nf_conntrack_l3proto_ipv4.c

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/* (C) 1999-2001 Paul `Rusty' Russell
 * (C) 2002-2004 Netfilter Core Team <[email protected]>
 *
 * 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.
 */

#include <linux/types.h>
#include <linux/ip.h>
#include <linux/netfilter.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/icmp.h>
#include <linux/sysctl.h>
#include <net/route.h>
#include <net/ip.h>

#include <linux/netfilter_ipv4.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_l4proto.h>
#include <net/netfilter/nf_conntrack_l3proto.h>
#include <net/netfilter/nf_conntrack_zones.h>
#include <net/netfilter/nf_conntrack_core.h>
#include <net/netfilter/ipv4/nf_conntrack_ipv4.h>
#include <net/netfilter/nf_nat_helper.h>
#include <net/netfilter/ipv4/nf_defrag_ipv4.h>
#include <net/netfilter/nf_log.h>

static bool ipv4_pkt_to_tuple(const struct sk_buff *skb, unsigned int nhoff,
                  struct nf_conntrack_tuple *tuple)
{
    const __be32 *ap;
    __be32 _addrs[2];
    ap = skb_header_pointer(skb, nhoff + offsetof(struct iphdr, saddr),
                sizeof(u_int32_t) * 2, _addrs);
    if (ap == NULL)
        return false;

    tuple->src.u3.ip = ap[0];
    tuple->dst.u3.ip = ap[1];

    return true;
}

static bool ipv4_invert_tuple(struct nf_conntrack_tuple *tuple,
                  const struct nf_conntrack_tuple *orig)
{
    tuple->src.u3.ip = orig->dst.u3.ip;
    tuple->dst.u3.ip = orig->src.u3.ip;

    return true;
}

static int ipv4_print_tuple(struct seq_file *s,
                const struct nf_conntrack_tuple *tuple)
{
    return seq_printf(s, "src=%pI4 dst=%pI4 ",
              &tuple->src.u3.ip, &tuple->dst.u3.ip);
}

static int ipv4_get_l4proto(const struct sk_buff *skb, unsigned int nhoff,
                unsigned int *dataoff, u_int8_t *protonum)
{
    const struct iphdr *iph;
    struct iphdr _iph;

    iph = skb_header_pointer(skb, nhoff, sizeof(_iph), &_iph);
    if (iph == NULL)
        return -NF_ACCEPT;

    /* Conntrack defragments packets, we might still see fragments
     * inside ICMP packets though. */
    if (iph->frag_off & htons(IP_OFFSET))
        return -NF_ACCEPT;

    *dataoff = nhoff + (iph->ihl << 2);
    *protonum = iph->protocol;

    /* Check bogus IP headers */
    if (*dataoff > skb->len) {
        pr_debug("nf_conntrack_ipv4: bogus IPv4 packet: "
             "nhoff %u, ihl %u, skblen %u\n",
             nhoff, iph->ihl << 2, skb->len);
        return -NF_ACCEPT;
    }

    return NF_ACCEPT;
}

static unsigned int ipv4_helper(unsigned int hooknum,
                struct sk_buff *skb,
                const struct net_device *in,
                const struct net_device *out,
                int (*okfn)(struct sk_buff *))
{
    struct nf_conn *ct;
    enum ip_conntrack_info ctinfo;
    const struct nf_conn_help *help;
    const struct nf_conntrack_helper *helper;
    unsigned int ret;

    /* This is where we call the helper: as the packet goes out. */
    ct = nf_ct_get(skb, &ctinfo);
    if (!ct || ctinfo == IP_CT_RELATED_REPLY)
        return NF_ACCEPT;

    help = nfct_help(ct);
    if (!help)
        return NF_ACCEPT;

