![Pablo Neira Ayuso](/assets/img/avatar_default.png)
Connection tracking helpers have to drop packets under exceptional situations. Currently, the user gets the following logging message in case that happens: nf_ct_%s: dropping packet ... However, depending on the helper, there are different reasons why a packet can be dropped. This patch modifies the existing code to provide more specific error message in the scope of each helper to help users to debug the reason why the packet has been dropped, ie: nf_ct_%s: dropping packet: reason ... Thanks to Joe Perches for many formatting suggestions. Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
292 lines
7.9 KiB
C
292 lines
7.9 KiB
C
/* 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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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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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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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("irc");
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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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/* strlen("\1DCC SENT t AAAAAAAA P\1\n")=24
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* 5+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=14 */
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while (data < data_limit - (19 + MINMATCHLEN)) {
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if (memcmp(data, "\1DCC ", 5)) {
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data++;
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continue;
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}
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data += 5;
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/* we have at least (19+MINMATCHLEN)-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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* (19+MINMATCHLEN)-5-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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tuple->dst.u3.ip != dcc_ip) {
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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) {
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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 void nf_conntrack_irc_fini(void);
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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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printk(KERN_ERR "nf_ct_irc: max_dcc_channels must not be zero\n");
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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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irc[i].tuple.src.l3num = AF_INET;
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irc[i].tuple.src.u.tcp.port = htons(ports[i]);
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irc[i].tuple.dst.protonum = IPPROTO_TCP;
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irc[i].expect_policy = &irc_exp_policy;
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irc[i].me = THIS_MODULE;
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irc[i].help = help;
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if (ports[i] == IRC_PORT)
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sprintf(irc[i].name, "irc");
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else
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sprintf(irc[i].name, "irc-%u", i);
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ret = nf_conntrack_helper_register(&irc[i]);
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if (ret) {
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printk(KERN_ERR "nf_ct_irc: failed to register helper "
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"for pf: %u port: %u\n",
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irc[i].tuple.src.l3num, ports[i]);
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nf_conntrack_irc_fini();
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return ret;
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}
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}
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return 0;
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}
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/* This function is intentionally _NOT_ defined as __exit, because
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* it is needed by the init function */
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static void nf_conntrack_irc_fini(void)
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{
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int i;
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for (i = 0; i < ports_c; i++)
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nf_conntrack_helper_unregister(&irc[i]);
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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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