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// SPDX-License-Identifier: GPL-2.0
/*
* 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>
*/
#include <linux/netdevice.h>
#include <net/llc.h>
#include <net/llc_pdu.h>
#if 0
#define dprintk(args...) printk(KERN_DEBUG args)
#else
#define dprintk(args...)
#endif
/**
* 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_un *pdu;
if (unlikely(!pskb_may_pull(skb, sizeof(*pdu))))
return 0;
pdu = (struct llc_pdu_un *)skb->data;
if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) == LLC_PDU_TYPE_U)
llc_len = 1;
llc_len += 2;
if (unlikely(!pskb_may_pull(skb, llc_len)))
return 0;
skb_pull(skb, llc_len);
skb_reset_transport_header(skb);
if (skb->protocol == htons(ETH_P_802_2)) {
__be16 pdulen;
s32 data_size;
if (skb->mac_len < ETH_HLEN)
return 0;
pdulen = eth_hdr(skb)->h_proto;
data_size = ntohs(pdulen) - llc_len;
if (data_size < 0 ||
!pskb_may_pull(skb, data_size))
return 0;
if (unlikely(pskb_trim_rcsum(skb, data_size)))
return 0;
}
return 1;
}
/**
* llc_rcv - 802.2 entry point from net lower layers
* @skb: received pdu
* @dev: device that receive pdu
* @pt: packet type
* @orig_dev: the original receive net device
*
* When the system receives a 802.2 frame this function is called. It
* looks up the SAP the pdu is addressed to and passes the frame to its
* handler, dropping it if the SAP is unknown or has no handler.
*/
int llc_rcv(struct sk_buff *skb, struct net_device *dev,
struct packet_type *pt, struct net_device *orig_dev)
{
int (*rcv)(struct sk_buff *, struct net_device *,
struct packet_type *, struct net_device *);
struct llc_pdu_un *pdu;
struct llc_sap *sap;
/*
* 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", __func__);
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_un_hdr(skb);
sap = llc_sap_find(pdu->dsap);
if (unlikely(!sap)) {/* unknown SAP */
dprintk("%s: llc_sap_find(%02X) failed!\n", __func__,
pdu->dsap);
goto drop;
}
rcv = rcu_dereference(sap->rcv_func);
if (likely(rcv))
rcv(skb, dev, pt, orig_dev);
else
kfree_skb(skb);
llc_sap_put(sap);
out:
return 0;
drop:
kfree_skb(skb);
goto out;
}
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