// SPDX-License-Identifier: GPL-2.0
/*
 * DECnet       An implementation of the DECnet protocol suite for the LINUX
 *              operating system.  DECnet is implemented using the  BSD Socket
 *              interface as the means of communication with the user level.
 *
 *              DECnet Neighbour Functions (Adjacency Database and
 *                                                        On-Ethernet Cache)
 *
 * Author:      Steve Whitehouse <SteveW@ACM.org>
 *
 *
 * Changes:
 *     Steve Whitehouse     : Fixed router listing routine
 *     Steve Whitehouse     : Added error_report functions
 *     Steve Whitehouse     : Added default router detection
 *     Steve Whitehouse     : Hop counts in outgoing messages
 *     Steve Whitehouse     : Fixed src/dst in outgoing messages so
 *                            forwarding now stands a good chance of
 *                            working.
 *     Steve Whitehouse     : Fixed neighbour states (for now anyway).
 *     Steve Whitehouse     : Made error_report functions dummies. This
 *                            is not the right place to return skbs.
 *     Steve Whitehouse     : Convert to seq_file
 *
 */

#include <linux/net.h>
#include <linux/module.h>
#include <linux/socket.h>
#include <linux/if_arp.h>
#include <linux/slab.h>
#include <linux/if_ether.h>
#include <linux/init.h>
#include <linux/proc_fs.h>
#include <linux/string.h>
#include <linux/netfilter_decnet.h>
#include <linux/spinlock.h>
#include <linux/seq_file.h>
#include <linux/rcupdate.h>
#include <linux/jhash.h>
#include <linux/atomic.h>
#include <net/net_namespace.h>
#include <net/neighbour.h>
#include <net/dst.h>
#include <net/flow.h>
#include <net/dn.h>
#include <net/dn_dev.h>
#include <net/dn_neigh.h>
#include <net/dn_route.h>

static int dn_neigh_construct(struct neighbour *);
static void dn_neigh_error_report(struct neighbour *, struct sk_buff *);
static int dn_neigh_output(struct neighbour *neigh, struct sk_buff *skb);

/*
 * Operations for adding the link layer header.
 */
static const struct neigh_ops dn_neigh_ops = {
        .family =               AF_DECnet,
        .error_report =         dn_neigh_error_report,
        .output =               dn_neigh_output,
        .connected_output =     dn_neigh_output,
};

static u32 dn_neigh_hash(const void *pkey,
                         const struct net_device *dev,
                         __u32 *hash_rnd)
{
        return jhash_2words(*(__u16 *)pkey, 0, hash_rnd[0]);
}

static bool dn_key_eq(const struct neighbour *neigh, const void *pkey)
{
        return neigh_key_eq16(neigh, pkey);
}

struct neigh_table dn_neigh_table = {
        .family =                       PF_DECnet,
        .entry_size =                   NEIGH_ENTRY_SIZE(sizeof(struct dn_neigh)),
        .key_len =                      sizeof(__le16),
        .protocol =                     cpu_to_be16(ETH_P_DNA_RT),
        .hash =                         dn_neigh_hash,
        .key_eq =                       dn_key_eq,
        .constructor =                  dn_neigh_construct,
        .id =                           "dn_neigh_cache",
        .parms ={
                .tbl =                  &dn_neigh_table,
                .reachable_time =       30 * HZ,
                .data = {
                        [NEIGH_VAR_MCAST_PROBES] = 0,
                        [NEIGH_VAR_UCAST_PROBES] = 0,
                        [NEIGH_VAR_APP_PROBES] = 0,
                        [NEIGH_VAR_RETRANS_TIME] = 1 * HZ,
                        [NEIGH_VAR_BASE_REACHABLE_TIME] = 30 * HZ,
                        [NEIGH_VAR_DELAY_PROBE_TIME] = 5 * HZ,
                        [NEIGH_VAR_GC_STALETIME] = 60 * HZ,
                        [NEIGH_VAR_QUEUE_LEN_BYTES] = SK_WMEM_MAX,
                        [NEIGH_VAR_PROXY_QLEN] = 0,
                        [NEIGH_VAR_ANYCAST_DELAY] = 0,
                        [NEIGH_VAR_PROXY_DELAY] = 0,
                        [NEIGH_VAR_LOCKTIME] = 1 * HZ,
                },
        },
        .gc_interval =                  30 * HZ,
        .gc_thresh1 =                   128,
        .gc_thresh2 =                   512,
        .gc_thresh3 =                   1024,
};