    /* rcu_read_lock()ed by nf_hook_slow */
    helper = rcu_dereference(help->helper);
    if (!helper)
        return NF_ACCEPT;

    ret = helper->help(skb, skb_network_offset(skb) + ip_hdrlen(skb),
               ct, ctinfo);
    if (ret != NF_ACCEPT && (ret & NF_VERDICT_MASK) != NF_QUEUE) {
        nf_log_packet(NFPROTO_IPV4, hooknum, skb, in, out, NULL,
                  "nf_ct_%s: dropping packet", helper->name);
    }
    return ret;
}

static unsigned int ipv4_confirm(unsigned int hooknum,
                 struct sk_buff *skb,
                 const struct net_device *in,
                 const struct net_device *out,
                 int (*okfn)(struct sk_buff *))
{
    struct nf_conn *ct;
    enum ip_conntrack_info ctinfo;

    ct = nf_ct_get(skb, &ctinfo);
    if (!ct || ctinfo == IP_CT_RELATED_REPLY)
        goto out;

    /* adjust seqs for loopback traffic only in outgoing direction */
    if (test_bit(IPS_SEQ_ADJUST_BIT, &ct->status) &&
        !nf_is_loopback_packet(skb)) {
        typeof(nf_nat_seq_adjust_hook) seq_adjust;

        seq_adjust = rcu_dereference(nf_nat_seq_adjust_hook);
        if (!seq_adjust ||
            !seq_adjust(skb, ct, ctinfo, ip_hdrlen(skb))) {
            NF_CT_STAT_INC_ATOMIC(nf_ct_net(ct), drop);
            return NF_DROP;
        }
    }
out:
    /* We've seen it coming out the other side: confirm it */
    return nf_conntrack_confirm(skb);
}

static unsigned int ipv4_conntrack_in(unsigned int hooknum,
                      struct sk_buff *skb,
                      const struct net_device *in,
                      const struct net_device *out,
                      int (*okfn)(struct sk_buff *))
{
    return nf_conntrack_in(dev_net(in), PF_INET, hooknum, skb);
}

static unsigned int ipv4_conntrack_local(unsigned int hooknum,
                     struct sk_buff *skb,
                     const struct net_device *in,
                     const struct net_device *out,
                     int (*okfn)(struct sk_buff *))
{
    /* root is playing with raw sockets. */
    if (skb->len < sizeof(struct iphdr) ||
        ip_hdrlen(skb) < sizeof(struct iphdr))
        return NF_ACCEPT;
    return nf_conntrack_in(dev_net(out), PF_INET, hooknum, skb);
}

/* Connection tracking may drop packets, but never alters them, so
   make it the first hook. */
static struct nf_hook_ops ipv4_conntrack_ops[] __read_mostly = {
    {
        .hook       = ipv4_conntrack_in,
        .owner      = THIS_MODULE,
        .pf     = NFPROTO_IPV4,
        .hooknum    = NF_INET_PRE_ROUTING,
        .priority   = NF_IP_PRI_CONNTRACK,
    },
    {
        .hook       = ipv4_conntrack_local,
        .owner      = THIS_MODULE,
        .pf     = NFPROTO_IPV4,
        .hooknum    = NF_INET_LOCAL_OUT,
        .priority   = NF_IP_PRI_CONNTRACK,
    },
    {
        .hook       = ipv4_helper,
        .owner      = THIS_MODULE,
        .pf     = NFPROTO_IPV4,
        .hooknum    = NF_INET_POST_ROUTING,
        .priority   = NF_IP_PRI_CONNTRACK_HELPER,
    },
    {
        .hook       = ipv4_confirm,
        .owner      = THIS_MODULE,
        .pf     = NFPROTO_IPV4,
        .hooknum    = NF_INET_POST_ROUTING,
        .priority   = NF_IP_PRI_CONNTRACK_CONFIRM,
    },
    {
        .hook       = ipv4_helper,
        .owner      = THIS_MODULE,
        .pf     = NFPROTO_IPV4,
        .hooknum    = NF_INET_LOCAL_IN,
        .priority   = NF_IP_PRI_CONNTRACK_HELPER,
    },
    {
        .hook       = ipv4_confirm,
        .owner      = THIS_MODULE,
        .pf     = NFPROTO_IPV4,
        .hooknum    = NF_INET_LOCAL_IN,
        .priority   = NF_IP_PRI_CONNTRACK_CONFIRM,
    },
};

