blob: 8ff4d22f10b2a14d9486686a7dddcb56204f5d3b [file] [log] [blame]
/*
* Copyright (c) 2013 Patrick McHardy <kaber@trash.net>
*
* 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/skbuff.h>
#include <asm/unaligned.h>
#include <net/tcp.h>
#include <net/netns/generic.h>
#include <linux/proc_fs.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_tcpudp.h>
#include <linux/netfilter/xt_SYNPROXY.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_extend.h>
#include <net/netfilter/nf_conntrack_seqadj.h>
#include <net/netfilter/nf_conntrack_synproxy.h>
#include <net/netfilter/nf_conntrack_zones.h>
unsigned int synproxy_net_id;
EXPORT_SYMBOL_GPL(synproxy_net_id);
bool
synproxy_parse_options(const struct sk_buff *skb, unsigned int doff,
const struct tcphdr *th, struct synproxy_options *opts)
{
int length = (th->doff * 4) - sizeof(*th);
u8 buf[40], *ptr;
ptr = skb_header_pointer(skb, doff + sizeof(*th), length, buf);
if (ptr == NULL)
return false;
opts->options = 0;
while (length > 0) {
int opcode = *ptr++;
int opsize;
switch (opcode) {
case TCPOPT_EOL:
return true;
case TCPOPT_NOP:
length--;
continue;
default:
opsize = *ptr++;
if (opsize < 2)
return true;
if (opsize > length)
return true;
switch (opcode) {
case TCPOPT_MSS:
if (opsize == TCPOLEN_MSS) {
opts->mss = get_unaligned_be16(ptr);
opts->options |= XT_SYNPROXY_OPT_MSS;
}
break;
case TCPOPT_WINDOW:
if (opsize == TCPOLEN_WINDOW) {
opts->wscale = *ptr;
if (opts->wscale > TCP_MAX_WSCALE)
opts->wscale = TCP_MAX_WSCALE;
opts->options |= XT_SYNPROXY_OPT_WSCALE;
}
break;
case TCPOPT_TIMESTAMP:
if (opsize == TCPOLEN_TIMESTAMP) {
opts->tsval = get_unaligned_be32(ptr);
opts->tsecr = get_unaligned_be32(ptr + 4);
opts->options |= XT_SYNPROXY_OPT_TIMESTAMP;
}
break;
case TCPOPT_SACK_PERM:
if (opsize == TCPOLEN_SACK_PERM)
opts->options |= XT_SYNPROXY_OPT_SACK_PERM;
break;
}
ptr += opsize - 2;
length -= opsize;
}
}
return true;
}
EXPORT_SYMBOL_GPL(synproxy_parse_options);
unsigned int synproxy_options_size(const struct synproxy_options *opts)
{
unsigned int size = 0;
if (opts->options & XT_SYNPROXY_OPT_MSS)
size += TCPOLEN_MSS_ALIGNED;
if (opts->options & XT_SYNPROXY_OPT_TIMESTAMP)
size += TCPOLEN_TSTAMP_ALIGNED;
else if (opts->options & XT_SYNPROXY_OPT_SACK_PERM)
size += TCPOLEN_SACKPERM_ALIGNED;
if (opts->options & XT_SYNPROXY_OPT_WSCALE)
size += TCPOLEN_WSCALE_ALIGNED;
return size;
}
EXPORT_SYMBOL_GPL(synproxy_options_size);
void
synproxy_build_options(struct tcphdr *th, const struct synproxy_options *opts)
{
__be32 *ptr = (__be32 *)(th + 1);
u8 options = opts->options;
if (options & XT_SYNPROXY_OPT_MSS)
*ptr++ = htonl((TCPOPT_MSS << 24) |
(TCPOLEN_MSS << 16) |
opts->mss);
if (options & XT_SYNPROXY_OPT_TIMESTAMP) {
if (options & XT_SYNPROXY_OPT_SACK_PERM)
*ptr++ = htonl((TCPOPT_SACK_PERM << 24) |
(TCPOLEN_SACK_PERM << 16) |
(TCPOPT_TIMESTAMP << 8) |
TCPOLEN_TIMESTAMP);
else
*ptr++ = htonl((TCPOPT_NOP << 24) |
(TCPOPT_NOP << 16) |
(TCPOPT_TIMESTAMP << 8) |
