227 lines
5.9 KiB
C
Executable File
227 lines
5.9 KiB
C
Executable File
/*
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* llc_input.c - Minimal input path for LLC
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*
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* Copyright (c) 1997 by Procom Technology, Inc.
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* 2001-2003 by Arnaldo Carvalho de Melo <acme@conectiva.com.br>
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*
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* This program can be redistributed or modified under the terms of the
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* GNU General Public License as published by the Free Software Foundation.
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* This program is distributed without any warranty or implied warranty
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* of merchantability or fitness for a particular purpose.
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*
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* See the GNU General Public License for more details.
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*/
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#include <linux/netdevice.h>
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#include <linux/slab.h>
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#include <linux/export.h>
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#include <net/net_namespace.h>
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#include <net/llc.h>
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#include <net/llc_pdu.h>
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#include <net/llc_sap.h>
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#if 0
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#define dprintk(args...) printk(KERN_DEBUG args)
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#else
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#define dprintk(args...)
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#endif
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/*
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* Packet handler for the station, registerable because in the minimal
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* LLC core that is taking shape only the very minimal subset of LLC that
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* is needed for things like IPX, Appletalk, etc will stay, with all the
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* rest in the llc1 and llc2 modules.
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*/
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static void (*llc_station_handler)(struct sk_buff *skb);
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/*
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* Packet handlers for LLC_DEST_SAP and LLC_DEST_CONN.
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*/
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static void (*llc_type_handlers[2])(struct llc_sap *sap,
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struct sk_buff *skb);
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void llc_add_pack(int type, void (*handler)(struct llc_sap *sap,
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struct sk_buff *skb))
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{
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smp_wmb(); /* ensure initialisation is complete before it's called */
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if (type == LLC_DEST_SAP || type == LLC_DEST_CONN)
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llc_type_handlers[type - 1] = handler;
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}
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void llc_remove_pack(int type)
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{
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if (type == LLC_DEST_SAP || type == LLC_DEST_CONN)
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llc_type_handlers[type - 1] = NULL;
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synchronize_net();
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}
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void llc_set_station_handler(void (*handler)(struct sk_buff *skb))
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{
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/* Ensure initialisation is complete before it's called */
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if (handler)
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smp_wmb();
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llc_station_handler = handler;
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if (!handler)
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synchronize_net();
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}
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/**
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* llc_pdu_type - returns which LLC component must handle for PDU
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* @skb: input skb
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*
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* This function returns which LLC component must handle this PDU.
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*/
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static __inline__ int llc_pdu_type(struct sk_buff *skb)
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{
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int type = LLC_DEST_CONN; /* I-PDU or S-PDU type */
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struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb);
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if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) != LLC_PDU_TYPE_U)
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goto out;
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switch (LLC_U_PDU_CMD(pdu)) {
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case LLC_1_PDU_CMD_XID:
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case LLC_1_PDU_CMD_UI:
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case LLC_1_PDU_CMD_TEST:
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type = LLC_DEST_SAP;
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break;
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case LLC_2_PDU_CMD_SABME:
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case LLC_2_PDU_CMD_DISC:
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case LLC_2_PDU_RSP_UA:
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case LLC_2_PDU_RSP_DM:
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case LLC_2_PDU_RSP_FRMR:
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break;
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default:
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type = LLC_DEST_INVALID;
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break;
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}
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out:
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return type;
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}
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/**
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* llc_fixup_skb - initializes skb pointers
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* @skb: This argument points to incoming skb
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*
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* Initializes internal skb pointer to start of network layer by deriving
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* length of LLC header; finds length of LLC control field in LLC header
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* by looking at the two lowest-order bits of the first control field
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* byte; field is either 3 or 4 bytes long.
