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xt_FULLCONENAT.c
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xt_FULLCONENAT.c
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/*
* Copyright (c) 2018 Chion Tang <[email protected]>
*
* 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/kernel.h>
#include <linux/module.h>
#include <linux/version.h>
#include <linux/types.h>
#include <linux/list.h>
#include <linux/hashtable.h>
#include <linux/netdevice.h>
#include <linux/inetdevice.h>
#include <linux/workqueue.h>
#ifdef CONFIG_NF_CONNTRACK_CHAIN_EVENTS
#include <linux/notifier.h>
#endif
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#if IS_ENABLED(CONFIG_NF_NAT_IPV6) || (IS_ENABLED(CONFIG_IPV6) && LINUX_VERSION_CODE >= KERNEL_VERSION(5, 1, 0))
#include <linux/netfilter_ipv6.h>
#include <linux/ipv6.h>
#include <net/addrconf.h>
#endif
#include <linux/netfilter/x_tables.h>
#include <net/netfilter/nf_nat.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_zones.h>
#include <net/netfilter/nf_conntrack_tuple.h>
#include <net/netfilter/nf_conntrack_core.h>
#include <net/netfilter/nf_conntrack_ecache.h>
#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 2, 0)
#include <net/netfilter/nf_nat_masquerade.h>
#elif LINUX_VERSION_CODE >= KERNEL_VERSION(3, 18, 0)
#include <net/netfilter/ipv4/nf_nat_masquerade.h>
#if IS_ENABLED(CONFIG_NF_NAT_MASQUERADE_IPV6)
#include <net/netfilter/ipv6/nf_nat_masquerade.h>
#endif
#endif
#define HASH_2(x, y) ((x + y) / 2 * (x + y + 1) + y)
#define HASHTABLE_BUCKET_BITS 10
#ifndef NF_NAT_RANGE_PROTO_RANDOM_FULLY
#define NF_NAT_RANGE_PROTO_RANDOM_FULLY (1 << 4)
#endif
#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 10, 0)
static inline int nf_ct_netns_get(struct net *net, u8 nfproto) { return 0; }
static inline void nf_ct_netns_put(struct net *net, u8 nfproto) {}
static inline struct net_device *xt_in(const struct xt_action_param *par) {
return (struct net_device *)par->in;
}
static inline struct net_device *xt_out(const struct xt_action_param *par) {
return (struct net_device *)par->out;
}
static inline unsigned int xt_hooknum(const struct xt_action_param *par) {
return par->hooknum;
}
#endif
struct nat_mapping_original_tuple {
struct nf_conntrack_tuple tuple;
struct list_head node;
};
struct nat_mapping {
uint16_t port; /* external source port */
__be32 addr; /* external source ip address */
__be32 int_addr; /* internal source ip address */
uint16_t int_port; /* internal source port */
int refer_count; /* how many references linked to this mapping
* aka. length of original_tuple_list */
struct list_head original_tuple_list;
struct hlist_node node_by_ext_port;
struct hlist_node node_by_int_src;
};
#if IS_ENABLED(CONFIG_NF_NAT_IPV6) || (IS_ENABLED(CONFIG_IPV6) && LINUX_VERSION_CODE >= KERNEL_VERSION(5, 1, 0))
struct nat_mapping6 {
uint16_t port; /* external source port */
union nf_inet_addr addr; /* external source ip address */
union nf_inet_addr int_addr; /* internal source ip address */
uint16_t int_port; /* internal source port */
int refer_count; /* how many references linked to this mapping
* aka. length of original_tuple_list */
struct list_head original_tuple_list;
struct hlist_node node_by_ext_port;
struct hlist_node node_by_int_src;
};
#endif
struct tuple_list {
struct nf_conntrack_tuple tuple_original;
struct nf_conntrack_tuple tuple_reply;
struct list_head list;
};
#ifdef CONFIG_NF_CONNTRACK_CHAIN_EVENTS
struct notifier_block ct_event_notifier;
#else
struct nf_ct_event_notifier ct_event_notifier;
#endif
int tg_refer_count = 0;
int ct_event_notifier_registered = 0;
static DEFINE_MUTEX(nf_ct_net_event_lock);
static DEFINE_HASHTABLE(mapping_table_by_ext_port, HASHTABLE_BUCKET_BITS);
static DEFINE_HASHTABLE(mapping_table_by_int_src, HASHTABLE_BUCKET_BITS);
static DEFINE_SPINLOCK(fullconenat_lock);
#if IS_ENABLED(CONFIG_NF_NAT_IPV6) || (IS_ENABLED(CONFIG_IPV6) && LINUX_VERSION_CODE >= KERNEL_VERSION(5, 1, 0))
static DEFINE_HASHTABLE(mapping6_table_by_ext_port, HASHTABLE_BUCKET_BITS);
