nfnetlink_cttimeout.c

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/*
 * (C) 2012 by Pablo Neira Ayuso <[email protected]>
 * (C) 2012 by Vyatta Inc. <http://www.vyatta.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 (or any later at your option).
 */
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/rculist.h>
#include <linux/rculist_nulls.h>
#include <linux/types.h>
#include <linux/timer.h>
#include <linux/security.h>
#include <linux/skbuff.h>
#include <linux/errno.h>
#include <linux/netlink.h>
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <linux/slab.h>

#include <linux/netfilter.h>
#include <net/netlink.h>
#include <net/sock.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_core.h>
#include <net/netfilter/nf_conntrack_l3proto.h>
#include <net/netfilter/nf_conntrack_l4proto.h>
#include <net/netfilter/nf_conntrack_tuple.h>
#include <net/netfilter/nf_conntrack_timeout.h>

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

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Pablo Neira Ayuso <[email protected]>");
MODULE_DESCRIPTION("cttimeout: Extended Netfilter Connection Tracking timeout tuning");

static LIST_HEAD(cttimeout_list);

static const struct nla_policy cttimeout_nla_policy[CTA_TIMEOUT_MAX+1] = {
    [CTA_TIMEOUT_NAME]  = { .type = NLA_NUL_STRING,
                    .len  = CTNL_TIMEOUT_NAME_MAX - 1},
    [CTA_TIMEOUT_L3PROTO]   = { .type = NLA_U16 },
    [CTA_TIMEOUT_L4PROTO]   = { .type = NLA_U8 },
    [CTA_TIMEOUT_DATA]  = { .type = NLA_NESTED },
};

static int
ctnl_timeout_parse_policy(struct ctnl_timeout *timeout,
              struct nf_conntrack_l4proto *l4proto,
              struct net *net,
              const struct nlattr *attr)
{
    int ret = 0;

    if (likely(l4proto->ctnl_timeout.nlattr_to_obj)) {
        struct nlattr *tb[l4proto->ctnl_timeout.nlattr_max+1];

        nla_parse_nested(tb, l4proto->ctnl_timeout.nlattr_max,
                 attr, l4proto->ctnl_timeout.nla_policy);

        ret = l4proto->ctnl_timeout.nlattr_to_obj(tb, net,
                              &timeout->data);
    }
    return ret;
}

static int
cttimeout_new_timeout(struct sock *ctnl, struct sk_buff *skb,
              const struct nlmsghdr *nlh,
              const struct nlattr * const cda[])
{
    __u16 l3num;
    __u8 l4num;
    struct nf_conntrack_l4proto *l4proto;
    struct ctnl_timeout *timeout, *matching = NULL;
    struct net *net = sock_net(skb->sk);
    char *name;
    int ret;

    if (!cda[CTA_TIMEOUT_NAME] ||
        !cda[CTA_TIMEOUT_L3PROTO] ||
        !cda[CTA_TIMEOUT_L4PROTO] ||
        !cda[CTA_TIMEOUT_DATA])
        return -EINVAL;

    name = nla_data(cda[CTA_TIMEOUT_NAME]);
    l3num = ntohs(nla_get_be16(cda[CTA_TIMEOUT_L3PROTO]));
    l4num = nla_get_u8(cda[CTA_TIMEOUT_L4PROTO]);

    list_for_each_entry(timeout, &cttimeout_list, head) {
        if (strncmp(timeout->name, name, CTNL_TIMEOUT_NAME_MAX) != 0)
            continue;

        if (nlh->nlmsg_flags & NLM_F_EXCL)
            return -EEXIST;

        matching = timeout;
        break;
    }

    l4proto = nf_ct_l4proto_find_get(l3num, l4num);

    /* This protocol is not supportted, skip. */
    if (l4proto->l4proto != l4num) {
        ret = -EOPNOTSUPP;
        goto err_proto_put;
    }

    if (matching) {
        if (nlh->nlmsg_flags & NLM_F_REPLACE) {
            /* You cannot replace one timeout policy by another of
             * different kind, sorry.
             */
            if (matching->l3num != l3num ||
                matching->l4proto->l4proto != l4num) {
                ret = -EINVAL;
                goto err_proto_put;
            }

            ret = ctnl_timeout_parse_policy(matching, l4proto, net,
                            cda[CTA_TIMEOUT_DATA]);
            return ret;
        }
        ret = -EBUSY;
        goto err_proto_put;
    }

    timeout = kzalloc(sizeof(struct ctnl_timeout) +
              l4proto->ctnl_timeout.obj_size, GFP_KERNEL);
    if (timeout == NULL) {
        ret = -ENOMEM;
        goto err_proto_put;
    }

    ret = ctnl_timeout_parse_policy(timeout, l4proto, net,
                    cda[CTA_TIMEOUT_DATA]);
    if (ret < 0)
        goto err;

    strcpy(timeout->name, nla_data(cda[CTA_TIMEOUT_NAME]));
    timeout->l3num = l3num;
    timeout->l4proto = l4proto;
    atomic_set(&timeout->refcnt, 1);
    list_add_tail_rcu(&timeout->head, &cttimeout_list);