TCPOLEN_TIMESTAMP);
*ptr++ = htonl(opts->tsval);
*ptr++ = htonl(opts->tsecr);
} else if (options & XT_SYNPROXY_OPT_SACK_PERM)
*ptr++ = htonl((TCPOPT_NOP << 24) |
(TCPOPT_NOP << 16) |
(TCPOPT_SACK_PERM << 8) |
TCPOLEN_SACK_PERM);
if (options & XT_SYNPROXY_OPT_WSCALE)
*ptr++ = htonl((TCPOPT_NOP << 24) |
(TCPOPT_WINDOW << 16) |
(TCPOLEN_WINDOW << 8) |
opts->wscale);
}
EXPORT_SYMBOL_GPL(synproxy_build_options);
void synproxy_init_timestamp_cookie(const struct xt_synproxy_info *info,
struct synproxy_options *opts)
{
opts->tsecr = opts->tsval;
opts->tsval = tcp_time_stamp_raw() & ~0x3f;
if (opts->options & XT_SYNPROXY_OPT_WSCALE) {
opts->tsval |= opts->wscale;
opts->wscale = info->wscale;
} else
opts->tsval |= 0xf;
if (opts->options & XT_SYNPROXY_OPT_SACK_PERM)
opts->tsval |= 1 << 4;
if (opts->options & XT_SYNPROXY_OPT_ECN)
opts->tsval |= 1 << 5;
}
EXPORT_SYMBOL_GPL(synproxy_init_timestamp_cookie);
void synproxy_check_timestamp_cookie(struct synproxy_options *opts)
{
opts->wscale = opts->tsecr & 0xf;
if (opts->wscale != 0xf)
opts->options |= XT_SYNPROXY_OPT_WSCALE;
opts->options |= opts->tsecr & (1 << 4) ? XT_SYNPROXY_OPT_SACK_PERM : 0;
opts->options |= opts->tsecr & (1 << 5) ? XT_SYNPROXY_OPT_ECN : 0;
}
EXPORT_SYMBOL_GPL(synproxy_check_timestamp_cookie);
unsigned int synproxy_tstamp_adjust(struct sk_buff *skb,
unsigned int protoff,
struct tcphdr *th,
struct nf_conn *ct,
enum ip_conntrack_info ctinfo,
const struct nf_conn_synproxy *synproxy)
{
unsigned int optoff, optend;
__be32 *ptr, old;
if (synproxy->tsoff == 0)
return 1;
optoff = protoff + sizeof(struct tcphdr);
optend = protoff + th->doff * 4;
if (!skb_make_writable(skb, optend))
return 0;
while (optoff < optend) {
unsigned char *op = skb->data + optoff;
switch (op[0]) {
case TCPOPT_EOL:
return 1;
case TCPOPT_NOP:
optoff++;
continue;
default:
if (optoff + 1 == optend ||
optoff + op[1] > optend ||
op[1] < 2)
return 0;
if (op[0] == TCPOPT_TIMESTAMP &&
op[1] == TCPOLEN_TIMESTAMP) {
if (CTINFO2DIR(ctinfo) == IP_CT_DIR_REPLY) {
ptr = (__be32 *)&op[2];
old = *ptr;
*ptr = htonl(ntohl(*ptr) -
synproxy->tsoff);
} else {
ptr = (__be32 *)&op[6];
old = *ptr;
*ptr = htonl(ntohl(*ptr) +
synproxy->tsoff);
}
inet_proto_csum_replace4(&th->check, skb,
old, *ptr, false);
return 1;
}
optoff += op[1];
}
}
return 1;
}
EXPORT_SYMBOL_GPL(synproxy_tstamp_adjust);
static struct nf_ct_ext_type nf_ct_synproxy_extend __read_mostly = {
.len = sizeof(struct nf_conn_synproxy),
.align = __alignof__(struct nf_conn_synproxy),
.id = NF_CT_EXT_SYNPROXY,
};
#ifdef CONFIG_PROC_FS
static void *synproxy_cpu_seq_start(struct seq_file *seq, loff_t *pos)
{
struct synproxy_net *snet = synproxy_pernet(seq_file_net(seq));
int cpu;
if (*pos == 0)
return SEQ_START_TOKEN;
for (cpu = *pos - 1; cpu < nr_cpu_ids; cpu++) {
if (!cpu_possible(cpu))
continue;
*pos = cpu + 1;
return per_cpu_ptr(snet->stats, cpu);
}
return NULL;
}
static void *synproxy_cpu_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