static DEFINE_HASHTABLE(mapping6_table_by_int_src, HASHTABLE_BUCKET_BITS);
static DEFINE_SPINLOCK(fullconenat6_lock);
#endif
static LIST_HEAD(dying_tuple_list);
static DEFINE_SPINLOCK(dying_tuple_list_lock);
static void gc_worker(struct work_struct *work);
static struct workqueue_struct *wq __read_mostly = NULL;
static DECLARE_DELAYED_WORK(gc_worker_wk, gc_worker);
static char tuple_tmp_string[512];
#if IS_ENABLED(CONFIG_NF_NAT_IPV6) || (IS_ENABLED(CONFIG_IPV6) && LINUX_VERSION_CODE >= KERNEL_VERSION(5, 1, 0))
/* non-atomic: can only be called serially within lock zones. */
static char* nf_ct_stringify_tuple6(const struct nf_conntrack_tuple *t) {
snprintf(tuple_tmp_string, sizeof(tuple_tmp_string), "[%pI6c]:%hu -> [%pI6c]:%hu",
&t->src.u3.ip6, be16_to_cpu(t->src.u.all),
&t->dst.u3.ip6, be16_to_cpu(t->dst.u.all));
return tuple_tmp_string;
}
static struct nat_mapping6* allocate_mapping6(const union nf_inet_addr *int_addr, const uint16_t int_port, const uint16_t port, const union nf_inet_addr *addr) {
struct nat_mapping6 *p_new;
u32 hash_src;
p_new = kmalloc(sizeof(struct nat_mapping6), GFP_ATOMIC);
if (p_new == NULL) {
pr_debug("xt_FULLCONENAT: ERROR: kmalloc() for new nat_mapping failed.\n");
return NULL;
}
p_new->addr = *addr;
p_new->port = port;
p_new->int_addr = *int_addr;
p_new->int_port = int_port;
p_new->refer_count = 0;
(p_new->original_tuple_list).next = &(p_new->original_tuple_list);
(p_new->original_tuple_list).prev = &(p_new->original_tuple_list);
hash_src = jhash2((u32 *)int_addr->all, 4, (u32)int_port);
hash_add(mapping6_table_by_ext_port, &p_new->node_by_ext_port, port);
hash_add(mapping6_table_by_int_src, &p_new->node_by_int_src, hash_src);
pr_debug("xt_FULLCONENAT: new mapping allocated for [%pI6c]:%d ==> [%pI6c]:%d\n",
&p_new->int_addr, p_new->int_port, &p_new->addr, p_new->port);
return p_new;
}
static void add_original_tuple_to_mapping6(struct nat_mapping6 *mapping, const struct nf_conntrack_tuple* original_tuple) {
struct nat_mapping_original_tuple *item = kmalloc(sizeof(struct nat_mapping_original_tuple), GFP_ATOMIC);
if (item == NULL) {
pr_debug("xt_FULLCONENAT: ERROR: kmalloc() for nat_mapping_original_tuple failed.\n");
return;
}
memcpy(&item->tuple, original_tuple, sizeof(struct nf_conntrack_tuple));
list_add(&item->node, &mapping->original_tuple_list);
(mapping->refer_count)++;
}
static struct nat_mapping6* get_mapping6_by_int_src(const union nf_inet_addr *src_ip, const uint16_t src_port, const union nf_inet_addr *ext_ip) {
struct nat_mapping6 *p_current;
u32 hash_src = jhash2((u32 *)src_ip->all, 4, (u32)src_port);
hash_for_each_possible(mapping6_table_by_int_src, p_current, node_by_int_src, hash_src) {
if (nf_inet_addr_cmp(&p_current->int_addr, src_ip) && p_current->int_port == src_port && nf_inet_addr_cmp(&p_current->addr, ext_ip)) {
return p_current;
}
}
return NULL;
}
static struct nat_mapping6* get_mapping6_by_int_src_inrange(const union nf_inet_addr *src_ip, const uint16_t src_port, const union nf_inet_addr *min_ip, const union nf_inet_addr *max_ip) {
struct nat_mapping6 *p_current;
u32 hash_src = jhash2((u32 *)src_ip->all, 4, (u32)src_port);
hash_for_each_possible(mapping6_table_by_int_src, p_current, node_by_int_src, hash_src) {
if (nf_inet_addr_cmp(&p_current->int_addr, src_ip) && p_current->int_port == src_port && memcmp(&p_current->addr, min_ip, sizeof(union nf_inet_addr)) >= 0 && memcmp(&p_current->addr, max_ip, sizeof(union nf_inet_addr)) <= 0) {
return p_current;
}
}
return NULL;
}
static void kill_mapping6(struct nat_mapping6 *mapping) {
struct list_head *iter, *tmp;
struct nat_mapping_original_tuple *original_tuple_item;
if (mapping == NULL) {
return;
}
list_for_each_safe(iter, tmp, &mapping->original_tuple_list) {
original_tuple_item = list_entry(iter, struct nat_mapping_original_tuple, node);
list_del(&original_tuple_item->node);
kfree(original_tuple_item);
}
hash_del(&mapping->node_by_ext_port);
hash_del(&mapping->node_by_int_src);
kfree(mapping);
}
/* check if a mapping is valid.
* possibly delete and free an invalid mapping.
