/* NAT for netfilter; shared with compatibility layer. */ /* (C) 1999-2001 Paul `Rusty' Russell * (C) 2002-2006 Netfilter Core Team * * 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 #include #include #include #include #include #include #include #include /* For tcp_prot in getorigdst */ #include #include #include #include #include #include #include #include #include #include #include #include #include static DEFINE_SPINLOCK(nf_nat_lock); static struct nf_conntrack_l3proto *l3proto __read_mostly; #define MAX_IP_NAT_PROTO 256 static const struct nf_nat_protocol __rcu *nf_nat_protos[MAX_IP_NAT_PROTO] __read_mostly; static inline const struct nf_nat_protocol * __nf_nat_proto_find(u_int8_t protonum) { return rcu_dereference(nf_nat_protos[protonum]); } /* We keep an extra hash for each conntrack, for fast searching. */ static inline unsigned int hash_by_src(const struct net *net, u16 zone, const struct nf_conntrack_tuple *tuple) { unsigned int hash; /* Original src, to ensure we map it consistently if poss. */ hash = jhash_3words((__force u32)tuple->src.u3.ip, (__force u32)tuple->src.u.all ^ zone, tuple->dst.protonum, nf_conntrack_hash_rnd); return ((u64)hash * net->ipv4.nat_htable_size) >> 32; } /* Is this tuple already taken? (not by us) */ int nf_nat_used_tuple(const struct nf_conntrack_tuple *tuple, const struct nf_conn *ignored_conntrack) { /* Conntrack tracking doesn't keep track of outgoing tuples; only incoming ones. NAT means they don't have a fixed mapping, so we invert the tuple and look for the incoming reply. We could keep a separate hash if this proves too slow. */ struct nf_conntrack_tuple reply; nf_ct_invert_tuplepr(&reply, tuple); return nf_conntrack_tuple_taken(&reply, ignored_conntrack); } EXPORT_SYMBOL(nf_nat_used_tuple); /* If we source map this tuple so reply looks like reply_tuple, will * that meet the constraints of range. */ static int in_range(const struct nf_conntrack_tuple *tuple, const struct nf_nat_ipv4_range *range) { const struct nf_nat_protocol *proto; int ret = 0; /* If we are supposed to map IPs, then we must be in the range specified, otherwise let this drag us onto a new src IP. */ if (range->flags & NF_NAT_RANGE_MAP_IPS) { if (ntohl(tuple->src.u3.ip) < ntohl(range->min_ip) || ntohl(tuple->src.u3.ip) > ntohl(range->max_ip)) return 0; } rcu_read_lock(); proto = __nf_nat_proto_find(tuple->dst.protonum); if (!(range->flags & NF_NAT_RANGE_PROTO_SPECIFIED) || proto->in_range(tuple, NF_NAT_MANIP_SRC, &range->min, &range->max)) ret = 1; rcu_read_unlock(); return ret; } static inline int same_src(const struct nf_conn *ct, const struct nf_conntrack_tuple *tuple) { const struct nf_conntrack_tuple *t; t = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple; return (t->dst.protonum == tuple->dst.protonum && t->src.u3.ip == tuple->src.u3.ip && t->src.u.all == tuple->src.u.all); } /* Only called for SRC manip */ static int find_appropriate_src(struct net *net, u16 zone, const struct nf_conntrack_tuple *tuple, struct nf_conntrack_tuple *result, const struct nf_nat_ipv4_range *range) { unsigned int h = hash_by_src(net, zone, tuple); const struct nf_conn_nat *nat; const struct nf_conn *ct; const struct hlist_node *n; rcu_read_lock(); hlist_for_each_entry_rcu(nat, n, &net->ipv4.nat_bysource[h], bysource) { ct = nat->ct; if (same_src(ct, tuple) && nf_ct_zone(ct) == zone) { /* Copy source part from reply tuple. */ nf_ct_invert_tuplepr(result, &ct->tuplehash[IP_CT_DIR_REPLY].tuple); result->dst = tuple->dst; if (in_range(result, range)) { rcu_read_unlock(); return 1; } } } rcu_read_unlock(); return 0; } /* For [FUTURE] fragmentation handling, we want the least-used src-ip/dst-ip/proto triple. Fairness doesn't come into it. Thus if the range specifies 1.2.3.4 ports 10000-10005 and 1.2.3.5 ports 1-65535, we don't do pro-rata allocation based on ports; we choose the ip with the lowest src-ip/dst-ip/proto usage. */ static void find_best_ips_proto(u16 zone, struct nf_conntrack_tuple *tuple, const struct nf_nat_ipv4_range *range, const struct nf_conn *ct, enum nf_nat_manip_type maniptype) { __be32 *var_ipp; /* Host order */ u_int32_t minip, maxip, j; /* No IP mapping? Do nothing. */ if (!(range->flags & NF_NAT_RANGE_MAP_IPS)) return; if (maniptype == NF_NAT_MANIP_SRC) var_ipp = &tuple->src.u3.ip; else var_ipp = &tuple->dst.u3.ip; /* Fast path: only one choice. */ if (range->min_ip == range->max_ip) { *var_ipp = range->min_ip; return; } /* Hashing source and destination IPs gives a fairly even * spread in practice (if there are a small number of IPs * involved, there usually aren't that many connections * anyway). The consistency means that servers see the same * client coming from the same IP (some Internet Banking sites * like this), even across reboots. */ minip = ntohl(range->min_ip); maxip = ntohl(range->max_ip); j = jhash_2words((__force u32)tuple->src.u3.ip, range->flags & NF_NAT_RANGE_PERSISTENT ? 0 : (__force u32)tuple->dst.u3.ip ^ zone, 0); j = ((u64)j * (maxip - minip + 1)) >> 32; *var_ipp = htonl(minip + j); } /* Manipulate the tuple into the range given. For NF_INET_POST_ROUTING, * we change the source to map into the range. For NF_INET_PRE_ROUTING * and NF_INET_LOCAL_OUT, we change the destination to map into the * range. It might not be possible to get a unique tuple, but we try. * At worst (or if we race), we will end up with a final duplicate in * __ip_conntrack_confirm and drop the packet. */ static void get_unique_tuple(struct nf_conntrack_tuple *tuple, const struct nf_conntrack_tuple *orig_tuple, const struct nf_nat_ipv4_range *range, struct nf_conn *ct, enum nf_nat_manip_type maniptype) { struct net *net = nf_ct_net(ct); const struct nf_nat_protocol *proto; u16 zone = nf_ct_zone(ct); /* 1) If this srcip/proto/src-proto-part is currently mapped, and that same mapping gives a unique tuple within the given range, use that. This is only required for source (ie. NAT/masq) mappings. So far, we don't do local source mappings, so multiple manips not an issue. */ if (maniptype == NF_NAT_MANIP_SRC && !(range->flags & NF_NAT_RANGE_PROTO_RANDOM)) { /* try the original tuple first */ if (in_range(orig_tuple, range)) { if (!nf_nat_used_tuple(orig_tuple, ct)) { *tuple = *orig_tuple; return; } } else if (find_appropriate_src(net, zone, orig_tuple, tuple, range)) { pr_debug("get_unique_tuple: Found current src map\n"); if (!nf_nat_used_tuple(tuple, ct)) return; } } /* 2) Select the least-used IP/proto combination in the given range. */ *tuple = *orig_tuple; find_best_ips_proto(zone, tuple, range, ct, maniptype); /* 3) The per-protocol part of the manip is made to map into the range to make a unique tuple. */ rcu_read_lock(); proto = __nf_nat_proto_find(orig_tuple->dst.protonum); /* Only bother mapping if it's not already in range and unique */ if (!