#if defined(CONFIG_SYSCTL) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
static int log_invalid_proto_min = 0;
static int log_invalid_proto_max = 255;

static ctl_table ip_ct_sysctl_table[] = {
    {
        .procname   = "ip_conntrack_max",
        .maxlen     = sizeof(int),
        .mode       = 0644,
        .proc_handler   = proc_dointvec,
    },
    {
        .procname   = "ip_conntrack_count",
        .maxlen     = sizeof(int),
        .mode       = 0444,
        .proc_handler   = proc_dointvec,
    },
    {
        .procname   = "ip_conntrack_buckets",
        .maxlen     = sizeof(unsigned int),
        .mode       = 0444,
        .proc_handler   = proc_dointvec,
    },
    {
        .procname   = "ip_conntrack_checksum",
        .maxlen     = sizeof(int),
        .mode       = 0644,
        .proc_handler   = proc_dointvec,
    },
    {
        .procname   = "ip_conntrack_log_invalid",
        .maxlen     = sizeof(unsigned int),
        .mode       = 0644,
        .proc_handler   = proc_dointvec_minmax,
        .extra1     = &log_invalid_proto_min,
        .extra2     = &log_invalid_proto_max,
    },
    { }
};
#endif /* CONFIG_SYSCTL && CONFIG_NF_CONNTRACK_PROC_COMPAT */

/* Fast function for those who don't want to parse /proc (and I don't
   blame them). */
/* Reversing the socket's dst/src point of view gives us the reply
   mapping. */
static int
getorigdst(struct sock *sk, int optval, void __user *user, int *len)
{
    const struct inet_sock *inet = inet_sk(sk);
    const struct nf_conntrack_tuple_hash *h;
    struct nf_conntrack_tuple tuple;

    memset(&tuple, 0, sizeof(tuple));
    tuple.src.u3.ip = inet->inet_rcv_saddr;
    tuple.src.u.tcp.port = inet->inet_sport;
    tuple.dst.u3.ip = inet->inet_daddr;
    tuple.dst.u.tcp.port = inet->inet_dport;
    tuple.src.l3num = PF_INET;
    tuple.dst.protonum = sk->sk_protocol;

    /* We only do TCP and SCTP at the moment: is there a better way? */
    if (sk->sk_protocol != IPPROTO_TCP && sk->sk_protocol != IPPROTO_SCTP) {
        pr_debug("SO_ORIGINAL_DST: Not a TCP/SCTP socket\n");
        return -ENOPROTOOPT;
    }

    if ((unsigned int) *len < sizeof(struct sockaddr_in)) {
        pr_debug("SO_ORIGINAL_DST: len %d not %Zu\n",
             *len, sizeof(struct sockaddr_in));
        return -EINVAL;
    }

    h = nf_conntrack_find_get(sock_net(sk), NF_CT_DEFAULT_ZONE, &tuple);
    if (h) {
        struct sockaddr_in sin;
        struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(h);

        sin.sin_family = AF_INET;
        sin.sin_port = ct->tuplehash[IP_CT_DIR_ORIGINAL]
            .tuple.dst.u.tcp.port;
        sin.sin_addr.s_addr = ct->tuplehash[IP_CT_DIR_ORIGINAL]
            .tuple.dst.u3.ip;
        memset(sin.sin_zero, 0, sizeof(sin.sin_zero));

        pr_debug("SO_ORIGINAL_DST: %pI4 %u\n",
             &sin.sin_addr.s_addr, ntohs(sin.sin_port));
        nf_ct_put(ct);
        if (copy_to_user(user, &sin, sizeof(sin)) != 0)
            return -EFAULT;
        else
            return 0;
    }
    pr_debug("SO_ORIGINAL_DST: Can't find %pI4/%u-%pI4/%u.\n",
         &tuple.src.u3.ip, ntohs(tuple.src.u.tcp.port),
         &tuple.dst.u3.ip, ntohs(tuple.dst.u.tcp.port));
    return -ENOENT;
}

