af_phonet.c

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/*
 * File: af_phonet.c
 *
 * Phonet protocols family
 *
 * Copyright (C) 2008 Nokia Corporation.
 *
 * Authors: Sakari Ailus <[email protected]>
 *          Rémi Denis-Courmont
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <asm/unaligned.h>
#include <net/sock.h>

#include <linux/if_phonet.h>
#include <linux/phonet.h>
#include <net/phonet/phonet.h>
#include <net/phonet/pn_dev.h>

/* Transport protocol registration */
static struct phonet_protocol *proto_tab[PHONET_NPROTO] __read_mostly;

static struct phonet_protocol *phonet_proto_get(unsigned int protocol)
{
    struct phonet_protocol *pp;

    if (protocol >= PHONET_NPROTO)
        return NULL;

    rcu_read_lock();
    pp = rcu_dereference(proto_tab[protocol]);
    if (pp && !try_module_get(pp->prot->owner))
        pp = NULL;
    rcu_read_unlock();

    return pp;
}

static inline void phonet_proto_put(struct phonet_protocol *pp)
{
    module_put(pp->prot->owner);
}

/* protocol family functions */

static int pn_socket_create(struct net *net, struct socket *sock, int protocol,
                int kern)
{
    struct sock *sk;
    struct pn_sock *pn;
    struct phonet_protocol *pnp;
    int err;

    if (!capable(CAP_SYS_ADMIN))
        return -EPERM;

    if (protocol == 0) {
        /* Default protocol selection */
        switch (sock->type) {
        case SOCK_DGRAM:
            protocol = PN_PROTO_PHONET;
            break;
        case SOCK_SEQPACKET:
            protocol = PN_PROTO_PIPE;
            break;
        default:
            return -EPROTONOSUPPORT;
        }
    }

    pnp = phonet_proto_get(protocol);
    if (pnp == NULL &&
        request_module("net-pf-%d-proto-%d", PF_PHONET, protocol) == 0)
        pnp = phonet_proto_get(protocol);

    if (pnp == NULL)
        return -EPROTONOSUPPORT;
    if (sock->type != pnp->sock_type) {
        err = -EPROTONOSUPPORT;
        goto out;
    }

    sk = sk_alloc(net, PF_PHONET, GFP_KERNEL, pnp->prot);
    if (sk == NULL) {
        err = -ENOMEM;
        goto out;
    }

    sock_init_data(sock, sk);
    sock->state = SS_UNCONNECTED;
    sock->ops = pnp->ops;
    sk->sk_backlog_rcv = sk->sk_prot->backlog_rcv;
    sk->sk_protocol = protocol;
    pn = pn_sk(sk);
    pn->sobject = 0;
    pn->dobject = 0;
    pn->resource = 0;
    sk->sk_prot->init(sk);
    err = 0;

out:
    phonet_proto_put(pnp);
    return err;
}

static const struct net_proto_family phonet_proto_family = {
    .family = PF_PHONET,
    .create = pn_socket_create,
    .owner = THIS_MODULE,
};

/* Phonet device header operations */
static int pn_header_create(struct sk_buff *skb, struct net_device *dev,
                unsigned short type, const void *daddr,
                const void *saddr, unsigned int len)
{
    u8 *media = skb_push(skb, 1);

    if (type != ETH_P_PHONET)
        return -1;

    if (!saddr)
        saddr = dev->dev_addr;
    *media = *(const u8 *)saddr;
    return 1;
}

static int pn_header_parse(const struct sk_buff *skb, unsigned char *haddr)
{
    const u8 *media = skb_mac_header(skb);
    *haddr = *media;
    return 1;
}

struct header_ops phonet_header_ops = {
    .create = pn_header_create,
    .parse = pn_header_parse,
};
EXPORT_SYMBOL(phonet_header_ops);

/*
 * Prepends an ISI header and sends a datagram.
 */
static int pn_send(struct sk_buff *skb, struct net_device *dev,
            u16 dst, u16 src, u8 res, u8 irq)
{
    struct phonethdr *ph;
    int err;

    if (skb->len + 2 > 0xffff /* Phonet length field limit */ ||
        skb->len + sizeof(struct phonethdr) > dev->mtu) {
        err = -EMSGSIZE;
        goto drop;
    }

