// SPDX-License-Identifier: GPL-2.0-only
/*
 * File: af_phonet.c
 *
 * Phonet protocols family
 *
 * Copyright (C) 2008 Nokia Corporation.
 *
 * Authors: Sakari Ailus <sakari.ailus@nokia.com>
 *          Rémi Denis-Courmont
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/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 const struct phonet_protocol __rcu *proto_tab[PHONET_NPROTO] __read_mostly;

static const struct phonet_protocol *phonet_proto_get(unsigned int protocol)
{
        const 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(const 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;
        const 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, kern);
        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,
                           const struct net_device *dev,
                           unsigned char *haddr)
{
        const u8 *media = skb_mac_header(skb);

        *haddr = *media;
        return 1;
}

const 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)
{
        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 = netif_rx(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);
}

/*
 * 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);
        dev_put(dev);
        return err;

drop:
        kfree_skb(skb);
        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;

        skb = skb_share_check(skb, GFP_ATOMIC);
        if (!skb)
                return NET_RX_DROP;

        /* 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) {
                        net_dbg_ratelimited("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) {
                        net_dbg_ratelimited("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,
                                const 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,
                        const struct phonet_protocol *pp)
{
        mutex_lock(&proto_tab_lock);
        BUG_ON(rcu_access_pointer(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);