    return 0;
err:
    kfree(timeout);
err_proto_put:
    nf_ct_l4proto_put(l4proto);
    return ret;
}

static int
ctnl_timeout_fill_info(struct sk_buff *skb, u32 portid, u32 seq, u32 type,
               int event, struct ctnl_timeout *timeout)
{
    struct nlmsghdr *nlh;
    struct nfgenmsg *nfmsg;
    unsigned int flags = portid ? NLM_F_MULTI : 0;
    struct nf_conntrack_l4proto *l4proto = timeout->l4proto;

    event |= NFNL_SUBSYS_CTNETLINK_TIMEOUT << 8;
    nlh = nlmsg_put(skb, portid, seq, event, sizeof(*nfmsg), flags);
    if (nlh == NULL)
        goto nlmsg_failure;

    nfmsg = nlmsg_data(nlh);
    nfmsg->nfgen_family = AF_UNSPEC;
    nfmsg->version = NFNETLINK_V0;
    nfmsg->res_id = 0;

    if (nla_put_string(skb, CTA_TIMEOUT_NAME, timeout->name) ||
        nla_put_be16(skb, CTA_TIMEOUT_L3PROTO, htons(timeout->l3num)) ||
        nla_put_u8(skb, CTA_TIMEOUT_L4PROTO, timeout->l4proto->l4proto) ||
        nla_put_be32(skb, CTA_TIMEOUT_USE,
             htonl(atomic_read(&timeout->refcnt))))
        goto nla_put_failure;

    if (likely(l4proto->ctnl_timeout.obj_to_nlattr)) {
        struct nlattr *nest_parms;
        int ret;

        nest_parms = nla_nest_start(skb,
                        CTA_TIMEOUT_DATA | NLA_F_NESTED);
        if (!nest_parms)
            goto nla_put_failure;

        ret = l4proto->ctnl_timeout.obj_to_nlattr(skb, &timeout->data);
        if (ret < 0)
            goto nla_put_failure;

        nla_nest_end(skb, nest_parms);
    }

    nlmsg_end(skb, nlh);
    return skb->len;

nlmsg_failure:
nla_put_failure:
    nlmsg_cancel(skb, nlh);
    return -1;
}

static int
ctnl_timeout_dump(struct sk_buff *skb, struct netlink_callback *cb)
{
    struct ctnl_timeout *cur, *last;

    if (cb->args[2])
        return 0;

    last = (struct ctnl_timeout *)cb->args[1];
    if (cb->args[1])
        cb->args[1] = 0;

    rcu_read_lock();
    list_for_each_entry_rcu(cur, &cttimeout_list, head) {
        if (last && cur != last)
            continue;

        if (ctnl_timeout_fill_info(skb, NETLINK_CB(cb->skb).portid,
                       cb->nlh->nlmsg_seq,
                       NFNL_MSG_TYPE(cb->nlh->nlmsg_type),
                       IPCTNL_MSG_TIMEOUT_NEW, cur) < 0) {
            cb->args[1] = (unsigned long)cur;
            break;
        }
    }
    if (!cb->args[1])
        cb->args[2] = 1;
    rcu_read_unlock();
    return skb->len;
}

static int
cttimeout_get_timeout(struct sock *ctnl, struct sk_buff *skb,
              const struct nlmsghdr *nlh,
              const struct nlattr * const cda[])
{
    int ret = -ENOENT;
    char *name;
    struct ctnl_timeout *cur;

    if (nlh->nlmsg_flags & NLM_F_DUMP) {
        struct netlink_dump_control c = {
            .dump = ctnl_timeout_dump,
        };
        return netlink_dump_start(ctnl, skb, nlh, &c);
    }

    if (!cda[CTA_TIMEOUT_NAME])
        return -EINVAL;
    name = nla_data(cda[CTA_TIMEOUT_NAME]);

    list_for_each_entry(cur, &cttimeout_list, head) {
        struct sk_buff *skb2;

        if (strncmp(cur->name, name, CTNL_TIMEOUT_NAME_MAX) != 0)
            continue;

        skb2 = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
        if (skb2 == NULL) {
            ret = -ENOMEM;
            break;
        }

        ret = ctnl_timeout_fill_info(skb2, NETLINK_CB(skb).portid,
                         nlh->nlmsg_seq,
                         NFNL_MSG_TYPE(nlh->nlmsg_type),
                         IPCTNL_MSG_TIMEOUT_NEW, cur);
        if (ret <= 0) {
            kfree_skb(skb2);
            break;
        }
        ret = netlink_unicast(ctnl, skb2, NETLINK_CB(skb).portid,
                    MSG_DONTWAIT);
        if (ret > 0)
            ret = 0;

        /* this avoids a loop in nfnetlink. */
        return ret == -EAGAIN ? -ENOBUFS : ret;
    }
    return ret;
}

/* try to delete object, fail if it is still in use. */
static int ctnl_timeout_try_del(struct ctnl_timeout *timeout)
{
    int ret = 0;

