release/src-rt-6.x.4708/linux/linux-2.6.36/net/llc/llc_input.c

   1 /*
   2  * llc_input.c - Minimal input path for LLC
   3  *
   4  * Copyright (c) 1997 by Procom Technology, Inc.
   5  *               2001-2003 by Arnaldo Carvalho de Melo <acme@conectiva.com.br>
   6  *
   7  * This program can be redistributed or modified under the terms of the
   8  * GNU General Public License as published by the Free Software Foundation.
   9  * This program is distributed without any warranty or implied warranty
  10  * of merchantability or fitness for a particular purpose.
  11  *
  12  * See the GNU General Public License for more details.
  13  */
  14 #include <linux/netdevice.h>
  15 #include <linux/slab.h>
  16 #include <net/net_namespace.h>
  17 #include <net/llc.h>
  18 #include <net/llc_pdu.h>
  19 #include <net/llc_sap.h>
  20
  21 #define dprintk(args...)
  22
  23 /*
  24  * Packet handler for the station, registerable because in the minimal
  25  * LLC core that is taking shape only the very minimal subset of LLC that
  26  * is needed for things like IPX, Appletalk, etc will stay, with all the
  27  * rest in the llc1 and llc2 modules.
  28  */
  29 static void (*llc_station_handler)(struct sk_buff *skb);
  30
  31 /*
  32  * Packet handlers for LLC_DEST_SAP and LLC_DEST_CONN.
  33  */
  34 static void (*llc_type_handlers[2])(struct llc_sap *sap,
  35                                     struct sk_buff *skb);
  36
  37 void llc_add_pack(int type, void (*handler)(struct llc_sap *sap,
  38                                             struct sk_buff *skb))
  39 {
  40         if (type == LLC_DEST_SAP || type == LLC_DEST_CONN)
  41                 llc_type_handlers[type - 1] = handler;
  42 }
  43
  44 void llc_remove_pack(int type)
  45 {
  46         if (type == LLC_DEST_SAP || type == LLC_DEST_CONN)
  47                 llc_type_handlers[type - 1] = NULL;
  48 }
  49
  50 void llc_set_station_handler(void (*handler)(struct sk_buff *skb))
  51 {
  52         llc_station_handler = handler;
  53 }
  54
  55 /**
  56  *      llc_pdu_type - returns which LLC component must handle for PDU
  57  *      @skb: input skb
  58  *
  59  *      This function returns which LLC component must handle this PDU.
  60  */
  61 static __inline__ int llc_pdu_type(struct sk_buff *skb)
  62 {
  63         int type = LLC_DEST_CONN; /* I-PDU or S-PDU type */
  64         struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb);
  65
  66         if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) != LLC_PDU_TYPE_U)
  67                 goto out;
  68         switch (LLC_U_PDU_CMD(pdu)) {
  69         case LLC_1_PDU_CMD_XID:
  70         case LLC_1_PDU_CMD_UI:
  71         case LLC_1_PDU_CMD_TEST:
  72                 type = LLC_DEST_SAP;
  73                 break;
  74         case LLC_2_PDU_CMD_SABME:
  75         case LLC_2_PDU_CMD_DISC:
  76         case LLC_2_PDU_RSP_UA:
  77         case LLC_2_PDU_RSP_DM:
  78         case LLC_2_PDU_RSP_FRMR:
  79                 break;
  80         default:
  81                 type = LLC_DEST_INVALID;
  82                 break;
  83         }
  84 out:
  85         return type;
  86 }
  87
  88 /**
  89  *      llc_fixup_skb - initializes skb pointers
  90  *      @skb: This argument points to incoming skb
  91  *
  92  *      Initializes internal skb pointer to start of network layer by deriving
  93  *      length of LLC header; finds length of LLC control field in LLC header
  94  *      by looking at the two lowest-order bits of the first control field
  95  *      byte; field is either 3 or 4 bytes long.