* the mapping should not be used anymore after check_mapping6() returns 0. */
#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 3, 0)
static int check_mapping6(struct nat_mapping6* mapping, struct net *net, const struct nf_conntrack_zone *zone) {
#else
static int check_mapping6(struct nat_mapping6* mapping, struct net *net, const u16 zone) {
#endif
struct list_head *iter, *tmp;
struct nat_mapping_original_tuple *original_tuple_item;
struct nf_conntrack_tuple_hash *tuple_hash;
struct nf_conn *ct;
/* for dying/unconfirmed conntrack tuples, an IPCT_DESTROY event may NOT be fired.
* so we manually kill one of those tuples once we acquire one. */
list_for_each_safe(iter, tmp, &mapping->original_tuple_list) {
original_tuple_item = list_entry(iter, struct nat_mapping_original_tuple, node);
tuple_hash = nf_conntrack_find_get(net, zone, &original_tuple_item->tuple);
if (tuple_hash == NULL) {
pr_debug("xt_FULLCONENAT: check_mapping6(): tuple %s dying/unconfirmed. free this tuple.\n", nf_ct_stringify_tuple6(&original_tuple_item->tuple));
list_del(&original_tuple_item->node);
kfree(original_tuple_item);
(mapping->refer_count)--;
} else {
ct = nf_ct_tuplehash_to_ctrack(tuple_hash);
if (likely(ct != NULL))
nf_ct_put(ct);
}
}
/* kill the mapping if need */
pr_debug("xt_FULLCONENAT: check_mapping6() refer_count for mapping at ext_port %d is now %d\n", mapping->port, mapping->refer_count);
if (mapping->refer_count <= 0) {
pr_debug("xt_FULLCONENAT: check_mapping6(): kill dying/unconfirmed mapping at ext port %d\n", mapping->port);
kill_mapping6(mapping);
return 0;
} else {
return 1;
}
}
#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 3, 0)
static struct nat_mapping6* get_mapping6_by_ext_port(const uint16_t port, const union nf_inet_addr *ext_ip, struct net *net, const struct nf_conntrack_zone *zone) {
#else
static struct nat_mapping6* get_mapping6_by_ext_port(const uint16_t port, const union nf_inet_addr *ext_ip, struct net *net, const u16 zone) {
#endif
struct nat_mapping6 *p_current;
struct hlist_node *tmp;
hash_for_each_possible_safe(mapping6_table_by_ext_port, p_current, tmp, node_by_ext_port, port) {
if (p_current->port == port && check_mapping6(p_current, net, zone) && nf_inet_addr_cmp(&p_current->addr, ext_ip)) {
return p_current;
}
}
return NULL;
}
#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 3, 0)
static uint16_t find_appropriate_port6(struct net *net, const struct nf_conntrack_zone *zone, const uint16_t original_port, const union nf_inet_addr *ext_ip, const struct nf_nat_range *range) {
#else
static uint16_t find_appropriate_port6(struct net *net, const u16 zone, const uint16_t original_port, const union nf_inet_addr *ext_ip, const struct nf_nat_range *range) {
#endif
uint16_t min, start, selected, range_size, i;
struct nat_mapping6* mapping = NULL;
if (range->flags & NF_NAT_RANGE_PROTO_SPECIFIED) {
min = be16_to_cpu((range->min_proto).udp.port);
range_size = be16_to_cpu((range->max_proto).udp.port) - min + 1;
} else {
/* minimum port is 1024. same behavior as default linux NAT. */
min = 1024;
range_size = 65535 - min + 1;
}
if ((range->flags & NF_NAT_RANGE_PROTO_RANDOM)
|| (range->flags & NF_NAT_RANGE_PROTO_RANDOM_FULLY)) {
/* for now we do the same thing for both --random and --random-fully */
/* select a random starting point */
#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 11, 0)
start = (uint16_t)(get_random_u32() % (u32)range_size);
#else
start = (uint16_t)(prandom_u32() % (u32)range_size);
#endif
} else {
if ((original_port >= min && original_port <= min + range_size - 1)
|| !(range->flags & NF_NAT_RANGE_PROTO_SPECIFIED)) {
/* 1. try to preserve the port if it's available */
mapping = get_mapping6_by_ext_port(original_port, ext_ip, net, zone);
if (mapping == NULL) {
return original_port;
}
}
/* otherwise, we start from zero */
start = 0;
}
for (i = 0; i < range_size; i++) {
/* 2. try to find an available port */
selected = min + ((start + i) % range_size);
mapping = get_mapping6_by_ext_port(selected, ext_ip, net, zone);
if (mapping == NULL) {
return selected;
}
}
/* 3. at least we tried. override a previous mapping. */
selected = min + start;
mapping = get_mapping6_by_ext_port(selected, ext_ip, net, zone);
kill_mapping6(mapping);
return selected;
}
#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 3, 0)
static void find_leastused_ip6(const struct nf_conntrack_zone *zone, const struct nf_nat_range *range, const union nf_inet_addr *src, const union nf_inet_addr *dst, union nf_inet_addr *var_ipp)
#else
static void find_leastused_ip6(const u16 zone, const struct nf_nat_range *range, const union nf_inet_addr *src, const union nf_inet_addr *dst, union nf_inet_addr *var_ipp)
#endif
{
unsigned int i;
