llc_sap.c

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/*
 * llc_sap.c - driver routines for SAP component.
 *
 * Copyright (c) 1997 by Procom Technology, Inc.
 *       2001-2003 by Arnaldo Carvalho de Melo <[email protected]>
 *
 * 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;
}

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);
}

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;
}

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;
}

static int llc_exec_sap_trans_actions(struct llc_sap *sap,
                      struct llc_sap_state_trans *trans,
                      struct sk_buff *skb)
{
    int rc = 0;
    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;
}

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;
}

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);
}

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);
}

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);
}

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->sk = sk;
    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 &&
      llc_mac_match(llc->laddr.mac, laddr->mac);
}

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_DESTROY_BY_RCU */
            if (unlikely(!atomic_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]);
    }
}

static void llc_sap_mcast(struct llc_sap *sap,
              const struct llc_addr *laddr,
              struct sk_buff *skb)
{
    int i = 0, count = 256 / sizeof(struct sock *);
    struct sock *sk, *stack[count];
    struct hlist_node *node;
    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, node, dev_hb, dev_hash_node) {

        sk = &llc->sk;

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

        sock_hold(sk);
        if (i < count)
            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 (llc_mac_multicast(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);
    }
}