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/net_namespace.h>
  16 #include <net/llc.h>
  17 #include <net/llc_pdu.h>
  18 #include <net/llc_sap.h>
  19
  20 #if 0
  21 #define dprintk(args...) printk(KERN_DEBUG args)
  22 #else
  23 #define dprintk(args...)
  24 #endif
  25
  26 /*
  27  * Packet handler for the station, registerable because in the minimal
  28  * LLC core that is taking shape only the very minimal subset of LLC that
  29  * is needed for things like IPX, Appletalk, etc will stay, with all the
  30  * rest in the llc1 and llc2 modules.
  31  */
  32 static void (*llc_station_handler)(struct sk_buff *skb);
  33
  34 /*
  35  * Packet handlers for LLC_DEST_SAP and LLC_DEST_CONN.
  36  */
  37 static void (*llc_type_handlers[2])(struct llc_sap *sap,
  38                                     struct sk_buff *skb);
  39
  40 void llc_add_pack(int type, void (*handler)(struct llc_sap *sap,
  41                                             struct sk_buff *skb))
  42 {
  43         if (type == LLC_DEST_SAP || type == LLC_DEST_CONN)
  44                 llc_type_handlers[type - 1] = handler;
  45 }
  46
  47 void llc_remove_pack(int type)
  48 {
  49         if (type == LLC_DEST_SAP || type == LLC_DEST_CONN)
  50                 llc_type_handlers[type - 1] = NULL;
  51 }
  52
  53 void llc_set_station_handler(void (*handler)(struct sk_buff *skb))
  54 {
  55         llc_station_handler = handler;
  56 }
  57
  58 /**
  59  *      llc_pdu_type - returns which LLC component must handle for PDU
  60  *      @skb: input skb
  61  *
  62  *      This function returns which LLC component must handle this PDU.
  63  */
  64 static __inline__ int llc_pdu_type(struct sk_buff *skb)
  65 {
  66         int type = LLC_DEST_CONN; /* I-PDU or S-PDU type */
  67         struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb);
  68
  69         if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) != LLC_PDU_TYPE_U)
  70                 goto out;
  71         switch (LLC_U_PDU_CMD(pdu)) {
  72         case LLC_1_PDU_CMD_XID:
  73         case LLC_1_PDU_CMD_UI:
  74         case LLC_1_PDU_CMD_TEST:
  75                 type = LLC_DEST_SAP;
  76                 break;
  77         case LLC_2_PDU_CMD_SABME:
  78         case LLC_2_PDU_CMD_DISC:
  79         case LLC_2_PDU_RSP_UA:
  80         case LLC_2_PDU_RSP_DM:
  81         case LLC_2_PDU_RSP_FRMR:
  82                 break;
  83         default:
  84                 type = LLC_DEST_INVALID;
  85                 break;
  86         }
  87 out:
  88         return type;
  89 }
  90
  91 /**
  92  *      llc_fixup_skb - initializes skb pointers
  93  *      @skb: This argument points to incoming skb
  94  *
  95  *      Initializes internal skb pointer to start of network layer by deriving
  96  *      length of LLC header; finds length of LLC control field in LLC header
  97  *      by looking at the two lowest-order bits of the first control field
  98  *      byte; field is either 3 or 4 bytes long.