static int dn_neigh_construct(struct neighbour *neigh)
{
        struct net_device *dev = neigh->dev;
        struct dn_neigh *dn = container_of(neigh, struct dn_neigh, n);
        struct dn_dev *dn_db;
        struct neigh_parms *parms;

        rcu_read_lock();
        dn_db = rcu_dereference(dev->dn_ptr);
        if (dn_db == NULL) {
                rcu_read_unlock();
                return -EINVAL;
        }

        parms = dn_db->neigh_parms;
        if (!parms) {
                rcu_read_unlock();
                return -EINVAL;
        }

        __neigh_parms_put(neigh->parms);
        neigh->parms = neigh_parms_clone(parms);
        rcu_read_unlock();

        neigh->ops = &dn_neigh_ops;
        neigh->nud_state = NUD_NOARP;
        neigh->output = neigh->ops->connected_output;

        if ((dev->type == ARPHRD_IPGRE) || (dev->flags & IFF_POINTOPOINT))
                memcpy(neigh->ha, dev->broadcast, dev->addr_len);
        else if ((dev->type == ARPHRD_ETHER) || (dev->type == ARPHRD_LOOPBACK))
                dn_dn2eth(neigh->ha, dn->addr);
        else {
                net_dbg_ratelimited("Trying to create neigh for hw %d\n",
                                    dev->type);
                return -EINVAL;
        }

        /*
         * Make an estimate of the remote block size by assuming that its
         * two less then the device mtu, which it true for ethernet (and
         * other things which support long format headers) since there is
         * an extra length field (of 16 bits) which isn't part of the
         * ethernet headers and which the DECnet specs won't admit is part
         * of the DECnet routing headers either.
         *
         * If we over estimate here its no big deal, the NSP negotiations
         * will prevent us from sending packets which are too large for the
         * remote node to handle. In any case this figure is normally updated
         * by a hello message in most cases.
         */
        dn->blksize = dev->mtu - 2;

        return 0;
}

static void dn_neigh_error_report(struct neighbour *neigh, struct sk_buff *skb)
{
        printk(KERN_DEBUG "dn_neigh_error_report: called\n");
        kfree_skb(skb);
}

static int dn_neigh_output(struct neighbour *neigh, struct sk_buff *skb)
{
        struct dst_entry *dst = skb_dst(skb);
        struct dn_route *rt = (struct dn_route *)dst;
        struct net_device *dev = neigh->dev;
        char mac_addr[ETH_ALEN];
        unsigned int seq;
        int err;

        dn_dn2eth(mac_addr, rt->rt_local_src);
        do {
                seq = read_seqbegin(&neigh->ha_lock);
                err = dev_hard_header(skb, dev, ntohs(skb->protocol),
                                      neigh->ha, mac_addr, skb->len);
        } while (read_seqretry(&neigh->ha_lock, seq));

        if (err >= 0)
                err = dev_queue_xmit(skb);
        else {
                kfree_skb(skb);
                err = -EINVAL;
        }
        return err;
}

static int dn_neigh_output_packet(struct net *net, struct sock *sk, struct sk_buff *skb)
{
        struct dst_entry *dst = skb_dst(skb);
        struct dn_route *rt = (struct dn_route *)dst;
        struct neighbour *neigh = rt->n;

        return neigh->output(neigh, skb);
}

/*
 * For talking to broadcast devices: Ethernet & PPP
 */
static int dn_long_output(struct neighbour *neigh, struct sock *sk,
                          struct sk_buff *skb)
{
        struct net_device *dev = neigh->dev;
        int headroom = dev->hard_header_len + sizeof(struct dn_long_packet) + 3;
        unsigned char *data;
        struct dn_long_packet *lp;
        struct dn_skb_cb *cb = DN_SKB_CB(skb);


        if (skb_headroom(skb) < headroom) {
                struct sk_buff *skb2 = skb_realloc_headroom(skb, headroom);
                if (skb2 == NULL) {
                        net_crit_ratelimited("dn_long_output: no memory\n");
                        kfree_skb(skb);
                        return -ENOBUFS;
                }
                consume_skb(skb);
                skb = skb2;
                net_info_ratelimited("dn_long_output: Increasing headroom\n");
        }

        data = skb_push(skb, sizeof(struct dn_long_packet) + 3);
        lp = (struct dn_long_packet *)(data+3);

