// SPDX-License-Identifier: GPL-2.0-or-later
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/* IRC extension for IP connection tracking, Version 1.21
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* (C) 2000-2002 by Harald Welte <laforge@gnumonks.org>
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* based on RR's ip_conntrack_ftp.c
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* (C) 2006-2012 Patrick McHardy <kaber@trash.net>
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/module.h>
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#include <linux/moduleparam.h>
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#include <linux/skbuff.h>
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#include <linux/in.h>
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#include <linux/ip.h>
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#include <linux/tcp.h>
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#include <linux/netfilter.h>
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#include <linux/slab.h>
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#include <net/netfilter/nf_conntrack.h>
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#include <net/netfilter/nf_conntrack_expect.h>
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#include <net/netfilter/nf_conntrack_helper.h>
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#include <linux/netfilter/nf_conntrack_irc.h>
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#define MAX_PORTS 8
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static unsigned short ports[MAX_PORTS];
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static unsigned int ports_c;
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static unsigned int max_dcc_channels = 8;
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static unsigned int dcc_timeout __read_mostly = 300;
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/* This is slow, but it's simple. --RR */
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static char *irc_buffer;
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static DEFINE_SPINLOCK(irc_buffer_lock);
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unsigned int (*nf_nat_irc_hook)(struct sk_buff *skb,
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enum ip_conntrack_info ctinfo,
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unsigned int protoff,
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unsigned int matchoff,
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unsigned int matchlen,
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struct nf_conntrack_expect *exp) __read_mostly;
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EXPORT_SYMBOL_GPL(nf_nat_irc_hook);
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#define HELPER_NAME "irc"
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MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
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MODULE_DESCRIPTION("IRC (DCC) connection tracking helper");
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MODULE_LICENSE("GPL");
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MODULE_ALIAS("ip_conntrack_irc");
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MODULE_ALIAS_NFCT_HELPER(HELPER_NAME);
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module_param_array(ports, ushort, &ports_c, 0400);
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MODULE_PARM_DESC(ports, "port numbers of IRC servers");
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module_param(max_dcc_channels, uint, 0400);
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MODULE_PARM_DESC(max_dcc_channels, "max number of expected DCC channels per "
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"IRC session");
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module_param(dcc_timeout, uint, 0400);
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MODULE_PARM_DESC(dcc_timeout, "timeout on for unestablished DCC channels");
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static const char *const dccprotos[] = {
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"SEND ", "CHAT ", "MOVE ", "TSEND ", "SCHAT "
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};
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#define MINMATCHLEN 5
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/* tries to get the ip_addr and port out of a dcc command
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* return value: -1 on failure, 0 on success
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* data pointer to first byte of DCC command data
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* data_end pointer to last byte of dcc command data
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* ip returns parsed ip of dcc command
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* port returns parsed port of dcc command
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* ad_beg_p returns pointer to first byte of addr data
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* ad_end_p returns pointer to last byte of addr data
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*/
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static int parse_dcc(char *data, const char *data_end, __be32 *ip,
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u_int16_t *port, char **ad_beg_p, char **ad_end_p)
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{
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char *tmp;
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/* at least 12: "AAAAAAAA P\1\n" */
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while (*data++ != ' ')
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if (data > data_end - 12)
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return -1;
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/* Make sure we have a newline character within the packet boundaries
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* because simple_strtoul parses until the first invalid character. */
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for (tmp = data; tmp <= data_end; tmp++)
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if (*tmp == '\n')
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break;
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if (tmp > data_end || *tmp != '\n')
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return -1;
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*ad_beg_p = data;
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*ip = cpu_to_be32(simple_strtoul(data, &data, 10));
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/* skip blanks between ip and port */
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while (*data == ' ') {
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if (data >= data_end)
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return -1;
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data++;
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}
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*port = simple_strtoul(data, &data, 10);
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*ad_end_p = data;
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return 0;
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}
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static int help(struct sk_buff *skb, unsigned int protoff,
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struct nf_conn *ct, enum ip_conntrack_info ctinfo)
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{
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unsigned int dataoff;
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const struct iphdr *iph;
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const struct tcphdr *th;
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struct tcphdr _tcph;
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const char *data_limit;
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char *data, *ib_ptr;
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int dir = CTINFO2DIR(ctinfo);
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struct nf_conntrack_expect *exp;
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struct nf_conntrack_tuple *tuple;
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__be32 dcc_ip;
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u_int16_t dcc_port;
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__be16 port;
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int i, ret = NF_ACCEPT;
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char *addr_beg_p, *addr_end_p;
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typeof(nf_nat_irc_hook) nf_nat_irc;
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/* If packet is coming from IRC server */
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if (dir == IP_CT_DIR_REPLY)
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return NF_ACCEPT;
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/* Until there's been traffic both ways, don't look in packets. */
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if (ctinfo != IP_CT_ESTABLISHED && ctinfo != IP_CT_ESTABLISHED_REPLY)
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return NF_ACCEPT;
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/* Not a full tcp header? */
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th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
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if (th == NULL)
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return NF_ACCEPT;
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/* No data? */
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dataoff = protoff + th->doff*4;
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if (dataoff >= skb->len)
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return NF_ACCEPT;
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spin_lock_bh(&irc_buffer_lock);
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ib_ptr = skb_header_pointer(skb, dataoff, skb->len - dataoff,
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irc_buffer);
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BUG_ON(ib_ptr == NULL);
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data = ib_ptr;
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data_limit = ib_ptr + skb->len - dataoff;