  96  */
  97 static inline int llc_fixup_skb(struct sk_buff *skb)
  98 {
  99         u8 llc_len = 2;
 100         struct llc_pdu_un *pdu;
 101
 102         if (unlikely(!pskb_may_pull(skb, sizeof(*pdu))))
 103                 return 0;
 104
 105         pdu = (struct llc_pdu_un *)skb->data;
 106         if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) == LLC_PDU_TYPE_U)
 107                 llc_len = 1;
 108         llc_len += 2;
 109
 110         if (unlikely(!pskb_may_pull(skb, llc_len)))
 111                 return 0;
 112
 113         skb->transport_header += llc_len;
 114         skb_pull(skb, llc_len);
 115         if (skb->protocol == htons(ETH_P_802_2)) {
 116                 __be16 pdulen = eth_hdr(skb)->h_proto;
 117                 s32 data_size = ntohs(pdulen) - llc_len;
 118
 119                 if (data_size < 0 ||
 120                     ((skb_tail_pointer(skb) -
 121                       (u8 *)pdu) - llc_len) < data_size)
 122                         return 0;
 123                 if (unlikely(pskb_trim_rcsum(skb, data_size)))
 124                         return 0;
 125         }
 126         return 1;
 127 }
 128
 129 /**
 130  *      llc_rcv - 802.2 entry point from net lower layers
 131  *      @skb: received pdu
 132  *      @dev: device that receive pdu
 133  *      @pt: packet type
 134  *
 135  *      When the system receives a 802.2 frame this function is called. It
 136  *      checks SAP and connection of received pdu and passes frame to
 137  *      llc_{station,sap,conn}_rcv for sending to proper state machine. If
 138  *      the frame is related to a busy connection (a connection is sending
 139  *      data now), it queues this frame in the connection's backlog.
 140  */
 141 int llc_rcv(struct sk_buff *skb, struct net_device *dev,
 142             struct packet_type *pt, struct net_device *orig_dev)
 143 {
 144         struct llc_sap *sap;
 145         struct llc_pdu_sn *pdu;
 146         int dest;
 147         int (*rcv)(struct sk_buff *, struct net_device *,
 148                    struct packet_type *, struct net_device *);
 149
 150         if (!net_eq(dev_net(dev), &init_net))
 151                 goto drop;
 152
 153         /*
 154          * When the interface is in promisc. mode, drop all the crap that it
 155          * receives, do not try to analyse it.
 156          */
 157         if (unlikely(skb->pkt_type == PACKET_OTHERHOST)) {
 158                 dprintk("%s: PACKET_OTHERHOST\n", __func__);
 159                 goto drop;
 160         }
 161         skb = skb_share_check(skb, GFP_ATOMIC);
 162         if (unlikely(!skb))
 163                 goto out;
 164         if (unlikely(!llc_fixup_skb(skb)))
 165                 goto drop;
 166         pdu = llc_pdu_sn_hdr(skb);
 167         if (unlikely(!pdu->dsap)) /* NULL DSAP, refer to station */
 168                goto handle_station;
 169         sap = llc_sap_find(pdu->dsap);
 170         if (unlikely(!sap)) {/* unknown SAP */
 171                 dprintk("%s: llc_sap_find(%02X) failed!\n", __func__,
 172                         pdu->dsap);
 173                 goto drop;
 174         }
 175         /*
 176          * First the upper layer protocols that don't need the full
 177          * LLC functionality
 178          */
 179         rcv = rcu_dereference(sap->rcv_func);
 180         if (rcv) {
 181                 struct sk_buff *cskb = skb_clone(skb, GFP_ATOMIC);
 182                 if (cskb)
 183                         rcv(cskb, dev, pt, orig_dev);
 184         }
 185         dest = llc_pdu_type(skb);
 186         if (unlikely(!dest || !llc_type_handlers[dest - 1]))
 187                 goto drop_put;
 188         llc_type_handlers[dest - 1](sap, skb);
 189 out_put:
 190         llc_sap_put(sap);
 191 out:
 192         return 0;
 193 drop:
 194         kfree_skb(skb);
 195         goto out;
 196 drop_put:
 197         kfree_skb(skb);
 198         goto out_put;
 199 handle_station:
 200         if (!llc_station_handler)
 201                 goto drop;
 202         llc_station_handler(skb);
 203         goto out;
 204 }
 205
 206 EXPORT_SYMBOL(llc_add_pack);
 207 EXPORT_SYMBOL(llc_remove_pack);
 208 EXPORT_SYMBOL(llc_set_station_handler);