/* NAT for netfilter; shared with compatibility layer. */ /* (C) 1999-2001 Paul `Rusty' Russell * (C) 2002-2004 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 #include /* For tcp_prot in getorigdst */ #include #include #include #include #include #include #include #include #include #include #include #if 0 #define DEBUGP printk #else #define DEBUGP(format, args...) #endif DEFINE_RWLOCK(ip_nat_lock); /* Calculated at init based on memory size */ static unsigned int ip_nat_htable_size; static struct list_head *bysource; #define MAX_IP_NAT_PROTO 256 static struct ip_nat_protocol *ip_nat_protos[MAX_IP_NAT_PROTO]; static inline struct ip_nat_protocol * __ip_nat_proto_find(u_int8_t protonum) { return ip_nat_protos[protonum]; } struct ip_nat_protocol * ip_nat_proto_find_get(u_int8_t protonum) { struct ip_nat_protocol *p; /* we need to disable preemption to make sure 'p' doesn't get * removed until we've grabbed the reference */ preempt_disable(); p = __ip_nat_proto_find(protonum); if (!try_module_get(p->me)) p = &ip_nat_unknown_protocol; preempt_enable(); return p; } EXPORT_SYMBOL_GPL(ip_nat_proto_find_get); void ip_nat_proto_put(struct ip_nat_protocol *p) { module_put(p->me); } EXPORT_SYMBOL_GPL(ip_nat_proto_put); /* We keep an extra hash for each conntrack, for fast searching. */ static inline unsigned int hash_by_src(const struct ip_conntrack_tuple *tuple) { /* Original src, to ensure we map it consistently if poss. */ return jhash_3words((__force u32)tuple->src.ip, tuple->src.u.all, tuple->dst.protonum, 0) % ip_nat_htable_size; } /* Noone using conntrack by the time this called. */ static void ip_nat_cleanup_conntrack(struct ip_conntrack *conn) { if (!(conn->status & IPS_NAT_DONE_MASK)) return; write_lock_bh(&ip_nat_lock); list_del(&conn->nat.info.bysource); write_unlock_bh(&ip_nat_lock); } /* Is this tuple already taken? (not by us) */ int ip_nat_used_tuple(const struct ip_conntrack_tuple *tuple, const struct ip_conntrack *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 ip_conntrack_tuple reply; invert_tuplepr(&reply, tuple); return ip_conntrack_tuple_taken(&reply, ignored_conntrack); } EXPORT_SYMBOL(ip_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 ip_conntrack_tuple *tuple, const struct ip_nat_range *range) { struct ip_nat_protocol *proto = __ip_nat_proto_find(tuple->dst.protonum); /* 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 & IP_NAT_RANGE_MAP_IPS) { if (ntohl(tuple->src.ip) < ntohl(range->min_ip) || ntohl(tuple->src.ip) > ntohl(range->max_ip)) return 0; } if (!(range->flags & IP_NAT_RANGE_PROTO_SPECIFIED) || proto->in_range(tuple, IP_NAT_MANIP_SRC, &range->min, &range->max)) return 1; return 0; } static inline int same_src(const struct ip_conntrack *ct, const struct ip_conntrack_tuple *tuple) { return (ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.protonum == tuple->dst.protonum && ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip == tuple->src.ip && ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.all == tuple->src.u.all); } /* Only called for SRC manip */ static int find_appropriate_src(const struct ip_conntrack_tuple *tuple, struct ip_conntrack_tuple *result, const struct ip_nat_range *range) { unsigned int h = hash_by_src(tuple); struct ip_conntrack *ct; read_lock_bh(&ip_nat_lock); list_for_each_entry(ct, &bysource[h], nat.info.bysource) { if (same_src(ct, tuple)) { /* Copy source part from reply tuple. */ invert_tuplepr(result, &ct->tuplehash[IP_CT_DIR_REPLY].tuple); result->dst = tuple->dst; if (in_range(result, range)) { read_unlock_bh(&ip_nat_lock); return 1; } } } read_unlock_bh(&ip_nat_lock); 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(struct ip_conntrack_tuple *tuple, const struct ip_nat_range *range, const struct ip_conntrack *conntrack, enum ip_nat_manip_type maniptype) { __be32 *var_ipp; /* Host order */ u_int32_t minip, maxip, j; /* No IP mapping? Do nothing. */ if (!(range->flags & IP_NAT_RANGE_MAP_IPS)) return; if (maniptype == IP_NAT_MANIP_SRC) var_ipp = &tuple->src.ip; else var_ipp = &tuple->dst.