/* Cluster IP hashmark target
 * (C) 2003-2004 by Harald Welte <laforge@netfilter.org>
 * based on ideas of Fabio Olive Leite <olive@unixforge.org>
 *
 * Development of this code funded by SuSE Linux AG, http://www.suse.com/
 *
 * 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.
 *
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/jhash.h>
#include <linux/bitops.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <linux/ip.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <linux/icmp.h>
#include <linux/if_arp.h>
#include <linux/seq_file.h>
#include <linux/netfilter_arp.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv4/ipt_CLUSTERIP.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/net_namespace.h>
#include <net/netns/generic.h>
#include <net/checksum.h>
#include <net/ip.h>

#define CLUSTERIP_VERSION "0.8"

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
MODULE_DESCRIPTION("Xtables: CLUSTERIP target");

struct clusterip_config {
        struct list_head list;                  /* list of all configs */
        atomic_t refcount;                      /* reference count */
        atomic_t entries;                       /* number of entries/rules
                                                 * referencing us */

        __be32 clusterip;                       /* the IP address */
        u_int8_t clustermac[ETH_ALEN];          /* the MAC address */
        struct net_device *dev;                 /* device */
        u_int16_t num_total_nodes;              /* total number of nodes */
        unsigned long local_nodes;              /* node number array */

#ifdef CONFIG_PROC_FS
        struct proc_dir_entry *pde;             /* proc dir entry */
#endif
        enum clusterip_hashmode hash_mode;      /* which hashing mode */
        u_int32_t hash_initval;                 /* hash initialization */
        struct rcu_head rcu;
};

#ifdef CONFIG_PROC_FS
static const struct file_operations clusterip_proc_fops;
#endif

static unsigned int clusterip_net_id __read_mostly;

struct clusterip_net {
        struct list_head configs;
        /* lock protects the configs list */
        spinlock_t lock;

#ifdef CONFIG_PROC_FS
        struct proc_dir_entry *procdir;
#endif
};

static inline void
clusterip_config_get(struct clusterip_config *c)
{
        atomic_inc(&c->refcount);
}


static void clusterip_config_rcu_free(struct rcu_head *head)
{
        kfree(container_of(head, struct clusterip_config, rcu));
}

static inline void
clusterip_config_put(struct clusterip_config *c)
{
        if (atomic_dec_and_test(&c->refcount))
                call_rcu_bh(&c->rcu, clusterip_config_rcu_free);
}

/* decrease the count of entries using/referencing this config.  If last
 * entry(rule) is removed, remove the config from lists, but don't free it
 * yet, since proc-files could still be holding references */
static inline void
clusterip_config_entry_put(struct clusterip_config *c)
{
        struct net *net = dev_net(c->dev);
        struct clusterip_net *cn = net_generic(net, clusterip_net_id);

        local_bh_disable();
        if (atomic_dec_and_lock(&c->entries, &cn->lock)) {
                list_del_rcu(&c->list);
                spin_unlock(&cn->lock);
                local_bh_enable();

                dev_mc_del(c->dev, c->clustermac);
                dev_put(c->dev);

                /* In case anyone still accesses the file, the open/close
                 * functions are also incrementing the refcount on their own,
                 * so it's safe to remove the entry even if it's in use. */
#ifdef CONFIG_PROC_FS
                proc_remove(c->pde);
#endif
                return;
        }
        local_bh_enable();
}

static struct clusterip_config *
__clusterip_config_find(struct net *net, __be32 clusterip)
{
        struct clusterip_config *c;
        struct clusterip_net *cn = net_generic(net, clusterip_net_id);

        list_for_each_entry_rcu(c, &cn->configs, list) {
                if (c->clusterip == clusterip)
                        return c;
        }

        return NULL;
}

static inline struct clusterip_config *
clusterip_config_find_get(struct net *net, __be32 clusterip, int entry)
{
        struct clusterip_config *c;

        rcu_read_lock_bh();
        c = __clusterip_config_find(net, clusterip);
        if (c) {
#ifdef CONFIG_PROC_FS
                if (!c->pde)
                        c = NULL;
                else
#endif
                if (unlikely(!atomic_inc_not_zero(&c->refcount)))
                        c = NULL;
                else if (entry)
                        atomic_inc(&c->entries);
        }
        rcu_read_unlock_bh();

