The Design and Implementation of the FreeBSD Operating System, Second Edition
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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: src/sys/netgraph/ng_l2tp.c,v 1.14 2005/01/11 11:51:17 glebius Exp $
   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           16                      /* 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 /*
  104  * Sequence number state
  105  *
  106  * Invariants:
  107  *    - If cwnd < ssth, we're doing slow start, otherwise congestion avoidance
  108  *    - The number of unacknowledged xmit packets is (ns - rack) <= seq->wmax
  109  *    - The first (ns - rack) mbuf's in xwin[] array are copies of these
  110  *      unacknowledged packets; the remainder of xwin[] consists first of
  111  *      zero or more further untransmitted packets in the transmit queue
  112  *    - We try to keep the peer's receive window as full as possible.
  113  *      Therefore, (i < cwnd && xwin[i] != NULL) implies (ns - rack) > i.
  114  *    - rack_timer is running iff (ns - rack) > 0 (unack'd xmit'd pkts)
  115  *    - If xack != nr, there are unacknowledged recv packet(s) (delayed ack)
  116  *    - xack_timer is running iff xack != nr (unack'd rec'd pkts)
  117  */
  118 struct l2tp_seq {
  119         u_int16_t               ns;             /* next xmit seq we send */
  120         u_int16_t               nr;             /* next recv seq we expect */
  121         u_int16_t               rack;           /* last 'nr' we rec'd */
  122         u_int16_t               xack;           /* last 'nr' we sent */
  123         u_int16_t               wmax;           /* peer's max recv window */
  124         u_int16_t               cwnd;           /* current congestion window */
  125         u_int16_t               ssth;           /* slow start threshold */
  126         u_int16_t               acks;           /* # consecutive acks rec'd */
  127         u_int16_t               rexmits;        /* # retransmits sent */
  128         u_int16_t               max_rexmits;    /* max # retransmits sent */
  129         u_int16_t               max_rexmit_to;  /* max retransmit timeout */
  130         struct callout          rack_timer;     /* retransmit timer */
  131         struct callout          xack_timer;     /* delayed ack timer */
  132         struct mbuf             *xwin[L2TP_MAX_XWIN];   /* transmit window */
  133 };
  134 
  135 /* Node private data */
  136 struct ng_l2tp_private {
  137         node_p                  node;           /* back pointer to node */
  138         hook_p                  ctrl;           /* hook to upper layers */
  139         hook_p                  lower;          /* hook to lower layers */
  140         struct ng_l2tp_config   conf;           /* node configuration */
  141         struct ng_l2tp_stats    stats;          /* node statistics */
  142         struct l2tp_seq         seq;            /* ctrl sequence number state */
  143         ng_ID_t                 ftarget;        /* failure message target */
  144 };
  145 typedef struct ng_l2tp_private *priv_p;
  146 
  147 /* Hook private data (data session hooks only) */
  148 struct ng_l2tp_hook_private {
  149         struct ng_l2tp_sess_config      conf;   /* hook/session config */
  150         struct ng_l2tp_session_stats    stats;  /* per sessions statistics */
  151         u_int16_t                       ns;     /* data ns sequence number */
  152         u_int16_t                       nr;     /* data nr sequence number */
  153 };
  154 typedef struct ng_l2tp_hook_private *hookpriv_p;
  155 
  156 /* Netgraph node methods */
  157 static ng_constructor_t ng_l2tp_constructor;
  158 static ng_rcvmsg_t      ng_l2tp_rcvmsg;
  159 static ng_shutdown_t    ng_l2tp_shutdown;
  160 static ng_newhook_t     ng_l2tp_newhook;
  161 static ng_rcvdata_t     ng_l2tp_rcvdata;
  162 static ng_disconnect_t  ng_l2tp_disconnect;
  163 
  164 /* Internal functions */
  165 static int      ng_l2tp_recv_lower(node_p node, item_p item);
  166 static int      ng_l2tp_recv_ctrl(node_p node, item_p item);
  167 static int      ng_l2tp_recv_data(node_p node, item_p item, hookpriv_p hpriv);
  168 
  169 static int      ng_l2tp_xmit_ctrl(priv_p priv, struct mbuf *m, u_int16_t ns);
  170 
  171 static void     ng_l2tp_seq_init(priv_p priv);
  172 static int      ng_l2tp_seq_set(priv_p priv,
  173                         const struct ng_l2tp_seq_config *conf);
  174 static int      ng_l2tp_seq_adjust(priv_p priv,
  175                         const struct ng_l2tp_config *conf);
  176 static void     ng_l2tp_seq_reset(priv_p priv);
  177 static void     ng_l2tp_seq_failure(priv_p priv);
  178 static void     ng_l2tp_seq_recv_nr(priv_p priv, u_int16_t nr);
  179 static int      ng_l2tp_seq_recv_ns(priv_p priv, u_int16_t ns);
  180 static void     ng_l2tp_seq_xack_timeout(node_p node, hook_p hook,
  181                     void *arg1, int arg2);
  182 static void     ng_l2tp_seq_rack_timeout(node_p node, hook_p hook,
  183                     void *arg1, int arg2);
  184 
  185 static ng_fn_eachhook   ng_l2tp_find_session;
  186 static ng_fn_eachhook   ng_l2tp_reset_session;
  187 
  188 #ifdef INVARIANTS
  189 static void     ng_l2tp_seq_check(struct l2tp_seq *seq);
  190 #endif
  191 
  192 /* Parse type for struct ng_l2tp_seq_config. */
  193 static const struct ng_parse_struct_field
  194         ng_l2tp_seq_config_fields[] = NG_L2TP_SEQ_CONFIG_TYPE_INFO;
  195 static const struct ng_parse_type ng_l2tp_seq_config_type = {
  196         &ng_parse_struct_type,
  197         &ng_l2tp_seq_config_fields
  198 };
  199 
  200 /* Parse type for struct ng_l2tp_config */
  201 static const struct ng_parse_struct_field
  202         ng_l2tp_config_type_fields[] = NG_L2TP_CONFIG_TYPE_INFO;
  203 static const struct ng_parse_type ng_l2tp_config_type = {
  204         &ng_parse_struct_type,
  205         &ng_l2tp_config_type_fields,
  206 };
  207 
  208 /* Parse type for struct ng_l2tp_sess_config */
  209 static const struct ng_parse_struct_field
  210         ng_l2tp_sess_config_type_fields[] = NG_L2TP_SESS_CONFIG_TYPE_INFO;
  211 static const struct ng_parse_type ng_l2tp_sess_config_type = {
  212         &ng_parse_struct_type,
  213         &ng_l2tp_sess_config_type_fields,
  214 };
  215 
  216 /* Parse type for struct ng_l2tp_stats */
  217 static const struct ng_parse_struct_field
  218         ng_l2tp_stats_type_fields[] = NG_L2TP_STATS_TYPE_INFO;
  219 static const struct ng_parse_type ng_l2tp_stats_type = {
  220         &ng_parse_struct_type,
  221         &ng_l2tp_stats_type_fields
  222 };
  223 
  224 /* Parse type for struct ng_l2tp_session_stats. */
  225 static const struct ng_parse_struct_field
  226         ng_l2tp_session_stats_type_fields[] = NG_L2TP_SESSION_STATS_TYPE_INFO;
  227 static const struct ng_parse_type ng_l2tp_session_stats_type = {
  228         &ng_parse_struct_type,