    /* Broadcast sending is not implemented */
    if (pn_addr(dst) == PNADDR_BROADCAST) {
        err = -EOPNOTSUPP;
        goto drop;
    }

    skb_reset_transport_header(skb);
    WARN_ON(skb_headroom(skb) & 1); /* HW assumes word alignment */
    skb_push(skb, sizeof(struct phonethdr));
    skb_reset_network_header(skb);
    ph = pn_hdr(skb);
    ph->pn_rdev = pn_dev(dst);
    ph->pn_sdev = pn_dev(src);
    ph->pn_res = res;
    ph->pn_length = __cpu_to_be16(skb->len + 2 - sizeof(*ph));
    ph->pn_robj = pn_obj(dst);
    ph->pn_sobj = pn_obj(src);

    skb->protocol = htons(ETH_P_PHONET);
    skb->priority = 0;
    skb->dev = dev;

    if (skb->pkt_type == PACKET_LOOPBACK) {
        skb_reset_mac_header(skb);
        skb_orphan(skb);
        err = (irq ? netif_rx(skb) : netif_rx_ni(skb)) ? -ENOBUFS : 0;
    } else {
        err = dev_hard_header(skb, dev, ntohs(skb->protocol),
                    NULL, NULL, skb->len);
        if (err < 0) {
            err = -EHOSTUNREACH;
            goto drop;
        }
        err = dev_queue_xmit(skb);
        if (unlikely(err > 0))
            err = net_xmit_errno(err);
    }

    return err;
drop:
    kfree_skb(skb);
    return err;
}

static int pn_raw_send(const void *data, int len, struct net_device *dev,
            u16 dst, u16 src, u8 res)
{
    struct sk_buff *skb = alloc_skb(MAX_PHONET_HEADER + len, GFP_ATOMIC);
    if (skb == NULL)
        return -ENOMEM;

    if (phonet_address_lookup(dev_net(dev), pn_addr(dst)) == 0)
        skb->pkt_type = PACKET_LOOPBACK;

    skb_reserve(skb, MAX_PHONET_HEADER);
    __skb_put(skb, len);
    skb_copy_to_linear_data(skb, data, len);
    return pn_send(skb, dev, dst, src, res, 1);
}

/*
 * Create a Phonet header for the skb and send it out. Returns
 * non-zero error code if failed. The skb is freed then.
 */
int pn_skb_send(struct sock *sk, struct sk_buff *skb,
        const struct sockaddr_pn *target)
{
    struct net *net = sock_net(sk);
    struct net_device *dev;
    struct pn_sock *pn = pn_sk(sk);
    int err;
    u16 src, dst;
    u8 daddr, saddr, res;

    src = pn->sobject;
    if (target != NULL) {
        dst = pn_sockaddr_get_object(target);
        res = pn_sockaddr_get_resource(target);
    } else {
        dst = pn->dobject;
        res = pn->resource;
    }
    daddr = pn_addr(dst);

    err = -EHOSTUNREACH;
    if (sk->sk_bound_dev_if)
        dev = dev_get_by_index(net, sk->sk_bound_dev_if);
    else if (phonet_address_lookup(net, daddr) == 0) {
        dev = phonet_device_get(net);
        skb->pkt_type = PACKET_LOOPBACK;
    } else if (dst == 0) {
        /* Resource routing (small race until phonet_rcv()) */
        struct sock *sk = pn_find_sock_by_res(net, res);
        if (sk) {
            sock_put(sk);
            dev = phonet_device_get(net);
            skb->pkt_type = PACKET_LOOPBACK;
        } else
            dev = phonet_route_output(net, daddr);
    } else
        dev = phonet_route_output(net, daddr);

    if (!dev || !(dev->flags & IFF_UP))
        goto drop;

    saddr = phonet_address_get(dev, daddr);
    if (saddr == PN_NO_ADDR)
        goto drop;

    if (!pn_addr(src))
        src = pn_object(saddr, pn_obj(src));

    err = pn_send(skb, dev, dst, src, res, 0);
    dev_put(dev);
    return err;

drop:
    kfree_skb(skb);
    if (dev)
        dev_put(dev);
    return err;
}
EXPORT_SYMBOL(pn_skb_send);