        return c;
}

static void
clusterip_config_init_nodelist(struct clusterip_config *c,
                               const struct ipt_clusterip_tgt_info *i)
{
        int n;

        for (n = 0; n < i->num_local_nodes; n++)
                set_bit(i->local_nodes[n] - 1, &c->local_nodes);
}

static struct clusterip_config *
clusterip_config_init(const struct ipt_clusterip_tgt_info *i, __be32 ip,
                      struct net_device *dev)
{
        struct net *net = dev_net(dev);
        struct clusterip_config *c;
        struct clusterip_net *cn = net_generic(net, clusterip_net_id);

        c = kzalloc(sizeof(*c), GFP_ATOMIC);
        if (!c)
                return ERR_PTR(-ENOMEM);

        c->dev = dev;
        c->clusterip = ip;
        memcpy(&c->clustermac, &i->clustermac, ETH_ALEN);
        c->num_total_nodes = i->num_total_nodes;
        clusterip_config_init_nodelist(c, i);
        c->hash_mode = i->hash_mode;
        c->hash_initval = i->hash_initval;
        atomic_set(&c->refcount, 1);
        atomic_set(&c->entries, 1);

        spin_lock_bh(&cn->lock);
        if (__clusterip_config_find(net, ip)) {
                spin_unlock_bh(&cn->lock);
                kfree(c);

                return ERR_PTR(-EBUSY);
        }

        list_add_rcu(&c->list, &cn->configs);
        spin_unlock_bh(&cn->lock);

#ifdef CONFIG_PROC_FS
        {
                char buffer[16];

                /* create proc dir entry */
                sprintf(buffer, "%pI4", &ip);
                c->pde = proc_create_data(buffer, S_IWUSR|S_IRUSR,
                                          cn->procdir,
                                          &clusterip_proc_fops, c);
                if (!c->pde) {
                        spin_lock_bh(&cn->lock);
                        list_del_rcu(&c->list);
                        spin_unlock_bh(&cn->lock);
                        kfree(c);

                        return ERR_PTR(-ENOMEM);
                }
        }
#endif

        return c;
}

#ifdef CONFIG_PROC_FS
static int
clusterip_add_node(struct clusterip_config *c, u_int16_t nodenum)
{

        if (nodenum == 0 ||
            nodenum > c->num_total_nodes)
                return 1;

        /* check if we already have this number in our bitfield */
        if (test_and_set_bit(nodenum - 1, &c->local_nodes))
                return 1;

        return 0;
}

static bool
clusterip_del_node(struct clusterip_config *c, u_int16_t nodenum)
{
        if (nodenum == 0 ||
            nodenum > c->num_total_nodes)
                return true;

        if (test_and_clear_bit(nodenum - 1, &c->local_nodes))
                return false;

        return true;
}
#endif

static inline u_int32_t
clusterip_hashfn(const struct sk_buff *skb,
                 const struct clusterip_config *config)
{
        const struct iphdr *iph = ip_hdr(skb);
        unsigned long hashval;
        u_int16_t sport = 0, dport = 0;
        int poff;

        poff = proto_ports_offset(iph->protocol);
        if (poff >= 0) {
                const u_int16_t *ports;
                u16 _ports[2];

                ports = skb_header_pointer(skb, iph->ihl * 4 + poff, 4, _ports);
                if (ports) {
                        sport = ports[0];
                        dport = ports[1];
                }
        } else {
                net_info_ratelimited("unknown protocol %u\n", iph->protocol);
        }

        switch (config->hash_mode) {
        case CLUSTERIP_HASHMODE_SIP:
                hashval = jhash_1word(ntohl(iph->saddr),
                                      config->hash_initval);
                break;
        case CLUSTERIP_HASHMODE_SIP_SPT:
                hashval = jhash_2words(ntohl(iph->saddr), sport,
                                       config->hash_initval);
                break;
        case CLUSTERIP_HASHMODE_SIP_SPT_DPT:
                hashval = jhash_3words(ntohl(iph->saddr), sport, dport,
                                       config->hash_initval);
                break;
        default:
                /* to make gcc happy */
                hashval = 0;
                /* This cannot happen, unless the check function wasn't called
                 * at rule load time */
                pr_info("unknown mode %u\n", config->hash_mode);
                BUG();
                break;
        }