  229         &ng_l2tp_session_stats_type_fields
  230 };
  231 
  232 /* List of commands and how to convert arguments to/from ASCII */
  233 static const struct ng_cmdlist ng_l2tp_cmdlist[] = {
  234         {
  235           NGM_L2TP_COOKIE,
  236           NGM_L2TP_SET_CONFIG,
  237           "setconfig",
  238           &ng_l2tp_config_type,
  239           NULL
  240         },
  241         {
  242           NGM_L2TP_COOKIE,
  243           NGM_L2TP_GET_CONFIG,
  244           "getconfig",
  245           NULL,
  246           &ng_l2tp_config_type
  247         },
  248         {
  249           NGM_L2TP_COOKIE,
  250           NGM_L2TP_SET_SESS_CONFIG,
  251           "setsessconfig",
  252           &ng_l2tp_sess_config_type,
  253           NULL
  254         },
  255         {
  256           NGM_L2TP_COOKIE,
  257           NGM_L2TP_GET_SESS_CONFIG,
  258           "getsessconfig",
  259           &ng_parse_hint16_type,
  260           &ng_l2tp_sess_config_type
  261         },
  262         {
  263           NGM_L2TP_COOKIE,
  264           NGM_L2TP_GET_STATS,
  265           "getstats",
  266           NULL,
  267           &ng_l2tp_stats_type
  268         },
  269         {
  270           NGM_L2TP_COOKIE,
  271           NGM_L2TP_CLR_STATS,
  272           "clrstats",
  273           NULL,
  274           NULL
  275         },
  276         {
  277           NGM_L2TP_COOKIE,
  278           NGM_L2TP_GETCLR_STATS,
  279           "getclrstats",
  280           NULL,
  281           &ng_l2tp_stats_type
  282         },
  283         {
  284           NGM_L2TP_COOKIE,
  285           NGM_L2TP_GET_SESSION_STATS,
  286           "getsessstats",
  287           &ng_parse_int16_type,
  288           &ng_l2tp_session_stats_type
  289         },
  290         {
  291           NGM_L2TP_COOKIE,
  292           NGM_L2TP_CLR_SESSION_STATS,
  293           "clrsessstats",
  294           &ng_parse_int16_type,
  295           NULL
  296         },
  297         {
  298           NGM_L2TP_COOKIE,
  299           NGM_L2TP_GETCLR_SESSION_STATS,
  300           "getclrsessstats",
  301           &ng_parse_int16_type,
  302           &ng_l2tp_session_stats_type
  303         },
  304         {
  305           NGM_L2TP_COOKIE,
  306           NGM_L2TP_ACK_FAILURE,
  307           "ackfailure",
  308           NULL,
  309           NULL
  310         },
  311         {
  312           NGM_L2TP_COOKIE,
  313           NGM_L2TP_SET_SEQ,
  314           "setsequence",
  315           &ng_l2tp_seq_config_type,
  316           NULL
  317         },
  318         { 0 }
  319 };
  320 
  321 /* Node type descriptor */
  322 static struct ng_type ng_l2tp_typestruct = {
  323         .version =      NG_ABI_VERSION,
  324         .name =         NG_L2TP_NODE_TYPE,
  325         .constructor =  ng_l2tp_constructor,
  326         .rcvmsg =       ng_l2tp_rcvmsg,
  327         .shutdown =     ng_l2tp_shutdown,
  328         .newhook =      ng_l2tp_newhook,
  329         .rcvdata =      ng_l2tp_rcvdata,
  330         .disconnect =   ng_l2tp_disconnect,
  331         .cmdlist =      ng_l2tp_cmdlist,
  332 };
  333 NETGRAPH_INIT(l2tp, &ng_l2tp_typestruct);
  334 
  335 /* Sequence number state sanity checking */
  336 #ifdef INVARIANTS
  337 #define L2TP_SEQ_CHECK(seq)     ng_l2tp_seq_check(seq)
  338 #else
  339 #define L2TP_SEQ_CHECK(x)       do { } while (0)
  340 #endif
  341 
  342 /* memmove macro */
  343 #define memmove(d, s, l)        bcopy(s, d, l)
  344 
  345 /* Whether to use m_copypacket() or m_dup() */
  346 #define L2TP_COPY_MBUF          m_copypacket
  347 
  348 /************************************************************************
  349                         NETGRAPH NODE STUFF
  350 ************************************************************************/
  351 
  352 /*
  353  * Node type constructor
  354  */
  355 static int
  356 ng_l2tp_constructor(node_p node)
  357 {
  358         priv_p priv;
  359 
  360         /* Allocate private structure */
  361         MALLOC(priv, priv_p, sizeof(*priv), M_NETGRAPH_L2TP, M_NOWAIT | M_ZERO);
  362         if (priv == NULL)
  363                 return (ENOMEM);
  364         NG_NODE_SET_PRIVATE(node, priv);
  365         priv->node = node;
  366 
  367         /* Apply a semi-reasonable default configuration */
  368         priv->conf.peer_win = 1;
  369         priv->conf.rexmit_max = L2TP_MAX_REXMIT;
  370         priv->conf.rexmit_max_to = L2TP_MAX_REXMIT_TO;
  371 
  372         /* Initialize sequence number state */
  373         ng_l2tp_seq_init(priv);
  374 
  375         /* Done */
  376         return (0);
  377 }
  378 
  379 /*
  380  * Give our OK for a hook to be added.
  381  */
  382 static int
  383 ng_l2tp_newhook(node_p node, hook_p hook, const char *name)
  384 {
  385         const priv_p priv = NG_NODE_PRIVATE(node);
  386 
  387         /* Check hook name */
  388         if (strcmp(name, NG_L2TP_HOOK_CTRL) == 0) {
  389                 if (priv->ctrl != NULL)
  390                         return (EISCONN);
  391                 priv->ctrl = hook;
  392         } else if (strcmp(name, NG_L2TP_HOOK_LOWER) == 0) {
  393                 if (priv->lower != NULL)
  394                         return (EISCONN);
  395                 priv->lower = hook;
  396         } else {
  397                 static const char hexdig[16] = "0123456789abcdef";
  398                 u_int16_t session_id;
  399                 hookpriv_p hpriv;
  400                 const char *hex;
  401                 int i;
  402                 int j;
  403 
  404                 /* Parse hook name to get session ID */
  405                 if (strncmp(name, NG_L2TP_HOOK_SESSION_P,
  406                     sizeof(NG_L2TP_HOOK_SESSION_P) - 1) != 0)
  407                         return (EINVAL);
  408                 hex = name + sizeof(NG_L2TP_HOOK_SESSION_P) - 1;
  409                 for (session_id = i = 0; i < 4; i++) {
  410                         for (j = 0; j < 16 && hex[i] != hexdig[j]; j++);
  411                         if (j == 16)
  412                                 return (EINVAL);
  413                         session_id = (session_id << 4) | j;
  414                 }
  415                 if (hex[i] != '\0')
  416                         return (EINVAL);
  417 
  418                 /* Create hook private structure */
  419                 MALLOC(hpriv, hookpriv_p,
  420                     sizeof(*hpriv), M_NETGRAPH_L2TP, M_NOWAIT | M_ZERO);
  421                 if (hpriv == NULL)
  422                         return (ENOMEM);
  423                 hpriv->conf.session_id = htons(session_id);
  424                 hpriv->conf.control_dseq = L2TP_CONTROL_DSEQ;
  425                 hpriv->conf.enable_dseq = L2TP_ENABLE_DSEQ;
  426                 NG_HOOK_SET_PRIVATE(hook, hpriv);
  427         }
  428 
  429         /* Done */
  430         return (0);
  431 }
  432 
  433 /*
  434  * Receive a control message.
