/*
 * llc_sap.c - driver routines for SAP component.
 *
 * 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 <net/llc.h>
#include <net/llc_if.h>
#include <net/llc_conn.h>
#include <net/llc_pdu.h>
#include <net/llc_sap.h>
#include <net/llc_s_ac.h>
#include <net/llc_s_ev.h>
#include <net/llc_s_st.h>
#include <net/sock.h>
#include <net/tcp_states.h>
#include <linux/llc.h>
#include <linux/slab.h>

static int llc_mac_header_len(unsigned short devtype)
{
        switch (devtype) {
        case ARPHRD_ETHER:
        case ARPHRD_LOOPBACK:
                return sizeof(struct ethhdr);
        }
        return 0;
}

/**
 *      llc_alloc_frame - allocates sk_buff for frame
 *      @dev: network device this skb will be sent over
 *      @type: pdu type to allocate
 *      @data_size: data size to allocate
 *
 *      Allocates an sk_buff for frame and initializes sk_buff fields.
 *      Returns allocated skb or %NULL when out of memory.
 */
struct sk_buff *llc_alloc_frame(struct sock *sk, struct net_device *dev,
                                u8 type, u32 data_size)
{
        int hlen = type == LLC_PDU_TYPE_U ? 3 : 4;
        struct sk_buff *skb;

        hlen += llc_mac_header_len(dev->type);
        skb = alloc_skb(hlen + data_size, GFP_ATOMIC);

        if (skb) {
                skb_reset_mac_header(skb);
                skb_reserve(skb, hlen);
                skb_reset_network_header(skb);
                skb_reset_transport_header(skb);
                skb->protocol = htons(ETH_P_802_2);
                skb->dev      = dev;
                if (sk != NULL)
                        skb_set_owner_w(skb, sk);
        }
        return skb;
}

void llc_save_primitive(struct sock *sk, struct sk_buff *skb, u8 prim)
{
        struct sockaddr_llc *addr;

       /* save primitive for use by the user. */
        addr              = llc_ui_skb_cb(skb);

        memset(addr, 0, sizeof(*addr));
        addr->sllc_family = sk->sk_family;
        addr->sllc_arphrd = skb->dev->type;
        addr->sllc_test   = prim == LLC_TEST_PRIM;
        addr->sllc_xid    = prim == LLC_XID_PRIM;
        addr->sllc_ua     = prim == LLC_DATAUNIT_PRIM;
        llc_pdu_decode_sa(skb, addr->sllc_mac);
        llc_pdu_decode_ssap(skb, &addr->sllc_sap);
}

/**
 *      llc_sap_rtn_pdu - Informs upper layer on rx of an UI, XID or TEST pdu.
 *      @sap: pointer to SAP
 *      @skb: received pdu
 */
void llc_sap_rtn_pdu(struct llc_sap *sap, struct sk_buff *skb)
{
        struct llc_sap_state_ev *ev = llc_sap_ev(skb);
        struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);

        switch (LLC_U_PDU_RSP(pdu)) {
        case LLC_1_PDU_CMD_TEST:
                ev->prim = LLC_TEST_PRIM;       break;
        case LLC_1_PDU_CMD_XID:
                ev->prim = LLC_XID_PRIM;        break;
        case LLC_1_PDU_CMD_UI:
                ev->prim = LLC_DATAUNIT_PRIM;   break;
        }
        ev->ind_cfm_flag = LLC_IND;
}

/**
 *      llc_find_sap_trans - finds transition for event
 *      @sap: pointer to SAP
 *      @skb: happened event
 *
 *      This function finds transition that matches with happened event.
 *      Returns the pointer to found transition on success or %NULL for
 *      failure.
 */
static struct llc_sap_state_trans *llc_find_sap_trans(struct llc_sap *sap,
                                                      struct sk_buff *skb)
{
        int i = 0;
        struct llc_sap_state_trans *rc = NULL;
        struct llc_sap_state_trans **next_trans;
        struct llc_sap_state *curr_state = &llc_sap_state_table[sap->state - 1];
        /*
         * Search thru events for this state until list exhausted or until
         * its obvious the event is not valid for the current state
         */
        for (next_trans = curr_state->transitions; next_trans[i]->ev; i++)
                if (!next_trans[i]->ev(sap, skb)) {
                        rc = next_trans[i]; /* got event match; return it */
                        break;
                }
        return rc;
}

/**
 *      llc_exec_sap_trans_actions - execute actions related to event
 *      @sap: pointer to SAP
 *      @trans: pointer to transition that it's actions must be performed
 *      @skb: happened event.
 *
 *      This function executes actions that is related to happened event.
 *      Returns 0 for success and 1 for failure of at least one action.
 */
static int llc_exec_sap_trans_actions(struct llc_sap *sap,
                                      struct llc_sap_state_trans *trans,
                                      struct sk_buff *skb)
{
        int rc = 0;
        const llc_sap_action_t *next_action = trans->ev_actions;

        for (; next_action && *next_action; next_action++)
                if ((*next_action)(sap, skb))
                        rc = 1;
        return rc;
}