        /* node numbers are 1..n, not 0..n */
        return reciprocal_scale(hashval, config->num_total_nodes) + 1;
}

static inline int
clusterip_responsible(const struct clusterip_config *config, u_int32_t hash)
{
        return test_bit(hash - 1, &config->local_nodes);
}

/***********************************************************************
 * IPTABLES TARGET
 ***********************************************************************/

static unsigned int
clusterip_tg(struct sk_buff *skb, const struct xt_action_param *par)
{
        const struct ipt_clusterip_tgt_info *cipinfo = par->targinfo;
        struct nf_conn *ct;
        enum ip_conntrack_info ctinfo;
        u_int32_t hash;

        /* don't need to clusterip_config_get() here, since refcount
         * is only decremented by destroy() - and ip_tables guarantees
         * that the ->target() function isn't called after ->destroy() */

        ct = nf_ct_get(skb, &ctinfo);
        if (ct == NULL)
                return NF_DROP;

        /* special case: ICMP error handling. conntrack distinguishes between
         * error messages (RELATED) and information requests (see below) */
        if (ip_hdr(skb)->protocol == IPPROTO_ICMP &&
            (ctinfo == IP_CT_RELATED ||
             ctinfo == IP_CT_RELATED_REPLY))
                return XT_CONTINUE;

        /* ip_conntrack_icmp guarantees us that we only have ICMP_ECHO,
         * TIMESTAMP, INFO_REQUEST or ADDRESS type icmp packets from here
         * on, which all have an ID field [relevant for hashing]. */

        hash = clusterip_hashfn(skb, cipinfo->config);

        switch (ctinfo) {
        case IP_CT_NEW:
                ct->mark = hash;
                break;
        case IP_CT_RELATED:
        case IP_CT_RELATED_REPLY:
                /* FIXME: we don't handle expectations at the moment.
                 * They can arrive on a different node than
                 * the master connection (e.g. FTP passive mode) */
        case IP_CT_ESTABLISHED:
        case IP_CT_ESTABLISHED_REPLY:
                break;
        default:                        /* Prevent gcc warnings */
                break;
        }

#ifdef DEBUG
        nf_ct_dump_tuple_ip(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
#endif
        pr_debug("hash=%u ct_hash=%u ", hash, ct->mark);
        if (!clusterip_responsible(cipinfo->config, hash)) {
                pr_debug("not responsible\n");
                return NF_DROP;
        }
        pr_debug("responsible\n");

        /* despite being received via linklayer multicast, this is
         * actually a unicast IP packet. TCP doesn't like PACKET_MULTICAST */
        skb->pkt_type = PACKET_HOST;

        return XT_CONTINUE;
}

static int clusterip_tg_check(const struct xt_tgchk_param *par)
{
        struct ipt_clusterip_tgt_info *cipinfo = par->targinfo;
        const struct ipt_entry *e = par->entryinfo;
        struct clusterip_config *config;
        int ret;

        if (par->nft_compat) {
                pr_err("cannot use CLUSTERIP target from nftables compat\n");
                return -EOPNOTSUPP;
        }

        if (cipinfo->hash_mode != CLUSTERIP_HASHMODE_SIP &&
            cipinfo->hash_mode != CLUSTERIP_HASHMODE_SIP_SPT &&
            cipinfo->hash_mode != CLUSTERIP_HASHMODE_SIP_SPT_DPT) {
                pr_info("unknown mode %u\n", cipinfo->hash_mode);
                return -EINVAL;

        }
        if (e->ip.dmsk.s_addr != htonl(0xffffffff) ||
            e->ip.dst.s_addr == 0) {
                pr_info("Please specify destination IP\n");
                return -EINVAL;
        }