  435  */
  436 static int
  437 ng_l2tp_rcvmsg(node_p node, item_p item, hook_p lasthook)
  438 {
  439         const priv_p priv = NG_NODE_PRIVATE(node);
  440         struct ng_mesg *resp = NULL;
  441         struct ng_mesg *msg;
  442         int error = 0;
  443 
  444         NGI_GET_MSG(item, msg);
  445         switch (msg->header.typecookie) {
  446         case NGM_L2TP_COOKIE:
  447                 switch (msg->header.cmd) {
  448                 case NGM_L2TP_SET_CONFIG:
  449                     {
  450                         struct ng_l2tp_config *const conf =
  451                                 (struct ng_l2tp_config *)msg->data;
  452 
  453                         /* Check for invalid or illegal config */
  454                         if (msg->header.arglen != sizeof(*conf)) {
  455                                 error = EINVAL;
  456                                 break;
  457                         }
  458                         conf->enabled = !!conf->enabled;
  459                         conf->match_id = !!conf->match_id;
  460                         conf->tunnel_id = htons(conf->tunnel_id);
  461                         conf->peer_id = htons(conf->peer_id);
  462                         if (priv->conf.enabled
  463                             && ((priv->conf.tunnel_id != 0
  464                                && conf->tunnel_id != priv->conf.tunnel_id)
  465                               || ((priv->conf.peer_id != 0
  466                                && conf->peer_id != priv->conf.peer_id)))) {
  467                                 error = EBUSY;
  468                                 break;
  469                         }
  470 
  471                         /* Save calling node as failure target */
  472                         priv->ftarget = NGI_RETADDR(item);
  473 
  474                         /* Adjust sequence number state */
  475                         if ((error = ng_l2tp_seq_adjust(priv, conf)) != 0)
  476                                 break;
  477 
  478                         /* Update node's config */
  479                         priv->conf = *conf;
  480                         break;
  481                     }
  482                 case NGM_L2TP_GET_CONFIG:
  483                     {
  484                         struct ng_l2tp_config *conf;
  485 
  486                         NG_MKRESPONSE(resp, msg, sizeof(*conf), M_NOWAIT);
  487                         if (resp == NULL) {
  488                                 error = ENOMEM;
  489                                 break;
  490                         }
  491                         conf = (struct ng_l2tp_config *)resp->data;
  492                         *conf = priv->conf;
  493 
  494                         /* Put ID's in host order */
  495                         conf->tunnel_id = ntohs(conf->tunnel_id);
  496                         conf->peer_id = ntohs(conf->peer_id);
  497                         break;
  498                     }
  499                 case NGM_L2TP_SET_SESS_CONFIG:
  500                     {
  501                         struct ng_l2tp_sess_config *const conf =
  502                             (struct ng_l2tp_sess_config *)msg->data;
  503                         hookpriv_p hpriv;
  504                         hook_p hook;
  505 
  506                         /* Check for invalid or illegal config. */
  507                         if (msg->header.arglen != sizeof(*conf)) {
  508                                 error = EINVAL;
  509                                 break;
  510                         }
  511 
  512                         /* Put ID's in network order */
  513                         conf->session_id = htons(conf->session_id);
  514                         conf->peer_id = htons(conf->peer_id);
  515 
  516                         /* Find matching hook */
  517                         NG_NODE_FOREACH_HOOK(node, ng_l2tp_find_session,
  518                             (void *)(uintptr_t)conf->session_id, hook);
  519                         if (hook == NULL) {
  520                                 error = ENOENT;
  521                                 break;
  522                         }
  523                         hpriv = NG_HOOK_PRIVATE(hook);
  524 
  525                         /* Update hook's config */
  526                         hpriv->conf = *conf;
  527                         break;
  528                     }
  529                 case NGM_L2TP_GET_SESS_CONFIG:
  530                     {
  531                         struct ng_l2tp_sess_config *conf;
  532                         u_int16_t session_id;
  533                         hookpriv_p hpriv;
  534                         hook_p hook;
  535 
  536                         /* Get session ID */
  537                         if (msg->header.arglen != sizeof(session_id)) {
  538                                 error = EINVAL;
  539                                 break;
  540                         }
  541                         memcpy(&session_id, msg->data, 2);
  542                         session_id = htons(session_id);
  543 
  544                         /* Find matching hook */
  545                         NG_NODE_FOREACH_HOOK(node, ng_l2tp_find_session,
  546                             (void *)(uintptr_t)session_id, hook);
  547                         if (hook == NULL) {
  548                                 error = ENOENT;
  549                                 break;
  550                         }
  551                         hpriv = NG_HOOK_PRIVATE(hook);
  552 
  553                         /* Send response */
  554                         NG_MKRESPONSE(resp, msg, sizeof(hpriv->conf), M_NOWAIT);
  555                         if (resp == NULL) {
  556                                 error = ENOMEM;
  557                                 break;
  558                         }
  559                         conf = (struct ng_l2tp_sess_config *)resp->data;
  560                         *conf = hpriv->conf;
  561 
  562                         /* Put ID's in host order */
  563                         conf->session_id = ntohs(conf->session_id);
  564                         conf->peer_id = ntohs(conf->peer_id);
  565                         break;
  566                     }
  567                 case NGM_L2TP_GET_STATS:
  568                 case NGM_L2TP_CLR_STATS:
  569                 case NGM_L2TP_GETCLR_STATS:
  570                     {
  571                         if (msg->header.cmd != NGM_L2TP_CLR_STATS) {
  572                                 NG_MKRESPONSE(resp, msg,
  573                                     sizeof(priv->stats), M_NOWAIT);
  574                                 if (resp == NULL) {
  575                                         error = ENOMEM;
  576                                         break;
  577                                 }
  578                                 memcpy(resp->data,
  579                                     &priv->stats, sizeof(priv->stats));
  580                         }
  581                         if (msg->header.cmd != NGM_L2TP_GET_STATS)
  582                                 memset(&priv->stats, 0, sizeof(priv->stats));
  583                         break;
  584                     }
  585                 case NGM_L2TP_GET_SESSION_STATS:
  586                 case NGM_L2TP_CLR_SESSION_STATS:
  587                 case NGM_L2TP_GETCLR_SESSION_STATS:
  588                     {
  589                         uint16_t session_id;
  590                         hookpriv_p hpriv;
  591                         hook_p hook;
  592 
  593                         /* Get session ID. */
  594                         if (msg->header.arglen != sizeof(session_id)) {
  595                                 error = EINVAL;
  596                                 break;
  597                         }
  598                         bcopy(msg->data, &session_id, sizeof(uint16_t));
  599                         session_id = htons(session_id);
  600 
  601                         /* Find matching hook. */
  602                         NG_NODE_FOREACH_HOOK(node, ng_l2tp_find_session,
  603                             (void *)(uintptr_t)session_id, hook);
  604                         if (hook == NULL) {
  605                                 error = ENOENT;
  606                                 break;
  607                         }
  608                         hpriv = NG_HOOK_PRIVATE(hook);
  609 
  610                         if (msg->header.cmd != NGM_L2TP_CLR_SESSION_STATS) {
  611                                 NG_MKRESPONSE(resp, msg,
  612                                     sizeof(hpriv->stats), M_NOWAIT);
  613                                 if (resp == NULL) {
  614                                         error = ENOMEM;
  615                                         break;
  616                                 }
  617                                 bcopy(&hpriv->stats, resp->data,
  618                                         sizeof(hpriv->stats));
  619                         }
  620                         if (msg->header.cmd != NGM_L2TP_GET_SESSION_STATS)
  621                                 bzero(&hpriv->stats, sizeof(hpriv->stats));
  622                         break;
  623                     }
  624                 case NGM_L2TP_SET_SEQ:
  625                     {
  626                         struct ng_l2tp_seq_config *const conf =
  627                                 (struct ng_l2tp_seq_config *)msg->data;
  628 
  629                         /* Check for invalid or illegal seq config. */
  630                         if (msg->header.arglen != sizeof(*conf)) {
  631                                 error = EINVAL;
  632                                 break;
  633                         }
  634                         conf->ns = htons(conf->ns);
  635                         conf->nr = htons(conf->nr);
  636                         conf->rack = htons(conf->rack);
  637                         conf->xack = htons(conf->xack);
  638 
  639                         /* Set sequence numbers. */
  640                         error = ng_l2tp_seq_set(priv, conf);
  641                         break;
  642                     }
  643                 default:
  644                         error = EINVAL;
  645                         break;
  646                 }
  647                 break;
  648         default:
  649                 error = EINVAL;
  650                 break;
  651         }
  652 
  653         /* Done */
  654         NG_RESPOND_MSG(error, node, item, resp);
  655         NG_FREE_MSG(msg);
  656         return (error);
  657 }
  658 
  659 /*
  660  * Receive incoming data on a hook.
