| 1 | |
| 2 | |
| 3 | * llc_input.c - Minimal input path for LLC
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| 4 | *
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| 5 | * Copyright (c) 1997 by Procom Technology, Inc.
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| 6 | * 2001-2003 by Arnaldo Carvalho de Melo <[email protected]>
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| 7 |
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| 8 | #include <linux/netdevice.h>
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| 9 | #include <linux/slab.h>
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| 10 | #include <linux/export.h>
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| 11 | #include <net/net_namespace.h>
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| 12 | #include <net/llc.h>
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| 13 | #include <net/llc_pdu.h>
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| 14 | #include <net/llc_sap.h>
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| 15 |
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| 16 | #if 0 |
| 17 | #define dprintk(args...) printk(KERN_DEBUG args)
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| 18 | #else
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| 19 | #define dprintk(args...)
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| 20 | #endif
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| 21 |
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| 22 | |
| 23 | * Packet handler for the station, registerable because in the minimal
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| 24 | * LLC core that is taking shape only the very minimal subset of LLC that
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| 25 | * is needed for things like IPX, Appletalk, etc will stay, with all the
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| 26 | * rest in the llc1 and llc2 modules.
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| 27 |
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| 28 | static void (*llc_station_handler)(struct sk_buff *skb);
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| 29 |
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| 30 | |
| 31 | * Packet handlers for LLC_DEST_SAP and LLC_DEST_CONN.
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| 32 |
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| 33 | static void (*llc_type_handlers[2])(struct llc_sap *sap,
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| 34 | struct sk_buff *skb);
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| 35 |
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| 36 | void llc_add_pack(int type, void (*handler)(struct llc_sap *sap,
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| 37 | struct sk_buff *skb))
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| 38 | {
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| 39 | smp_wmb();
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| 40 | if (type == LLC_DEST_SAP || type == LLC_DEST_CONN)
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| 41 | llc_type_handlers[type - 1] = handler;
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| 42 | }
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| 43 |
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| 44 | void llc_remove_pack(int type)
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| 45 | {
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| 46 | if (type == LLC_DEST_SAP || type == LLC_DEST_CONN)
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| 47 | llc_type_handlers[type - 1] = NULL;
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| 48 | synchronize_net();
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| 49 | }
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| 50 |
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| 51 | void llc_set_station_handler(void (*handler)(struct sk_buff *skb))
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| 52 | {
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| 53 |
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| 54 | if (handler)
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| 55 | smp_wmb();
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| 56 |
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| 57 | llc_station_handler = handler;
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| 58 |
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| 59 | if (!handler)
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| 60 | synchronize_net();
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| 61 | }
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| 62 |
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| 63 | |
| 64 | * llc_pdu_type - returns which LLC component must handle for PDU
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| 65 | * @skb: input skb
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| 66 | *
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| 67 | * This function returns which LLC component must handle this PDU.
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| 68 |
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| 69 | static __inline__ int llc_pdu_type(struct sk_buff *skb)
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| 70 | {
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| 71 | int type = LLC_DEST_CONN;
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| 72 | struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb);
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| 73 |
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| 74 | if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) != LLC_PDU_TYPE_U)
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| 75 | goto out;
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| 76 | switch (LLC_U_PDU_CMD(pdu)) {
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| 77 | case LLC_1_PDU_CMD_XID:
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| 78 | case LLC_1_PDU_CMD_UI:
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| 79 | case LLC_1_PDU_CMD_TEST:
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| 80 | type = LLC_DEST_SAP;
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| 81 | break;
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| 82 | case LLC_2_PDU_CMD_SABME:
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| 83 | case LLC_2_PDU_CMD_DISC:
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| 84 | case LLC_2_PDU_RSP_UA:
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| 85 | case LLC_2_PDU_RSP_DM:
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| 86 | case LLC_2_PDU_RSP_FRMR:
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| 87 | break;
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| 88 | default:
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| 89 | type = LLC_DEST_INVALID;
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| 90 | break;
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| 91 | }
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| 92 | out:
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| 93 | return type;
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| 94 | }
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| 95 |
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| 96 | |
| 97 | * llc_fixup_skb - initializes skb pointers
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| 98 | * @skb: This argument points to incoming skb
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| 99 | *
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| 100 | * Initializes internal skb pointer to start of network layer by deriving
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| 101 | * length of LLC header; finds length of LLC control field in LLC header
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| 102 | * by looking at the two lowest-order bits of the first control field
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| 103 | * byte; field is either 3 or 4 bytes long.