        /* FIXME: further sanity checks */

        config = clusterip_config_find_get(par->net, e->ip.dst.s_addr, 1);
        if (!config) {
                if (!(cipinfo->flags & CLUSTERIP_FLAG_NEW)) {
                        pr_info("no config found for %pI4, need 'new'\n",
                                &e->ip.dst.s_addr);
                        return -EINVAL;
                } else {
                        struct net_device *dev;

                        if (e->ip.iniface[0] == '\0') {
                                pr_info("Please specify an interface name\n");
                                return -EINVAL;
                        }

                        dev = dev_get_by_name(par->net, e->ip.iniface);
                        if (!dev) {
                                pr_info("no such interface %s\n",
                                        e->ip.iniface);
                                return -ENOENT;
                        }

                        config = clusterip_config_init(cipinfo,
                                                        e->ip.dst.s_addr, dev);
                        if (IS_ERR(config)) {
                                dev_put(dev);
                                return PTR_ERR(config);
                        }
                        dev_mc_add(config->dev, config->clustermac);
                }
        }
        cipinfo->config = config;

        ret = nf_ct_netns_get(par->net, par->family);
        if (ret < 0)
                pr_info("cannot load conntrack support for proto=%u\n",
                        par->family);

        if (!par->net->xt.clusterip_deprecated_warning) {
                pr_info("ipt_CLUSTERIP is deprecated and it will removed soon, "
                        "use xt_cluster instead\n");
                par->net->xt.clusterip_deprecated_warning = true;
        }

        return ret;
}

/* drop reference count of cluster config when rule is deleted */
static void clusterip_tg_destroy(const struct xt_tgdtor_param *par)
{
        const struct ipt_clusterip_tgt_info *cipinfo = par->targinfo;

        /* if no more entries are referencing the config, remove it
         * from the list and destroy the proc entry */
        clusterip_config_entry_put(cipinfo->config);

        clusterip_config_put(cipinfo->config);

        nf_ct_netns_put(par->net, par->family);
}

#ifdef CONFIG_COMPAT
struct compat_ipt_clusterip_tgt_info
{
        u_int32_t       flags;
        u_int8_t        clustermac[6];
        u_int16_t       num_total_nodes;
        u_int16_t       num_local_nodes;
        u_int16_t       local_nodes[CLUSTERIP_MAX_NODES];
        u_int32_t       hash_mode;
        u_int32_t       hash_initval;
        compat_uptr_t   config;
};
#endif /* CONFIG_COMPAT */

static struct xt_target clusterip_tg_reg __read_mostly = {
        .name           = "CLUSTERIP",
        .family         = NFPROTO_IPV4,
        .target         = clusterip_tg,
        .checkentry     = clusterip_tg_check,
        .destroy        = clusterip_tg_destroy,
        .targetsize     = sizeof(struct ipt_clusterip_tgt_info),
        .usersize       = offsetof(struct ipt_clusterip_tgt_info, config),
#ifdef CONFIG_COMPAT
        .compatsize     = sizeof(struct compat_ipt_clusterip_tgt_info),
#endif /* CONFIG_COMPAT */
        .me             = THIS_MODULE
};


/***********************************************************************
 * ARP MANGLING CODE
 ***********************************************************************/

/* hardcoded for 48bit ethernet and 32bit ipv4 addresses */
struct arp_payload {
        u_int8_t src_hw[ETH_ALEN];
        __be32 src_ip;
        u_int8_t dst_hw[ETH_ALEN];
        __be32 dst_ip;
} __packed;

#ifdef DEBUG
static void arp_print(struct arp_payload *payload)
{
#define HBUFFERLEN 30
        char hbuffer[HBUFFERLEN];
        int j, k;

        for (k = 0, j = 0; k < HBUFFERLEN - 3 && j < ETH_ALEN; j++) {
                hbuffer[k++] = hex_asc_hi(payload->src_hw[j]);
                hbuffer[k++] = hex_asc_lo(payload->src_hw[j]);
                hbuffer[k++] = ':';
        }
        hbuffer[--k] = '\0';

        pr_debug("src %pI4@%s, dst %pI4\n",
                 &payload->src_ip, hbuffer, &payload->dst_ip);
}
#endif

static unsigned int
arp_mangle(void *priv,
           struct sk_buff *skb,
           const struct nf_hook_state *state)
{
        struct arphdr *arp = arp_hdr(skb);
        struct arp_payload *payload;
        struct clusterip_config *c;
        struct net *net = state->net;