struct synproxy_net *snet = synproxy_pernet(seq_file_net(seq));
int cpu;
for (cpu = *pos; cpu < nr_cpu_ids; cpu++) {
if (!cpu_possible(cpu))
continue;
*pos = cpu + 1;
return per_cpu_ptr(snet->stats, cpu);
}
return NULL;
}
static void synproxy_cpu_seq_stop(struct seq_file *seq, void *v)
{
return;
}
static int synproxy_cpu_seq_show(struct seq_file *seq, void *v)
{
struct synproxy_stats *stats = v;
if (v == SEQ_START_TOKEN) {
seq_puts(seq, "entries\t\tsyn_received\t"
"cookie_invalid\tcookie_valid\t"
"cookie_retrans\tconn_reopened\n");
return 0;
}
seq_printf(seq, "%08x\t%08x\t%08x\t%08x\t%08x\t%08x\n", 0,
stats->syn_received,
stats->cookie_invalid,
stats->cookie_valid,
stats->cookie_retrans,
stats->conn_reopened);
return 0;
}
static const struct seq_operations synproxy_cpu_seq_ops = {
.start = synproxy_cpu_seq_start,
.next = synproxy_cpu_seq_next,
.stop = synproxy_cpu_seq_stop,
.show = synproxy_cpu_seq_show,
};
static int __net_init synproxy_proc_init(struct net *net)
{
if (!proc_create_net("synproxy", 0444, net->proc_net_stat,
&synproxy_cpu_seq_ops, sizeof(struct seq_net_private)))
return -ENOMEM;
return 0;
}
static void __net_exit synproxy_proc_exit(struct net *net)
{
remove_proc_entry("synproxy", net->proc_net_stat);
}
#else
static int __net_init synproxy_proc_init(struct net *net)
{
return 0;
}
static void __net_exit synproxy_proc_exit(struct net *net)
{
return;
}
#endif /* CONFIG_PROC_FS */
static int __net_init synproxy_net_init(struct net *net)
{
struct synproxy_net *snet = synproxy_pernet(net);
struct nf_conn *ct;
int err = -ENOMEM;
ct = nf_ct_tmpl_alloc(net, &nf_ct_zone_dflt, GFP_KERNEL);
if (!ct)
goto err1;
if (!nfct_seqadj_ext_add(ct))
goto err2;
if (!nfct_synproxy_ext_add(ct))
goto err2;
__set_bit(IPS_CONFIRMED_BIT, &ct->status);
nf_conntrack_get(&ct->ct_general);
snet->tmpl = ct;
snet->stats = alloc_percpu(struct synproxy_stats);
if (snet->stats == NULL)
goto err2;
err = synproxy_proc_init(net);
if (err < 0)
goto err3;
return 0;
err3:
free_percpu(snet->stats);
err2:
nf_ct_tmpl_free(ct);
err1:
return err;
}
static void __net_exit synproxy_net_exit(struct net *net)
{
struct synproxy_net *snet = synproxy_pernet(net);
nf_ct_put(snet->tmpl);
synproxy_proc_exit(net);
free_percpu(snet->stats);
}
static struct pernet_operations synproxy_net_ops = {
.init = synproxy_net_init,
.exit = synproxy_net_exit,
.id = &synproxy_net_id,
.size = sizeof(struct synproxy_net),
};
static int __init synproxy_core_init(void)
{
int err;
err = nf_ct_extend_register(&nf_ct_synproxy_extend);
if (err < 0)
goto err1;
err = register_pernet_subsys(&synproxy_net_ops);
if (err < 0)
goto err2;
return 0;
err2:
nf_ct_extend_unregister(&nf_ct_synproxy_extend);
err1:
return err;
}
static void __exit synproxy_core_exit(void)
{
unregister_pernet_subsys(&synproxy_net_ops);
nf_ct_extend_unregister(&nf_ct_synproxy_extend);
}
module_init(synproxy_core_init);
module_exit(synproxy_core_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");