  661  */
  662 static int
  663 ng_l2tp_rcvdata(hook_p hook, item_p item)
  664 {
  665         const node_p node = NG_HOOK_NODE(hook);
  666         const priv_p priv = NG_NODE_PRIVATE(node);
  667         int error;
  668 
  669         /* Sanity check */
  670         L2TP_SEQ_CHECK(&priv->seq);
  671 
  672         /* If not configured, reject */
  673         if (!priv->conf.enabled) {
  674                 NG_FREE_ITEM(item);
  675                 return (ENXIO);
  676         }
  677 
  678         /* Handle incoming frame from below */
  679         if (hook == priv->lower) {
  680                 error = ng_l2tp_recv_lower(node, item);
  681                 goto done;
  682         }
  683 
  684         /* Handle outgoing control frame */
  685         if (hook == priv->ctrl) {
  686                 error = ng_l2tp_recv_ctrl(node, item);
  687                 goto done;
  688         }
  689 
  690         /* Handle outgoing data frame */
  691         error = ng_l2tp_recv_data(node, item, NG_HOOK_PRIVATE(hook));
  692 
  693 done:
  694         /* Done */
  695         L2TP_SEQ_CHECK(&priv->seq);
  696         return (error);
  697 }
  698 
  699 /*
  700  * Destroy node
  701  */
  702 static int
  703 ng_l2tp_shutdown(node_p node)
  704 {
  705         const priv_p priv = NG_NODE_PRIVATE(node);
  706         struct l2tp_seq *const seq = &priv->seq;
  707 
  708         /* Sanity check */
  709         L2TP_SEQ_CHECK(seq);
  710 
  711         /* Reset sequence number state */
  712         ng_l2tp_seq_reset(priv);
  713 
  714         /* Free private data if neither timer is running */
  715         ng_uncallout(&seq->rack_timer, node);
  716         ng_uncallout(&seq->xack_timer, node);
  717 
  718         FREE(priv, M_NETGRAPH_L2TP);
  719 
  720         /* Unref node */
  721         NG_NODE_UNREF(node);
  722         return (0);
  723 }
  724 
  725 /*
  726  * Hook disconnection
  727  */
  728 static int
  729 ng_l2tp_disconnect(hook_p hook)
  730 {
  731         const node_p node = NG_HOOK_NODE(hook);
  732         const priv_p priv = NG_NODE_PRIVATE(node);
  733 
  734         /* Zero out hook pointer */
  735         if (hook == priv->ctrl)
  736                 priv->ctrl = NULL;
  737         else if (hook == priv->lower)
  738                 priv->lower = NULL;
  739         else {
  740                 FREE(NG_HOOK_PRIVATE(hook), M_NETGRAPH_L2TP);
  741                 NG_HOOK_SET_PRIVATE(hook, NULL);
  742         }
  743 
  744         /* Go away if no longer connected to anything */
  745         if (NG_NODE_NUMHOOKS(node) == 0 && NG_NODE_IS_VALID(node))
  746                 ng_rmnode_self(node);
  747         return (0);
  748 }
  749 
  750 /*************************************************************************
  751                         INTERNAL FUNCTIONS
  752 *************************************************************************/
  753 
  754 /*
  755  * Find the hook with a given session ID.
  756  */
  757 static int
  758 ng_l2tp_find_session(hook_p hook, void *arg)
  759 {
  760         const hookpriv_p hpriv = NG_HOOK_PRIVATE(hook);
  761         const u_int16_t sid = (u_int16_t)(uintptr_t)arg;
  762 
  763         if (hpriv == NULL || hpriv->conf.session_id != sid)
  764                 return (-1);
  765         return (0);
  766 }
  767 
  768 /*
  769  * Reset a hook's session state.
  770  */
  771 static int
  772 ng_l2tp_reset_session(hook_p hook, void *arg)
  773 {
  774         const hookpriv_p hpriv = NG_HOOK_PRIVATE(hook);
  775 
  776         if (hpriv != NULL) {
  777                 hpriv->conf.control_dseq = 0;
  778                 hpriv->conf.enable_dseq = 0;
  779                 bzero(&hpriv->conf, sizeof(struct ng_l2tp_session_stats));
  780                 hpriv->nr = 0;
  781                 hpriv->ns = 0;
  782         }
  783         return (-1);
  784 }
  785 
  786 /*
  787  * Handle an incoming frame from below.
  788  */
  789 static int
  790 ng_l2tp_recv_lower(node_p node, item_p item)
  791 {
  792         static const u_int16_t req_bits[2][2] = {
  793                 { L2TP_DATA_0BITS, L2TP_DATA_1BITS },
  794                 { L2TP_CTRL_0BITS, L2TP_CTRL_1BITS },
  795         };
  796         const priv_p priv = NG_NODE_PRIVATE(node);
  797         hookpriv_p hpriv = NULL;
  798         hook_p hook = NULL;
  799         u_int16_t ids[2];
  800         struct mbuf *m;
  801         u_int16_t hdr;
  802         u_int16_t ns;
  803         u_int16_t nr;
  804         int is_ctrl;
  805         int error;
  806         int len, plen;
  807 
  808         /* Grab mbuf */
  809         NGI_GET_M(item, m);
  810 
  811         /* Remember full packet length; needed for per session accounting. */
  812         plen = m->m_pkthdr.len;
  813 
  814         /* Update stats */
  815         priv->stats.recvPackets++;
  816         priv->stats.recvOctets += plen;
  817 
  818         /* Get initial header */
  819         if (m->m_pkthdr.len < 6) {
  820                 priv->stats.recvRunts++;
  821                 NG_FREE_ITEM(item);
  822                 NG_FREE_M(m);
  823                 return (EINVAL);
  824         }
  825         if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
  826                 priv->stats.memoryFailures++;
  827                 NG_FREE_ITEM(item);
  828                 return (EINVAL);
  829         }
  830         hdr = ntohs(*mtod(m, u_int16_t *));
  831         m_adj(m, 2);
  832 
  833         /* Check required header bits and minimum length */
  834         is_ctrl = (hdr & L2TP_HDR_CTRL) != 0;
  835         if ((hdr & req_bits[is_ctrl][0]) != 0
  836             || (~hdr & req_bits[is_ctrl][1]) != 0) {
  837                 priv->stats.recvInvalid++;
  838                 NG_FREE_ITEM(item);
  839                 NG_FREE_M(m);
  840                 return (EINVAL);
  841         }
  842         if (m->m_pkthdr.len < 4                         /* tunnel, session id */
  843             + (2 * ((hdr & L2TP_HDR_LEN) != 0))         /* length field */
  844             + (4 * ((hdr & L2TP_HDR_SEQ) != 0))         /* seq # fields */
  845             + (2 * ((hdr & L2TP_HDR_OFF) != 0))) {      /* offset field */
  846                 priv->stats.recvRunts++;
  847                 NG_FREE_ITEM(item);
  848                 NG_FREE_M(m);
  849                 return (EINVAL);
  850         }
  851 
  852         /* Get and validate length field if present */
  853         if ((hdr & L2TP_HDR_LEN) != 0) {
  854                 if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