        *((__le16 *)data) = cpu_to_le16(skb->len - 2);
        *(data + 2) = 1 | DN_RT_F_PF; /* Padding */

        lp->msgflg   = DN_RT_PKT_LONG|(cb->rt_flags&(DN_RT_F_IE|DN_RT_F_RQR|DN_RT_F_RTS));
        lp->d_area   = lp->d_subarea = 0;
        dn_dn2eth(lp->d_id, cb->dst);
        lp->s_area   = lp->s_subarea = 0;
        dn_dn2eth(lp->s_id, cb->src);
        lp->nl2      = 0;
        lp->visit_ct = cb->hops & 0x3f;
        lp->s_class  = 0;
        lp->pt       = 0;

        skb_reset_network_header(skb);

        return NF_HOOK(NFPROTO_DECNET, NF_DN_POST_ROUTING,
                       &init_net, sk, skb, NULL, neigh->dev,
                       dn_neigh_output_packet);
}

/*
 * For talking to pointopoint and multidrop devices: DDCMP and X.25
 */
static int dn_short_output(struct neighbour *neigh, struct sock *sk,
                           struct sk_buff *skb)
{
        struct net_device *dev = neigh->dev;
        int headroom = dev->hard_header_len + sizeof(struct dn_short_packet) + 2;
        struct dn_short_packet *sp;
        unsigned char *data;
        struct dn_skb_cb *cb = DN_SKB_CB(skb);


        if (skb_headroom(skb) < headroom) {
                struct sk_buff *skb2 = skb_realloc_headroom(skb, headroom);
                if (skb2 == NULL) {
                        net_crit_ratelimited("dn_short_output: no memory\n");
                        kfree_skb(skb);
                        return -ENOBUFS;
                }
                consume_skb(skb);
                skb = skb2;
                net_info_ratelimited("dn_short_output: Increasing headroom\n");
        }

        data = skb_push(skb, sizeof(struct dn_short_packet) + 2);
        *((__le16 *)data) = cpu_to_le16(skb->len - 2);
        sp = (struct dn_short_packet *)(data+2);

        sp->msgflg     = DN_RT_PKT_SHORT|(cb->rt_flags&(DN_RT_F_RQR|DN_RT_F_RTS));
        sp->dstnode    = cb->dst;
        sp->srcnode    = cb->src;
        sp->forward    = cb->hops & 0x3f;

        skb_reset_network_header(skb);

        return NF_HOOK(NFPROTO_DECNET, NF_DN_POST_ROUTING,
                       &init_net, sk, skb, NULL, neigh->dev,
                       dn_neigh_output_packet);
}

/*
 * For talking to DECnet phase III nodes
 * Phase 3 output is the same as short output, execpt that
 * it clears the area bits before transmission.
 */
static int dn_phase3_output(struct neighbour *neigh, struct sock *sk,
                            struct sk_buff *skb)
{
        struct net_device *dev = neigh->dev;
        int headroom = dev->hard_header_len + sizeof(struct dn_short_packet) + 2;
        struct dn_short_packet *sp;
        unsigned char *data;
        struct dn_skb_cb *cb = DN_SKB_CB(skb);

        if (skb_headroom(skb) < headroom) {
                struct sk_buff *skb2 = skb_realloc_headroom(skb, headroom);
                if (skb2 == NULL) {
                        net_crit_ratelimited("dn_phase3_output: no memory\n");
                        kfree_skb(skb);
                        return -ENOBUFS;
                }
                consume_skb(skb);
                skb = skb2;
                net_info_ratelimited("dn_phase3_output: Increasing headroom\n");
        }

        data = skb_push(skb, sizeof(struct dn_short_packet) + 2);
        *((__le16 *)data) = cpu_to_le16(skb->len - 2);
        sp = (struct dn_short_packet *)(data + 2);

        sp->msgflg   = DN_RT_PKT_SHORT|(cb->rt_flags&(DN_RT_F_RQR|DN_RT_F_RTS));
        sp->dstnode  = cb->dst & cpu_to_le16(0x03ff);
        sp->srcnode  = cb->src & cpu_to_le16(0x03ff);
        sp->forward  = cb->hops & 0x3f;

        skb_reset_network_header(skb);