/* Do not send an error message in response to an error message */
static inline int can_respond(struct sk_buff *skb)
{
    const struct phonethdr *ph;
    const struct phonetmsg *pm;
    u8 submsg_id;

    if (!pskb_may_pull(skb, 3))
        return 0;

    ph = pn_hdr(skb);
    if (ph->pn_res == PN_PREFIX && !pskb_may_pull(skb, 5))
        return 0;
    if (ph->pn_res == PN_COMMGR) /* indications */
        return 0;

    ph = pn_hdr(skb); /* re-acquires the pointer */
    pm = pn_msg(skb);
    if (pm->pn_msg_id != PN_COMMON_MESSAGE)
        return 1;
    submsg_id = (ph->pn_res == PN_PREFIX)
        ? pm->pn_e_submsg_id : pm->pn_submsg_id;
    if (submsg_id != PN_COMM_ISA_ENTITY_NOT_REACHABLE_RESP &&
        pm->pn_e_submsg_id != PN_COMM_SERVICE_NOT_IDENTIFIED_RESP)
        return 1;
    return 0;
}

static int send_obj_unreachable(struct sk_buff *rskb)
{
    const struct phonethdr *oph = pn_hdr(rskb);
    const struct phonetmsg *opm = pn_msg(rskb);
    struct phonetmsg resp;

    memset(&resp, 0, sizeof(resp));
    resp.pn_trans_id = opm->pn_trans_id;
    resp.pn_msg_id = PN_COMMON_MESSAGE;
    if (oph->pn_res == PN_PREFIX) {
        resp.pn_e_res_id = opm->pn_e_res_id;
        resp.pn_e_submsg_id = PN_COMM_ISA_ENTITY_NOT_REACHABLE_RESP;
        resp.pn_e_orig_msg_id = opm->pn_msg_id;
        resp.pn_e_status = 0;
    } else {
        resp.pn_submsg_id = PN_COMM_ISA_ENTITY_NOT_REACHABLE_RESP;
        resp.pn_orig_msg_id = opm->pn_msg_id;
        resp.pn_status = 0;
    }
    return pn_raw_send(&resp, sizeof(resp), rskb->dev,
                pn_object(oph->pn_sdev, oph->pn_sobj),
                pn_object(oph->pn_rdev, oph->pn_robj),
                oph->pn_res);
}

static int send_reset_indications(struct sk_buff *rskb)
{
    struct phonethdr *oph = pn_hdr(rskb);
    static const u8 data[4] = {
        0x00 /* trans ID */, 0x10 /* subscribe msg */,
        0x00 /* subscription count */, 0x00 /* dummy */
    };

    return pn_raw_send(data, sizeof(data), rskb->dev,
                pn_object(oph->pn_sdev, 0x00),
                pn_object(oph->pn_rdev, oph->pn_robj),
                PN_COMMGR);
}


/* packet type functions */

/*
 * Stuff received packets to associated sockets.
 * On error, returns non-zero and releases the skb.
 */
static int phonet_rcv(struct sk_buff *skb, struct net_device *dev,
            struct packet_type *pkttype,
            struct net_device *orig_dev)
{
    struct net *net = dev_net(dev);
    struct phonethdr *ph;
    struct sockaddr_pn sa;
    u16 len;

    /* check we have at least a full Phonet header */
    if (!pskb_pull(skb, sizeof(struct phonethdr)))
        goto out;

    /* check that the advertised length is correct */
    ph = pn_hdr(skb);
    len = get_unaligned_be16(&ph->pn_length);
    if (len < 2)
        goto out;
    len -= 2;
    if ((len > skb->len) || pskb_trim(skb, len))
        goto out;
    skb_reset_transport_header(skb);

    pn_skb_get_dst_sockaddr(skb, &sa);

    /* check if this is broadcasted */
    if (pn_sockaddr_get_addr(&sa) == PNADDR_BROADCAST) {
        pn_deliver_sock_broadcast(net, skb);
        goto out;
    }

    /* resource routing */
    if (pn_sockaddr_get_object(&sa) == 0) {
        struct sock *sk = pn_find_sock_by_res(net, sa.spn_resource);
        if (sk)
            return sk_receive_skb(sk, skb, 0);
    }