  855                         priv->stats.memoryFailures++;
  856                         NG_FREE_ITEM(item);
  857                         return (EINVAL);
  858                 }
  859                 len = (u_int16_t)ntohs(*mtod(m, u_int16_t *)) - 4;
  860                 m_adj(m, 2);
  861                 if (len < 0 || len > m->m_pkthdr.len) {
  862                         priv->stats.recvInvalid++;
  863                         NG_FREE_ITEM(item);
  864                         NG_FREE_M(m);
  865                         return (EINVAL);
  866                 }
  867                 if (len < m->m_pkthdr.len)              /* trim extra bytes */
  868                         m_adj(m, -(m->m_pkthdr.len - len));
  869         }
  870 
  871         /* Get tunnel ID and session ID */
  872         if (m->m_len < 4 && (m = m_pullup(m, 4)) == NULL) {
  873                 priv->stats.memoryFailures++;
  874                 NG_FREE_ITEM(item);
  875                 return (EINVAL);
  876         }
  877         memcpy(ids, mtod(m, u_int16_t *), 4);
  878         m_adj(m, 4);
  879 
  880         /* Check tunnel ID */
  881         if (ids[0] != priv->conf.tunnel_id
  882             && (priv->conf.match_id || ids[0] != 0)) {
  883                 priv->stats.recvWrongTunnel++;
  884                 NG_FREE_ITEM(item);
  885                 NG_FREE_M(m);
  886                 return (EADDRNOTAVAIL);
  887         }
  888 
  889         /* Check session ID (for data packets only) */
  890         if ((hdr & L2TP_HDR_CTRL) == 0) {
  891                 NG_NODE_FOREACH_HOOK(node, ng_l2tp_find_session,
  892                     (void *)(uintptr_t)ids[1], hook);
  893                 if (hook == NULL) {
  894                         priv->stats.recvUnknownSID++;
  895                         NG_FREE_ITEM(item);
  896                         NG_FREE_M(m);
  897                         return (ENOTCONN);
  898                 }
  899                 hpriv = NG_HOOK_PRIVATE(hook);
  900         }
  901 
  902         /* Get Ns, Nr fields if present */
  903         if ((hdr & L2TP_HDR_SEQ) != 0) {
  904                 if (m->m_len < 4 && (m = m_pullup(m, 4)) == NULL) {
  905                         priv->stats.memoryFailures++;
  906                         NG_FREE_ITEM(item);
  907                         return (EINVAL);
  908                 }
  909                 memcpy(&ns, &mtod(m, u_int16_t *)[0], 2);
  910                 ns = ntohs(ns);
  911                 memcpy(&nr, &mtod(m, u_int16_t *)[1], 2);
  912                 nr = ntohs(nr);
  913                 m_adj(m, 4);
  914         }
  915 
  916         /* Strip offset padding if present */
  917         if ((hdr & L2TP_HDR_OFF) != 0) {
  918                 u_int16_t offset;
  919 
  920                 /* Get length of offset padding */
  921                 if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
  922                         priv->stats.memoryFailures++;
  923                         NG_FREE_ITEM(item);
  924                         return (EINVAL);
  925                 }
  926                 memcpy(&offset, mtod(m, u_int16_t *), 2);
  927                 offset = ntohs(offset);
  928 
  929                 /* Trim offset padding */
  930                 if ((2+offset) > m->m_pkthdr.len) {
  931                         priv->stats.recvInvalid++;
  932                         NG_FREE_ITEM(item);
  933                         NG_FREE_M(m);
  934                         return (EINVAL);
  935                 }
  936                 m_adj(m, 2+offset);
  937         }
  938 
  939         /* Handle control packets */
  940         if ((hdr & L2TP_HDR_CTRL) != 0) {
  941 
  942                 /* Handle receive ack sequence number Nr */
  943                 ng_l2tp_seq_recv_nr(priv, nr);
  944 
  945                 /* Discard ZLB packets */
  946                 if (m->m_pkthdr.len == 0) {
  947                         priv->stats.recvZLBs++;
  948                         NG_FREE_ITEM(item);
  949                         NG_FREE_M(m);
  950                         return (0);
  951                 }
  952 
  953                 /*
  954                  * Prepend session ID to packet here: we don't want to accept
  955                  * the send sequence number Ns if we have to drop the packet
  956                  * later because of a memory error, because then the upper
  957                  * layer would never get the packet.
  958                  */
  959                 M_PREPEND(m, 2, M_DONTWAIT);
  960                 if (m == NULL) {
  961                         priv->stats.memoryFailures++;
  962                         NG_FREE_ITEM(item);
  963                         return (ENOBUFS);
  964                 }
  965                 memcpy(mtod(m, u_int16_t *), &ids[1], 2);
  966 
  967                 /* Now handle send sequence number */
  968                 if (ng_l2tp_seq_recv_ns(priv, ns) == -1) {
  969                         NG_FREE_ITEM(item);
  970                         NG_FREE_M(m);
  971                         return (0);
  972                 }
  973 
  974                 /* Deliver packet to upper layers */
  975                 NG_FWD_NEW_DATA(error, item, priv->ctrl, m);
  976                 return (error);
  977         }
  978 
  979         /* Per session packet, account it. */
  980         hpriv->stats.recvPackets++;
  981         hpriv->stats.recvOctets += plen;
  982 
  983         /* Follow peer's lead in data sequencing, if configured to do so */
  984         if (!hpriv->conf.control_dseq)
  985                 hpriv->conf.enable_dseq = ((hdr & L2TP_HDR_SEQ) != 0);
  986 
  987         /* Handle data sequence numbers if present and enabled */
  988         if ((hdr & L2TP_HDR_SEQ) != 0) {
  989                 if (hpriv->conf.enable_dseq
  990                     && L2TP_SEQ_DIFF(ns, hpriv->nr) < 0) {
  991                         NG_FREE_ITEM(item);     /* duplicate or out of order */
  992                         NG_FREE_M(m);
  993                         priv->stats.recvDataDrops++;
  994                         return (0);
  995                 }
  996                 hpriv->nr = ns + 1;
  997         }
  998 
  999         /* Drop empty data packets */
 1000         if (m->m_pkthdr.len == 0) {
 1001                 NG_FREE_ITEM(item);
 1002                 NG_FREE_M(m);
 1003                 return (0);
 1004         }
 1005 
 1006         /* Deliver data */
 1007         NG_FWD_NEW_DATA(error, item, hook, m);
 1008         return (error);
 1009 }
 1010 
 1011 /*
 1012  * Handle an outgoing control frame.
