nf_conntrack_amanda.c

Go to the documentation of this file.

/* Amanda extension for IP connection tracking
 *
 * (C) 2002 by Brian J. Murrell <[email protected]>
 * based on HW's ip_conntrack_irc.c as well as other modules
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/textsearch.h>
#include <linux/skbuff.h>
#include <linux/in.h>
#include <linux/udp.h>
#include <linux/netfilter.h>
#include <linux/gfp.h>

#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_expect.h>
#include <net/netfilter/nf_conntrack_ecache.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <linux/netfilter/nf_conntrack_amanda.h>

static unsigned int master_timeout __read_mostly = 300;
static char *ts_algo = "kmp";

MODULE_AUTHOR("Brian J. Murrell <[email protected]>");
MODULE_DESCRIPTION("Amanda connection tracking module");
MODULE_LICENSE("GPL");
MODULE_ALIAS("ip_conntrack_amanda");
MODULE_ALIAS_NFCT_HELPER("amanda");

module_param(master_timeout, uint, 0600);
MODULE_PARM_DESC(master_timeout, "timeout for the master connection");
module_param(ts_algo, charp, 0400);
MODULE_PARM_DESC(ts_algo, "textsearch algorithm to use (default kmp)");

unsigned int (*nf_nat_amanda_hook)(struct sk_buff *skb,
                   enum ip_conntrack_info ctinfo,
                   unsigned int protoff,
                   unsigned int matchoff,
                   unsigned int matchlen,
                   struct nf_conntrack_expect *exp)
                   __read_mostly;
EXPORT_SYMBOL_GPL(nf_nat_amanda_hook);

enum amanda_strings {
    SEARCH_CONNECT,
    SEARCH_NEWLINE,
    SEARCH_DATA,
    SEARCH_MESG,
    SEARCH_INDEX,
};

static struct {
    const char      *string;
    size_t          len;
    struct ts_config    *ts;
} search[] __read_mostly = {
    [SEARCH_CONNECT] = {
        .string = "CONNECT ",
        .len    = 8,
    },
    [SEARCH_NEWLINE] = {
        .string = "\n",
        .len    = 1,
    },
    [SEARCH_DATA] = {
        .string = "DATA ",
        .len    = 5,
    },
    [SEARCH_MESG] = {
        .string = "MESG ",
        .len    = 5,
    },
    [SEARCH_INDEX] = {
        .string = "INDEX ",
        .len    = 6,
    },
};

static int amanda_help(struct sk_buff *skb,
               unsigned int protoff,
               struct nf_conn *ct,
               enum ip_conntrack_info ctinfo)
{
    struct ts_state ts;
    struct nf_conntrack_expect *exp;
    struct nf_conntrack_tuple *tuple;
    unsigned int dataoff, start, stop, off, i;
    char pbuf[sizeof("65535")], *tmp;
    u_int16_t len;
    __be16 port;
    int ret = NF_ACCEPT;
    typeof(nf_nat_amanda_hook) nf_nat_amanda;

    /* Only look at packets from the Amanda server */
    if (CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL)
        return NF_ACCEPT;

    /* increase the UDP timeout of the master connection as replies from
     * Amanda clients to the server can be quite delayed */
    nf_ct_refresh(ct, skb, master_timeout * HZ);

    /* No data? */
    dataoff = protoff + sizeof(struct udphdr);
    if (dataoff >= skb->len) {
        net_err_ratelimited("amanda_help: skblen = %u\n", skb->len);
        return NF_ACCEPT;
    }

    memset(&ts, 0, sizeof(ts));
    start = skb_find_text(skb, dataoff, skb->len,
                  search[SEARCH_CONNECT].ts, &ts);
    if (start == UINT_MAX)
        goto out;
    start += dataoff + search[SEARCH_CONNECT].len;

    memset(&ts, 0, sizeof(ts));
    stop = skb_find_text(skb, start, skb->len,
                 search[SEARCH_NEWLINE].ts, &ts);
    if (stop == UINT_MAX)
        goto out;
    stop += start;

    for (i = SEARCH_DATA; i <= SEARCH_INDEX; i++) {
        memset(&ts, 0, sizeof(ts));
        off = skb_find_text(skb, start, stop, search[i].ts, &ts);
        if (off == UINT_MAX)
            continue;
        off += start + search[i].len;

        len = min_t(unsigned int, sizeof(pbuf) - 1, stop - off);
        if (skb_copy_bits(skb, off, pbuf, len))
            break;
        pbuf[len] = '\0';

        port = htons(simple_strtoul(pbuf, &tmp, 10));
        len = tmp - pbuf;
        if (port == 0 || len > 5)
            break;

        exp = nf_ct_expect_alloc(ct);
        if (exp == NULL) {
            ret = NF_DROP;
            goto out;
        }
        tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
        nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
                  nf_ct_l3num(ct),
                  &tuple->src.u3, &tuple->dst.u3,
                  IPPROTO_TCP, NULL, &port);

        nf_nat_amanda = rcu_dereference(nf_nat_amanda_hook);
        if (nf_nat_amanda && ct->status & IPS_NAT_MASK)
            ret = nf_nat_amanda(skb, ctinfo, protoff,
                        off - dataoff, len, exp);
        else if (nf_ct_expect_related(exp) != 0)
            ret = NF_DROP;
        nf_ct_expect_put(exp);
    }

out:
    return ret;
}

static const struct nf_conntrack_expect_policy amanda_exp_policy = {
    .max_expected       = 3,
    .timeout        = 180,
};

static struct nf_conntrack_helper amanda_helper[2] __read_mostly = {
    {
        .name           = "amanda",
        .me         = THIS_MODULE,
        .help           = amanda_help,
        .tuple.src.l3num    = AF_INET,
        .tuple.src.u.udp.port   = cpu_to_be16(10080),
        .tuple.dst.protonum = IPPROTO_UDP,
        .expect_policy      = &amanda_exp_policy,
    },
    {
        .name           = "amanda",
        .me         = THIS_MODULE,
        .help           = amanda_help,
        .tuple.src.l3num    = AF_INET6,
        .tuple.src.u.udp.port   = cpu_to_be16(10080),
        .tuple.dst.protonum = IPPROTO_UDP,
        .expect_policy      = &amanda_exp_policy,
    },
};

static void __exit nf_conntrack_amanda_fini(void)
{
    int i;

    nf_conntrack_helper_unregister(&amanda_helper[0]);
    nf_conntrack_helper_unregister(&amanda_helper[1]);
    for (i = 0; i < ARRAY_SIZE(search); i++)
        textsearch_destroy(search[i].ts);
}

static int __init nf_conntrack_amanda_init(void)
{
    int ret, i;

    for (i = 0; i < ARRAY_SIZE(search); i++) {
        search[i].ts = textsearch_prepare(ts_algo, search[i].string,
                          search[i].len,
                          GFP_KERNEL, TS_AUTOLOAD);
        if (IS_ERR(search[i].ts)) {
            ret = PTR_ERR(search[i].ts);
            goto err1;
        }
    }
    ret = nf_conntrack_helper_register(&amanda_helper[0]);
    if (ret < 0)
        goto err1;
    ret = nf_conntrack_helper_register(&amanda_helper[1]);
    if (ret < 0)
        goto err2;
    return 0;

err2:
    nf_conntrack_helper_unregister(&amanda_helper[0]);
err1:
    while (--i >= 0)
        textsearch_destroy(search[i].ts);

    return ret;
}

module_init(nf_conntrack_amanda_init);
module_exit(nf_conntrack_amanda_fini);