/**
 *      llc_sap_next_state - finds transition, execs actions & change SAP state
 *      @sap: pointer to SAP
 *      @skb: happened event
 *
 *      This function finds transition that matches with happened event, then
 *      executes related actions and finally changes state of SAP. It returns
 *      0 on success and 1 for failure.
 */
static int llc_sap_next_state(struct llc_sap *sap, struct sk_buff *skb)
{
        int rc = 1;
        struct llc_sap_state_trans *trans;

        if (sap->state > LLC_NR_SAP_STATES)
                goto out;
        trans = llc_find_sap_trans(sap, skb);
        if (!trans)
                goto out;
        /*
         * Got the state to which we next transition; perform the actions
         * associated with this transition before actually transitioning to the
         * next state
         */
        rc = llc_exec_sap_trans_actions(sap, trans, skb);
        if (rc)
                goto out;
        /*
         * Transition SAP to next state if all actions execute successfully
         */
        sap->state = trans->next_state;
out:
        return rc;
}

/**
 *      llc_sap_state_process - sends event to SAP state machine
 *      @sap: sap to use
 *      @skb: pointer to occurred event
 *
 *      After executing actions of the event, upper layer will be indicated
 *      if needed(on receiving an UI frame). sk can be null for the
 *      datalink_proto case.
 */
static void llc_sap_state_process(struct llc_sap *sap, struct sk_buff *skb)
{
        struct llc_sap_state_ev *ev = llc_sap_ev(skb);

        /*
         * We have to hold the skb, because llc_sap_next_state
         * will kfree it in the sending path and we need to
         * look at the skb->cb, where we encode llc_sap_state_ev.
         */
        skb_get(skb);
        ev->ind_cfm_flag = 0;
        llc_sap_next_state(sap, skb);
        if (ev->ind_cfm_flag == LLC_IND) {
                if (skb->sk->sk_state == TCP_LISTEN)
                        kfree_skb(skb);
                else {
                        llc_save_primitive(skb->sk, skb, ev->prim);

                        /* queue skb to the user. */
                        if (sock_queue_rcv_skb(skb->sk, skb))
                                kfree_skb(skb);
                }
        }
        kfree_skb(skb);
}

/**
 *      llc_build_and_send_test_pkt - TEST interface for upper layers.
 *      @sap: sap to use
 *      @skb: packet to send
 *      @dmac: destination mac address
 *      @dsap: destination sap
 *
 *      This function is called when upper layer wants to send a TEST pdu.
 *      Returns 0 for success, 1 otherwise.
 */
void llc_build_and_send_test_pkt(struct llc_sap *sap,
                                 struct sk_buff *skb, u8 *dmac, u8 dsap)
{
        struct llc_sap_state_ev *ev = llc_sap_ev(skb);

        ev->saddr.lsap = sap->laddr.lsap;
        ev->daddr.lsap = dsap;
        memcpy(ev->saddr.mac, skb->dev->dev_addr, IFHWADDRLEN);
        memcpy(ev->daddr.mac, dmac, IFHWADDRLEN);

        ev->type      = LLC_SAP_EV_TYPE_PRIM;
        ev->prim      = LLC_TEST_PRIM;
        ev->prim_type = LLC_PRIM_TYPE_REQ;
        llc_sap_state_process(sap, skb);
}

/**
 *      llc_build_and_send_xid_pkt - XID interface for upper layers
 *      @sap: sap to use
 *      @skb: packet to send
 *      @dmac: destination mac address
 *      @dsap: destination sap
 *
 *      This function is called when upper layer wants to send a XID pdu.
 *      Returns 0 for success, 1 otherwise.
 */
void llc_build_and_send_xid_pkt(struct llc_sap *sap, struct sk_buff *skb,
                                u8 *dmac, u8 dsap)
{
        struct llc_sap_state_ev *ev = llc_sap_ev(skb);

        ev->saddr.lsap = sap->laddr.lsap;
        ev->daddr.lsap = dsap;
        memcpy(ev->saddr.mac, skb->dev->dev_addr, IFHWADDRLEN);
        memcpy(ev->daddr.mac, dmac, IFHWADDRLEN);

        ev->type      = LLC_SAP_EV_TYPE_PRIM;
        ev->prim      = LLC_XID_PRIM;
        ev->prim_type = LLC_PRIM_TYPE_REQ;
        llc_sap_state_process(sap, skb);
}