/* Host order */
u32 minip, maxip, j, dist;
bool full_range;
#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 3, 0)
j = jhash2((u32 *)src, 4, range->flags & NF_NAT_RANGE_PERSISTENT ? 0 : dst->all[3] ^ zone->id);
#else
j = jhash2((u32 *)src, 4, range->flags & NF_NAT_RANGE_PERSISTENT ? 0 : dst->all[3] ^ zone);
#endif
full_range = false;
for (i = 0; i <= 3; i++) {
/* If first bytes of the address are at the maximum, use the
* distance. Otherwise use the full range. */
if (!full_range) {
minip = ntohl(range->min_addr.all[i]);
maxip = ntohl(range->max_addr.all[i]);
dist = maxip - minip + 1;
} else {
minip = 0;
dist = ~0;
}
var_ipp->all[i] = (__force __be32) htonl(minip + reciprocal_scale(j, dist));
if (var_ipp->all[i] != range->max_addr.all[i])
full_range = true;
if (!(range->flags & NF_NAT_RANGE_PERSISTENT))
j ^= (__force u32)dst->all[i];
}
}
static unsigned int fullconenat_tg6(struct sk_buff *skb, const struct xt_action_param *par)
{
const struct nf_nat_range *range;
#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 3, 0)
const struct nf_conntrack_zone *zone;
#else
u16 zone;
#endif
struct net *net;
struct nf_conn *ct;
enum ip_conntrack_info ctinfo;
struct nf_conn_nat *nat;
struct nf_conntrack_tuple *ct_tuple, *ct_tuple_origin;
struct nat_mapping6 *mapping, *src_mapping;
unsigned int ret;
#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 18, 0)
struct nf_nat_range2 newrange;
#else
struct nf_nat_range newrange;
#endif
union nf_inet_addr *ip;
uint16_t port, original_port, want_port;
uint8_t protonum;
ip = NULL;
original_port = 0;
src_mapping = NULL;
range = par->targinfo;
mapping = NULL;
ret = XT_CONTINUE;
ct = nf_ct_get(skb, &ctinfo);
net = nf_ct_net(ct);
zone = nf_ct_zone(ct);
newrange.flags = range->flags | NF_NAT_RANGE_MAP_IPS;
newrange.min_proto = range->min_proto;
newrange.max_proto = range->max_proto;
if (xt_hooknum(par) == NF_INET_PRE_ROUTING) {
/* inbound packets */
ct_tuple_origin = &(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
protonum = (ct_tuple_origin->dst).protonum;
if (protonum != IPPROTO_UDP) {
return ret;
}
ip = &(ct_tuple_origin->dst).u3;
port = be16_to_cpu((ct_tuple_origin->dst).u.udp.port);
spin_lock_bh(&fullconenat6_lock);
/* find an active mapping based on the inbound port */
mapping = get_mapping6_by_ext_port(port, ip, net, zone);
if (mapping != NULL) {
newrange.flags = NF_NAT_RANGE_MAP_IPS | NF_NAT_RANGE_PROTO_SPECIFIED;
newrange.min_addr = mapping->int_addr;
newrange.max_addr = mapping->int_addr;
newrange.min_proto.udp.port = cpu_to_be16(mapping->int_port);
newrange.max_proto = newrange.min_proto;
pr_debug("xt_FULLCONENAT: <INBOUND DNAT> %s ==> [%pI6c]:%d\n", nf_ct_stringify_tuple6(ct_tuple_origin), &mapping->int_addr, mapping->int_port);
ret = nf_nat_setup_info(ct, &newrange, HOOK2MANIP(xt_hooknum(par)));
if (ret == NF_ACCEPT) {
add_original_tuple_to_mapping6(mapping, ct_tuple_origin);
pr_debug("xt_FULLCONENAT: fullconenat_tg6(): INBOUND: refer_count for mapping at ext_port %d is now %d\n", mapping->port, mapping->refer_count);
}
}
spin_unlock_bh(&fullconenat6_lock);
return ret;
} else if (xt_hooknum(par) == NF_INET_POST_ROUTING) {
/* outbound packets */
ct_tuple_origin = &(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
protonum = (ct_tuple_origin->dst).protonum;
if(range->flags & NF_NAT_RANGE_MAP_IPS) {
newrange.min_addr = range->min_addr;
newrange.max_addr = range->max_addr;
} else {
if (unlikely(ipv6_dev_get_saddr(nf_ct_net(ct), xt_out(par), &ipv6_hdr(skb)->daddr, 0, (struct in6_addr*)&newrange.min_addr) < 0))
return NF_DROP;
newrange.max_addr = newrange.min_addr;
#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 16, 0)
nat = nf_ct_nat_ext_add(ct);
#else
nat = nfct_nat(ct);
#endif
if (likely(nat))
nat->masq_index = xt_out(par)->ifindex;
}
if (protonum == IPPROTO_UDP) {
ip = &(ct_tuple_origin->src).u3;
original_port = be16_to_cpu((ct_tuple_origin->src).u.udp.port);
spin_lock_bh(&fullconenat6_lock);
if (!nf_inet_addr_cmp(&newrange.min_addr, &newrange.max_addr))
src_mapping = get_mapping6_by_int_src_inrange(ip, original_port, &newrange.min_addr, &newrange.max_addr);
else
src_mapping = get_mapping6_by_int_src(ip, original_port, &newrange.min_addr);
if (src_mapping != NULL && check_mapping6(src_mapping, net, zone)) {
/* outbound nat: if a previously established mapping is active,
* we will reuse that mapping. */
newrange.flags = NF_NAT_RANGE_MAP_IPS | NF_NAT_RANGE_PROTO_SPECIFIED;
newrange.min_proto.udp.port = cpu_to_be16(src_mapping->port);
newrange.max_proto = newrange.min_proto;
if (!nf_inet_addr_cmp(&newrange.min_addr, &newrange.max_addr)) {
newrange.min_addr = src_mapping->addr;
newrange.max_addr = newrange.min_addr;
}
} else {
/* if not, we find a new external IP:port to map to.
