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root/net/netfilter/nf_conntrack_sane.c

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DEFINITIONS

This source file includes following definitions.
  1. help
  2. nf_conntrack_sane_fini
  3. nf_conntrack_sane_init

/* SANE connection tracking helper
 * (SANE = Scanner Access Now Easy)
 * For documentation about the SANE network protocol see
 * http://www.sane-project.org/html/doc015.html
 */

/* Copyright (C) 2007 Red Hat, Inc.
 * Author: Michal Schmidt <mschmidt@redhat.com>
 * Based on the FTP conntrack helper (net/netfilter/nf_conntrack_ftp.c):
 *  (C) 1999-2001 Paul `Rusty' Russell
 *  (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
 *  (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
 *  (C) 2003 Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
 *
 * 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/module.h>
#include <linux/moduleparam.h>
#include <linux/netfilter.h>
#include <linux/in.h>
#include <linux/tcp.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_expect.h>
#include <linux/netfilter/nf_conntrack_sane.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Michal Schmidt <mschmidt@redhat.com>");
MODULE_DESCRIPTION("SANE connection tracking helper");

static char *sane_buffer;

static DEFINE_SPINLOCK(nf_sane_lock);

#define MAX_PORTS 8
static u_int16_t ports[MAX_PORTS];
static unsigned int ports_c;
module_param_array(ports, ushort, &ports_c, 0400);

struct sane_request {
        __be32 RPC_code;
#define SANE_NET_START      7   /* RPC code */

        __be32 handle;
};

struct sane_reply_net_start {
        __be32 status;
#define SANE_STATUS_SUCCESS 0

        __be16 zero;
        __be16 port;
        /* other fields aren't interesting for conntrack */
};

static int help(struct sk_buff *skb,
                unsigned int protoff,
                struct nf_conn *ct,
                enum ip_conntrack_info ctinfo)
{
        unsigned int dataoff, datalen;
        const struct tcphdr *th;
        struct tcphdr _tcph;
        void *sb_ptr;
        int ret = NF_ACCEPT;
        int dir = CTINFO2DIR(ctinfo);
        struct nf_ct_sane_master *ct_sane_info;
        struct nf_conntrack_expect *exp;
        struct nf_conntrack_tuple *tuple;
        struct sane_request *req;
        struct sane_reply_net_start *reply;

        ct_sane_info = &nfct_help(ct)->help.ct_sane_info;
        /* Until there's been traffic both ways, don't look in packets. */
        if (ctinfo != IP_CT_ESTABLISHED &&
            ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY)
                return NF_ACCEPT;

        /* Not a full tcp header? */
        th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
        if (th == NULL)
                return NF_ACCEPT;

        /* No data? */
        dataoff = protoff + th->doff * 4;
        if (dataoff >= skb->len)
                return NF_ACCEPT;

        datalen = skb->len - dataoff;

        spin_lock_bh(&nf_sane_lock);
        sb_ptr = skb_header_pointer(skb, dataoff, datalen, sane_buffer);
        BUG_ON(sb_ptr == NULL);

        if (dir == IP_CT_DIR_ORIGINAL) {
                if (datalen != sizeof(struct sane_request))
                        goto out;

                req = sb_ptr;
                if (req->RPC_code != htonl(SANE_NET_START)) {
                        /* Not an interesting command */
                        ct_sane_info->state = SANE_STATE_NORMAL;
                        goto out;
                }

                /* We're interested in the next reply */
                ct_sane_info->state = SANE_STATE_START_REQUESTED;
                goto out;
        }

        /* Is it a reply to an uninteresting command? */
        if (ct_sane_info->state != SANE_STATE_START_REQUESTED)
                goto out;

        /* It's a reply to SANE_NET_START. */
        ct_sane_info->state = SANE_STATE_NORMAL;

        if (datalen < sizeof(struct sane_reply_net_start)) {
                pr_debug("nf_ct_sane: NET_START reply too short\n");
                goto out;
        }

        reply = sb_ptr;
        if (reply->status != htonl(SANE_STATUS_SUCCESS)) {
                /* saned refused the command */
                pr_debug("nf_ct_sane: unsuccessful SANE_STATUS = %u\n",
                         ntohl(reply->status));
                goto out;
        }

        /* Invalid saned reply? Ignore it. */
        if (reply->zero != 0)
                goto out;

        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, &reply->port);

        pr_debug("nf_ct_sane: expect: ");
        nf_ct_dump_tuple(&exp->tuple);

        /* Can't expect this?  Best to drop packet now. */
        if (nf_ct_expect_related(exp) != 0)
                ret = NF_DROP;

        nf_ct_expect_put(exp);

out:
        spin_unlock_bh(&nf_sane_lock);
        return ret;
}

static struct nf_conntrack_helper sane[MAX_PORTS][2] __read_mostly;
static char sane_names[MAX_PORTS][2][sizeof("sane-65535")] __read_mostly;

static const struct nf_conntrack_expect_policy sane_exp_policy = {
        .max_expected   = 1,
        .timeout        = 5 * 60,
};

/* don't make this __exit, since it's called from __init ! */
static void nf_conntrack_sane_fini(void)
{
        int i, j;

        for (i = 0; i < ports_c; i++) {
                for (j = 0; j < 2; j++) {
                        pr_debug("nf_ct_sane: unregistering helper for pf: %d "
                                 "port: %d\n",
                                 sane[i][j].tuple.src.l3num, ports[i]);
                        nf_conntrack_helper_unregister(&sane[i][j]);
                }
        }

        kfree(sane_buffer);
}

static int __init nf_conntrack_sane_init(void)
{
        int i, j = -1, ret = 0;
        char *tmpname;

        sane_buffer = kmalloc(65536, GFP_KERNEL);
        if (!sane_buffer)
                return -ENOMEM;

        if (ports_c == 0)
                ports[ports_c++] = SANE_PORT;

        /* FIXME should be configurable whether IPv4 and IPv6 connections
                 are tracked or not - YK */
        for (i = 0; i < ports_c; i++) {
                sane[i][0].tuple.src.l3num = PF_INET;
                sane[i][1].tuple.src.l3num = PF_INET6;
                for (j = 0; j < 2; j++) {
                        sane[i][j].tuple.src.u.tcp.port = htons(ports[i]);
                        sane[i][j].tuple.dst.protonum = IPPROTO_TCP;
                        sane[i][j].expect_policy = &sane_exp_policy;
                        sane[i][j].me = THIS_MODULE;
                        sane[i][j].help = help;
                        tmpname = &sane_names[i][j][0];
                        if (ports[i] == SANE_PORT)
                                sprintf(tmpname, "sane");
                        else
                                sprintf(tmpname, "sane-%d", ports[i]);
                        sane[i][j].name = tmpname;

                        pr_debug("nf_ct_sane: registering helper for pf: %d "
                                 "port: %d\n",
                                 sane[i][j].tuple.src.l3num, ports[i]);
                        ret = nf_conntrack_helper_register(&sane[i][j]);
                        if (ret) {
                                printk(KERN_ERR "nf_ct_sane: failed to "
                                       "register helper for pf: %d port: %d\n",
                                        sane[i][j].tuple.src.l3num, ports[i]);
                                nf_conntrack_sane_fini();
                                return ret;
                        }
                }
        }

        return 0;
}

module_init(nf_conntrack_sane_init);
module_exit(nf_conntrack_sane_fini);

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