        return NF_HOOK(NFPROTO_DECNET, NF_DN_POST_ROUTING,
                       &init_net, sk, skb, NULL, neigh->dev,
                       dn_neigh_output_packet);
}

int dn_to_neigh_output(struct net *net, struct sock *sk, struct sk_buff *skb)
{
        struct dst_entry *dst = skb_dst(skb);
        struct dn_route *rt = (struct dn_route *) dst;
        struct neighbour *neigh = rt->n;
        struct dn_neigh *dn = container_of(neigh, struct dn_neigh, n);
        struct dn_dev *dn_db;
        bool use_long;

        rcu_read_lock();
        dn_db = rcu_dereference(neigh->dev->dn_ptr);
        if (dn_db == NULL) {
                rcu_read_unlock();
                return -EINVAL;
        }
        use_long = dn_db->use_long;
        rcu_read_unlock();

        if (dn->flags & DN_NDFLAG_P3)
                return dn_phase3_output(neigh, sk, skb);
        if (use_long)
                return dn_long_output(neigh, sk, skb);
        else
                return dn_short_output(neigh, sk, skb);
}

/*
 * Unfortunately, the neighbour code uses the device in its hash
 * function, so we don't get any advantage from it. This function
 * basically does a neigh_lookup(), but without comparing the device
 * field. This is required for the On-Ethernet cache
 */

/*
 * Pointopoint link receives a hello message
 */
void dn_neigh_pointopoint_hello(struct sk_buff *skb)
{
        kfree_skb(skb);
}

/*
 * Ethernet router hello message received
 */
int dn_neigh_router_hello(struct net *net, struct sock *sk, struct sk_buff *skb)
{
        struct rtnode_hello_message *msg = (struct rtnode_hello_message *)skb->data;

        struct neighbour *neigh;
        struct dn_neigh *dn;
        struct dn_dev *dn_db;
        __le16 src;

        src = dn_eth2dn(msg->id);

        neigh = __neigh_lookup(&dn_neigh_table, &src, skb->dev, 1);

        dn = container_of(neigh, struct dn_neigh, n);

        if (neigh) {
                write_lock(&neigh->lock);

                neigh->used = jiffies;
                dn_db = rcu_dereference(neigh->dev->dn_ptr);

                if (!(neigh->nud_state & NUD_PERMANENT)) {
                        neigh->updated = jiffies;

                        if (neigh->dev->type == ARPHRD_ETHER)
                                memcpy(neigh->ha, &eth_hdr(skb)->h_source, ETH_ALEN);

                        dn->blksize  = le16_to_cpu(msg->blksize);
                        dn->priority = msg->priority;

                        dn->flags &= ~DN_NDFLAG_P3;

                        switch (msg->iinfo & DN_RT_INFO_TYPE) {
                        case DN_RT_INFO_L1RT:
                                dn->flags &=~DN_NDFLAG_R2;
                                dn->flags |= DN_NDFLAG_R1;
                                break;
                        case DN_RT_INFO_L2RT:
                                dn->flags |= DN_NDFLAG_R2;
                        }
                }

                /* Only use routers in our area */
                if ((le16_to_cpu(src)>>10) == (le16_to_cpu((decnet_address))>>10)) {
                        if (!dn_db->router) {
                                dn_db->router = neigh_clone(neigh);
                        } else {
                                if (msg->priority > ((struct dn_neigh *)dn_db->router)->priority)
                                        neigh_release(xchg(&dn_db->router, neigh_clone(neigh)));
                        }
                }
                write_unlock(&neigh->lock);
                neigh_release(neigh);
        }

        kfree_skb(skb);
        return 0;
}

/*
 * Endnode hello message received
 */
int dn_neigh_endnode_hello(struct net *net, struct sock *sk, struct sk_buff *skb)
{
        struct endnode_hello_message *msg = (struct endnode_hello_message *)skb->data;
        struct neighbour *neigh;
        struct dn_neigh *dn;
        __le16 src;

        src = dn_eth2dn(msg->id);

        neigh = __neigh_lookup(&dn_neigh_table, &src, skb->dev, 1);

        dn = container_of(neigh, struct dn_neigh, n);

        if (neigh) {
                write_lock(&neigh->lock);

                neigh->used = jiffies;

                if (!(neigh->nud_state & NUD_PERMANENT)) {
                        neigh->updated = jiffies;