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*/
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static inline int llc_fixup_skb(struct sk_buff *skb)
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{
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u8 llc_len = 2;
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struct llc_pdu_un *pdu;
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if (unlikely(!pskb_may_pull(skb, sizeof(*pdu))))
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return 0;
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pdu = (struct llc_pdu_un *)skb->data;
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if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) == LLC_PDU_TYPE_U)
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llc_len = 1;
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llc_len += 2;
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if (unlikely(!pskb_may_pull(skb, llc_len)))
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return 0;
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skb->transport_header += llc_len;
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skb_pull(skb, llc_len);
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if (skb->protocol == htons(ETH_P_802_2)) {
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__be16 pdulen = eth_hdr(skb)->h_proto;
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s32 data_size = ntohs(pdulen) - llc_len;
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if (data_size < 0 ||
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!pskb_may_pull(skb, data_size))
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return 0;
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if (unlikely(pskb_trim_rcsum(skb, data_size)))
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return 0;
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}
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return 1;
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}
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/**
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* llc_rcv - 802.2 entry point from net lower layers
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* @skb: received pdu
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* @dev: device that receive pdu
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* @pt: packet type
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*
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* When the system receives a 802.2 frame this function is called. It
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* checks SAP and connection of received pdu and passes frame to
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* llc_{station,sap,conn}_rcv for sending to proper state machine. If
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* the frame is related to a busy connection (a connection is sending
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* data now), it queues this frame in the connection's backlog.
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*/
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int llc_rcv(struct sk_buff *skb, struct net_device *dev,
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struct packet_type *pt, struct net_device *orig_dev)
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{
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struct llc_sap *sap;
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struct llc_pdu_sn *pdu;
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int dest;
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int (*rcv)(struct sk_buff *, struct net_device *,
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struct packet_type *, struct net_device *);
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void (*sta_handler)(struct sk_buff *skb);
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void (*sap_handler)(struct llc_sap *sap, struct sk_buff *skb);
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if (!net_eq(dev_net(dev), &init_net))
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goto drop;
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/*
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* When the interface is in promisc. mode, drop all the crap that it
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* receives, do not try to analyse it.
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*/
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if (unlikely(skb->pkt_type == PACKET_OTHERHOST)) {
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dprintk("%s: PACKET_OTHERHOST\n", __func__);
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goto drop;
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}
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skb = skb_share_check(skb, GFP_ATOMIC);
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if (unlikely(!skb))
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goto out;
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if (unlikely(!llc_fixup_skb(skb)))
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goto drop;
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pdu = llc_pdu_sn_hdr(skb);
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if (unlikely(!pdu->dsap)) /* NULL DSAP, refer to station */
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goto handle_station;
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sap = llc_sap_find(pdu->dsap);
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if (unlikely(!sap)) {/* unknown SAP */
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dprintk("%s: llc_sap_find(%02X) failed!\n", __func__,
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pdu->dsap);
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goto drop;
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}
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/*
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* First the upper layer protocols that don't need the full
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* LLC functionality
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*/
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rcv = rcu_dereference(sap->rcv_func);
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dest = llc_pdu_type(skb);
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sap_handler = dest ? ACCESS_ONCE(llc_type_handlers[dest - 1]) : NULL;
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if (unlikely(!sap_handler)) {
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if (rcv)
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rcv(skb, dev, pt, orig_dev);
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else
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kfree_skb(skb);
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} else {
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if (rcv) {
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struct sk_buff *cskb = skb_clone(skb, GFP_ATOMIC);
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if (cskb)
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rcv(cskb, dev, pt, orig_dev);
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}
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sap_handler(sap, skb);
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}
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llc_sap_put(sap);
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out:
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return 0;
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drop:
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kfree_skb(skb);
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goto out;
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handle_station:
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sta_handler = ACCESS_ONCE(llc_station_handler);
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if (!sta_handler)
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goto drop;
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sta_handler(skb);
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goto out;
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}
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EXPORT_SYMBOL(llc_add_pack);
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EXPORT_SYMBOL(llc_remove_pack);
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EXPORT_SYMBOL(llc_set_station_handler);
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