/**
 *      llc_sap_rcv - sends received pdus to the sap state machine
 *      @sap: current sap component structure.
 *      @skb: received frame.
 *
 *      Sends received pdus to the sap state machine.
 */
static void llc_sap_rcv(struct llc_sap *sap, struct sk_buff *skb,
                        struct sock *sk)
{
        struct llc_sap_state_ev *ev = llc_sap_ev(skb);

        ev->type   = LLC_SAP_EV_TYPE_PDU;
        ev->reason = 0;
        skb_orphan(skb);
        sock_hold(sk);
        skb->sk = sk;
        skb->destructor = sock_efree;
        llc_sap_state_process(sap, skb);
}

static inline bool llc_dgram_match(const struct llc_sap *sap,
                                   const struct llc_addr *laddr,
                                   const struct sock *sk)
{
     struct llc_sock *llc = llc_sk(sk);

     return sk->sk_type == SOCK_DGRAM &&
          llc->laddr.lsap == laddr->lsap &&
          ether_addr_equal(llc->laddr.mac, laddr->mac);
}

/**
 *      llc_lookup_dgram - Finds dgram socket for the local sap/mac
 *      @sap: SAP
 *      @laddr: address of local LLC (MAC + SAP)
 *
 *      Search socket list of the SAP and finds connection using the local
 *      mac, and local sap. Returns pointer for socket found, %NULL otherwise.
 */
static struct sock *llc_lookup_dgram(struct llc_sap *sap,
                                     const struct llc_addr *laddr)
{
        struct sock *rc;
        struct hlist_nulls_node *node;
        int slot = llc_sk_laddr_hashfn(sap, laddr);
        struct hlist_nulls_head *laddr_hb = &sap->sk_laddr_hash[slot];

        rcu_read_lock_bh();
again:
        sk_nulls_for_each_rcu(rc, node, laddr_hb) {
                if (llc_dgram_match(sap, laddr, rc)) {
                        /* Extra checks required by SLAB_TYPESAFE_BY_RCU */
                        if (unlikely(!refcount_inc_not_zero(&rc->sk_refcnt)))
                                goto again;
                        if (unlikely(llc_sk(rc)->sap != sap ||
                                     !llc_dgram_match(sap, laddr, rc))) {
                                sock_put(rc);
                                continue;
                        }
                        goto found;
                }
        }
        rc = NULL;
        /*
         * if the nulls value we got at the end of this lookup is
         * not the expected one, we must restart lookup.
         * We probably met an item that was moved to another chain.
         */
        if (unlikely(get_nulls_value(node) != slot))
                goto again;
found:
        rcu_read_unlock_bh();
        return rc;
}

static inline bool llc_mcast_match(const struct llc_sap *sap,
                                   const struct llc_addr *laddr,
                                   const struct sk_buff *skb,
                                   const struct sock *sk)
{
     struct llc_sock *llc = llc_sk(sk);

     return sk->sk_type == SOCK_DGRAM &&
          llc->laddr.lsap == laddr->lsap &&
          llc->dev == skb->dev;
}

static void llc_do_mcast(struct llc_sap *sap, struct sk_buff *skb,
                         struct sock **stack, int count)
{
        struct sk_buff *skb1;
        int i;

        for (i = 0; i < count; i++) {
                skb1 = skb_clone(skb, GFP_ATOMIC);
                if (!skb1) {
                        sock_put(stack[i]);
                        continue;
                }

                llc_sap_rcv(sap, skb1, stack[i]);
                sock_put(stack[i]);
        }
}

/**
 *      llc_sap_mcast - Deliver multicast PDU's to all matching datagram sockets.
 *      @sap: SAP
 *      @laddr: address of local LLC (MAC + SAP)
 *
 *      Search socket list of the SAP and finds connections with same sap.
 *      Deliver clone to each.
 */
static void llc_sap_mcast(struct llc_sap *sap,
                          const struct llc_addr *laddr,
                          struct sk_buff *skb)
{
        int i = 0;
        struct sock *sk;
        struct sock *stack[256 / sizeof(struct sock *)];
        struct llc_sock *llc;
        struct hlist_head *dev_hb = llc_sk_dev_hash(sap, skb->dev->ifindex);

        spin_lock_bh(&sap->sk_lock);
        hlist_for_each_entry(llc, dev_hb, dev_hash_node) {

                sk = &llc->sk;

                if (!llc_mcast_match(sap, laddr, skb, sk))
                        continue;

                sock_hold(sk);
                if (i < ARRAY_SIZE(stack))
                        stack[i++] = sk;
                else {
                        llc_do_mcast(sap, skb, stack, i);
                        i = 0;
                }
        }
        spin_unlock_bh(&sap->sk_lock);

        llc_do_mcast(sap, skb, stack, i);
}


void llc_sap_handler(struct llc_sap *sap, struct sk_buff *skb)
{
        struct llc_addr laddr;

        llc_pdu_decode_da(skb, laddr.mac);
        llc_pdu_decode_dsap(skb, &laddr.lsap);

        if (is_multicast_ether_addr(laddr.mac)) {
                llc_sap_mcast(sap, &laddr, skb);
                kfree_skb(skb);
        } else {
                struct sock *sk = llc_lookup_dgram(sap, &laddr);
                if (sk) {
                        llc_sap_rcv(sap, skb, sk);
                        sock_put(sk);
                } else
                        kfree_skb(skb);
        }
}