root/net/netfilter/nf_conntrack_tftp.c

DEFINITIONS

1. tftp_help
2. nf_conntrack_tftp_fini
3. nf_conntrack_tftp_init

/* (C) 2001-2002 Magnus Boden <mb@ozaba.mine.nu>
 *
 * 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/in.h>
#include <linux/udp.h>
#include <linux/netfilter.h>

#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_tuple.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_tftp.h>

MODULE_AUTHOR("Magnus Boden <mb@ozaba.mine.nu>");
MODULE_DESCRIPTION("TFTP connection tracking helper");
MODULE_LICENSE("GPL");
MODULE_ALIAS("ip_conntrack_tftp");

#define MAX_PORTS 8
static unsigned short ports[MAX_PORTS];
static unsigned int ports_c;
module_param_array(ports, ushort, &ports_c, 0400);
MODULE_PARM_DESC(ports, "Port numbers of TFTP servers");

unsigned int (*nf_nat_tftp_hook)(struct sk_buff *skb,
                                 enum ip_conntrack_info ctinfo,
                                 struct nf_conntrack_expect *exp) __read_mostly;
EXPORT_SYMBOL_GPL(nf_nat_tftp_hook);

static int tftp_help(struct sk_buff *skb,
                     unsigned int protoff,
                     struct nf_conn *ct,
                     enum ip_conntrack_info ctinfo)
{
        const struct tftphdr *tfh;
        struct tftphdr _tftph;
        struct nf_conntrack_expect *exp;
        struct nf_conntrack_tuple *tuple;
        unsigned int ret = NF_ACCEPT;
        typeof(nf_nat_tftp_hook) nf_nat_tftp;

        tfh = skb_header_pointer(skb, protoff + sizeof(struct udphdr),
                                 sizeof(_tftph), &_tftph);
        if (tfh == NULL)
                return NF_ACCEPT;

        switch (ntohs(tfh->opcode)) {
        case TFTP_OPCODE_READ:
        case TFTP_OPCODE_WRITE:
                /* RRQ and WRQ works the same way */
                nf_ct_dump_tuple(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
                nf_ct_dump_tuple(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);

                exp = nf_ct_expect_alloc(ct);
                if (exp == NULL)
                        return NF_DROP;
                tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
                nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
                                  nf_ct_l3num(ct),
                                  &tuple->src.u3, &tuple->dst.u3,
                                  IPPROTO_UDP, NULL, &tuple->dst.u.udp.port);

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

                nf_nat_tftp = rcu_dereference(nf_nat_tftp_hook);
                if (nf_nat_tftp && ct->status & IPS_NAT_MASK)
                        ret = nf_nat_tftp(skb, ctinfo, exp);
                else if (nf_ct_expect_related(exp) != 0)
                        ret = NF_DROP;
                nf_ct_expect_put(exp);
                break;
        case TFTP_OPCODE_DATA:
        case TFTP_OPCODE_ACK:
                pr_debug("Data/ACK opcode\n");
                break;
        case TFTP_OPCODE_ERROR:
                pr_debug("Error opcode\n");
                break;
        default:
                pr_debug("Unknown opcode\n");
        }
        return ret;
}

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

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

static void nf_conntrack_tftp_fini(void)
{
        int i, j;

        for (i = 0; i < ports_c; i++) {
                for (j = 0; j < 2; j++)
                        nf_conntrack_helper_unregister(&tftp[i][j]);
        }
}

static int __init nf_conntrack_tftp_init(void)
{
        int i, j, ret;
        char *tmpname;

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

        for (i = 0; i < ports_c; i++) {
                memset(&tftp[i], 0, sizeof(tftp[i]));

                tftp[i][0].tuple.src.l3num = AF_INET;
                tftp[i][1].tuple.src.l3num = AF_INET6;
                for (j = 0; j < 2; j++) {
                        tftp[i][j].tuple.dst.protonum = IPPROTO_UDP;
                        tftp[i][j].tuple.src.u.udp.port = htons(ports[i]);
                        tftp[i][j].expect_policy = &tftp_exp_policy;
                        tftp[i][j].me = THIS_MODULE;
                        tftp[i][j].help = tftp_help;

                        tmpname = &tftp_names[i][j][0];
                        if (ports[i] == TFTP_PORT)
                                sprintf(tmpname, "tftp");
                        else
                                sprintf(tmpname, "tftp-%u", i);
                        tftp[i][j].name = tmpname;

                        ret = nf_conntrack_helper_register(&tftp[i][j]);
                        if (ret) {
                                printk("nf_ct_tftp: failed to register helper "
                                       "for pf: %u port: %u\n",
                                        tftp[i][j].tuple.src.l3num, ports[i]);
                                nf_conntrack_tftp_fini();
                                return ret;
                        }
                }
        }
        return 0;
}

module_init(nf_conntrack_tftp_init);
module_exit(nf_conntrack_tftp_fini);