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/* Skip any whitespace */
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while (data < data_limit - 10) {
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if (*data == ' ' || *data == '\r' || *data == '\n')
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data++;
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else
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break;
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}
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/* strlen("PRIVMSG x ")=10 */
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if (data < data_limit - 10) {
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if (strncasecmp("PRIVMSG ", data, 8))
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goto out;
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data += 8;
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}
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/* strlen(" :\1DCC SENT t AAAAAAAA P\1\n")=26
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* 7+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=26
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*/
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while (data < data_limit - (21 + MINMATCHLEN)) {
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/* Find first " :", the start of message */
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if (memcmp(data, " :", 2)) {
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data++;
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continue;
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}
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data += 2;
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/* then check that place only for the DCC command */
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if (memcmp(data, "\1DCC ", 5))
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goto out;
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data += 5;
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/* we have at least (21+MINMATCHLEN)-(2+5) bytes valid data left */
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iph = ip_hdr(skb);
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pr_debug("DCC found in master %pI4:%u %pI4:%u\n",
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&iph->saddr, ntohs(th->source),
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&iph->daddr, ntohs(th->dest));
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for (i = 0; i < ARRAY_SIZE(dccprotos); i++) {
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if (memcmp(data, dccprotos[i], strlen(dccprotos[i]))) {
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/* no match */
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continue;
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}
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data += strlen(dccprotos[i]);
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pr_debug("DCC %s detected\n", dccprotos[i]);
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/* we have at least
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* (21+MINMATCHLEN)-7-dccprotos[i].matchlen bytes valid
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* data left (== 14/13 bytes) */
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if (parse_dcc(data, data_limit, &dcc_ip,
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&dcc_port, &addr_beg_p, &addr_end_p)) {
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pr_debug("unable to parse dcc command\n");
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continue;
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}
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pr_debug("DCC bound ip/port: %pI4:%u\n",
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&dcc_ip, dcc_port);
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/* dcc_ip can be the internal OR external (NAT'ed) IP */
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tuple = &ct->tuplehash[dir].tuple;
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if ((tuple->src.u3.ip != dcc_ip &&
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ct->tuplehash[!dir].tuple.dst.u3.ip != dcc_ip) ||
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dcc_port == 0) {
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net_warn_ratelimited("Forged DCC command from %pI4: %pI4:%u\n",
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&tuple->src.u3.ip,
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&dcc_ip, dcc_port);
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continue;
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}
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exp = nf_ct_expect_alloc(ct);
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if (exp == NULL) {
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nf_ct_helper_log(skb, ct,
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"cannot alloc expectation");
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ret = NF_DROP;
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goto out;
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}
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tuple = &ct->tuplehash[!dir].tuple;
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port = htons(dcc_port);
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nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
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tuple->src.l3num,
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NULL, &tuple->dst.u3,
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IPPROTO_TCP, NULL, &port);
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nf_nat_irc = rcu_dereference(nf_nat_irc_hook);
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if (nf_nat_irc && ct->status & IPS_NAT_MASK)
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ret = nf_nat_irc(skb, ctinfo, protoff,
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addr_beg_p - ib_ptr,
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addr_end_p - addr_beg_p,
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exp);
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else if (nf_ct_expect_related(exp, 0) != 0) {
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nf_ct_helper_log(skb, ct,
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"cannot add expectation");
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ret = NF_DROP;
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}
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nf_ct_expect_put(exp);
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goto out;
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}
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}
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out:
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spin_unlock_bh(&irc_buffer_lock);
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return ret;
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}
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static struct nf_conntrack_helper irc[MAX_PORTS] __read_mostly;
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static struct nf_conntrack_expect_policy irc_exp_policy;
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static int __init nf_conntrack_irc_init(void)
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{
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int i, ret;
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if (max_dcc_channels < 1) {
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pr_err("max_dcc_channels must not be zero\n");
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return -EINVAL;
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}
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if (max_dcc_channels > NF_CT_EXPECT_MAX_CNT) {
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pr_err("max_dcc_channels must not be more than %u\n",
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NF_CT_EXPECT_MAX_CNT);
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return -EINVAL;
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}
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irc_exp_policy.max_expected = max_dcc_channels;
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irc_exp_policy.timeout = dcc_timeout;
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irc_buffer = kmalloc(65536, GFP_KERNEL);
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if (!irc_buffer)
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return -ENOMEM;
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/* If no port given, default to standard irc port */
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if (ports_c == 0)
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ports[ports_c++] = IRC_PORT;
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for (i = 0; i < ports_c; i++) {
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nf_ct_helper_init(&irc[i], AF_INET, IPPROTO_TCP, HELPER_NAME,
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IRC_PORT, ports[i], i, &irc_exp_policy,
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0, help, NULL, THIS_MODULE);
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}
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ret = nf_conntrack_helpers_register(&irc[0], ports_c);
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if (ret) {
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pr_err("failed to register helpers\n");
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kfree(irc_buffer);
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return ret;
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}
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return 0;
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}
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static void __exit nf_conntrack_irc_fini(void)
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{
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nf_conntrack_helpers_unregister(irc, ports_c);
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kfree(irc_buffer);
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}
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module_init(nf_conntrack_irc_init);
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module_exit(nf_conntrack_irc_fini);
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