ax25_in.c

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/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * Copyright (C) Alan Cox GW4PTS ([email protected])
 * Copyright (C) Jonathan Naylor G4KLX ([email protected])
 * Copyright (C) Joerg Reuter DL1BKE ([email protected])
 * Copyright (C) Hans-Joachim Hetscher DD8NE ([email protected])
 */
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/kernel.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/slab.h>
#include <net/ax25.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/netfilter.h>
#include <net/sock.h>
#include <net/tcp_states.h>
#include <asm/uaccess.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/interrupt.h>

/*
 *  Given a fragment, queue it on the fragment queue and if the fragment
 *  is complete, send it back to ax25_rx_iframe.
 */
static int ax25_rx_fragment(ax25_cb *ax25, struct sk_buff *skb)
{
    struct sk_buff *skbn, *skbo;

    if (ax25->fragno != 0) {
        if (!(*skb->data & AX25_SEG_FIRST)) {
            if ((ax25->fragno - 1) == (*skb->data & AX25_SEG_REM)) {
                /* Enqueue fragment */
                ax25->fragno = *skb->data & AX25_SEG_REM;
                skb_pull(skb, 1);   /* skip fragno */
                ax25->fraglen += skb->len;
                skb_queue_tail(&ax25->frag_queue, skb);

                /* Last fragment received ? */
                if (ax25->fragno == 0) {
                    skbn = alloc_skb(AX25_MAX_HEADER_LEN +
                             ax25->fraglen,
                             GFP_ATOMIC);
                    if (!skbn) {
                        skb_queue_purge(&ax25->frag_queue);
                        return 1;
                    }

                    skb_reserve(skbn, AX25_MAX_HEADER_LEN);

                    skbn->dev   = ax25->ax25_dev->dev;
                    skb_reset_network_header(skbn);
                    skb_reset_transport_header(skbn);

                    /* Copy data from the fragments */
                    while ((skbo = skb_dequeue(&ax25->frag_queue)) != NULL) {
                        skb_copy_from_linear_data(skbo,
                              skb_put(skbn, skbo->len),
                                      skbo->len);
                        kfree_skb(skbo);
                    }

                    ax25->fraglen = 0;

                    if (ax25_rx_iframe(ax25, skbn) == 0)
                        kfree_skb(skbn);
                }

                return 1;
            }
        }
    } else {
        /* First fragment received */
        if (*skb->data & AX25_SEG_FIRST) {
            skb_queue_purge(&ax25->frag_queue);
            ax25->fragno = *skb->data & AX25_SEG_REM;
            skb_pull(skb, 1);       /* skip fragno */
            ax25->fraglen = skb->len;
            skb_queue_tail(&ax25->frag_queue, skb);
            return 1;
        }
    }

    return 0;
}

/*
 *  This is where all valid I frames are sent to, to be dispatched to
 *  whichever protocol requires them.
 */
int ax25_rx_iframe(ax25_cb *ax25, struct sk_buff *skb)
{
    int (*func)(struct sk_buff *, ax25_cb *);
    unsigned char pid;
    int queued = 0;

    if (skb == NULL) return 0;

    ax25_start_idletimer(ax25);

    pid = *skb->data;

    if (pid == AX25_P_IP) {
        /* working around a TCP bug to keep additional listeners
         * happy. TCP re-uses the buffer and destroys the original
         * content.
         */
        struct sk_buff *skbn = skb_copy(skb, GFP_ATOMIC);
        if (skbn != NULL) {
            kfree_skb(skb);
            skb = skbn;
        }

        skb_pull(skb, 1);   /* Remove PID */
        skb->mac_header = skb->network_header;
        skb_reset_network_header(skb);
        skb->dev      = ax25->ax25_dev->dev;
        skb->pkt_type = PACKET_HOST;
        skb->protocol = htons(ETH_P_IP);
        netif_rx(skb);
        return 1;
    }
    if (pid == AX25_P_SEGMENT) {
        skb_pull(skb, 1);   /* Remove PID */
        return ax25_rx_fragment(ax25, skb);
    }

    if ((func = ax25_protocol_function(pid)) != NULL) {
        skb_pull(skb, 1);   /* Remove PID */
        return (*func)(skb, ax25);
    }

    if (ax25->sk != NULL && ax25->ax25_dev->values[AX25_VALUES_CONMODE] == 2) {
        if ((!ax25->pidincl && ax25->sk->sk_protocol == pid) ||
            ax25->pidincl) {
            if (sock_queue_rcv_skb(ax25->sk, skb) == 0)
                queued = 1;
            else
                ax25->condition |= AX25_COND_OWN_RX_BUSY;
        }
    }

    return queued;
}

/*
 *  Higher level upcall for a LAPB frame
 */
static int ax25_process_rx_frame(ax25_cb *ax25, struct sk_buff *skb, int type, int dama)
{
    int queued = 0;

    if (ax25->state == AX25_STATE_0)
        return 0;

    switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
    case AX25_PROTO_STD_SIMPLEX:
    case AX25_PROTO_STD_DUPLEX:
        queued = ax25_std_frame_in(ax25, skb, type);
        break;