 1013  */
 1014 static int
 1015 ng_l2tp_recv_ctrl(node_p node, item_p item)
 1016 {
 1017         const priv_p priv = NG_NODE_PRIVATE(node);
 1018         struct l2tp_seq *const seq = &priv->seq;
 1019         struct mbuf *m;
 1020         int i;
 1021 
 1022         /* Grab mbuf and discard other stuff XXX */
 1023         NGI_GET_M(item, m);
 1024         NG_FREE_ITEM(item);
 1025 
 1026         /* Packet should have session ID prepended */
 1027         if (m->m_pkthdr.len < 2) {
 1028                 priv->stats.xmitInvalid++;
 1029                 m_freem(m);
 1030                 return (EINVAL);
 1031         }
 1032 
 1033         /* Check max length */
 1034         if (m->m_pkthdr.len >= 0x10000 - 14) {
 1035                 priv->stats.xmitTooBig++;
 1036                 m_freem(m);
 1037                 return (EOVERFLOW);
 1038         }
 1039 
 1040         /* Find next empty slot in transmit queue */
 1041         for (i = 0; i < L2TP_MAX_XWIN && seq->xwin[i] != NULL; i++);
 1042         if (i == L2TP_MAX_XWIN) {
 1043                 priv->stats.xmitDrops++;
 1044                 m_freem(m);
 1045                 return (ENOBUFS);
 1046         }
 1047         seq->xwin[i] = m;
 1048 
 1049         /* Sanity check receive ack timer state */
 1050         KASSERT((i == 0) ^ callout_pending(&seq->rack_timer),
 1051             ("%s: xwin %d full but rack timer %s running",
 1052             __FUNCTION__, i, callout_pending(&seq->rack_timer) ? "" : "not "));
 1053 
 1054         /* If peer's receive window is already full, nothing else to do */
 1055         if (i >= seq->cwnd)
 1056                 return (0);
 1057 
 1058         /* Start retransmit timer if not already running */
 1059         if (!callout_pending(&seq->rack_timer))
 1060                 ng_callout(&seq->rack_timer, node, NULL,
 1061                     hz, ng_l2tp_seq_rack_timeout, NULL, 0);
 1062 
 1063         /* Copy packet */
 1064         if ((m = L2TP_COPY_MBUF(seq->xwin[i], M_DONTWAIT)) == NULL) {
 1065                 priv->stats.memoryFailures++;
 1066                 return (ENOBUFS);
 1067         }
 1068 
 1069         /* Send packet and increment xmit sequence number */
 1070         return (ng_l2tp_xmit_ctrl(priv, m, seq->ns++));
 1071 }
 1072 
 1073 /*
 1074  * Handle an outgoing data frame.
 1075  */
 1076 static int
 1077 ng_l2tp_recv_data(node_p node, item_p item, hookpriv_p hpriv)
 1078 {
 1079         const priv_p priv = NG_NODE_PRIVATE(node);
 1080         struct mbuf *m;
 1081         u_int16_t hdr;
 1082         int error;
 1083         int i = 1;
 1084 
 1085         /* Get mbuf */
 1086         NGI_GET_M(item, m);
 1087 
 1088         /* Check max length */
 1089         if (m->m_pkthdr.len >= 0x10000 - 12) {
 1090                 priv->stats.xmitDataTooBig++;
 1091                 NG_FREE_ITEM(item);
 1092                 NG_FREE_M(m);
 1093                 return (EOVERFLOW);
 1094         }
 1095 
 1096         /* Prepend L2TP header */
 1097         M_PREPEND(m, 6
 1098             + (2 * (hpriv->conf.include_length != 0))
 1099             + (4 * (hpriv->conf.enable_dseq != 0)),
 1100             M_DONTWAIT);
 1101         if (m == NULL) {
 1102                 priv->stats.memoryFailures++;
 1103                 NG_FREE_ITEM(item);
 1104                 return (ENOBUFS);
 1105         }
 1106         hdr = L2TP_DATA_HDR;
 1107         if (hpriv->conf.include_length) {
 1108                 hdr |= L2TP_HDR_LEN;
 1109                 mtod(m, u_int16_t *)[i++] = htons(m->m_pkthdr.len);
 1110         }
 1111         mtod(m, u_int16_t *)[i++] = priv->conf.peer_id;
 1112         mtod(m, u_int16_t *)[i++] = hpriv->conf.peer_id;
 1113         if (hpriv->conf.enable_dseq) {
 1114                 hdr |= L2TP_HDR_SEQ;
 1115                 mtod(m, u_int16_t *)[i++] = htons(hpriv->ns);
 1116                 mtod(m, u_int16_t *)[i++] = htons(hpriv->nr);
 1117                 hpriv->ns++;
 1118         }
 1119         mtod(m, u_int16_t *)[0] = htons(hdr);
 1120 
 1121         /* Update per session stats. */
 1122         hpriv->stats.xmitPackets++;
 1123         hpriv->stats.xmitOctets += m->m_pkthdr.len;
 1124 
 1125         /* Send packet */
 1126         NG_FWD_NEW_DATA(error, item, priv->lower, m);
 1127         return (error);
 1128 }
 1129 
 1130 /*
 1131  * Send a message to our controlling node that we've failed.
 1132  */
 1133 static void
 1134 ng_l2tp_seq_failure(priv_p priv)
 1135 {
 1136         struct ng_mesg *msg;
 1137         int error;
 1138 
 1139         NG_MKMESSAGE(msg, NGM_L2TP_COOKIE, NGM_L2TP_ACK_FAILURE, 0, M_NOWAIT);
 1140         if (msg == NULL)
 1141                 return;
 1142         NG_SEND_MSG_ID(error, priv->node, msg, priv->ftarget, 0);
 1143 }
 1144 
 1145 /************************************************************************
 1146                         SEQUENCE NUMBER HANDLING
 1147 ************************************************************************/
 1148 
 1149 /*
 1150  * Initialize sequence number state.
 1151  */
 1152 static void
 1153 ng_l2tp_seq_init(priv_p priv)
 1154 {
 1155         struct l2tp_seq *const seq = &priv->seq;
 1156 
 1157         KASSERT(priv->conf.peer_win >= 1,
 1158             ("%s: peer_win is zero", __FUNCTION__));
 1159         memset(seq, 0, sizeof(*seq));
 1160         seq->cwnd = 1;
 1161         seq->wmax = priv->conf.peer_win;
 1162         if (seq->wmax > L2TP_MAX_XWIN)
 1163                 seq->wmax = L2TP_MAX_XWIN;
 1164         seq->ssth = seq->wmax;
 1165         seq->max_rexmits = priv->conf.rexmit_max;
 1166         seq->max_rexmit_to = priv->conf.rexmit_max_to;
 1167         ng_callout_init(&seq->rack_timer);
 1168         ng_callout_init(&seq->xack_timer);
 1169         L2TP_SEQ_CHECK(seq);
 1170 }
 1171 
 1172 /*
 1173  * Set sequence number state as given from user.
 1174  */
 1175 static int
 1176 ng_l2tp_seq_set(priv_p priv, const struct ng_l2tp_seq_config *conf)
 1177 {
 1178         struct l2tp_seq *const seq = &priv->seq;
 1179 
 1180         /* If node is enabled, deny update to sequence numbers. */
 1181         if (priv->conf.enabled)
 1182                 return (EBUSY);
 1183 
 1184         /* We only can handle the simple cases. */
 1185         if (conf->xack != conf->nr || conf->ns != conf->rack)
 1186                 return (EINVAL);
 1187 
 1188         /* Set ns,nr,rack,xack parameters. */
 1189         seq->ns = conf->ns;
 1190         seq->nr = conf->nr;
 1191         seq->rack = conf->rack;
 1192         seq->xack = conf->xack;
 1193 
 1194         return (0);
 1195 }
 1196 
 1197 /*
 1198  * Adjust sequence number state accordingly after reconfiguration.