#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)

#include <linux/netfilter/nfnetlink.h>
#include <linux/netfilter/nfnetlink_conntrack.h>

static int ipv4_tuple_to_nlattr(struct sk_buff *skb,
                const struct nf_conntrack_tuple *tuple)
{
    if (nla_put_be32(skb, CTA_IP_V4_SRC, tuple->src.u3.ip) ||
        nla_put_be32(skb, CTA_IP_V4_DST, tuple->dst.u3.ip))
        goto nla_put_failure;
    return 0;

nla_put_failure:
    return -1;
}

static const struct nla_policy ipv4_nla_policy[CTA_IP_MAX+1] = {
    [CTA_IP_V4_SRC] = { .type = NLA_U32 },
    [CTA_IP_V4_DST] = { .type = NLA_U32 },
};

static int ipv4_nlattr_to_tuple(struct nlattr *tb[],
                struct nf_conntrack_tuple *t)
{
    if (!tb[CTA_IP_V4_SRC] || !tb[CTA_IP_V4_DST])
        return -EINVAL;

    t->src.u3.ip = nla_get_be32(tb[CTA_IP_V4_SRC]);
    t->dst.u3.ip = nla_get_be32(tb[CTA_IP_V4_DST]);

    return 0;
}

static int ipv4_nlattr_tuple_size(void)
{
    return nla_policy_len(ipv4_nla_policy, CTA_IP_MAX + 1);
}
#endif

static struct nf_sockopt_ops so_getorigdst = {
    .pf     = PF_INET,
    .get_optmin = SO_ORIGINAL_DST,
    .get_optmax = SO_ORIGINAL_DST+1,
    .get        = &getorigdst,
    .owner      = THIS_MODULE,
};

static int ipv4_init_net(struct net *net)
{
#if defined(CONFIG_SYSCTL) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
    struct nf_ip_net *in = &net->ct.nf_ct_proto;
    in->ctl_table = kmemdup(ip_ct_sysctl_table,
                sizeof(ip_ct_sysctl_table),
                GFP_KERNEL);
    if (!in->ctl_table)
        return -ENOMEM;

    in->ctl_table[0].data = &nf_conntrack_max;
    in->ctl_table[1].data = &net->ct.count;
    in->ctl_table[2].data = &net->ct.htable_size;
    in->ctl_table[3].data = &net->ct.sysctl_checksum;
    in->ctl_table[4].data = &net->ct.sysctl_log_invalid;
#endif
    return 0;
}

struct nf_conntrack_l3proto nf_conntrack_l3proto_ipv4 __read_mostly = {
    .l3proto     = PF_INET,
    .name        = "ipv4",
    .pkt_to_tuple    = ipv4_pkt_to_tuple,
    .invert_tuple    = ipv4_invert_tuple,
    .print_tuple     = ipv4_print_tuple,
    .get_l4proto     = ipv4_get_l4proto,
#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
    .tuple_to_nlattr = ipv4_tuple_to_nlattr,
    .nlattr_tuple_size = ipv4_nlattr_tuple_size,
    .nlattr_to_tuple = ipv4_nlattr_to_tuple,
    .nla_policy  = ipv4_nla_policy,
#endif
#if defined(CONFIG_SYSCTL) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
    .ctl_table_path  = "net/ipv4/netfilter",
#endif
    .init_net    = ipv4_init_net,
    .me      = THIS_MODULE,
};

module_param_call(hashsize, nf_conntrack_set_hashsize, param_get_uint,
          &nf_conntrack_htable_size, 0600);