  99  */
 100 static inline int llc_fixup_skb(struct sk_buff *skb)
 101 {
 102         u8 llc_len = 2;
 103         struct llc_pdu_un *pdu;
 104
 105         if (unlikely(!pskb_may_pull(skb, sizeof(*pdu))))
 106                 return 0;
 107
 108         pdu = (struct llc_pdu_un *)skb->data;
 109         if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) == LLC_PDU_TYPE_U)
 110                 llc_len = 1;
 111         llc_len += 2;
 112
 113         if (unlikely(!pskb_may_pull(skb, llc_len)))
 114                 return 0;
 115
 116         skb->transport_header += llc_len;
 117         skb_pull(skb, llc_len);
 118         if (skb->protocol == htons(ETH_P_802_2)) {
 119                 __be16 pdulen = eth_hdr(skb)->h_proto;
 120                 s32 data_size = ntohs(pdulen) - llc_len;
 121
 122                 if (data_size < 0 ||
 123                     ((skb_tail_pointer(skb) -
 124                       (u8 *)pdu) - llc_len) < data_size)
 125                         return 0;
 126                 if (unlikely(pskb_trim_rcsum(skb, data_size)))
 127                         return 0;
 128         }
 129         return 1;
 130 }
 131
 132 /**
 133  *      llc_rcv - 802.2 entry point from net lower layers
 134  *      @skb: received pdu
 135  *      @dev: device that receive pdu
 136  *      @pt: packet type
 137  *
 138  *      When the system receives a 802.2 frame this function is called. It
 139  *      checks SAP and connection of received pdu and passes frame to
 140  *      llc_{station,sap,conn}_rcv for sending to proper state machine. If
 141  *      the frame is related to a busy connection (a connection is sending
 142  *      data now), it queues this frame in the connection's backlog.
 143  */
 144 int llc_rcv(struct sk_buff *skb, struct net_device *dev,
 145             struct packet_type *pt, struct net_device *orig_dev)
 146 {
 147         struct llc_sap *sap;
 148         struct llc_pdu_sn *pdu;
 149         int dest;
 150         int (*rcv)(struct sk_buff *, struct net_device *,
 151                    struct packet_type *, struct net_device *);
 152
 153         if (!net_eq(dev_net(dev), &init_net))
 154                 goto drop;
 155
 156         /*
 157          * When the interface is in promisc. mode, drop all the crap that it
 158          * receives, do not try to analyse it.
 159          */
 160         if (unlikely(skb->pkt_type == PACKET_OTHERHOST)) {
 161                 dprintk("%s: PACKET_OTHERHOST\n", __func__);
 162                 goto drop;
 163         }
 164         skb = skb_share_check(skb, GFP_ATOMIC);
 165         if (unlikely(!skb))
 166                 goto out;
 167         if (unlikely(!llc_fixup_skb(skb)))
 168                 goto drop;
 169         pdu = llc_pdu_sn_hdr(skb);
 170         if (unlikely(!pdu->dsap)) /* NULL DSAP, refer to station */
 171                goto handle_station;
 172         sap = llc_sap_find(pdu->dsap);
 173         if (unlikely(!sap)) {/* unknown SAP */
 174                 dprintk("%s: llc_sap_find(%02X) failed!\n", __func__,
 175                         pdu->dsap);
 176                 goto drop;
 177         }
 178         /*
 179          * First the upper layer protocols that don't need the full
 180          * LLC functionality
 181          */
 182         rcv = rcu_dereference(sap->rcv_func);
 183         if (rcv) {
 184                 struct sk_buff *cskb = skb_clone(skb, GFP_ATOMIC);
 185                 if (cskb)
 186                         rcv(cskb, dev, pt, orig_dev);
 187         }
 188         dest = llc_pdu_type(skb);
 189         if (unlikely(!dest || !llc_type_handlers[dest - 1]))
 190                 goto drop_put;
 191         llc_type_handlers[dest - 1](sap, skb);
 192 out_put:
 193         llc_sap_put(sap);
 194 out:
 195         return 0;
 196 drop:
 197         kfree_skb(skb);
 198         goto out;
 199 drop_put:
 200         kfree_skb(skb);
 201         goto out_put;
 202 handle_station:
 203         if (!llc_station_handler)
 204                 goto drop;
 205         llc_station_handler(skb);
 206         goto out;
 207 }
 208
 209 EXPORT_SYMBOL(llc_add_pack);
 210 EXPORT_SYMBOL(llc_remove_pack);
 211 EXPORT_SYMBOL(llc_set_station_handler);