/*
* llc_input.c - Minimal input path for LLC
*
* Copyright (c) 1997 by Procom Technology, Inc.
* 2001-2003 by Arnaldo Carvalho de Melo <acme@conectiva.com.br>
*
* This program can be redistributed or modified under the terms of the
* GNU General Public License as published by the Free Software Foundation.
* This program is distributed without any warranty or implied warranty
* of merchantability or fitness for a particular purpose.
*
* See the GNU General Public License for more details.
*/
#include <linux/netdevice.h>
#include <net/llc.h>
#include <net/llc_pdu.h>
#include <net/llc_sap.h>
#if 0
#define dprintk(args...) printk(KERN_DEBUG args)
#else
#define dprintk(args...)
#endif
/*
* Packet handler for the station, registerable because in the minimal
* LLC core that is taking shape only the very minimal subset of LLC that
* is needed for things like IPX, Appletalk, etc will stay, with all the
* rest in the llc1 and llc2 modules.
*/
static void (*llc_station_handler)(struct sk_buff *skb);
/*
* Packet handlers for LLC_DEST_SAP and LLC_DEST_CONN.
*/
static void (*llc_type_handlers[2])(struct llc_sap *sap,
struct sk_buff *skb);
void llc_add_pack(int type, void (*handler)(struct llc_sap *sap,
struct sk_buff *skb))
{
if (type == LLC_DEST_SAP || type == LLC_DEST_CONN)
llc_type_handlers[type - 1] = handler;
}
void llc_remove_pack(int type)
{
if (type == LLC_DEST_SAP || type == LLC_DEST_CONN)
llc_type_handlers[type - 1] = NULL;
}
void llc_set_station_handler(void (*handler)(struct sk_buff *skb))
{
llc_station_handler = handler;
}
/**
* llc_pdu_type - returns which LLC component must handle for PDU
* @skb: input skb
*
* This function returns which LLC component must handle this PDU.
*/
static __inline__ int llc_pdu_type(struct sk_buff *skb)
{
int type = LLC_DEST_CONN; /* I-PDU or S-PDU type */
struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb);
if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) != LLC_PDU_TYPE_U)
goto out;
switch (LLC_U_PDU_CMD(pdu)) {
case LLC_1_PDU_CMD_XID:
case LLC_1_PDU_CMD_UI:
case LLC_1_PDU_CMD_TEST:
type = LLC_DEST_SAP;
break;
case LLC_2_PDU_CMD_SABME:
case LLC_2_PDU_CMD_DISC:
case LLC_2_PDU_RSP_UA:
case LLC_2_PDU_RSP_DM:
case LLC_2_PDU_RSP_FRMR:
break;
default:
type = LLC_DEST_INVALID;
break;
}
out:
return type;
}
/**
* llc_fixup_skb - initializes skb pointers
* @skb: This argument points to incoming skb
*
* Initializes internal skb pointer to start of network layer by deriving
* length of LLC header; finds length of LLC control field in LLC header
* by looking at the two lowest-order bits of the first control field
* byte; field is either 3 or 4 bytes long.
*/
static inline int llc_fixup_skb(struct sk_buff *skb)
{
u8 llc_len = 2;
struct llc_pdu_sn *pdu;
if (!pskb_may_pull(skb, sizeof(*pdu)))
return 0;
pdu = (struct llc_pdu_sn *)skb->data;
if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) == LLC_PDU_TYPE_U)
llc_len = 1;
llc_len += 2;
skb->h.raw += llc_len;
skb_pull(skb, llc_len);
if (skb->protocol == htons(ETH_P_802_2)) {
u16 pdulen = eth_hdr(skb)->h_proto,
data_size = ntohs(pdulen) - llc_len;
skb_trim(skb, data_size);
}
return 1;
}
/**
* llc_rcv - 802.2 entry point from net lower layers
* @skb: received pdu
* @dev: device that receive pdu
* @pt: packet type
*
* When the system receives a 802.2 frame this function is called. It
* checks SAP and connection of received pdu and passes frame to
* llc_{station,sap,conn}_rcv for sending to proper state machine. If
* the frame is related to a busy connection (a connection is sending
* data now), it queues this frame in the connection's backlog.
*/
int llc_rcv(struct sk_buff *skb, struct net_device *dev,
struct packet_type *pt)
{
struct llc_sap *sap;
struct llc_pdu_sn *pdu;
int dest;
/*
* When the interface is in promisc. mode, drop all the crap that it
* receives, do not try to analyse it.
*/
if (unlikely(skb->pkt_type == PACKET_OTHERHOST)) {
dprintk("%s: PACKET_OTHERHOST\n", __FUNCTION__);
goto drop;
}
skb = skb_share_check(skb, GFP_ATOMIC);
if (unlikely(!skb))
goto out;
if (unlikely(!llc_fixup_skb(skb)))
goto drop;
pdu = llc_pdu_sn_hdr(skb);
if (unlikely(!pdu->dsap)) /* NULL DSAP, refer to station */
goto handle_station;
sap = llc_sap_find(pdu->dsap);
if (unlikely(!sap)) {/* unknown SAP */
dprintk("%s: llc_sap_find(%02X) failed!\n", __FUNCTION__,
pdu->dsap);
goto drop;
}
/*
* First the upper layer protocols that don't need the full
* LLC functionality
*/
if (sap->rcv_func) {
sap->rcv_func(skb, dev, pt);
goto out;
}
dest = llc_pdu_type(skb);
if (unlikely(!dest || !llc_type_handlers[dest - 1]))
goto drop;
llc_type_handlers[dest - 1](sap, skb);
out:
return 0;
drop:
kfree_skb(skb);
goto out;
handle_station:
if (!llc_station_handler)
goto drop;
llc_station_handler(skb);
goto out;
}
EXPORT_SYMBOL(llc_add_pack);
EXPORT_SYMBOL(llc_remove_pack);
EXPORT_SYMBOL(llc_set_station_handler);