#ifdef CONFIG_AX25_DAMA_SLAVE
    case AX25_PROTO_DAMA_SLAVE:
        if (dama || ax25->ax25_dev->dama.slave)
            queued = ax25_ds_frame_in(ax25, skb, type);
        else
            queued = ax25_std_frame_in(ax25, skb, type);
        break;
#endif
    }

    return queued;
}

static int ax25_rcv(struct sk_buff *skb, struct net_device *dev,
    ax25_address *dev_addr, struct packet_type *ptype)
{
    ax25_address src, dest, *next_digi = NULL;
    int type = 0, mine = 0, dama;
    struct sock *make, *sk;
    ax25_digi dp, reverse_dp;
    ax25_cb *ax25;
    ax25_dev *ax25_dev;

    /*
     *  Process the AX.25/LAPB frame.
     */

    skb_reset_transport_header(skb);

    if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL)
        goto free;

    /*
     *  Parse the address header.
     */

    if (ax25_addr_parse(skb->data, skb->len, &src, &dest, &dp, &type, &dama) == NULL)
        goto free;

    /*
     *  Ours perhaps ?
     */
    if (dp.lastrepeat + 1 < dp.ndigi)       /* Not yet digipeated completely */
        next_digi = &dp.calls[dp.lastrepeat + 1];

    /*
     *  Pull of the AX.25 headers leaving the CTRL/PID bytes
     */
    skb_pull(skb, ax25_addr_size(&dp));

    /* For our port addresses ? */
    if (ax25cmp(&dest, dev_addr) == 0 && dp.lastrepeat + 1 == dp.ndigi)
        mine = 1;

    /* Also match on any registered callsign from L3/4 */
    if (!mine && ax25_listen_mine(&dest, dev) && dp.lastrepeat + 1 == dp.ndigi)
        mine = 1;

    /* UI frame - bypass LAPB processing */
    if ((*skb->data & ~0x10) == AX25_UI && dp.lastrepeat + 1 == dp.ndigi) {
        skb_set_transport_header(skb, 2); /* skip control and pid */

        ax25_send_to_raw(&dest, skb, skb->data[1]);

        if (!mine && ax25cmp(&dest, (ax25_address *)dev->broadcast) != 0)
            goto free;

        /* Now we are pointing at the pid byte */
        switch (skb->data[1]) {
        case AX25_P_IP:
            skb_pull(skb,2);        /* drop PID/CTRL */
            skb_reset_transport_header(skb);
            skb_reset_network_header(skb);
            skb->dev      = dev;
            skb->pkt_type = PACKET_HOST;
            skb->protocol = htons(ETH_P_IP);
            netif_rx(skb);
            break;

        case AX25_P_ARP:
            skb_pull(skb,2);
            skb_reset_transport_header(skb);
            skb_reset_network_header(skb);
            skb->dev      = dev;
            skb->pkt_type = PACKET_HOST;
            skb->protocol = htons(ETH_P_ARP);
            netif_rx(skb);
            break;
        case AX25_P_TEXT:
            /* Now find a suitable dgram socket */
            sk = ax25_get_socket(&dest, &src, SOCK_DGRAM);
            if (sk != NULL) {
                bh_lock_sock(sk);
                if (atomic_read(&sk->sk_rmem_alloc) >=
                    sk->sk_rcvbuf) {
                    kfree_skb(skb);
                } else {
                    /*
                     *  Remove the control and PID.
                     */
                    skb_pull(skb, 2);
                    if (sock_queue_rcv_skb(sk, skb) != 0)
                        kfree_skb(skb);
                }
                bh_unlock_sock(sk);
                sock_put(sk);
            } else {
                kfree_skb(skb);
            }
            break;

        default:
            kfree_skb(skb); /* Will scan SOCK_AX25 RAW sockets */
            break;
        }

        return 0;
    }

    /*
     *  Is connected mode supported on this device ?
     *  If not, should we DM the incoming frame (except DMs) or
     *  silently ignore them. For now we stay quiet.
     */
    if (ax25_dev->values[AX25_VALUES_CONMODE] == 0)
        goto free;

