ipt_CLUSTERIP.c

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/* Cluster IP hashmark target
 * (C) 2003-2004 by Harald Welte <[email protected]>
 * based on ideas of Fabio Olive Leite <[email protected]>
 *
 * 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/checksum.h>
#include <net/ip.h>

#define CLUSTERIP_VERSION "0.8"

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Harald Welte <[email protected]>");
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;
};

static LIST_HEAD(clusterip_configs);

/* clusterip_lock protects the clusterip_configs list */
static DEFINE_SPINLOCK(clusterip_lock);

#ifdef CONFIG_PROC_FS
static const struct file_operations clusterip_proc_fops;
static struct proc_dir_entry *clusterip_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)
{
    local_bh_disable();
    if (atomic_dec_and_lock(&c->entries, &clusterip_lock)) {
        list_del_rcu(&c->list);
        spin_unlock(&clusterip_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
        remove_proc_entry(c->pde->name, c->pde->parent);
#endif
        return;
    }
    local_bh_enable();
}

static struct clusterip_config *
__clusterip_config_find(__be32 clusterip)
{
    struct clusterip_config *c;

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

    return NULL;
}

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

    rcu_read_lock_bh();
    c = __clusterip_config_find(clusterip);
    if (c) {
        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 clusterip_config *c;

    c = kzalloc(sizeof(*c), GFP_ATOMIC);
    if (!c)
        return NULL;

    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);

#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,
                      clusterip_procdir,
                      &clusterip_proc_fops, c);
        if (!c->pde) {
            kfree(c);
            return NULL;
        }
    }
#endif

    spin_lock_bh(&clusterip_lock);
    list_add_rcu(&c->list, &clusterip_configs);
    spin_unlock_bh(&clusterip_lock);

    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 (((u64)hashval * config->num_total_nodes) >> 32) + 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 (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(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(&init_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 (!config) {
                dev_put(dev);
                return -ENOMEM;
            }
            dev_mc_add(config->dev, config->clustermac);
        }
    }
    cipinfo->config = config;

    ret = nf_ct_l3proto_try_module_get(par->family);
    if (ret < 0)
        pr_info("cannot load conntrack support for proto=%u\n",
            par->family);
    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_l3proto_module_put(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),
#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(unsigned int hook,
       struct sk_buff *skb,
       const struct net_device *in,
       const struct net_device *out,
       int (*okfn)(struct sk_buff *))
{
    struct arphdr *arp = arp_hdr(skb);
    struct arp_payload *payload;
    struct clusterip_config *c;

    /* 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(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 != out) {
        pr_debug("not mangling arp reply on different "
             "interface: cip'%s'-skb'%s'\n",
             c->dev->name, 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(inode)->data;

        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(inode)->data;
    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(file->f_path.dentry->d_inode)->data;
#define PROC_WRITELEN   10
    char buffer[PROC_WRITELEN+1];
    unsigned long nodenum;

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

    if (*buffer == '+') {
        nodenum = simple_strtoul(buffer+1, NULL, 10);
        if (clusterip_add_node(c, nodenum))
            return -ENOMEM;
    } else if (*buffer == '-') {
        nodenum = simple_strtoul(buffer+1, NULL,10);
        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 __init clusterip_tg_init(void)
{
    int ret;

    ret = xt_register_target(&clusterip_tg_reg);
    if (ret < 0)
        return ret;

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

#ifdef CONFIG_PROC_FS
    clusterip_procdir = proc_mkdir("ipt_CLUSTERIP", init_net.proc_net);
    if (!clusterip_procdir) {
        pr_err("Unable to proc dir entry\n");
        ret = -ENOMEM;
        goto cleanup_hook;
    }
#endif /* CONFIG_PROC_FS */

    pr_info("ClusterIP Version %s loaded successfully\n",
        CLUSTERIP_VERSION);
    return 0;

#ifdef CONFIG_PROC_FS
cleanup_hook:
    nf_unregister_hook(&cip_arp_ops);
#endif /* CONFIG_PROC_FS */
cleanup_target:
    xt_unregister_target(&clusterip_tg_reg);
    return ret;
}

static void __exit clusterip_tg_exit(void)
{
    pr_info("ClusterIP Version %s unloading\n", CLUSTERIP_VERSION);
#ifdef CONFIG_PROC_FS
    remove_proc_entry(clusterip_procdir->name, clusterip_procdir->parent);
#endif
    nf_unregister_hook(&cip_arp_ops);
    xt_unregister_target(&clusterip_tg_reg);

    /* 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);