 1199  */
 1200 static int
 1201 ng_l2tp_seq_adjust(priv_p priv, const struct ng_l2tp_config *conf)
 1202 {
 1203         struct l2tp_seq *const seq = &priv->seq;
 1204         u_int16_t new_wmax;
 1205 
 1206         /* If disabling node, reset state sequence number */
 1207         if (!conf->enabled) {
 1208                 ng_l2tp_seq_reset(priv);
 1209                 return (0);
 1210         }
 1211 
 1212         /* Adjust peer's max recv window; it can only increase */
 1213         new_wmax = conf->peer_win;
 1214         if (new_wmax > L2TP_MAX_XWIN)
 1215                 new_wmax = L2TP_MAX_XWIN;
 1216         if (new_wmax == 0)
 1217                 return (EINVAL);
 1218         if (new_wmax < seq->wmax)
 1219                 return (EBUSY);
 1220         seq->wmax = new_wmax;
 1221 
 1222         /* Update retransmit parameters */
 1223         seq->max_rexmits = conf->rexmit_max;
 1224         seq->max_rexmit_to = conf->rexmit_max_to;
 1225 
 1226         /* Done */
 1227         return (0);
 1228 }
 1229 
 1230 /*
 1231  * Reset sequence number state.
 1232  */
 1233 static void
 1234 ng_l2tp_seq_reset(priv_p priv)
 1235 {
 1236         struct l2tp_seq *const seq = &priv->seq;
 1237         hook_p hook;
 1238         int i;
 1239 
 1240         /* Sanity check */
 1241         L2TP_SEQ_CHECK(seq);
 1242 
 1243         /* Stop timers */
 1244         ng_uncallout(&seq->rack_timer, priv->node);
 1245         ng_uncallout(&seq->xack_timer, priv->node);
 1246 
 1247         /* Free retransmit queue */
 1248         for (i = 0; i < L2TP_MAX_XWIN; i++) {
 1249                 if (seq->xwin[i] == NULL)
 1250                         break;
 1251                 m_freem(seq->xwin[i]);
 1252         }
 1253 
 1254         /* Reset session hooks' sequence number states */
 1255         NG_NODE_FOREACH_HOOK(priv->node, ng_l2tp_reset_session, NULL, hook);
 1256 
 1257         /* Reset node's sequence number state */
 1258         memset(seq, 0, sizeof(*seq));
 1259         seq->cwnd = 1;
 1260         seq->wmax = L2TP_MAX_XWIN;
 1261         seq->ssth = seq->wmax;
 1262 
 1263         /* Done */
 1264         L2TP_SEQ_CHECK(seq);
 1265 }
 1266 
 1267 /*
 1268  * Handle receipt of an acknowledgement value (Nr) from peer.
 1269  */
 1270 static void
 1271 ng_l2tp_seq_recv_nr(priv_p priv, u_int16_t nr)
 1272 {
 1273         struct l2tp_seq *const seq = &priv->seq;
 1274         struct mbuf *m;
 1275         int nack;
 1276         int i;
 1277 
 1278         /* Verify peer's ACK is in range */
 1279         if ((nack = L2TP_SEQ_DIFF(nr, seq->rack)) <= 0)
 1280                 return;                         /* duplicate ack */
 1281         if (L2TP_SEQ_DIFF(nr, seq->ns) > 0) {
 1282                 priv->stats.recvBadAcks++;      /* ack for packet not sent */
 1283                 return;
 1284         }
 1285         KASSERT(nack <= L2TP_MAX_XWIN,
 1286             ("%s: nack=%d > %d", __FUNCTION__, nack, L2TP_MAX_XWIN));
 1287 
 1288         /* Update receive ack stats */
 1289         seq->rack = nr;
 1290         seq->rexmits = 0;
 1291 
 1292         /* Free acknowledged packets and shift up packets in the xmit queue */
 1293         for (i = 0; i < nack; i++)
 1294                 m_freem(seq->xwin[i]);
 1295         memmove(seq->xwin, seq->xwin + nack,
 1296             (L2TP_MAX_XWIN - nack) * sizeof(*seq->xwin));
 1297         memset(seq->xwin + (L2TP_MAX_XWIN - nack), 0,
 1298             nack * sizeof(*seq->xwin));
 1299 
 1300         /*
 1301          * Do slow-start/congestion avoidance windowing algorithm described
 1302          * in RFC 2661, Appendix A. Here we handle a multiple ACK as if each
 1303          * ACK had arrived separately.
 1304          */
 1305         if (seq->cwnd < seq->wmax) {
 1306 
 1307                 /* Handle slow start phase */
 1308                 if (seq->cwnd < seq->ssth) {
 1309                         seq->cwnd += nack;
 1310                         nack = 0;
 1311                         if (seq->cwnd > seq->ssth) {    /* into cg.av. phase */
 1312                                 nack = seq->cwnd - seq->ssth;
 1313                                 seq->cwnd = seq->ssth;
 1314                         }
 1315                 }
 1316 
 1317                 /* Handle congestion avoidance phase */
 1318                 if (seq->cwnd >= seq->ssth) {
 1319                         seq->acks += nack;
 1320                         while (seq->acks >= seq->cwnd) {
 1321                                 seq->acks -= seq->cwnd;
 1322                                 if (seq->cwnd < seq->wmax)
 1323                                         seq->cwnd++;
 1324                         }
 1325                 }
 1326         }
 1327 
 1328         /* Stop xmit timer */
 1329         if (callout_pending(&seq->rack_timer))
 1330                 ng_uncallout(&seq->rack_timer, priv->node);
 1331 
 1332         /* If transmit queue is empty, we're done for now */
 1333         if (seq->xwin[0] == NULL)
 1334                 return;
 1335 
 1336         /* Start restransmit timer again */
 1337         ng_callout(&seq->rack_timer, priv->node, NULL,
 1338             hz, ng_l2tp_seq_rack_timeout, NULL, 0);
 1339 
 1340         /*
 1341          * Send more packets, trying to keep peer's receive window full.
 1342          * If there is a memory error, pretend packet was sent, as it
 1343          * will get retransmitted later anyway.
 1344          */
 1345         while ((i = L2TP_SEQ_DIFF(seq->ns, seq->rack)) < seq->cwnd
 1346             && seq->xwin[i] != NULL) {
 1347                 if ((m = L2TP_COPY_MBUF(seq->xwin[i], M_DONTWAIT)) == NULL)
 1348                         priv->stats.memoryFailures++;
 1349                 else
 1350                         ng_l2tp_xmit_ctrl(priv, m, seq->ns);
 1351                 seq->ns++;
 1352         }
 1353 }
 1354 
 1355 /*
 1356  * Handle receipt of a sequence number value (Ns) from peer.
 1357  * We make no attempt to re-order out of order packets.
 1358  *
 1359  * This function should only be called for non-ZLB packets.
 1360  *
 1361  * Returns:
 1362  *       0      Accept packet
 1363  *      -1      Drop packet
 1364  */
 1365 static int
 1366 ng_l2tp_seq_recv_ns(priv_p priv, u_int16_t ns)
 1367 {
 1368         struct l2tp_seq *const seq = &priv->seq;
 1369 
 1370         /* If not what we expect, drop packet and send an immediate ZLB ack */
 1371         if (ns != seq->nr) {
 1372                 if (L2TP_SEQ_DIFF(ns, seq->nr) < 0)
 1373                         priv->stats.recvDuplicates++;
 1374                 else
 1375                         priv->stats.recvOutOfOrder++;
 1376                 ng_l2tp_xmit_ctrl(priv, NULL, seq->ns);
 1377                 return (-1);
 1378         }
 1379 
 1380         /* Update recv sequence number */
 1381         seq->nr++;
 1382 
 1383         /* Start receive ack timer, if not already running */
 1384         if (!callout_pending(&seq->xack_timer))
 1385                 ng_callout(&seq->xack_timer, priv->node, NULL,
 1386                     L2TP_DELAYED_ACK, ng_l2tp_seq_xack_timeout, NULL, 0);
 1387 
 1388         /* Accept packet */
 1389         return (0);
 1390 }
 1391 
 1392 /*
 1393  * Handle an ack timeout. We have an outstanding ack that we
 1394  * were hoping to piggy-back, but haven't, so send a ZLB.