    /* we want to avoid races with nf_ct_timeout_find_get. */
    if (atomic_dec_and_test(&timeout->refcnt)) {
        /* We are protected by nfnl mutex. */
        list_del_rcu(&timeout->head);
        nf_ct_l4proto_put(timeout->l4proto);
        kfree_rcu(timeout, rcu_head);
    } else {
        /* still in use, restore reference counter. */
        atomic_inc(&timeout->refcnt);
        ret = -EBUSY;
    }
    return ret;
}

static int
cttimeout_del_timeout(struct sock *ctnl, struct sk_buff *skb,
              const struct nlmsghdr *nlh,
              const struct nlattr * const cda[])
{
    char *name;
    struct ctnl_timeout *cur;
    int ret = -ENOENT;

    if (!cda[CTA_TIMEOUT_NAME]) {
        list_for_each_entry(cur, &cttimeout_list, head)
            ctnl_timeout_try_del(cur);

        return 0;
    }
    name = nla_data(cda[CTA_TIMEOUT_NAME]);

    list_for_each_entry(cur, &cttimeout_list, head) {
        if (strncmp(cur->name, name, CTNL_TIMEOUT_NAME_MAX) != 0)
            continue;

        ret = ctnl_timeout_try_del(cur);
        if (ret < 0)
            return ret;

        break;
    }
    return ret;
}

#ifdef CONFIG_NF_CONNTRACK_TIMEOUT
static struct ctnl_timeout *ctnl_timeout_find_get(const char *name)
{
    struct ctnl_timeout *timeout, *matching = NULL;

    rcu_read_lock();
    list_for_each_entry_rcu(timeout, &cttimeout_list, head) {
        if (strncmp(timeout->name, name, CTNL_TIMEOUT_NAME_MAX) != 0)
            continue;

        if (!try_module_get(THIS_MODULE))
            goto err;

        if (!atomic_inc_not_zero(&timeout->refcnt)) {
            module_put(THIS_MODULE);
            goto err;
        }
        matching = timeout;
        break;
    }
err:
    rcu_read_unlock();
    return matching;
}

static void ctnl_timeout_put(struct ctnl_timeout *timeout)
{
    atomic_dec(&timeout->refcnt);
    module_put(THIS_MODULE);
}
#endif /* CONFIG_NF_CONNTRACK_TIMEOUT */

static const struct nfnl_callback cttimeout_cb[IPCTNL_MSG_TIMEOUT_MAX] = {
    [IPCTNL_MSG_TIMEOUT_NEW]    = { .call = cttimeout_new_timeout,
                        .attr_count = CTA_TIMEOUT_MAX,
                        .policy = cttimeout_nla_policy },
    [IPCTNL_MSG_TIMEOUT_GET]    = { .call = cttimeout_get_timeout,
                        .attr_count = CTA_TIMEOUT_MAX,
                        .policy = cttimeout_nla_policy },
    [IPCTNL_MSG_TIMEOUT_DELETE] = { .call = cttimeout_del_timeout,
                        .attr_count = CTA_TIMEOUT_MAX,
                        .policy = cttimeout_nla_policy },
};

static const struct nfnetlink_subsystem cttimeout_subsys = {
    .name               = "conntrack_timeout",
    .subsys_id          = NFNL_SUBSYS_CTNETLINK_TIMEOUT,
    .cb_count           = IPCTNL_MSG_TIMEOUT_MAX,
    .cb             = cttimeout_cb,
};

MODULE_ALIAS_NFNL_SUBSYS(NFNL_SUBSYS_CTNETLINK_TIMEOUT);

static int __init cttimeout_init(void)
{
    int ret;

    ret = nfnetlink_subsys_register(&cttimeout_subsys);
    if (ret < 0) {
        pr_err("cttimeout_init: cannot register cttimeout with "
            "nfnetlink.\n");
        goto err_out;
    }
#ifdef CONFIG_NF_CONNTRACK_TIMEOUT
    RCU_INIT_POINTER(nf_ct_timeout_find_get_hook, ctnl_timeout_find_get);
    RCU_INIT_POINTER(nf_ct_timeout_put_hook, ctnl_timeout_put);
#endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
    return 0;

err_out:
    return ret;
}

static void __exit cttimeout_exit(void)
{
    struct ctnl_timeout *cur, *tmp;

    pr_info("cttimeout: unregistering from nfnetlink.\n");

    nfnetlink_subsys_unregister(&cttimeout_subsys);
    list_for_each_entry_safe(cur, tmp, &cttimeout_list, head) {
        list_del_rcu(&cur->head);
        /* We are sure that our objects have no clients at this point,
         * it's safe to release them all without checking refcnt.
         */
        nf_ct_l4proto_put(cur->l4proto);
        kfree_rcu(cur, rcu_head);
    }
#ifdef CONFIG_NF_CONNTRACK_TIMEOUT
    RCU_INIT_POINTER(nf_ct_timeout_find_get_hook, NULL);
    RCU_INIT_POINTER(nf_ct_timeout_put_hook, NULL);
#endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
}

module_init(cttimeout_init);
module_exit(cttimeout_exit);