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