(range->flags & NF_NAT_RANGE_PROTO_RANDOM)) { if (range->flags & NF_NAT_RANGE_PROTO_SPECIFIED) { if (proto->in_range(tuple, maniptype, &range->min, &range->max) && (range->min.all == range->max.all || !nf_nat_used_tuple(tuple, ct))) goto out; } else if (!nf_nat_used_tuple(tuple, ct)) { goto out; } } /* Last change: get protocol to try to obtain unique tuple. */ proto->unique_tuple(tuple, range, maniptype, ct); out: rcu_read_unlock(); } unsigned int nf_nat_setup_info(struct nf_conn *ct, const struct nf_nat_ipv4_range *range, enum nf_nat_manip_type maniptype) { struct net *net = nf_ct_net(ct); struct nf_conntrack_tuple curr_tuple, new_tuple; struct nf_conn_nat *nat; /* nat helper or nfctnetlink also setup binding */ nat = nfct_nat(ct); if (!nat) { nat = nf_ct_ext_add(ct, NF_CT_EXT_NAT, GFP_ATOMIC); if (nat == NULL) { pr_debug("failed to add NAT extension\n"); return NF_ACCEPT; } } NF_CT_ASSERT(maniptype == NF_NAT_MANIP_SRC || maniptype == NF_NAT_MANIP_DST); BUG_ON(nf_nat_initialized(ct, maniptype)); /* What we've got will look like inverse of reply. Normally this is what is in the conntrack, except for prior manipulations (future optimization: if num_manips == 0, orig_tp = conntrack->tuplehash[IP_CT_DIR_ORIGINAL].tuple) */ nf_ct_invert_tuplepr(&curr_tuple, &ct->tuplehash[IP_CT_DIR_REPLY].tuple); get_unique_tuple(&new_tuple, &curr_tuple, range, ct, maniptype); if (!nf_ct_tuple_equal(&new_tuple, &curr_tuple)) { struct nf_conntrack_tuple reply; /* Alter conntrack table so will recognize replies. */ nf_ct_invert_tuplepr(&reply, &new_tuple); nf_conntrack_alter_reply(ct, &reply); /* Non-atomic: we own this at the moment. */ if (maniptype == NF_NAT_MANIP_SRC) ct->status |= IPS_SRC_NAT; else ct->status |= IPS_DST_NAT; } if (maniptype == NF_NAT_MANIP_SRC) { unsigned int srchash; srchash = hash_by_src(net, nf_ct_zone(ct), &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple); spin_lock_bh(&nf_nat_lock); /* nf_conntrack_alter_reply might re-allocate extension area */ nat = nfct_nat(ct); nat->ct = ct; hlist_add_head_rcu(&nat->bysource, &net->ipv4.nat_bysource[srchash]); spin_unlock_bh(&nf_nat_lock); } /* It's done. */ if (maniptype == NF_NAT_MANIP_DST) ct->status |= IPS_DST_NAT_DONE; else ct->status |= IPS_SRC_NAT_DONE; return NF_ACCEPT; } EXPORT_SYMBOL(nf_nat_setup_info); /* Returns true if succeeded. */ static bool manip_pkt(u_int16_t proto, struct sk_buff *skb, unsigned int iphdroff, const struct nf_conntrack_tuple *target, enum nf_nat_manip_type maniptype) { struct iphdr *iph; const struct nf_nat_protocol *p; if (!skb_make_writable(skb, iphdroff + sizeof(*iph))) return false; iph = (void *)skb->data + iphdroff; /* Manipulate protcol part. */ /* rcu_read_lock()ed by nf_hook_slow */ p = __nf_nat_proto_find(proto); if (!p->manip_pkt(skb, iphdroff, target, maniptype)) return false; iph = (void *)skb->data + iphdroff; if (maniptype == NF_NAT_MANIP_SRC) { csum_replace4(&iph->check, iph->saddr, target->src.u3.ip); iph->saddr = target->src.u3.ip; } else { csum_replace4(&iph->check, iph->daddr, target->dst.u3.ip); iph->daddr = target->dst.u3.ip; } return true; } /* Do packet manipulations according to nf_nat_setup_info. */ unsigned int nf_nat_packet(struct nf_conn *ct, enum ip_conntrack_info ctinfo, unsigned int hooknum, struct sk_buff *skb) { enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); unsigned long statusbit; enum nf_nat_manip_type mtype = HOOK2MANIP(hooknum); if (mtype == NF_NAT_MANIP_SRC) statusbit = IPS_SRC_NAT; else statusbit = IPS_DST_NAT; /* Invert if this is reply dir. */ if (dir == IP_CT_DIR_REPLY) statusbit ^= IPS_NAT_MASK; /* Non-atomic: these bits don't change. */ if (ct->status & statusbit) { struct nf_conntrack_tuple target; /* We are aiming to look like inverse of other direction. */ nf_ct_invert_tuplepr(&target, &ct->tuplehash[!dir].tuple); if (!manip_pkt(target.dst.protonum, skb, 0, &target, mtype)) return NF_DROP; } return NF_ACCEPT; } EXPORT_SYMBOL_GPL(nf_nat_packet); /* Dir is direction ICMP is coming from (opposite to packet it contains) */ int nf_nat_icmp_reply_translation(struct nf_conn *ct, enum ip_conntrack_info ctinfo, unsigned int hooknum, struct sk_buff *skb) { struct { struct icmphdr icmp; struct iphdr ip; } *inside; struct nf_conntrack_tuple target; int hdrlen = ip_hdrlen(skb); enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); unsigned long statusbit; enum nf_nat_manip_type manip = HOOK2MANIP(hooknum); if (!skb_make_writable(skb, hdrlen + sizeof(*inside))) return 0; inside = (void *)skb->data + hdrlen; /* We're actually going to mangle it beyond trivial checksum adjustment, so make sure the current checksum is correct. */ if (nf_ip_checksum(skb, hooknum, hdrlen, 0)) return 0; /* Must be RELATED */ NF_CT_ASSERT(skb->nfctinfo == IP_CT_RELATED || skb->nfctinfo == IP_CT_RELATED_REPLY); /* Redirects on non-null nats must be dropped, else they'll start talking to each other without our translation, and be confused... --RR */ if (inside->icmp.type == ICMP_REDIRECT) { /* If NAT isn't finished, assume it and drop. */ if ((ct->status & IPS_NAT_DONE_MASK) != IPS_NAT_DONE_MASK) return 0; if (ct->status & IPS_NAT_MASK) return 0; } if (manip == NF_NAT_MANIP_SRC) statusbit = IPS_SRC_NAT; else statusbit = IPS_DST_NAT; /* Invert if this is reply dir. */ if (dir == IP_CT_DIR_REPLY) statusbit ^= IPS_NAT_MASK; if (!(ct->status & statusbit)) return 1; pr_debug("icmp_reply_translation: translating error %p manip %u " "dir %s\n", skb, manip, dir == IP_CT_DIR_ORIGINAL ? "ORIG" : "REPLY"); /* Change inner back to look like incoming packet. We do the opposite manip on this hook to normal, because it might not pass all hooks (locally-generated ICMP). Consider incoming packet: PREROUTING (DST manip), routing produces ICMP, goes through POSTROUTING (which must correct the DST manip). */ if (!manip_pkt(inside->ip.protocol, skb, hdrlen + sizeof(inside->icmp), &ct->tuplehash[!dir].tuple, !manip)) return 0; if (skb->ip_summed != CHECKSUM_PARTIAL) { /* Reloading "inside" here since manip_pkt inner. */ inside = (void *)skb->data + hdrlen; inside->icmp.checksum = 0; inside->icmp.checksum = csum_fold(skb_checksum(skb, hdrlen, skb->len - hdrlen, 0)); } /* Change outer to look the reply to an incoming