    /* check if we are the destination */
    if (phonet_address_lookup(net, pn_sockaddr_get_addr(&sa)) == 0) {
        /* Phonet packet input */
        struct sock *sk = pn_find_sock_by_sa(net, &sa);

        if (sk)
            return sk_receive_skb(sk, skb, 0);

        if (can_respond(skb)) {
            send_obj_unreachable(skb);
            send_reset_indications(skb);
        }
    } else if (unlikely(skb->pkt_type == PACKET_LOOPBACK))
        goto out; /* Race between address deletion and loopback */
    else {
        /* Phonet packet routing */
        struct net_device *out_dev;

        out_dev = phonet_route_output(net, pn_sockaddr_get_addr(&sa));
        if (!out_dev) {
            LIMIT_NETDEBUG(KERN_WARNING"No Phonet route to %02X\n",
                    pn_sockaddr_get_addr(&sa));
            goto out;
        }

        __skb_push(skb, sizeof(struct phonethdr));
        skb->dev = out_dev;
        if (out_dev == dev) {
            LIMIT_NETDEBUG(KERN_ERR"Phonet loop to %02X on %s\n",
                    pn_sockaddr_get_addr(&sa), dev->name);
            goto out_dev;
        }
        /* Some drivers (e.g. TUN) do not allocate HW header space */
        if (skb_cow_head(skb, out_dev->hard_header_len))
            goto out_dev;

        if (dev_hard_header(skb, out_dev, ETH_P_PHONET, NULL, NULL,
                    skb->len) < 0)
            goto out_dev;
        dev_queue_xmit(skb);
        dev_put(out_dev);
        return NET_RX_SUCCESS;
out_dev:
        dev_put(out_dev);
    }

out:
    kfree_skb(skb);
    return NET_RX_DROP;
}

static struct packet_type phonet_packet_type __read_mostly = {
    .type = cpu_to_be16(ETH_P_PHONET),
    .func = phonet_rcv,
};

static DEFINE_MUTEX(proto_tab_lock);

int __init_or_module phonet_proto_register(unsigned int protocol,
                        struct phonet_protocol *pp)
{
    int err = 0;

    if (protocol >= PHONET_NPROTO)
        return -EINVAL;

    err = proto_register(pp->prot, 1);
    if (err)
        return err;

    mutex_lock(&proto_tab_lock);
    if (proto_tab[protocol])
        err = -EBUSY;
    else
        rcu_assign_pointer(proto_tab[protocol], pp);
    mutex_unlock(&proto_tab_lock);

    return err;
}
EXPORT_SYMBOL(phonet_proto_register);

void phonet_proto_unregister(unsigned int protocol, struct phonet_protocol *pp)
{
    mutex_lock(&proto_tab_lock);
    BUG_ON(proto_tab[protocol] != pp);
    RCU_INIT_POINTER(proto_tab[protocol], NULL);
    mutex_unlock(&proto_tab_lock);
    synchronize_rcu();
    proto_unregister(pp->prot);
}
EXPORT_SYMBOL(phonet_proto_unregister);

/* Module registration */
static int __init phonet_init(void)
{
    int err;

    err = phonet_device_init();
    if (err)
        return err;

    pn_sock_init();
    err = sock_register(&phonet_proto_family);
    if (err) {
        printk(KERN_ALERT
            "phonet protocol family initialization failed\n");
        goto err_sock;
    }

    dev_add_pack(&phonet_packet_type);
    phonet_sysctl_init();

    err = isi_register();
    if (err)
        goto err;
    return 0;

err:
    phonet_sysctl_exit();
    sock_unregister(PF_PHONET);
    dev_remove_pack(&phonet_packet_type);
err_sock:
    phonet_device_exit();
    return err;
}

static void __exit phonet_exit(void)
{
    isi_unregister();
    phonet_sysctl_exit();
    sock_unregister(PF_PHONET);
    dev_remove_pack(&phonet_packet_type);
    phonet_device_exit();
}

module_init(phonet_init);
module_exit(phonet_exit);
MODULE_DESCRIPTION("Phonet protocol stack for Linux");
MODULE_LICENSE("GPL");
MODULE_ALIAS_NETPROTO(PF_PHONET);