linux/net/netfilter/xt_TEE.c
<<
>>
Prefs
   1/*
   2 *      "TEE" target extension for Xtables
   3 *      Copyright © Sebastian Claßen, 2007
   4 *      Jan Engelhardt, 2007-2010
   5 *
   6 *      based on ipt_ROUTE.c from Cédric de Launois
   7 *      <delaunois@info.ucl.be>
   8 *
   9 *      This program is free software; you can redistribute it and/or
  10 *      modify it under the terms of the GNU General Public License
  11 *      version 2 or later, as published by the Free Software Foundation.
  12 */
  13#include <linux/ip.h>
  14#include <linux/module.h>
  15#include <linux/percpu.h>
  16#include <linux/route.h>
  17#include <linux/skbuff.h>
  18#include <linux/notifier.h>
  19#include <net/checksum.h>
  20#include <net/icmp.h>
  21#include <net/ip.h>
  22#include <net/ipv6.h>
  23#include <net/ip6_route.h>
  24#include <net/route.h>
  25#include <linux/netfilter/x_tables.h>
  26#include <linux/netfilter/xt_TEE.h>
  27
  28#if IS_ENABLED(CONFIG_NF_CONNTRACK)
  29#       define WITH_CONNTRACK 1
  30#       include <net/netfilter/nf_conntrack.h>
  31#endif
  32
  33struct xt_tee_priv {
  34        struct notifier_block   notifier;
  35        struct xt_tee_tginfo    *tginfo;
  36        int                     oif;
  37};
  38
  39static const union nf_inet_addr tee_zero_address;
  40static DEFINE_PER_CPU(bool, tee_active);
  41
  42static struct net *pick_net(struct sk_buff *skb)
  43{
  44#ifdef CONFIG_NET_NS
  45        const struct dst_entry *dst;
  46
  47        if (skb->dev != NULL)
  48                return dev_net(skb->dev);
  49        dst = skb_dst(skb);
  50        if (dst != NULL && dst->dev != NULL)
  51                return dev_net(dst->dev);
  52#endif
  53        return &init_net;
  54}
  55
  56static bool
  57tee_tg_route4(struct sk_buff *skb, const struct xt_tee_tginfo *info)
  58{
  59        const struct iphdr *iph = ip_hdr(skb);
  60        struct net *net = pick_net(skb);
  61        struct rtable *rt;
  62        struct flowi4 fl4;
  63
  64        memset(&fl4, 0, sizeof(fl4));
  65        if (info->priv) {
  66                if (info->priv->oif == -1)
  67                        return false;
  68                fl4.flowi4_oif = info->priv->oif;
  69        }
  70        fl4.daddr = info->gw.ip;
  71        fl4.flowi4_tos = RT_TOS(iph->tos);
  72        fl4.flowi4_scope = RT_SCOPE_UNIVERSE;
  73        rt = ip_route_output_key(net, &fl4);
  74        if (IS_ERR(rt))
  75                return false;
  76
  77        skb_dst_drop(skb);
  78        skb_dst_set(skb, &rt->dst);
  79        skb->dev      = rt->dst.dev;
  80        skb->protocol = htons(ETH_P_IP);
  81        return true;
  82}
  83
  84static unsigned int
  85tee_tg4(struct sk_buff *skb, const struct xt_action_param *par)
  86{
  87        const struct xt_tee_tginfo *info = par->targinfo;
  88        struct iphdr *iph;
  89
  90        if (__this_cpu_read(tee_active))
  91                return XT_CONTINUE;
  92        /*
  93         * Copy the skb, and route the copy. Will later return %XT_CONTINUE for
  94         * the original skb, which should continue on its way as if nothing has
  95         * happened. The copy should be independently delivered to the TEE
  96         * --gateway.
