                         return (ENOBUFS);
 1560                 }
 1561         }
 1562 
 1563         /* Fill in L2TP header */
 1564         mtod(m, u_int16_t *)[0] = htons(L2TP_CTRL_HDR);
 1565         mtod(m, u_int16_t *)[1] = htons(m->m_pkthdr.len);
 1566         mtod(m, u_int16_t *)[2] = priv->conf.peer_id;
 1567         mtod(m, u_int16_t *)[3] = session_id;
 1568         mtod(m, u_int16_t *)[4] = htons(ns);
 1569         mtod(m, u_int16_t *)[5] = htons(seq->nr);
 1570 
 1571         /* Update sequence number info and stats */
 1572         priv->stats.xmitPackets++;
 1573         priv->stats.xmitOctets += m->m_pkthdr.len;
 1574 
 1575         /* Send packet */
 1576         NG_SEND_DATA_ONLY(error, priv->lower, m);
 1577         return (error);
 1578 }
 1579 
 1580 #ifdef INVARIANTS
 1581 /*
 1582  * Sanity check sequence number state.
 1583  */
 1584 static void
 1585 ng_l2tp_seq_check(struct l2tp_seq *seq)
 1586 {
 1587         int self_unack, peer_unack;
 1588         int i;
 1589 
 1590 #define CHECK(p)        KASSERT((p), ("%s: not: %s", __func__, #p))
 1591 
 1592         mtx_lock(&seq->mtx);
 1593 
 1594         self_unack = L2TP_SEQ_DIFF(seq->nr, seq->xack);
 1595         peer_unack = L2TP_SEQ_DIFF(seq->ns, seq->rack);
 1596         CHECK(seq->wmax <= L2TP_MAX_XWIN);
 1597         CHECK(seq->cwnd >= 1);
 1598         CHECK(seq->cwnd <= seq->wmax);
 1599         CHECK(seq->ssth >= 1);
 1600         CHECK(seq->ssth <= seq->wmax);
 1601         if (seq->cwnd < seq->ssth)
 1602                 CHECK(seq->acks == 0);
 1603         else
 1604                 CHECK(seq->acks <= seq->cwnd);
 1605         CHECK(self_unack >= 0);
 1606         CHECK(peer_unack >= 0);
 1607         CHECK(peer_unack <= seq->wmax);
 1608         CHECK((self_unack == 0) ^ callout_active(&seq->xack_timer));
 1609         CHECK((peer_unack == 0) ^ callout_active(&seq->rack_timer));
 1610         for (i = 0; i < peer_unack; i++)
 1611                 CHECK(seq->xwin[i] != NULL);
 1612         for ( ; i < seq->cwnd; i++)         /* verify peer's recv window full */
 1613                 CHECK(seq->xwin[i] == NULL);
 1614 
 1615         mtx_unlock(&seq->mtx);
 1616 
 1617 #undef CHECK
 1618 }
 1619 #endif  /* INVARIANTS */

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