* the SNAT may fail so we should re-check the mapped port later. */
if (!nf_inet_addr_cmp(&newrange.min_addr, &newrange.max_addr)) {
find_leastused_ip6(zone, range, ip, &(ct_tuple_origin->dst).u3, &newrange.min_addr);
newrange.max_addr = newrange.min_addr;
}
want_port = find_appropriate_port6(net, zone, original_port, &newrange.min_addr, range);
newrange.flags = NF_NAT_RANGE_MAP_IPS | NF_NAT_RANGE_PROTO_SPECIFIED;
newrange.min_proto.udp.port = cpu_to_be16(want_port);
newrange.max_proto = newrange.min_proto;
src_mapping = NULL;
}
}
/* do SNAT now */
ret = nf_nat_setup_info(ct, &newrange, HOOK2MANIP(xt_hooknum(par)));
if (protonum != IPPROTO_UDP) {
/* non-UDP packets, bailout */
return ret;
}
if (ret != NF_ACCEPT) {
/* failed SNAT, bailout */
spin_unlock_bh(&fullconenat6_lock);
return ret;
}
/* the reply tuple contains the mapped port. */
ct_tuple = &(ct->tuplehash[IP_CT_DIR_REPLY].tuple);
/* this is the resulted mapped port. */
port = be16_to_cpu((ct_tuple->dst).u.udp.port);
pr_debug("xt_FULLCONENAT: <OUTBOUND SNAT> %s ==> %d\n", nf_ct_stringify_tuple6(ct_tuple_origin), port);
/* save the mapping information into our mapping table */
mapping = src_mapping;
if (mapping == NULL) {
mapping = allocate_mapping6(ip, original_port, port, &(ct_tuple->dst).u3);
}
if (likely(mapping != NULL)) {
add_original_tuple_to_mapping6(mapping, ct_tuple_origin);
pr_debug("xt_FULLCONENAT: fullconenat_tg6(): OUTBOUND: refer_count for mapping at ext_port %d is now %d\n", mapping->port, mapping->refer_count);
}
spin_unlock_bh(&fullconenat6_lock);
return ret;
}
return ret;
}
#endif
/* non-atomic: can only be called serially within lock zones. */
static char* nf_ct_stringify_tuple(const struct nf_conntrack_tuple *t) {
snprintf(tuple_tmp_string, sizeof(tuple_tmp_string), "%pI4:%hu -> %pI4:%hu",
&t->src.u3.ip, be16_to_cpu(t->src.u.all),
&t->dst.u3.ip, be16_to_cpu(t->dst.u.all));
return tuple_tmp_string;
}
static struct nat_mapping* allocate_mapping(const __be32 int_addr, const uint16_t int_port, const uint16_t port, const __be32 addr) {
struct nat_mapping *p_new;
u32 hash_src;
p_new = kmalloc(sizeof(struct nat_mapping), GFP_ATOMIC);
if (p_new == NULL) {
pr_debug("xt_FULLCONENAT: ERROR: kmalloc() for new nat_mapping failed.\n");
return NULL;
}
p_new->addr = addr;
p_new->port = port;
p_new->int_addr = int_addr;
p_new->int_port = int_port;
p_new->refer_count = 0;
(p_new->original_tuple_list).next = &(p_new->original_tuple_list);
(p_new->original_tuple_list).prev = &(p_new->original_tuple_list);
hash_src = HASH_2(int_addr, (u32)int_port);
hash_add(mapping_table_by_ext_port, &p_new->node_by_ext_port, port);
hash_add(mapping_table_by_int_src, &p_new->node_by_int_src, hash_src);
pr_debug("xt_FULLCONENAT: new mapping allocated for %pI4:%d ==> %pI4:%d\n",
&p_new->int_addr, p_new->int_port, &p_new->addr, p_new->port);
return p_new;
}
static void add_original_tuple_to_mapping(struct nat_mapping *mapping, const struct nf_conntrack_tuple* original_tuple) {
struct nat_mapping_original_tuple *item = kmalloc(sizeof(struct nat_mapping_original_tuple), GFP_ATOMIC);
if (item == NULL) {
pr_debug("xt_FULLCONENAT: ERROR: kmalloc() for nat_mapping_original_tuple failed.\n");
return;
}
memcpy(&item->tuple, original_tuple, sizeof(struct nf_conntrack_tuple));
list_add(&item->node, &mapping->original_tuple_list);
(mapping->refer_count)++;
}
static struct nat_mapping* get_mapping_by_int_src(const __be32 src_ip, const uint16_t src_port, const __be32 ext_ip) {
struct nat_mapping *p_current;
u32 hash_src = HASH_2(src_ip, (u32)src_port);
hash_for_each_possible(mapping_table_by_int_src, p_current, node_by_int_src, hash_src) {
if (p_current->int_addr == src_ip && p_current->int_port == src_port && p_current->addr == ext_ip) {
return p_current;
}
}
return NULL;
}
static struct nat_mapping* get_mapping_by_int_src_inrange(const __be32 src_ip, const uint16_t src_port, const __be32 min_ip, const __be32 max_ip) {