        /* we don't care about non-ethernet and non-ipv4 ARP */
        if (arp->ar_hrd != htons(ARPHRD_ETHER) ||
            arp->ar_pro != htons(ETH_P_IP) ||
            arp->ar_pln != 4 || arp->ar_hln != ETH_ALEN)
                return NF_ACCEPT;

        /* we only want to mangle arp requests and replies */
        if (arp->ar_op != htons(ARPOP_REPLY) &&
            arp->ar_op != htons(ARPOP_REQUEST))
                return NF_ACCEPT;

        payload = (void *)(arp+1);

        /* if there is no clusterip configuration for the arp reply's
         * source ip, we don't want to mangle it */
        c = clusterip_config_find_get(net, payload->src_ip, 0);
        if (!c)
                return NF_ACCEPT;

        /* normally the linux kernel always replies to arp queries of
         * addresses on different interfacs.  However, in the CLUSTERIP case
         * this wouldn't work, since we didn't subscribe the mcast group on
         * other interfaces */
        if (c->dev != state->out) {
                pr_debug("not mangling arp reply on different "
                         "interface: cip'%s'-skb'%s'\n",
                         c->dev->name, state->out->name);
                clusterip_config_put(c);
                return NF_ACCEPT;
        }

        /* mangle reply hardware address */
        memcpy(payload->src_hw, c->clustermac, arp->ar_hln);

#ifdef DEBUG
        pr_debug("mangled arp reply: ");
        arp_print(payload);
#endif

        clusterip_config_put(c);

        return NF_ACCEPT;
}

static struct nf_hook_ops cip_arp_ops __read_mostly = {
        .hook = arp_mangle,
        .pf = NFPROTO_ARP,
        .hooknum = NF_ARP_OUT,
        .priority = -1
};

/***********************************************************************
 * PROC DIR HANDLING
 ***********************************************************************/

#ifdef CONFIG_PROC_FS

struct clusterip_seq_position {
        unsigned int pos;       /* position */
        unsigned int weight;    /* number of bits set == size */
        unsigned int bit;       /* current bit */
        unsigned long val;      /* current value */
};

static void *clusterip_seq_start(struct seq_file *s, loff_t *pos)
{
        struct clusterip_config *c = s->private;
        unsigned int weight;
        u_int32_t local_nodes;
        struct clusterip_seq_position *idx;

        /* FIXME: possible race */
        local_nodes = c->local_nodes;
        weight = hweight32(local_nodes);
        if (*pos >= weight)
                return NULL;

        idx = kmalloc(sizeof(struct clusterip_seq_position), GFP_KERNEL);
        if (!idx)
                return ERR_PTR(-ENOMEM);

        idx->pos = *pos;
        idx->weight = weight;
        idx->bit = ffs(local_nodes);
        idx->val = local_nodes;
        clear_bit(idx->bit - 1, &idx->val);

        return idx;
}

static void *clusterip_seq_next(struct seq_file *s, void *v, loff_t *pos)
{
        struct clusterip_seq_position *idx = v;

        *pos = ++idx->pos;
        if (*pos >= idx->weight) {
                kfree(v);
                return NULL;
        }
        idx->bit = ffs(idx->val);
        clear_bit(idx->bit - 1, &idx->val);
        return idx;
}

static void clusterip_seq_stop(struct seq_file *s, void *v)
{
        if (!IS_ERR(v))
                kfree(v);
}

static int clusterip_seq_show(struct seq_file *s, void *v)
{
        struct clusterip_seq_position *idx = v;

        if (idx->pos != 0)
                seq_putc(s, ',');

        seq_printf(s, "%u", idx->bit);

        if (idx->pos == idx->weight - 1)
                seq_putc(s, '\n');

        return 0;
}

static const struct seq_operations clusterip_seq_ops = {
        .start  = clusterip_seq_start,
        .next   = clusterip_seq_next,
        .stop   = clusterip_seq_stop,
        .show   = clusterip_seq_show,
};

