/* * 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 <linux/slab.h> #include <linux/export.h> #include <net/net_namespace.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)) { smp_wmb(); /* ensure initialisation is complete before it's called */ 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; synchronize_net(); } void llc_set_station_handler(void (*handler)(struct sk_buff *skb)) { /* Ensure initialisation is complete before it's called */ if (handler) smp_wmb(); llc_station_handler = handler; if (!handler) synchronize_net(); } /** * 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_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->transport_header += llc_len; skb_pull(skb, llc_len); if (skb->protocol == htons(ETH_P_802_2)) { __be16 pdulen = eth_hdr(skb)->h_proto; s32 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 * * 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 net_device *orig_dev) { struct llc_sap *sap; struct llc_pdu_sn *pdu; int dest; int (*rcv)(struct sk_buff *, struct net_device *, struct packet_type *, struct net_device *); void (*sta_handler)(struct sk_buff *skb); void (*sap_handler)(struct llc_sap *sap, struct sk_buff *skb); if (!net_eq(dev_net(dev), &init_net)) goto drop; /* * 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_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", __func__, pdu->dsap); goto drop; } /* * First the upper layer protocols that don't need the full * LLC functionality */ rcv = rcu_dereference(sap->rcv_func); dest = llc_pdu_type(skb); sap_handler = dest ? ACCESS_ONCE(llc_type_handlers[dest - 1]) : NULL; if (unlikely(!sap_handler)) { if (rcv) rcv(skb, dev, pt, orig_dev); else kfree_skb(skb); } else { if (rcv) { struct sk_buff *cskb = skb_clone(skb, GFP_ATOMIC); if (cskb) rcv(cskb, dev, pt, orig_dev); } sap_handler(sap, skb); } llc_sap_put(sap); out: return 0; drop: kfree_skb(skb); goto out; handle_station: sta_handler = ACCESS_ONCE(llc_station_handler); if (!sta_handler) goto drop; sta_handler(skb); goto out; } EXPORT_SYMBOL(llc_add_pack); EXPORT_SYMBOL(llc_remove_pack); EXPORT_SYMBOL(llc_set_station_handler);