struct nat_mapping *p_current;
u32 hash_src = HASH_2(src_ip, (u32)src_port);
hash_for_each_possible(mapping_table_by_int_src, p_current, node_by_int_src, hash_src) {
if (p_current->int_addr == src_ip && p_current->int_port == src_port && memcmp(&p_current->addr, &min_ip, sizeof(__be32)) >=0 && memcmp(&p_current->addr, &max_ip, sizeof(__be32)) <= 0) {
return p_current;
}
}
return NULL;
}
static void kill_mapping(struct nat_mapping *mapping) {
struct list_head *iter, *tmp;
struct nat_mapping_original_tuple *original_tuple_item;
if (mapping == NULL) {
return;
}
list_for_each_safe(iter, tmp, &mapping->original_tuple_list) {
original_tuple_item = list_entry(iter, struct nat_mapping_original_tuple, node);
list_del(&original_tuple_item->node);
kfree(original_tuple_item);
}
hash_del(&mapping->node_by_ext_port);
hash_del(&mapping->node_by_int_src);
kfree(mapping);
}
static void destroy_mappings(void) {
struct nat_mapping *p_current;
#if IS_ENABLED(CONFIG_NF_NAT_IPV6) || (IS_ENABLED(CONFIG_IPV6) && LINUX_VERSION_CODE >= KERNEL_VERSION(5, 1, 0))
struct nat_mapping6 *p6_current;
#endif
struct hlist_node *tmp;
int i;
spin_lock_bh(&fullconenat_lock);
hash_for_each_safe(mapping_table_by_ext_port, i, tmp, p_current, node_by_ext_port) {
kill_mapping(p_current);
}
spin_unlock_bh(&fullconenat_lock);
#if IS_ENABLED(CONFIG_NF_NAT_IPV6) || (IS_ENABLED(CONFIG_IPV6) && LINUX_VERSION_CODE >= KERNEL_VERSION(5, 1, 0))
spin_lock_bh(&fullconenat6_lock);
hash_for_each_safe(mapping6_table_by_ext_port, i, tmp, p6_current, node_by_ext_port) {
kill_mapping6(p6_current);
}
spin_unlock_bh(&fullconenat6_lock);
#endif
}
/* check if a mapping is valid.
* possibly delete and free an invalid mapping.
* the mapping should not be used anymore after check_mapping() returns 0. */
#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 3, 0)
static int check_mapping(struct nat_mapping* mapping, struct net *net, const struct nf_conntrack_zone *zone) {
#else
static int check_mapping(struct nat_mapping* mapping, struct net *net, const u16 zone) {
#endif
struct list_head *iter, *tmp;
struct nat_mapping_original_tuple *original_tuple_item;
struct nf_conntrack_tuple_hash *tuple_hash;
struct nf_conn *ct;
/* for dying/unconfirmed conntrack tuples, an IPCT_DESTROY event may NOT be fired.
* so we manually kill one of those tuples once we acquire one. */
list_for_each_safe(iter, tmp, &mapping->original_tuple_list) {
original_tuple_item = list_entry(iter, struct nat_mapping_original_tuple, node);
tuple_hash = nf_conntrack_find_get(net, zone, &original_tuple_item->tuple);
if (tuple_hash == NULL) {
pr_debug("xt_FULLCONENAT: check_mapping(): tuple %s dying/unconfirmed. free this tuple.\n", nf_ct_stringify_tuple(&original_tuple_item->tuple));
list_del(&original_tuple_item->node);
kfree(original_tuple_item);
(mapping->refer_count)--;
} else {
ct = nf_ct_tuplehash_to_ctrack(tuple_hash);
if (likely(ct != NULL))
nf_ct_put(ct);
}
}
/* kill the mapping if need */
pr_debug("xt_FULLCONENAT: check_mapping() refer_count for mapping at ext_port %d is now %d\n", mapping->port, mapping->refer_count);
if (mapping->refer_count <= 0) {
pr_debug("xt_FULLCONENAT: check_mapping(): kill dying/unconfirmed mapping at ext port %d\n", mapping->port);
kill_mapping(mapping);
return 0;
} else {
return 1;
}
}
#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 3, 0)
static struct nat_mapping* get_mapping_by_ext_port(const uint16_t port, const __be32 ext_ip, struct net *net, const struct nf_conntrack_zone *zone) {
#else
static struct nat_mapping* get_mapping_by_ext_port(const uint16_t port, const __be32 ext_ip, struct net *net, const u16 zone) {
#endif
struct nat_mapping *p_current;
struct hlist_node *tmp;
hash_for_each_possible_safe(mapping_table_by_ext_port, p_current, tmp, node_by_ext_port, port) {