 1395  */
 1396 static void
 1397 ng_l2tp_seq_xack_timeout(node_p node, hook_p hook, void *arg1, int arg2)
 1398 {
 1399         const priv_p priv = NG_NODE_PRIVATE(node);
 1400         struct l2tp_seq *const seq = &priv->seq;
 1401 
 1402         /* Sanity check */
 1403         L2TP_SEQ_CHECK(seq);
 1404 
 1405         /* If ack is still outstanding, send a ZLB */
 1406         if (seq->xack != seq->nr)
 1407                 ng_l2tp_xmit_ctrl(priv, NULL, seq->ns);
 1408 
 1409         /* Done */
 1410         L2TP_SEQ_CHECK(seq);
 1411 }
 1412 
 1413 /* 
 1414  * Handle a transmit timeout. The peer has failed to respond
 1415  * with an ack for our packet, so retransmit it.
 1416  */
 1417 static void
 1418 ng_l2tp_seq_rack_timeout(node_p node, hook_p hook, void *arg1, int arg2)
 1419 {
 1420         const priv_p priv = NG_NODE_PRIVATE(node);
 1421         struct l2tp_seq *const seq = &priv->seq;
 1422         struct mbuf *m;
 1423         u_int delay;
 1424 
 1425         /* Sanity check */
 1426         L2TP_SEQ_CHECK(seq);
 1427 
 1428         /* Make sure peer's ack is still outstanding before doing anything */
 1429         if (seq->rack == seq->ns)
 1430                 goto done;
 1431 
 1432         priv->stats.xmitRetransmits++;
 1433 
 1434         /* Have we reached the retransmit limit? If so, notify owner. */
 1435         if (seq->rexmits++ >= seq->max_rexmits)
 1436                 ng_l2tp_seq_failure(priv);
 1437 
 1438         /* Restart timer, this time with an increased delay */
 1439         delay = (seq->rexmits > 12) ? (1 << 12) : (1 << seq->rexmits);
 1440         if (delay > seq->max_rexmit_to)
 1441                 delay = seq->max_rexmit_to;
 1442         ng_callout(&seq->rack_timer, node, NULL,
 1443             hz * delay, ng_l2tp_seq_rack_timeout, NULL, 0);
 1444 
 1445         /* Do slow-start/congestion algorithm windowing algorithm */
 1446         seq->ssth = (seq->cwnd + 1) / 2;
 1447         seq->cwnd = 1;
 1448         seq->acks = 0;
 1449 
 1450         /* Retransmit oldest unack'd packet */
 1451         if ((m = L2TP_COPY_MBUF(seq->xwin[0], M_DONTWAIT)) == NULL)
 1452                 priv->stats.memoryFailures++;
 1453         else
 1454                 ng_l2tp_xmit_ctrl(priv, m, seq->rack);
 1455 
 1456 done:
 1457         /* Done */
 1458         L2TP_SEQ_CHECK(seq);
 1459 }
 1460 
 1461 /*
 1462  * Transmit a control stream packet, payload optional.
 1463  * The transmit sequence number is not incremented.
 1464  */
 1465 static int
 1466 ng_l2tp_xmit_ctrl(priv_p priv, struct mbuf *m, u_int16_t ns)
 1467 {
 1468         struct l2tp_seq *const seq = &priv->seq;
 1469         u_int16_t session_id = 0;
 1470         int error;
 1471 
 1472         /* If no mbuf passed, send an empty packet (ZLB) */
 1473         if (m == NULL) {
 1474 
 1475                 /* Create a new mbuf for ZLB packet */
 1476                 MGETHDR(m, M_DONTWAIT, MT_DATA);
 1477                 if (m == NULL) {
 1478                         priv->stats.memoryFailures++;
 1479                         return (ENOBUFS);
 1480                 }
 1481                 m->m_len = m->m_pkthdr.len = 12;
 1482                 m->m_pkthdr.rcvif = NULL;
 1483                 priv->stats.xmitZLBs++;
 1484         } else {
 1485 
 1486                 /* Strip off session ID */
 1487                 if (m->m_len < 2 && (m = m_pullup(m, 2)) == NULL) {
 1488                         priv->stats.memoryFailures++;
 1489                         return (ENOBUFS);
 1490                 }
 1491                 memcpy(&session_id, mtod(m, u_int16_t *), 2);
 1492                 m_adj(m, 2);
 1493 
 1494                 /* Make room for L2TP header */
 1495                 M_PREPEND(m, 12, M_DONTWAIT);
 1496                 if (m == NULL) {
 1497                         priv->stats.memoryFailures++;
 1498                         return (ENOBUFS);
 1499                 }
 1500         }
 1501 
 1502         /* Fill in L2TP header */
 1503         mtod(m, u_int16_t *)[0] = htons(L2TP_CTRL_HDR);
 1504         mtod(m, u_int16_t *)[1] = htons(m->m_pkthdr.len);
 1505         mtod(m, u_int16_t *)[2] = priv->conf.peer_id;
 1506         mtod(m, u_int16_t *)[3] = session_id;
 1507         mtod(m, u_int16_t *)[4] = htons(ns);
 1508         mtod(m, u_int16_t *)[5] = htons(seq->nr);
 1509 
 1510         /* Update sequence number info and stats */
 1511         priv->stats.xmitPackets++;
 1512         priv->stats.xmitOctets += m->m_pkthdr.len;
 1513 
 1514         /* Stop ack timer: we're sending an ack with this packet */
 1515         if (callout_pending(&seq->xack_timer))
 1516                 ng_uncallout(&seq->xack_timer, priv->node);
 1517 
 1518         seq->xack = seq->nr;
 1519 
 1520         /* Send packet */
 1521         NG_SEND_DATA_ONLY(error, priv->lower, m);
 1522         return (error);
 1523 }
 1524 
 1525 #ifdef INVARIANTS
 1526 /*
 1527  * Sanity check sequence number state.
 1528  */
 1529 static void
 1530 ng_l2tp_seq_check(struct l2tp_seq *seq)
 1531 {
 1532         const int self_unack = L2TP_SEQ_DIFF(seq->nr, seq->xack);
 1533         const int peer_unack = L2TP_SEQ_DIFF(seq->ns, seq->rack);
 1534         int i;
 1535 
 1536 #define CHECK(p)        KASSERT((p), ("%s: not: %s", __FUNCTION__, #p))
 1537 
 1538         CHECK(seq->wmax <= L2TP_MAX_XWIN);
 1539         CHECK(seq->cwnd >= 1);
 1540         CHECK(seq->cwnd <= seq->wmax);
 1541         CHECK(seq->ssth >= 1);
 1542         CHECK(seq->ssth <= seq->wmax);
 1543         if (seq->cwnd < seq->ssth)
 1544                 CHECK(seq->acks == 0);
 1545         else
 1546                 CHECK(seq->acks <= seq->cwnd);
 1547         CHECK(self_unack >= 0);
 1548         CHECK(peer_unack >= 0);
 1549         CHECK(peer_unack <= seq->wmax);
 1550         CHECK((self_unack == 0) ^ callout_pending(&seq->xack_timer));
 1551         CHECK((peer_unack == 0) ^ callout_pending(&seq->rack_timer));
 1552         for (i = 0; i < peer_unack; i++)
 1553                 CHECK(seq->xwin[i] != NULL);
 1554         for ( ; i < seq->cwnd; i++)         /* verify peer's recv window full */
 1555                 CHECK(seq->xwin[i] == NULL);
 1556 
 1557 #undef CHECK
 1558 }
 1559 #endif  /* INVARIANTS */

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