packet * (proto 0 means don't invert per-proto part). */ nf_ct_invert_tuplepr(&target, &ct->tuplehash[!dir].tuple); if (!manip_pkt(0, skb, 0, &target, manip)) return 0; return 1; } EXPORT_SYMBOL_GPL(nf_nat_icmp_reply_translation); /* Protocol registration. */ int nf_nat_protocol_register(const struct nf_nat_protocol *proto) { int ret = 0; spin_lock_bh(&nf_nat_lock); if (rcu_dereference_protected( nf_nat_protos[proto->protonum], lockdep_is_held(&nf_nat_lock) ) != &nf_nat_unknown_protocol) { ret = -EBUSY; goto out; } RCU_INIT_POINTER(nf_nat_protos[proto->protonum], proto); out: spin_unlock_bh(&nf_nat_lock); return ret; } EXPORT_SYMBOL(nf_nat_protocol_register); /* No one stores the protocol anywhere; simply delete it. */ void nf_nat_protocol_unregister(const struct nf_nat_protocol *proto) { spin_lock_bh(&nf_nat_lock); RCU_INIT_POINTER(nf_nat_protos[proto->protonum], &nf_nat_unknown_protocol); spin_unlock_bh(&nf_nat_lock); synchronize_rcu(); } EXPORT_SYMBOL(nf_nat_protocol_unregister); /* No one using conntrack by the time this called. */ static void nf_nat_cleanup_conntrack(struct nf_conn *ct) { struct nf_conn_nat *nat = nf_ct_ext_find(ct, NF_CT_EXT_NAT); if (nat == NULL || nat->ct == NULL) return; NF_CT_ASSERT(nat->ct->status & IPS_SRC_NAT_DONE); spin_lock_bh(&nf_nat_lock); hlist_del_rcu(&nat->bysource); spin_unlock_bh(&nf_nat_lock); } static void nf_nat_move_storage(void *new, void *old) { struct nf_conn_nat *new_nat = new; struct nf_conn_nat *old_nat = old; struct nf_conn *ct = old_nat->ct; if (!ct || !(ct->status & IPS_SRC_NAT_DONE)) return; spin_lock_bh(&nf_nat_lock); hlist_replace_rcu(&old_nat->bysource, &new_nat->bysource); spin_unlock_bh(&nf_nat_lock); } static struct nf_ct_ext_type nat_extend __read_mostly = { .len = sizeof(struct nf_conn_nat), .align = __alignof__(struct nf_conn_nat), .destroy = nf_nat_cleanup_conntrack, .move = nf_nat_move_storage, .id = NF_CT_EXT_NAT, .flags = NF_CT_EXT_F_PREALLOC, }; #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE) #include #include static const struct nla_policy protonat_nla_policy[CTA_PROTONAT_MAX+1] = { [CTA_PROTONAT_PORT_MIN] = { .type = NLA_U16 }, [CTA_PROTONAT_PORT_MAX] = { .type = NLA_U16 }, }; static int nfnetlink_parse_nat_proto(struct nlattr *attr, const struct nf_conn *ct, struct nf_nat_ipv4_range *range) { struct nlattr *tb[CTA_PROTONAT_MAX+1]; const struct nf_nat_protocol *npt; int err; err = nla_parse_nested(tb, CTA_PROTONAT_MAX, attr, protonat_nla_policy); if (err < 0) return err; rcu_read_lock(); npt = __nf_nat_proto_find(nf_ct_protonum(ct)); if (npt->nlattr_to_range) err = npt->nlattr_to_range(tb, range); rcu_read_unlock(); return err; } static const struct nla_policy nat_nla_policy[CTA_NAT_MAX+1] = { [CTA_NAT_MINIP] = { .type = NLA_U32 }, [CTA_NAT_MAXIP] = { .type = NLA_U32 }, [CTA_NAT_PROTO] = { .type = NLA_NESTED }, }; static int nfnetlink_parse_nat(const struct nlattr *nat, const struct nf_conn *ct, struct nf_nat_ipv4_range *range) { struct nlattr *tb[CTA_NAT_MAX+1]; int err; memset(range, 0, sizeof(*range)); err = nla_parse_nested(tb, CTA_NAT_MAX, nat, nat_nla_policy); if (err < 0) return err; if (tb[CTA_NAT_MINIP]) range->min_ip = nla_get_be32(tb[CTA_NAT_MINIP]); if (!tb[CTA_NAT_MAXIP]) range->max_ip = range->min_ip; else