if (p_current->port == port && check_mapping(p_current, net, zone) && p_current->addr == ext_ip) {
return p_current;
}
}
return NULL;
}
static void handle_dying_tuples(void) {
struct list_head *iter, *tmp, *iter_2, *tmp_2;
struct tuple_list *item;
struct nf_conntrack_tuple *ct_tuple;
struct nat_mapping *mapping;
__be32 ip, ext_ip;
uint16_t port;
struct nat_mapping_original_tuple *original_tuple_item;
#if IS_ENABLED(CONFIG_NF_NAT_IPV6) || (IS_ENABLED(CONFIG_IPV6) && LINUX_VERSION_CODE >= KERNEL_VERSION(5, 1, 0))
struct nat_mapping6 *mapping6;
union nf_inet_addr *ip6, *ext_ip6;
spin_lock_bh(&fullconenat6_lock);
#endif
spin_lock_bh(&fullconenat_lock);
spin_lock_bh(&dying_tuple_list_lock);
list_for_each_safe(iter, tmp, &dying_tuple_list) {
item = list_entry(iter, struct tuple_list, list);
/* we dont know the conntrack direction for now so we try in both ways. */
ct_tuple = &(item->tuple_original);
#if IS_ENABLED(CONFIG_NF_NAT_IPV6) || (IS_ENABLED(CONFIG_IPV6) && LINUX_VERSION_CODE >= KERNEL_VERSION(5, 1, 0))
if (ct_tuple->src.l3num == PF_INET6) {
ip6 = &(ct_tuple->src).u3;
port = be16_to_cpu((ct_tuple->src).u.udp.port);
ext_ip6 = &item->tuple_reply.dst.u3;
mapping6 = get_mapping6_by_int_src(ip6, port, ext_ip6);
if (mapping6 == NULL) {
ext_ip6 = &(ct_tuple->dst).u3;
ct_tuple = &(item->tuple_reply);
ip6 = &(ct_tuple->src).u3;
port = be16_to_cpu((ct_tuple->src).u.udp.port);
mapping6 = get_mapping6_by_int_src(ip6, port, ext_ip6);
if (mapping6 != NULL) {
pr_debug("xt_FULLCONENAT: handle_dying_tuples(): INBOUND dying conntrack at ext port %d\n", mapping6->port);
}
} else {
pr_debug("xt_FULLCONENAT: handle_dying_tuples(): OUTBOUND dying conntrack at ext port %d\n", mapping6->port);
}
if (mapping6 == NULL) {
goto next;
}
/* look for the corresponding out-dated tuple and free it */
list_for_each_safe(iter_2, tmp_2, &mapping6->original_tuple_list) {
original_tuple_item = list_entry(iter_2, struct nat_mapping_original_tuple, node);
if (nf_ct_tuple_equal(&original_tuple_item->tuple, &(item->tuple_original))) {
pr_debug("xt_FULLCONENAT: handle_dying_tuples(): tuple %s expired. free this tuple.\n",
nf_ct_stringify_tuple6(&original_tuple_item->tuple));
list_del(&original_tuple_item->node);
kfree(original_tuple_item);
(mapping6->refer_count)--;
}
}
/* then kill the mapping if needed*/
pr_debug("xt_FULLCONENAT: handle_dying_tuples(): refer_count for mapping at ext_port %d is now %d\n", mapping6->port, mapping6->refer_count);
if (mapping6->refer_count <= 0) {
pr_debug("xt_FULLCONENAT: handle_dying_tuples(): kill expired mapping at ext port %d\n", mapping6->port);
kill_mapping6(mapping6);
}
goto next;
}
if (unlikely(ct_tuple->src.l3num != PF_INET))
#else
if (ct_tuple->src.l3num != PF_INET)
#endif
goto next;
ip = (ct_tuple->src).u3.ip;
port = be16_to_cpu((ct_tuple->src).u.udp.port);
ext_ip = item->tuple_reply.dst.u3.ip;
mapping = get_mapping_by_int_src(ip, port, ext_ip);
if (mapping == NULL) {
ext_ip = (ct_tuple->dst).u3.ip;
ct_tuple = &(item->tuple_reply);
ip = (ct_tuple->src).u3.ip;
port = be16_to_cpu((ct_tuple->src).u.udp.port);
mapping = get_mapping_by_int_src(ip, port, ext_ip);
if (mapping != NULL) {
pr_debug("xt_FULLCONENAT: handle_dying_tuples(): INBOUND dying conntrack at ext port %d\n", mapping->port);
}
} else {
pr_debug("xt_FULLCONENAT: handle_dying_tuples(): OUTBOUND dying conntrack at ext port %d\n", mapping->port);
}
if (mapping == NULL) {
goto next;
}
/* look for the corresponding out-dated tuple and free it */
list_for_each_safe(iter_2, tmp_2, &mapping->original_tuple_list) {
original_tuple_item = list_entry(iter_2, struct nat_mapping_original_tuple, node);
if (nf_ct_tuple_equal(&original_tuple_item->tuple, &(item->tuple_original))) {
pr_debug("xt_FULLCONENAT: handle_dying_tuples(): tuple %s expired. free this tuple.\n",
nf_ct_stringify_tuple(&original_tuple_item->tuple));