    /* LAPB */

    /* AX.25 state 1-4 */

    ax25_digi_invert(&dp, &reverse_dp);

    if ((ax25 = ax25_find_cb(&dest, &src, &reverse_dp, dev)) != NULL) {
        /*
         *  Process the frame. If it is queued up internally it
         *  returns one otherwise we free it immediately. This
         *  routine itself wakes the user context layers so we do
         *  no further work
         */
        if (ax25_process_rx_frame(ax25, skb, type, dama) == 0)
            kfree_skb(skb);

        ax25_cb_put(ax25);
        return 0;
    }

    /* AX.25 state 0 (disconnected) */

    /* a) received not a SABM(E) */

    if ((*skb->data & ~AX25_PF) != AX25_SABM &&
        (*skb->data & ~AX25_PF) != AX25_SABME) {
        /*
         *  Never reply to a DM. Also ignore any connects for
         *  addresses that are not our interfaces and not a socket.
         */
        if ((*skb->data & ~AX25_PF) != AX25_DM && mine)
            ax25_return_dm(dev, &src, &dest, &dp);

        goto free;
    }

    /* b) received SABM(E) */

    if (dp.lastrepeat + 1 == dp.ndigi)
        sk = ax25_find_listener(&dest, 0, dev, SOCK_SEQPACKET);
    else
        sk = ax25_find_listener(next_digi, 1, dev, SOCK_SEQPACKET);

    if (sk != NULL) {
        bh_lock_sock(sk);
        if (sk_acceptq_is_full(sk) ||
            (make = ax25_make_new(sk, ax25_dev)) == NULL) {
            if (mine)
                ax25_return_dm(dev, &src, &dest, &dp);
            kfree_skb(skb);
            bh_unlock_sock(sk);
            sock_put(sk);

            return 0;
        }

        ax25 = ax25_sk(make);
        skb_set_owner_r(skb, make);
        skb_queue_head(&sk->sk_receive_queue, skb);

        make->sk_state = TCP_ESTABLISHED;

        sk->sk_ack_backlog++;
        bh_unlock_sock(sk);
    } else {
        if (!mine)
            goto free;

        if ((ax25 = ax25_create_cb()) == NULL) {
            ax25_return_dm(dev, &src, &dest, &dp);
            goto free;
        }

        ax25_fillin_cb(ax25, ax25_dev);
    }

    ax25->source_addr = dest;
    ax25->dest_addr   = src;

    /*
     *  Sort out any digipeated paths.
     */
    if (dp.ndigi && !ax25->digipeat &&
        (ax25->digipeat = kmalloc(sizeof(ax25_digi), GFP_ATOMIC)) == NULL) {
        kfree_skb(skb);
        ax25_destroy_socket(ax25);
        if (sk)
            sock_put(sk);
        return 0;
    }

    if (dp.ndigi == 0) {
        kfree(ax25->digipeat);
        ax25->digipeat = NULL;
    } else {
        /* Reverse the source SABM's path */
        memcpy(ax25->digipeat, &reverse_dp, sizeof(ax25_digi));
    }

    if ((*skb->data & ~AX25_PF) == AX25_SABME) {
        ax25->modulus = AX25_EMODULUS;
        ax25->window  = ax25_dev->values[AX25_VALUES_EWINDOW];
    } else {
        ax25->modulus = AX25_MODULUS;
        ax25->window  = ax25_dev->values[AX25_VALUES_WINDOW];
    }

    ax25_send_control(ax25, AX25_UA, AX25_POLLON, AX25_RESPONSE);

#ifdef CONFIG_AX25_DAMA_SLAVE
    if (dama && ax25->ax25_dev->values[AX25_VALUES_PROTOCOL] == AX25_PROTO_DAMA_SLAVE)
        ax25_dama_on(ax25);
#endif

    ax25->state = AX25_STATE_3;

    ax25_cb_add(ax25);

    ax25_start_heartbeat(ax25);
    ax25_start_t3timer(ax25);
    ax25_start_idletimer(ax25);

    if (sk) {
        if (!sock_flag(sk, SOCK_DEAD))
            sk->sk_data_ready(sk, skb->len);
        sock_put(sk);
    } else {
free:
        kfree_skb(skb);
    }
    return 0;
}

/*
 *  Receive an AX.25 frame via a SLIP interface.
 */
int ax25_kiss_rcv(struct sk_buff *skb, struct net_device *dev,
          struct packet_type *ptype, struct net_device *orig_dev)
{
    skb_orphan(skb);

    if (!net_eq(dev_net(dev), &init_net)) {
        kfree_skb(skb);
        return 0;
    }

    if ((*skb->data & 0x0F) != 0) {
        kfree_skb(skb); /* Not a KISS data frame */
        return 0;
    }

    skb_pull(skb, AX25_KISS_HEADER_LEN);    /* Remove the KISS byte */

    return ax25_rcv(skb, dev, (ax25_address *)dev->dev_addr, ptype);
}