range->max_ip = nla_get_be32(tb[CTA_NAT_MAXIP]); if (range->min_ip) range->flags |= NF_NAT_RANGE_MAP_IPS; if (!tb[CTA_NAT_PROTO]) return 0; err = nfnetlink_parse_nat_proto(tb[CTA_NAT_PROTO], ct, range); if (err < 0) return err; return 0; } static int nfnetlink_parse_nat_setup(struct nf_conn *ct, enum nf_nat_manip_type manip, const struct nlattr *attr) { struct nf_nat_ipv4_range range; if (nfnetlink_parse_nat(attr, ct, &range) < 0) return -EINVAL; if (nf_nat_initialized(ct, manip)) return -EEXIST; return nf_nat_setup_info(ct, &range, manip); } #else static int nfnetlink_parse_nat_setup(struct nf_conn *ct, enum nf_nat_manip_type manip, const struct nlattr *attr) { return -EOPNOTSUPP; } #endif static int __net_init nf_nat_net_init(struct net *net) { /* Leave them the same for the moment. */ net->ipv4.nat_htable_size = net->ct.htable_size; net->ipv4.nat_bysource = nf_ct_alloc_hashtable(&net->ipv4.nat_htable_size, 0); if (!net->ipv4.nat_bysource) return -ENOMEM; return 0; } /* Clear NAT section of all conntracks, in case we're loaded again. */ static int clean_nat(struct nf_conn *i, void *data) { struct nf_conn_nat *nat = nfct_nat(i); if (!nat) return 0; memset(nat, 0, sizeof(*nat)); i->status &= ~(IPS_NAT_MASK | IPS_NAT_DONE_MASK | IPS_SEQ_ADJUST); return 0; } static void __net_exit nf_nat_net_exit(struct net *net) { nf_ct_iterate_cleanup(net, &clean_nat, NULL); synchronize_rcu(); nf_ct_free_hashtable(net->ipv4.nat_bysource, net->ipv4.nat_htable_size); } static struct pernet_operations nf_nat_net_ops = { .init = nf_nat_net_init, .exit = nf_nat_net_exit, }; static int __init nf_nat_init(void) { size_t i; int ret; need_ipv4_conntrack(); ret = nf_ct_extend_register(&nat_extend); if (ret < 0) { printk(KERN_ERR "nf_nat_core: Unable to register extension\n"); return ret; } ret = register_pernet_subsys(&nf_nat_net_ops); if (ret < 0) goto cleanup_extend; /* Sew in builtin protocols. */ spin_lock_bh(&nf_nat_lock); for (i = 0; i < MAX_IP_NAT_PROTO; i++) RCU_INIT_POINTER(nf_nat_protos[i], &nf_nat_unknown_protocol); RCU_INIT_POINTER(nf_nat_protos[IPPROTO_TCP], &nf_nat_protocol_tcp); RCU_INIT_POINTER(nf_nat_protos[IPPROTO_UDP], &nf_nat_protocol_udp); RCU_INIT_POINTER(nf_nat_protos[IPPROTO_ICMP], &nf_nat_protocol_icmp); spin_unlock_bh(&nf_nat_lock); /* Initialize fake conntrack so that NAT will skip it */ nf_ct_untracked_status_or(IPS_NAT_DONE_MASK); l3proto = nf_ct_l3proto_find_get((u_int16_t)AF_INET); BUG_ON(nf_nat_seq_adjust_hook != NULL); RCU_INIT_POINTER(nf_nat_seq_adjust_hook, nf_nat_seq_adjust); BUG_ON(nfnetlink_parse_nat_setup_hook != NULL); RCU_INIT_POINTER(nfnetlink_parse_nat_setup_hook, nfnetlink_parse_nat_setup); BUG_ON(nf_ct_nat_offset != NULL); RCU_INIT_POINTER(nf_ct_nat_offset, nf_nat_get_offset); return 0; cleanup_extend: nf_ct_extend_unregister(&nat_extend); return ret; } static void __exit nf_nat_cleanup(void) { unregister_pernet_subsys(&nf_nat_net_ops); nf_ct_l3proto_put(l3proto); nf_ct_extend_unregister(&nat_extend); RCU_INIT_POINTER(nf_nat_seq_adjust_hook, NULL); RCU_INIT_POINTER(nfnetlink_parse_nat_setup_hook, NULL); RCU_INIT_POINTER(nf_ct_nat_offset, NULL); synchronize_net(); } MODULE_LICENSE("GPL"); MODULE_ALIAS("nf-nat-ipv4"); module_init(nf_nat_init); module_exit(nf_nat_cleanup);