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-rw-r--r--net/ipv4/netfilter/ip_nat_rule.c319
1 files changed, 319 insertions, 0 deletions
diff --git a/net/ipv4/netfilter/ip_nat_rule.c b/net/ipv4/netfilter/ip_nat_rule.c
new file mode 100644
index 000000000000..581f097f5a24
--- /dev/null
+++ b/net/ipv4/netfilter/ip_nat_rule.c
@@ -0,0 +1,319 @@
+/* (C) 1999-2001 Paul `Rusty' Russell
+ * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
+ *
+ * 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.
+ */
+
+/* Everything about the rules for NAT. */
+#include <linux/types.h>
+#include <linux/ip.h>
+#include <linux/netfilter.h>
+#include <linux/netfilter_ipv4.h>
+#include <linux/module.h>
+#include <linux/kmod.h>
+#include <linux/skbuff.h>
+#include <linux/proc_fs.h>
+#include <net/checksum.h>
+#include <net/route.h>
+#include <linux/bitops.h>
+
+#define ASSERT_READ_LOCK(x) MUST_BE_READ_LOCKED(&ip_nat_lock)
+#define ASSERT_WRITE_LOCK(x) MUST_BE_WRITE_LOCKED(&ip_nat_lock)
+
+#include <linux/netfilter_ipv4/ip_tables.h>
+#include <linux/netfilter_ipv4/ip_nat.h>
+#include <linux/netfilter_ipv4/ip_nat_core.h>
+#include <linux/netfilter_ipv4/ip_nat_rule.h>
+#include <linux/netfilter_ipv4/listhelp.h>
+
+#if 0
+#define DEBUGP printk
+#else
+#define DEBUGP(format, args...)
+#endif
+
+#define NAT_VALID_HOOKS ((1<<NF_IP_PRE_ROUTING) | (1<<NF_IP_POST_ROUTING) | (1<<NF_IP_LOCAL_OUT))
+
+static struct
+{
+ struct ipt_replace repl;
+ struct ipt_standard entries[3];
+ struct ipt_error term;
+} nat_initial_table __initdata
+= { { "nat", NAT_VALID_HOOKS, 4,
+ sizeof(struct ipt_standard) * 3 + sizeof(struct ipt_error),
+ { [NF_IP_PRE_ROUTING] = 0,
+ [NF_IP_POST_ROUTING] = sizeof(struct ipt_standard),
+ [NF_IP_LOCAL_OUT] = sizeof(struct ipt_standard) * 2 },
+ { [NF_IP_PRE_ROUTING] = 0,
+ [NF_IP_POST_ROUTING] = sizeof(struct ipt_standard),
+ [NF_IP_LOCAL_OUT] = sizeof(struct ipt_standard) * 2 },
+ 0, NULL, { } },
+ {
+ /* PRE_ROUTING */
+ { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
+ 0,
+ sizeof(struct ipt_entry),
+ sizeof(struct ipt_standard),
+ 0, { 0, 0 }, { } },
+ { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
+ -NF_ACCEPT - 1 } },
+ /* POST_ROUTING */
+ { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
+ 0,
+ sizeof(struct ipt_entry),
+ sizeof(struct ipt_standard),
+ 0, { 0, 0 }, { } },
+ { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
+ -NF_ACCEPT - 1 } },
+ /* LOCAL_OUT */
+ { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
+ 0,
+ sizeof(struct ipt_entry),
+ sizeof(struct ipt_standard),
+ 0, { 0, 0 }, { } },
+ { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
+ -NF_ACCEPT - 1 } }
+ },
+ /* ERROR */
+ { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
+ 0,
+ sizeof(struct ipt_entry),
+ sizeof(struct ipt_error),
+ 0, { 0, 0 }, { } },
+ { { { { IPT_ALIGN(sizeof(struct ipt_error_target)), IPT_ERROR_TARGET } },
+ { } },
+ "ERROR"
+ }
+ }
+};
+
