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- /* 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/slab.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");
- MODULE_ALIAS_NFCT_HELPER("sane");
- 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 = nfct_help_data(ct);
- struct nf_conntrack_expect *exp;
- struct nf_conntrack_tuple *tuple;
- struct sane_request *req;
- struct sane_reply_net_start *reply;
- /* Until there's been traffic both ways, don't look in packets. */
- if (ctinfo != IP_CT_ESTABLISHED &&
- ctinfo != IP_CT_ESTABLISHED_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) {
- nf_ct_helper_log(skb, ct, "cannot alloc expectation");
- 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) {
- nf_ct_helper_log(skb, ct, "cannot add expectation");
- 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 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;
- 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].data_len = sizeof(struct nf_ct_sane_master);
- 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;
- if (ports[i] == SANE_PORT)
- sprintf(sane[i][j].name, "sane");
- else
- sprintf(sane[i][j].name, "sane-%d", ports[i]);
- 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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