list_del(&original_tuple_item->node);
kfree(original_tuple_item);
(mapping->refer_count)--;
}
}
/* then kill the mapping if needed*/
pr_debug("xt_FULLCONENAT: handle_dying_tuples(): refer_count for mapping at ext_port %d is now %d\n", mapping->port, mapping->refer_count);
if (mapping->refer_count <= 0) {
pr_debug("xt_FULLCONENAT: handle_dying_tuples(): kill expired mapping at ext port %d\n", mapping->port);
kill_mapping(mapping);
}
next:
list_del(&item->list);
kfree(item);
}
spin_unlock_bh(&dying_tuple_list_lock);
spin_unlock_bh(&fullconenat_lock);
#if IS_ENABLED(CONFIG_NF_NAT_IPV6) || (IS_ENABLED(CONFIG_IPV6) && LINUX_VERSION_CODE >= KERNEL_VERSION(5, 1, 0))
spin_unlock_bh(&fullconenat6_lock);
#endif
}
static void gc_worker(struct work_struct *work) {
handle_dying_tuples();
}
/* conntrack destroy event callback function */
#ifdef CONFIG_NF_CONNTRACK_CHAIN_EVENTS
static int ct_event_cb(struct notifier_block *this, unsigned long events, void *ptr) {
struct nf_ct_event *item = ptr;
#elif LINUX_VERSION_CODE >= KERNEL_VERSION(5, 15, 0)
static int ct_event_cb(unsigned int events, const struct nf_ct_event *item) {
#else
static int ct_event_cb(unsigned int events, struct nf_ct_event *item) {
#endif
struct nf_conn *ct;
struct nf_conntrack_tuple *ct_tuple_reply, *ct_tuple_original;
uint8_t protonum;
struct tuple_list *dying_tuple_item;
ct = item->ct;
/* we handle only conntrack destroy events */
if (ct == NULL || !(events & (1 << IPCT_DESTROY))) {
return 0;
}
ct_tuple_original = &(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
ct_tuple_reply = &(ct->tuplehash[IP_CT_DIR_REPLY].tuple);
protonum = (ct_tuple_original->dst).protonum;
if (protonum != IPPROTO_UDP) {
return 0;
}
dying_tuple_item = kmalloc(sizeof(struct tuple_list), GFP_ATOMIC);
if (dying_tuple_item == NULL) {
pr_debug("xt_FULLCONENAT: warning: ct_event_cb(): kmalloc failed.\n");
return 0;
}
memcpy(&(dying_tuple_item->tuple_original), ct_tuple_original, sizeof(struct nf_conntrack_tuple));
memcpy(&(dying_tuple_item->tuple_reply), ct_tuple_reply, sizeof(struct nf_conntrack_tuple));
spin_lock_bh(&dying_tuple_list_lock);
list_add(&(dying_tuple_item->list), &dying_tuple_list);
spin_unlock_bh(&dying_tuple_list_lock);
if (wq != NULL)
queue_delayed_work(wq, &gc_worker_wk, msecs_to_jiffies(100));
return 0;
}
#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 15, 0) && !defined(CONFIG_NF_CONNTRACK_CHAIN_EVENTS)
static int exp_event_cb(unsigned int events, const struct nf_exp_event *item) {
return 0;
}
#endif
static __be32 get_device_ip(const struct net_device* dev) {
struct in_device* in_dev;
struct in_ifaddr* if_info;
__be32 result;
if (dev == NULL) {
return 0;
}
rcu_read_lock();
in_dev = dev->ip_ptr;
if (in_dev == NULL) {
rcu_read_unlock();
return 0;
}
if_info = in_dev->ifa_list;
if (if_info) {
result = if_info->ifa_local;
rcu_read_unlock();
return result;
} else {
rcu_read_unlock();
return 0;
}
}
#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 3, 0)
static uint16_t find_appropriate_port(struct net *net, const struct nf_conntrack_zone *zone, const uint16_t original_port, const __be32 ext_ip, const struct nf_nat_ipv4_range *range) {
#else
static uint16_t find_appropriate_port(struct net *net, const u16 zone, const uint16_t original_port, const __be32 ext_ip, const struct nf_nat_ipv4_range *range) {
#endif
uint16_t min, start, selected, range_size, i;
struct nat_mapping* mapping = NULL;
if (range->flags & NF_NAT_RANGE_PROTO_SPECIFIED) {
min = be16_to_cpu((range->min).udp.port);
range_size = be16_to_cpu((range->max).udp.port) - min + 1;
} else {
/* minimum port is 1024. same behavior as default linux NAT. */
min = 1024;
range_size = 65535 - min + 1;
}
if ((range->flags & NF_NAT_RANGE_PROTO_RANDOM)
|| (range->flags & NF_NAT_RANGE_PROTO_RANDOM_FULLY)) {
/* for now we do the same thing for both --random and --random-fully */