+static struct ipt_table nat_table = {
+ .name = "nat",
+ .valid_hooks = NAT_VALID_HOOKS,
+ .lock = RW_LOCK_UNLOCKED,
+ .me = THIS_MODULE,
+};
+
+/* Source NAT */
+static unsigned int ipt_snat_target(struct sk_buff **pskb,
+ const struct net_device *in,
+ const struct net_device *out,
+ unsigned int hooknum,
+ const void *targinfo,
+ void *userinfo)
+{
+ struct ip_conntrack *ct;
+ enum ip_conntrack_info ctinfo;
+ const struct ip_nat_multi_range_compat *mr = targinfo;
+
+ IP_NF_ASSERT(hooknum == NF_IP_POST_ROUTING);
+
+ ct = ip_conntrack_get(*pskb, &ctinfo);
+
+ /* Connection must be valid and new. */
+ IP_NF_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED
+ || ctinfo == IP_CT_RELATED + IP_CT_IS_REPLY));
+ IP_NF_ASSERT(out);
+
+ return ip_nat_setup_info(ct, &mr->range[0], hooknum);
+}
+
+/* Before 2.6.11 we did implicit source NAT if required. Warn about change. */
+static void warn_if_extra_mangle(u32 dstip, u32 srcip)
+{
+ static int warned = 0;
+ struct flowi fl = { .nl_u = { .ip4_u = { .daddr = dstip } } };
+ struct rtable *rt;
+
+ if (ip_route_output_key(&rt, &fl) != 0)
+ return;
+
+ if (rt->rt_src != srcip && !warned) {
+ printk("NAT: no longer support implicit source local NAT\n");
+ printk("NAT: packet src %u.%u.%u.%u -> dst %u.%u.%u.%u\n",
+ NIPQUAD(srcip), NIPQUAD(dstip));
+ warned = 1;
+ }
+ ip_rt_put(rt);
+}
+
+static unsigned int ipt_dnat_target(struct sk_buff **pskb,
+ const struct net_device *in,
+ const struct net_device *out,
+ unsigned int hooknum,
+ const void *targinfo,
+ void *userinfo)
+{
+ struct ip_conntrack *ct;
+ enum ip_conntrack_info ctinfo;
+ const struct ip_nat_multi_range_compat *mr = targinfo;
+
+ IP_NF_ASSERT(hooknum == NF_IP_PRE_ROUTING
+ || hooknum == NF_IP_LOCAL_OUT);
+
+ ct = ip_conntrack_get(*pskb, &ctinfo);
+
+ /* Connection must be valid and new. */
+ IP_NF_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));
+
+ if (hooknum == NF_IP_LOCAL_OUT
+ && mr->range[0].flags & IP_NAT_RANGE_MAP_IPS)
+ warn_if_extra_mangle((*pskb)->nh.iph->daddr,
+ mr->range[0].min_ip);
+
+ return ip_nat_setup_info(ct, &mr->range[0], hooknum);
+}
+
+static int ipt_snat_checkentry(const char *tablename,
+ const struct ipt_entry *e,
+ void *targinfo,
+ unsigned int targinfosize,
+ unsigned int hook_mask)
+{
+ struct ip_nat_multi_range_compat *mr = targinfo;
+
+ /* Must be a valid range */
+ if (mr->rangesize != 1) {
+ printk("SNAT: multiple ranges no longer supported\n");
+ return 0;
+ }
+
+ if (targinfosize != IPT_ALIGN(sizeof(struct ip_nat_multi_range_compat))) {
+ DEBUGP("SNAT: Target size %u wrong for %u ranges\n",
+ targinfosize, mr->rangesize);
+ return 0;
+ }
+
+ /* Only allow these for NAT. */
+ if (strcmp(tablename, "nat") != 0) {
+ DEBUGP("SNAT: wrong table %s\n", tablename);
+ return 0;
+ }
+
+ if (hook_mask & ~(1 << NF_IP_POST_ROUTING)) {
+ DEBUGP("SNAT: hook mask 0x%x bad\n", hook_mask);
+ return 0;
+ }
+ return 1;
+}
+
+static int ipt_dnat_checkentry(const char *tablename,