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| 104 |
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| 105 | static inline int llc_fixup_skb(struct sk_buff *skb)
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| 106 | {
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| 107 | u8 llc_len = 2;
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| 108 | struct llc_pdu_un *pdu;
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| 109 |
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| 110 | if (unlikely(!pskb_may_pull(skb, sizeof(*pdu))))
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| 111 | return 0;
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| 112 |
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| 113 | pdu = (struct llc_pdu_un *)skb->data;
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| 114 | if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) == LLC_PDU_TYPE_U)
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| 115 | llc_len = 1;
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| 116 | llc_len += 2;
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| 117 |
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| 118 | if (unlikely(!pskb_may_pull(skb, llc_len)))
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| 119 | return 0;
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| 120 |
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| 121 | skb_pull(skb, llc_len);
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| 122 | skb_reset_transport_header(skb);
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| 123 | if (skb->protocol == htons(ETH_P_802_2)) {
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| 124 | __be16 pdulen;
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| 125 | s32 data_size;
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| 126 |
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| 127 | if (skb->mac_len < ETH_HLEN)
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| 128 | return 0;
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| 129 |
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| 130 | pdulen = eth_hdr(skb)->h_proto;
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| 131 | data_size = ntohs(pdulen) - llc_len;
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| 132 |
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| 133 | if (data_size < 0 ||
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| 134 | !pskb_may_pull(skb, data_size))
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| 135 | return 0;
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| 136 | if (unlikely(pskb_trim_rcsum(skb, data_size)))
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| 137 | return 0;
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| 138 | }
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| 139 | return 1;
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| 140 | }
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| 141 |
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| 142 | |
| 143 | * llc_rcv - 802.2 entry point from net lower layers
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| 144 | * @skb: received pdu
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| 145 | * @dev: device that receive pdu
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| 146 | * @pt: packet type
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| 147 | * @orig_dev: the original receive net device
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| 148 | *
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| 149 | * When the system receives a 802.2 frame this function is called. It
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| 150 | * checks SAP and connection of received pdu and passes frame to
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| 151 | * llc_{station,sap,conn}_rcv for sending to proper state machine. If
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| 152 | * the frame is related to a busy connection (a connection is sending
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| 153 | * data now), it queues this frame in the connection's backlog.
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| 154 |
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| 155 | int llc_rcv(struct sk_buff *skb, struct net_device *dev,
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| 156 | struct packet_type *pt, struct net_device *orig_dev)
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| 157 | {
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| 158 | struct llc_sap *sap;
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| 159 | struct llc_pdu_sn *pdu;
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| 160 | int dest;
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| 161 | int (*rcv)(struct sk_buff *, struct net_device *,
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| 162 | struct packet_type *, struct net_device *);
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| 163 | void (*sta_handler)(struct sk_buff *skb);
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| 164 | void (*sap_handler)(struct llc_sap *sap, struct sk_buff *skb);
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| 165 |
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| 166 | |
| 167 | * When the interface is in promisc. mode, drop all the crap that it
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| 168 | * receives, do not try to analyse it.
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| 169 |
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| 170 | if (unlikely(skb->pkt_type == PACKET_OTHERHOST)) {
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| 171 | dprintk("%s: PACKET_OTHERHOST\n", __func__);
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| 172 | goto drop;
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| 173 | }
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| 174 | skb = skb_share_check(skb, GFP_ATOMIC);
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| 175 | if (unlikely(!skb))
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| 176 | goto out;
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| 177 | if (unlikely(!llc_fixup_skb(skb)))
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| 178 | goto drop;
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| 179 | pdu = llc_pdu_sn_hdr(skb);
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| 180 | if (unlikely(!pdu->dsap))
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| 181 | goto handle_station;
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| 182 | sap = llc_sap_find(pdu->dsap);
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| 183 | if (unlikely(!sap)) {
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| 184 | dprintk("%s: llc_sap_find(%02X) failed!\n", __func__,
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| 185 | pdu->dsap);
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| 186 | goto drop;
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| 187 | }
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| 188 | |
| 189 | * First the upper layer protocols that don't need the full
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| 190 | * LLC functionality
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| 191 |
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| 192 | rcv = rcu_dereference(sap->rcv_func);
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| 193 | dest = llc_pdu_type(skb);
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| 194 | sap_handler = dest ? READ_ONCE(llc_type_handlers[dest - 1]) : NULL;
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| 195 | if (unlikely(!sap_handler)) {
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| 196 | if (rcv)
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| 197 | rcv(skb, dev, pt, orig_dev);
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| 198 | else
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| 199 | kfree_skb(skb);
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| 200 | } else {
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| 201 | if (rcv) {
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| 202 | struct sk_buff *cskb = skb_clone(skb, GFP_ATOMIC);
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| 203 | if (cskb)
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| 204 | rcv(cskb, dev, pt, orig_dev);
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| 205 | }
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| 206 | sap_handler(sap, skb);
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| 207 | }
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| 208 | llc_sap_put(sap);
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| 209 | out:
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| 210 | return 0;
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| 211 | drop:
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| 212 | kfree_skb(skb);
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| 213 | goto out;
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| 214 | handle_station:
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| 215 | sta_handler = READ_ONCE(llc_station_handler);
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| 216 | if (!sta_handler)
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| 217 | goto drop;
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| 218 | sta_handler(skb);
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| 219 | goto out;
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| 220 | }
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| 221 |
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| 222 | EXPORT_SYMBOL(llc_add_pack);
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| 223 | EXPORT_SYMBOL(llc_remove_pack);
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| 224 | EXPORT_SYMBOL(llc_set_station_handler);
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