MODULE_ALIAS("nf_conntrack-" __stringify(AF_INET));
MODULE_ALIAS("ip_conntrack");
MODULE_LICENSE("GPL");

static int ipv4_net_init(struct net *net)
{
    int ret = 0;

    ret = nf_conntrack_l4proto_register(net,
                        &nf_conntrack_l4proto_tcp4);
    if (ret < 0) {
        pr_err("nf_conntrack_l4proto_tcp4 :protocol register failed\n");
        goto out_tcp;
    }
    ret = nf_conntrack_l4proto_register(net,
                        &nf_conntrack_l4proto_udp4);
    if (ret < 0) {
        pr_err("nf_conntrack_l4proto_udp4 :protocol register failed\n");
        goto out_udp;
    }
    ret = nf_conntrack_l4proto_register(net,
                        &nf_conntrack_l4proto_icmp);
    if (ret < 0) {
        pr_err("nf_conntrack_l4proto_icmp4 :protocol register failed\n");
        goto out_icmp;
    }
    ret = nf_conntrack_l3proto_register(net,
                        &nf_conntrack_l3proto_ipv4);
    if (ret < 0) {
        pr_err("nf_conntrack_l3proto_ipv4 :protocol register failed\n");
        goto out_ipv4;
    }
    return 0;
out_ipv4:
    nf_conntrack_l4proto_unregister(net,
                    &nf_conntrack_l4proto_icmp);
out_icmp:
    nf_conntrack_l4proto_unregister(net,
                    &nf_conntrack_l4proto_udp4);
out_udp:
    nf_conntrack_l4proto_unregister(net,
                    &nf_conntrack_l4proto_tcp4);
out_tcp:
    return ret;
}

static void ipv4_net_exit(struct net *net)
{
    nf_conntrack_l3proto_unregister(net,
                    &nf_conntrack_l3proto_ipv4);
    nf_conntrack_l4proto_unregister(net,
                    &nf_conntrack_l4proto_icmp);
    nf_conntrack_l4proto_unregister(net,
                    &nf_conntrack_l4proto_udp4);
    nf_conntrack_l4proto_unregister(net,
                    &nf_conntrack_l4proto_tcp4);
}

static struct pernet_operations ipv4_net_ops = {
    .init = ipv4_net_init,
    .exit = ipv4_net_exit,
};

static int __init nf_conntrack_l3proto_ipv4_init(void)
{
    int ret = 0;

    need_conntrack();
    nf_defrag_ipv4_enable();

    ret = nf_register_sockopt(&so_getorigdst);
    if (ret < 0) {
        printk(KERN_ERR "Unable to register netfilter socket option\n");
        return ret;
    }

    ret = register_pernet_subsys(&ipv4_net_ops);
    if (ret < 0) {
        pr_err("nf_conntrack_ipv4: can't register pernet ops\n");
        goto cleanup_sockopt;
    }

    ret = nf_register_hooks(ipv4_conntrack_ops,
                ARRAY_SIZE(ipv4_conntrack_ops));
    if (ret < 0) {
        pr_err("nf_conntrack_ipv4: can't register hooks.\n");
        goto cleanup_pernet;
    }
#if defined(CONFIG_PROC_FS) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
    ret = nf_conntrack_ipv4_compat_init();
    if (ret < 0)
        goto cleanup_hooks;
#endif
    return ret;
#if defined(CONFIG_PROC_FS) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
 cleanup_hooks:
    nf_unregister_hooks(ipv4_conntrack_ops, ARRAY_SIZE(ipv4_conntrack_ops));
#endif
 cleanup_pernet:
    unregister_pernet_subsys(&ipv4_net_ops);
 cleanup_sockopt:
    nf_unregister_sockopt(&so_getorigdst);
    return ret;
}

static void __exit nf_conntrack_l3proto_ipv4_fini(void)
{
    synchronize_net();
#if defined(CONFIG_PROC_FS) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
    nf_conntrack_ipv4_compat_fini();
#endif
    nf_unregister_hooks(ipv4_conntrack_ops, ARRAY_SIZE(ipv4_conntrack_ops));
    unregister_pernet_subsys(&ipv4_net_ops);
    nf_unregister_sockopt(&so_getorigdst);
}

module_init(nf_conntrack_l3proto_ipv4_init);
module_exit(nf_conntrack_l3proto_ipv4_fini);

void need_ipv4_conntrack(void)
{
    return;
}
EXPORT_SYMBOL_GPL(need_ipv4_conntrack);