+ const struct ipt_entry *e,
+ void *targinfo,
+ unsigned int targinfosize,
+ unsigned int hook_mask)
+{
+ struct ip_nat_multi_range_compat *mr = targinfo;
+
+ /* Must be a valid range */
+ if (mr->rangesize != 1) {
+ printk("DNAT: multiple ranges no longer supported\n");
+ return 0;
+ }
+
+ if (targinfosize != IPT_ALIGN(sizeof(struct ip_nat_multi_range_compat))) {
+ DEBUGP("DNAT: Target size %u wrong for %u ranges\n",
+ targinfosize, mr->rangesize);
+ return 0;
+ }
+
+ /* Only allow these for NAT. */
+ if (strcmp(tablename, "nat") != 0) {
+ DEBUGP("DNAT: wrong table %s\n", tablename);
+ return 0;
+ }
+
+ if (hook_mask & ~((1 << NF_IP_PRE_ROUTING) | (1 << NF_IP_LOCAL_OUT))) {
+ DEBUGP("DNAT: hook mask 0x%x bad\n", hook_mask);
+ return 0;
+ }
+
+ return 1;
+}
+
+inline unsigned int
+alloc_null_binding(struct ip_conntrack *conntrack,
+ struct ip_nat_info *info,
+ unsigned int hooknum)
+{
+ /* Force range to this IP; let proto decide mapping for
+ per-proto parts (hence not IP_NAT_RANGE_PROTO_SPECIFIED).
+ Use reply in case it's already been mangled (eg local packet).
+ */
+ u_int32_t ip
+ = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
+ ? conntrack->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip
+ : conntrack->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip);
+ struct ip_nat_range range
+ = { IP_NAT_RANGE_MAP_IPS, ip, ip, { 0 }, { 0 } };
+
+ DEBUGP("Allocating NULL binding for %p (%u.%u.%u.%u)\n", conntrack,
+ NIPQUAD(ip));
+ return ip_nat_setup_info(conntrack, &range, hooknum);
+}
+
+int ip_nat_rule_find(struct sk_buff **pskb,
+ unsigned int hooknum,
+ const struct net_device *in,
+ const struct net_device *out,
+ struct ip_conntrack *ct,
+ struct ip_nat_info *info)
+{
+ int ret;
+
+ ret = ipt_do_table(pskb, hooknum, in, out, &nat_table, NULL);
+
+ if (ret == NF_ACCEPT) {
+ if (!ip_nat_initialized(ct, HOOK2MANIP(hooknum)))
+ /* NUL mapping */
+ ret = alloc_null_binding(ct, info, hooknum);
+ }
+ return ret;
+}
+
+static struct ipt_target ipt_snat_reg = {
+ .name = "SNAT",
+ .target = ipt_snat_target,
+ .checkentry = ipt_snat_checkentry,
+};
+
+static struct ipt_target ipt_dnat_reg = {
+ .name = "DNAT",
+ .target = ipt_dnat_target,
+ .checkentry = ipt_dnat_checkentry,
+};
+
+int __init ip_nat_rule_init(void)
+{
+ int ret;
+
+ ret = ipt_register_table(&nat_table, &nat_initial_table.repl);
+ if (ret != 0)
+ return ret;
+ ret = ipt_register_target(&ipt_snat_reg);
+ if (ret != 0)
+ goto unregister_table;
+
+ ret = ipt_register_target(&ipt_dnat_reg);
+ if (ret != 0)
+ goto unregister_snat;
+
+ return ret;
+
+ unregister_snat:
+ ipt_unregister_target(&ipt_snat_reg);
+ unregister_table:
+ ipt_unregister_table(&nat_table);
+
+ return ret;
+}
+
+void ip_nat_rule_cleanup(void)
+{
+ ipt_unregister_target(&ipt_dnat_reg);
+ ipt_unregister_target(&ipt_snat_reg);
+ ipt_unregister_table(&nat_table);
+}
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.