  97         */
  98        skb = pskb_copy(skb, GFP_ATOMIC);
  99        if (skb == NULL)
 100                return XT_CONTINUE;
 101
 102#ifdef WITH_CONNTRACK
 103        /* Avoid counting cloned packets towards the original connection. */
 104        nf_conntrack_put(skb->nfct);
 105        skb->nfct     = &nf_ct_untracked_get()->ct_general;
 106        skb->nfctinfo = IP_CT_NEW;
 107        nf_conntrack_get(skb->nfct);
 108#endif
 109        /*
 110         * If we are in PREROUTING/INPUT, the checksum must be recalculated
 111         * since the length could have changed as a result of defragmentation.
 112         *
 113         * We also decrease the TTL to mitigate potential TEE loops
 114         * between two hosts.
 115         *
 116         * Set %IP_DF so that the original source is notified of a potentially
 117         * decreased MTU on the clone route. IPv6 does this too.
 118         */
 119        iph = ip_hdr(skb);
 120        iph->frag_off |= htons(IP_DF);
 121        if (par->hooknum == NF_INET_PRE_ROUTING ||
 122            par->hooknum == NF_INET_LOCAL_IN)
 123                --iph->ttl;
 124        ip_send_check(iph);
 125
 126        if (tee_tg_route4(skb, info)) {
 127                __this_cpu_write(tee_active, true);
 128                ip_local_out(skb);
 129                __this_cpu_write(tee_active, false);
 130        } else {
 131                kfree_skb(skb);
 132        }
 133        return XT_CONTINUE;
 134}
 135
 136#if IS_ENABLED(CONFIG_IPV6)
 137static bool
 138tee_tg_route6(struct sk_buff *skb, const struct xt_tee_tginfo *info)
 139{
 140        const struct ipv6hdr *iph = ipv6_hdr(skb);
 141        struct net *net = pick_net(skb);
 142        struct dst_entry *dst;
 143        struct flowi6 fl6;
 144
 145        memset(&fl6, 0, sizeof(fl6));
 146        if (info->priv) {
 147                if (info->priv->oif == -1)
 148                        return false;
 149                fl6.flowi6_oif = info->priv->oif;
 150        }
 151        fl6.daddr = info->gw.in6;
 152        fl6.flowlabel = ((iph->flow_lbl[0] & 0xF) << 16) |
 153                           (iph->flow_lbl[1] << 8) | iph->flow_lbl[2];
 154        dst = ip6_route_output(net, NULL, &fl6);
 155        if (dst->error) {
 156                dst_release(dst);
 157                return false;
 158        }
 159        skb_dst_drop(skb);
 160        skb_dst_set(skb, dst);
 161        skb->dev      = dst->dev;
 162        skb->protocol = htons(ETH_P_IPV6);
 163        return true;
 164}
 165
 166static unsigned int
 167tee_tg6(struct sk_buff *skb, const struct xt_action_param *par)
 168{
 169        const struct xt_tee_tginfo *info = par->targinfo;
 170
 171        if (__this_cpu_read(tee_active))
 172                return XT_CONTINUE;
 173        skb = pskb_copy(skb, GFP_ATOMIC);
 174        if (skb == NULL)
 175                return XT_CONTINUE;
 176
 177#ifdef WITH_CONNTRACK
 178        nf_conntrack_put(skb->nfct);
 179        skb->nfct     = &nf_ct_untracked_get()->ct_general;
 180        skb->nfctinfo = IP_CT_NEW;
 181        nf_conntrack_get(skb->nfct);
 182#endif
 183        if (par->hooknum == NF_INET_PRE_ROUTING ||
 184            par->hooknum == NF_INET_LOCAL_IN) {
 185                struct ipv6hdr *iph = ipv6_hdr(skb);
 186                --iph->hop_limit;
 187        }
 188        if (tee_tg_route6(skb, info)) {
 189                __this_cpu_write(tee_active, true);
 190                ip6_local_out(skb);
 191                __this_cpu_write(tee_active, false);
 192        } else {
 193                kfree_skb(skb);
 194        }
 195        return XT_CONTINUE;
 196}
 197#endif
 198
 199static int tee_netdev_event(struct notifier_block *this, unsigned long event,
 200                            void *ptr)
