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 <net/llc.h>
  16 #include <net/llc_pdu.h>
  17 #include <net/llc_sap.h>
  18
  19 #if 0
  20 #define dprintk(args...) printk(KERN_DEBUG args)
  21 #else
  22 #define dprintk(args...)
  23 #endif
  24
  25 /*
  26  * Packet handler for the station, registerable because in the minimal
  27  * LLC core that is taking shape only the very minimal subset of LLC that
  28  * is needed for things like IPX, Appletalk, etc will stay, with all the
  29  * rest in the llc1 and llc2 modules.
  30  */
  31 static void (*llc_station_handler)(struct sk_buff *skb);
  32
  33 /*
  34  * Packet handlers for LLC_DEST_SAP and LLC_DEST_CONN.
  35  */
  36 static void (*llc_type_handlers[2])(struct llc_sap *sap,
  37                                     struct sk_buff *skb);
  38
  39 void llc_add_pack(int type, void (*handler)(struct llc_sap *sap,
  40                                             struct sk_buff *skb))
  41 {
  42         if (type == LLC_DEST_SAP || type == LLC_DEST_CONN)
  43                 llc_type_handlers[type - 1] = handler;
  44 }
  45
  46 void llc_remove_pack(int type)
  47 {
  48         if (type == LLC_DEST_SAP || type == LLC_DEST_CONN)
  49                 llc_type_handlers[type - 1] = NULL;
  50 }
  51
  52 void llc_set_station_handler(void (*handler)(struct sk_buff *skb))
  53 {
  54         llc_station_handler = handler;
  55 }
  56
  57 /**
  58  *      llc_pdu_type - returns which LLC component must handle for PDU
  59  *      @skb: input skb
  60  *
  61  *      This function returns which LLC component must handle this PDU.
  62  */
  63 static __inline__ int llc_pdu_type(struct sk_buff *skb)
  64 {
  65         int type = LLC_DEST_CONN; /* I-PDU or S-PDU type */
  66         struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb);
  67
  68         if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) != LLC_PDU_TYPE_U)
  69                 goto out;
  70         switch (LLC_U_PDU_CMD(pdu)) {
  71         case LLC_1_PDU_CMD_XID:
  72         case LLC_1_PDU_CMD_UI:
  73         case LLC_1_PDU_CMD_TEST:
  74                 type = LLC_DEST_SAP;
  75                 break;
  76         case LLC_2_PDU_CMD_SABME:
  77         case LLC_2_PDU_CMD_DISC:
  78         case LLC_2_PDU_RSP_UA:
  79         case LLC_2_PDU_RSP_DM:
  80         case LLC_2_PDU_RSP_FRMR:
  81                 break;
  82         default:
  83                 type = LLC_DEST_INVALID;
  84                 break;
  85         }
  86 out:
  87         return type;
  88 }
  89
  90 /**
  91  *      llc_fixup_skb - initializes skb pointers
  92  *      @skb: This argument points to incoming skb
  93  *
  94  *      Initializes internal skb pointer to start of network layer by deriving
  95  *      length of LLC header; finds length of LLC control field in LLC header
  96  *      by looking at the two lowest-order bits of the first control field
  97  *      byte; field is either 3 or 4 bytes long.
  98  */
  99 static inline int llc_fixup_skb(struct sk_buff *skb)
 100 {
 101         u8 llc_len = 2;
 102         struct llc_pdu_sn *pdu;
 103
 104         if (!pskb_may_pull(skb, sizeof(*pdu)))
 105                 return 0;
 106
 107         pdu = (struct llc_pdu_sn *)skb->data;
 108         if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) == LLC_PDU_TYPE_U)
 109                 llc_len = 1;
 110         llc_len += 2;
 111         skb->h.raw += llc_len;
 112         skb_pull(skb, llc_len);
 113         if (skb->protocol == htons(ETH_P_802_2)) {
 114                 u16 pdulen = eth_hdr(skb)->h_proto,
 115                     data_size = ntohs(pdulen) - llc_len;
 116
 117                 skb_trim(skb, data_size);
 118         }
 119         return 1;
 120 }
 121
 122 /**
 123  *      llc_rcv - 802.2 entry point from net lower layers
 124  *      @skb: received pdu
 125  *      @dev: device that receive pdu
 126  *      @pt: packet type
 127  *
 128  *      When the system receives a 802.2 frame this function is called. It
 129  *      checks SAP and connection of received pdu and passes frame to
 130  *      llc_{station,sap,conn}_rcv for sending to proper state machine. If
 131  *      the frame is related to a busy connection (a connection is sending
 132  *      data now), it queues this frame in the connection's backlog.
 133  */
 134 int llc_rcv(struct sk_buff *skb, struct net_device *dev,
 135             struct packet_type *pt)
 136 {
 137         struct llc_sap *sap;
 138         struct llc_pdu_sn *pdu;
 139         int dest;
 140
 141         /*
 142          * When the interface is in promisc. mode, drop all the crap that it
 143          * receives, do not try to analyse it.
 144          */
 145         if (unlikely(skb->pkt_type == PACKET_OTHERHOST)) {
 146                 dprintk("%s: PACKET_OTHERHOST\n", __FUNCTION__);
 147                 goto drop;
 148         }
 149         skb = skb_share_check(skb, GFP_ATOMIC);
 150         if (unlikely(!skb))
 151                 goto out;
 152         if (unlikely(!llc_fixup_skb(skb)))
 153                 goto drop;
 154         pdu = llc_pdu_sn_hdr(skb);
 155         if (unlikely(!pdu->dsap)) /* NULL DSAP, refer to station */
 156                goto handle_station;
 157         sap = llc_sap_find(pdu->dsap);
 158         if (unlikely(!sap)) {/* unknown SAP */
 159                 dprintk("%s: llc_sap_find(%02X) failed!\n", __FUNCTION__,
 160                         pdu->dsap);
 161                 goto drop;
 162         }
 163         /*
 164          * First the upper layer protocols that don't need the full
 165          * LLC functionality
 166          */
 167         if (sap->rcv_func) {
 168                 sap->rcv_func(skb, dev, pt);
 169                 goto out;
 170         }
 171         dest = llc_pdu_type(skb);
 172         if (unlikely(!dest || !llc_type_handlers[dest - 1]))
 173                 goto drop;
 174         llc_type_handlers[dest - 1](sap, skb);
 175 out:
 176         return 0;
 177 drop:
 178         kfree_skb(skb);
 179         goto out;
 180 handle_station:
 181         if (!llc_station_handler)
 182                 goto drop;
 183         llc_station_handler(skb);
 184         goto out;
 185 }
 186
 187 EXPORT_SYMBOL(llc_add_pack);
 188 EXPORT_SYMBOL(llc_remove_pack);
 189 EXPORT_SYMBOL(llc_set_station_handler);