                        if (neigh->dev->type == ARPHRD_ETHER)
                                memcpy(neigh->ha, &eth_hdr(skb)->h_source, ETH_ALEN);
                        dn->flags   &= ~(DN_NDFLAG_R1 | DN_NDFLAG_R2);
                        dn->blksize  = le16_to_cpu(msg->blksize);
                        dn->priority = 0;
                }

                write_unlock(&neigh->lock);
                neigh_release(neigh);
        }

        kfree_skb(skb);
        return 0;
}

static char *dn_find_slot(char *base, int max, int priority)
{
        int i;
        unsigned char *min = NULL;

        base += 6; /* skip first id */

        for(i = 0; i < max; i++) {
                if (!min || (*base < *min))
                        min = base;
                base += 7; /* find next priority */
        }

        if (!min)
                return NULL;

        return (*min < priority) ? (min - 6) : NULL;
}

struct elist_cb_state {
        struct net_device *dev;
        unsigned char *ptr;
        unsigned char *rs;
        int t, n;
};

static void neigh_elist_cb(struct neighbour *neigh, void *_info)
{
        struct elist_cb_state *s = _info;
        struct dn_neigh *dn;

        if (neigh->dev != s->dev)
                return;

        dn = container_of(neigh, struct dn_neigh, n);
        if (!(dn->flags & (DN_NDFLAG_R1|DN_NDFLAG_R2)))
                return;

        if (s->t == s->n)
                s->rs = dn_find_slot(s->ptr, s->n, dn->priority);
        else
                s->t++;
        if (s->rs == NULL)
                return;

        dn_dn2eth(s->rs, dn->addr);
        s->rs += 6;
        *(s->rs) = neigh->nud_state & NUD_CONNECTED ? 0x80 : 0x0;
        *(s->rs) |= dn->priority;
        s->rs++;
}

int dn_neigh_elist(struct net_device *dev, unsigned char *ptr, int n)
{
        struct elist_cb_state state;

        state.dev = dev;
        state.t = 0;
        state.n = n;
        state.ptr = ptr;
        state.rs = ptr;

        neigh_for_each(&dn_neigh_table, neigh_elist_cb, &state);

        return state.t;
}


#ifdef CONFIG_PROC_FS

static inline void dn_neigh_format_entry(struct seq_file *seq,
                                         struct neighbour *n)
{
        struct dn_neigh *dn = container_of(n, struct dn_neigh, n);
        char buf[DN_ASCBUF_LEN];

        read_lock(&n->lock);
        seq_printf(seq, "%-7s %s%s%s   %02x    %02d  %07ld %-8s\n",
                   dn_addr2asc(le16_to_cpu(dn->addr), buf),
                   (dn->flags&DN_NDFLAG_R1) ? "1" : "-",
                   (dn->flags&DN_NDFLAG_R2) ? "2" : "-",
                   (dn->flags&DN_NDFLAG_P3) ? "3" : "-",
                   dn->n.nud_state,
                   refcount_read(&dn->n.refcnt),
                   dn->blksize,
                   (dn->n.dev) ? dn->n.dev->name : "?");
        read_unlock(&n->lock);
}

static int dn_neigh_seq_show(struct seq_file *seq, void *v)
{
        if (v == SEQ_START_TOKEN) {
                seq_puts(seq, "Addr    Flags State Use Blksize Dev\n");
        } else {
                dn_neigh_format_entry(seq, v);
        }

        return 0;
}

static void *dn_neigh_seq_start(struct seq_file *seq, loff_t *pos)
{
        return neigh_seq_start(seq, pos, &dn_neigh_table,
                               NEIGH_SEQ_NEIGH_ONLY);
}

static const struct seq_operations dn_neigh_seq_ops = {
        .start = dn_neigh_seq_start,
        .next  = neigh_seq_next,
        .stop  = neigh_seq_stop,
        .show  = dn_neigh_seq_show,
};
#endif

void __init dn_neigh_init(void)
{
        neigh_table_init(NEIGH_DN_TABLE, &dn_neigh_table);
        proc_create_net("decnet_neigh", 0444, init_net.proc_net,
                        &dn_neigh_seq_ops, sizeof(struct neigh_seq_state));
}

void __exit dn_neigh_cleanup(void)
{
        remove_proc_entry("decnet_neigh", init_net.proc_net);
        neigh_table_clear(NEIGH_DN_TABLE, &dn_neigh_table);
}