 201{
 202        struct net_device *dev = ptr;
 203        struct xt_tee_priv *priv;
 204
 205        priv = container_of(this, struct xt_tee_priv, notifier);
 206        switch (event) {
 207        case NETDEV_REGISTER:
 208                if (!strcmp(dev->name, priv->tginfo->oif))
 209                        priv->oif = dev->ifindex;
 210                break;
 211        case NETDEV_UNREGISTER:
 212                if (dev->ifindex == priv->oif)
 213                        priv->oif = -1;
 214                break;
 215        case NETDEV_CHANGENAME:
 216                if (!strcmp(dev->name, priv->tginfo->oif))
 217                        priv->oif = dev->ifindex;
 218                else if (dev->ifindex == priv->oif)
 219                        priv->oif = -1;
 220                break;
 221        }
 222
 223        return NOTIFY_DONE;
 224}
 225
 226static int tee_tg_check(const struct xt_tgchk_param *par)
 227{
 228        struct xt_tee_tginfo *info = par->targinfo;
 229        struct xt_tee_priv *priv;
 230
 231        /* 0.0.0.0 and :: not allowed */
 232        if (memcmp(&info->gw, &tee_zero_address,
 233                   sizeof(tee_zero_address)) == 0)
 234                return -EINVAL;
 235
 236        if (info->oif[0]) {
 237                if (info->oif[sizeof(info->oif)-1] != '\0')
 238                        return -EINVAL;
 239
 240                priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 241                if (priv == NULL)
 242                        return -ENOMEM;
 243
 244                priv->tginfo  = info;
 245                priv->oif     = -1;
 246                priv->notifier.notifier_call = tee_netdev_event;
 247                info->priv    = priv;
 248
 249                register_netdevice_notifier(&priv->notifier);
 250        } else
 251                info->priv = NULL;
 252
 253        return 0;
 254}
 255
 256static void tee_tg_destroy(const struct xt_tgdtor_param *par)
 257{
 258        struct xt_tee_tginfo *info = par->targinfo;
 259
 260        if (info->priv) {
 261                unregister_netdevice_notifier(&info->priv->notifier);
 262                kfree(info->priv);
 263        }
 264}
 265
 266static struct xt_target tee_tg_reg[] __read_mostly = {
 267        {
 268                .name       = "TEE",
 269                .revision   = 1,
 270                .family     = NFPROTO_IPV4,
 271                .target     = tee_tg4,
 272                .targetsize = sizeof(struct xt_tee_tginfo),
 273                .checkentry = tee_tg_check,
 274                .destroy    = tee_tg_destroy,
 275                .me         = THIS_MODULE,
 276        },
 277#if IS_ENABLED(CONFIG_IPV6)
 278        {
 279                .name       = "TEE",
 280                .revision   = 1,
 281                .family     = NFPROTO_IPV6,
 282                .target     = tee_tg6,
 283                .targetsize = sizeof(struct xt_tee_tginfo),
 284                .checkentry = tee_tg_check,
 285                .destroy    = tee_tg_destroy,
 286                .me         = THIS_MODULE,
 287        },
 288#endif
 289};
 290
 291static int __init tee_tg_init(void)
 292{
 293        return xt_register_targets(tee_tg_reg, ARRAY_SIZE(tee_tg_reg));
 294}
 295
 296static void __exit tee_tg_exit(void)
 297{
 298        xt_unregister_targets(tee_tg_reg, ARRAY_SIZE(tee_tg_reg));
 299}
 300
 301module_init(tee_tg_init);
 302module_exit(tee_tg_exit);
 303MODULE_AUTHOR("Sebastian Claßen <sebastian.classen@freenet.ag>");
 304MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
 305MODULE_DESCRIPTION("Xtables: Reroute packet copy");
 306MODULE_LICENSE("GPL");
 307MODULE_ALIAS("ipt_TEE");
 308MODULE_ALIAS("ip6t_TEE");
 309
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.