static int clusterip_proc_open(struct inode *inode, struct file *file)
{
        int ret = seq_open(file, &clusterip_seq_ops);

        if (!ret) {
                struct seq_file *sf = file->private_data;
                struct clusterip_config *c = PDE_DATA(inode);

                sf->private = c;

                clusterip_config_get(c);
        }

        return ret;
}

static int clusterip_proc_release(struct inode *inode, struct file *file)
{
        struct clusterip_config *c = PDE_DATA(inode);
        int ret;

        ret = seq_release(inode, file);

        if (!ret)
                clusterip_config_put(c);

        return ret;
}

static ssize_t clusterip_proc_write(struct file *file, const char __user *input,
                                size_t size, loff_t *ofs)
{
        struct clusterip_config *c = PDE_DATA(file_inode(file));
#define PROC_WRITELEN   10
        char buffer[PROC_WRITELEN+1];
        unsigned long nodenum;
        int rc;

        if (size > PROC_WRITELEN)
                return -EIO;
        if (copy_from_user(buffer, input, size))
                return -EFAULT;
        buffer[size] = 0;

        if (*buffer == '+') {
                rc = kstrtoul(buffer+1, 10, &nodenum);
                if (rc)
                        return rc;
                if (clusterip_add_node(c, nodenum))
                        return -ENOMEM;
        } else if (*buffer == '-') {
                rc = kstrtoul(buffer+1, 10, &nodenum);
                if (rc)
                        return rc;
                if (clusterip_del_node(c, nodenum))
                        return -ENOENT;
        } else
                return -EIO;

        return size;
}

static const struct file_operations clusterip_proc_fops = {
        .owner   = THIS_MODULE,
        .open    = clusterip_proc_open,
        .read    = seq_read,
        .write   = clusterip_proc_write,
        .llseek  = seq_lseek,
        .release = clusterip_proc_release,
};

#endif /* CONFIG_PROC_FS */

static int clusterip_net_init(struct net *net)
{
        struct clusterip_net *cn = net_generic(net, clusterip_net_id);

        INIT_LIST_HEAD(&cn->configs);

        spin_lock_init(&cn->lock);

#ifdef CONFIG_PROC_FS
        cn->procdir = proc_mkdir("ipt_CLUSTERIP", net->proc_net);
        if (!cn->procdir) {
                pr_err("Unable to proc dir entry\n");
                return -ENOMEM;
        }
#endif /* CONFIG_PROC_FS */

        return 0;
}

static void clusterip_net_exit(struct net *net)
{
#ifdef CONFIG_PROC_FS
        struct clusterip_net *cn = net_generic(net, clusterip_net_id);
        proc_remove(cn->procdir);
#endif
}

static struct pernet_operations clusterip_net_ops = {
        .init = clusterip_net_init,
        .exit = clusterip_net_exit,
        .id   = &clusterip_net_id,
        .size = sizeof(struct clusterip_net),
};

static int __init clusterip_tg_init(void)
{
        int ret;

        ret = register_pernet_subsys(&clusterip_net_ops);
        if (ret < 0)
                return ret;

        ret = xt_register_target(&clusterip_tg_reg);
        if (ret < 0)
                goto cleanup_subsys;

        ret = nf_register_hook(&cip_arp_ops);
        if (ret < 0)
                goto cleanup_target;

        pr_info("ClusterIP Version %s loaded successfully\n",
                CLUSTERIP_VERSION);

        return 0;

cleanup_target:
        xt_unregister_target(&clusterip_tg_reg);
cleanup_subsys:
        unregister_pernet_subsys(&clusterip_net_ops);
        return ret;
}

static void __exit clusterip_tg_exit(void)
{
        pr_info("ClusterIP Version %s unloading\n", CLUSTERIP_VERSION);

        nf_unregister_hook(&cip_arp_ops);
        xt_unregister_target(&clusterip_tg_reg);
        unregister_pernet_subsys(&clusterip_net_ops);

        /* Wait for completion of call_rcu_bh()'s (clusterip_config_rcu_free) */
        rcu_barrier_bh();
}

module_init(clusterip_tg_init);
module_exit(clusterip_tg_exit);