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.ip, (__force u32)tuple->dst.ip, 0); *var_ipp = htonl(minip + j % (maxip - minip + 1)); } /* Manipulate the tuple into the range given. For NF_IP_POST_ROUTING, * we change the source to map into the range. For NF_IP_PRE_ROUTING * and NF_IP_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 ip_conntrack_tuple *tuple, const struct ip_conntrack_tuple *orig_tuple, const struct ip_nat_range *range, struct ip_conntrack *conntrack, enum ip_nat_manip_type maniptype) { struct ip_nat_protocol *proto; /* 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 == IP_NAT_MANIP_SRC) { if (find_appropriate_src(orig_tuple, tuple, range)) { DEBUGP("get_unique_tuple: Found current src map\n"); if (!(range->flags & IP_NAT_RANGE_PROTO_RANDOM)) if (!ip_nat_used_tuple(tuple, conntrack)) return; } } /* 2) Select the least-used IP/proto combination in the given range. */ *tuple = *orig_tuple; find_best_ips_proto(tuple, range, conntrack, maniptype); /* 3) The per-protocol part of the manip is made to map into the range to make a unique tuple. */ proto = ip_nat_proto_find_get(orig_tuple->dst.protonum); /* Change protocol info to have some randomization */ if (range->flags & IP_NAT_RANGE_PROTO_RANDOM) { proto->unique_tuple(tuple, range, maniptype, conntrack); ip_nat_proto_put(proto); return; } /* Only bother mapping if it's not already in range and unique */ if ((!(range->flags & IP_NAT_RANGE_PROTO_SPECIFIED) || proto->in_range(tuple, maniptype, &range->min, &range->max)) && !ip_nat_used_tuple(tuple, conntrack)) { ip_nat_proto_put(proto); return; } /* Last change: get protocol to try to obtain unique tuple. */ proto->unique_tuple(tuple, range, maniptype, conntrack); ip_nat_proto_put(proto); } unsigned int ip_nat_setup_info(struct ip_conntrack *conntrack, const struct ip_nat_range *range, unsigned int hooknum) { struct ip_conntrack_tuple curr_tuple, new_tuple; struct ip_nat_info *info = &conntrack->nat.info; int have_to_hash = !(conntrack->status & IPS_NAT_DONE_MASK); enum ip_nat_manip_type maniptype = HOOK2MANIP(hooknum); IP_NF_ASSERT(hooknum == NF_IP_PRE_ROUTING || hooknum == NF_IP_POST_ROUTING || hooknum == NF_IP_LOCAL_IN || hooknum == NF_IP_LOCAL_OUT); BUG_ON(ip_nat_initialized(conntrack, 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) */ invert_tuplepr(&curr_tuple, &conntrack->tuplehash[IP_CT_DIR_REPLY].tuple); get_unique_tuple(&new_tuple, &curr_tuple, range, conntrack, maniptype); if (!ip_ct_tuple_equal(&new_tuple, &curr_tuple)) { struct ip_conntrack_tuple reply; /* Alter conntrack table so will recognize replies. */ invert_tuplepr(&reply, &new_tuple); ip_conntrack_alter_reply(conntrack, &reply); /* Non-atomic: we own this at the moment. */ if (maniptype == IP_NAT_MANIP_SRC) conntrack->status |= IPS_SRC_NAT; else conntrack->status |= IPS_DST_NAT; } /* Place in source hash if this is the first time. */ if (have_to_hash) { unsigned int srchash = hash_by_src(&conntrack->tuplehash[IP_CT_DIR_ORIGINAL] .tuple); write_lock_bh(&ip_nat_lock); list_add(&info->bysource, &bysource[srchash]); write_unlock_bh(&ip_nat_lock); } /* It's done. */ if (maniptype == IP_NAT_MANIP_DST) set_bit(IPS_DST_NAT_DONE_BIT, &conntrack->status); else set_bit(IPS_SRC_NAT_DONE_BIT, &conntrack->status); return NF_ACCEPT; } EXPORT_SYMBOL(ip_nat_setup_info); /* Returns true if succeeded. */ static int manip_pkt(u_int16_t proto, struct sk_buff **pskb, unsigned int iphdroff, const struct ip_conntrack_tuple *target, enum ip_nat_manip_type maniptype) { struct iphdr *iph; struct ip_nat_protocol *p; if (!skb_make_writable(pskb, iphdroff + sizeof(*iph))) return 0; iph = (void *)(*pskb)->data + iphdroff; /* Manipulate protcol part. */ p = ip_nat_proto_find_get(proto); if (!p->manip_pkt(pskb, iphdroff, target, maniptype)) { ip_nat_proto_put(p); return 0; } ip_nat_proto_put(p); iph = (void *)(*pskb)->data + iphdroff; if (maniptype == IP_NAT_MANIP_SRC) { nf_csum_replace4(&iph->check, iph->saddr, target->src.ip); iph->saddr = target->src.ip; } else { nf_csum_replace4(&iph->check, iph->daddr, target->dst.ip); iph->daddr = target->dst.ip; } return 1; } /* Do packet manipulations according to ip_nat_setup_info. */ unsigned int ip_nat_packet(struct ip_conntrack *ct, enum ip_conntrack_info ctinfo, unsigned int hooknum, struct sk_buff **pskb) { enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); unsigned long statusbit; enum ip_nat_manip_type mtype = HOOK2MANIP(hooknum); if (mtype == IP_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 ip_conntrack_tuple target; /* We are aiming to look like inverse of other direction. */ invert_tuplepr(&target, &ct->tuplehash[!dir].tuple); if (!manip_pkt(target.dst.protonum, pskb, 0, &target, mtype)) return NF_DROP; } return NF_ACCEPT; } EXPORT_SYMBOL_GPL(ip_nat_packet); /* Dir is direction ICMP is coming from (opposite to packet it contains) */ int ip_nat_icmp_reply_translation(struct ip_conntrack *ct, enum ip_conntrack_info ctinfo, unsigned int hooknum, struct sk_buff **pskb) { struct { struct icmphdr icmp; struct iphdr ip; } *inside; struct ip_conntrack_tuple inner, target; int hdrlen = (*pskb)->nh.iph->ihl * 4; enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); unsigned long statusbit; enum ip_nat_manip_type manip = HOOK2MANIP(hooknum); if (!skb_make_writable(pskb, hdrlen + sizeof(*inside))) return 0; inside = (void *)(*pskb)->data + (*pskb)->nh.iph->ihl*4; /* We're actually going to mangle it beyond trivial checksum adjustment, so make sure the current checksum is correct. */ if (nf_ip_checksum(*pskb, hooknum, hdrlen, 0)) return 0; /* Must be RELATED */ IP_NF_ASSERT((*pskb)->nfctinfo == IP_CT_RELATED || (*pskb)->nfctinfo == IP_CT_RELATED+IP_CT_IS_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; } DEBUGP("icmp_reply_translation: translating error %p manp %u dir %s\n", *pskb, manip, dir == IP_CT_DIR_ORIGINAL ? "ORIG" : "REPLY"); if (!ip_ct_get_tuple(&inside->ip, *pskb, (*pskb)->nh.iph->ihl*4 + sizeof(struct icmphdr) + inside->ip.ihl*4, &inner, __ip_conntrack_proto_find(inside->ip.protocol))) return 0; /* 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, pskb, (*pskb)->nh.iph->ihl*4 + sizeof(inside->icmp), &ct->tuplehash[!dir].tuple, !manip)) return 0; if ((*pskb)->ip_summed != CHECKSUM_PARTIAL) { /* Reloading "inside" here since manip_pkt inner. */ inside = (void *)(*pskb)->data + (*pskb)->nh.iph->ihl*4; inside->icmp.checksum = 0; inside->icmp.checksum = csum_fold(skb_checksum(*pskb, hdrlen, (*pskb)->len - hdrlen, 0)); } /* Change outer to look the reply to an incoming packet * (proto 0 means don't invert per-proto part). */ if (manip == IP_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) { invert_tuplepr(&target, &ct->tuplehash[!dir].tuple); if (!manip_pkt(0, pskb, 0, &target, manip)) return 0; } return 1; } EXPORT_SYMBOL_GPL(ip_nat_icmp_reply_translation); /* Protocol registration. */ int ip_nat_protocol_register(struct ip_nat_protocol *proto) { int ret = 0; write_lock_bh(&ip_nat_lock); if (ip_nat_protos[proto->protonum] != &ip_nat_unknown_protocol) { ret = -EBUSY; goto out; } ip_nat_protos[proto->protonum] = proto; out: write_unlock_bh(&ip_nat_lock); return ret; } EXPORT_SYMBOL(ip_nat_protocol_register); /* Noone stores the protocol anywhere; simply delete it. */ void ip_nat_protocol_unregister(struct ip_nat_protocol *proto) { write_lock_bh(&ip_nat_lock); ip_nat_protos[proto->protonum] = &ip_nat_unknown_protocol; write_unlock_bh(&ip_nat_lock); /* Someone could be still looking at the proto in a bh. */ synchronize_net(); } EXPORT_SYMBOL(ip_nat_protocol_unregister); #if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \ defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE) int ip_nat_port_range_to_nfattr(struct sk_buff *skb, const struct ip_nat_range *range) { NFA_PUT(skb, CTA_PROTONAT_PORT_MIN, sizeof(__be16), &range->min.tcp.port); NFA_PUT(skb, CTA_PROTONAT_PORT_MAX, sizeof(__be16), &range->max.tcp.port); return 0; nfattr_failure: return -1; } int ip_nat_port_nfattr_to_range(struct nfattr *tb[], struct ip_nat_range *range) { int ret = 0; /* we have to return whether we actually parsed something or not */ if (tb[CTA_PROTONAT_PORT_MIN-1]) { ret = 1; range->min.tcp.port = *(__be16 *)NFA_DATA(tb[CTA_PROTONAT_PORT_MIN-1]); } if (!tb[CTA_PROTONAT_PORT_MAX-1]) { if (ret) range->max.tcp.port = range->min.tcp.port; } else { ret = 1; range->max.tcp.port = *(__be16 *)NFA_DATA(tb[CTA_PROTONAT_PORT_MAX-1]); } return ret; } EXPORT_SYMBOL_GPL(ip_nat_port_nfattr_to_range); EXPORT_SYMBOL_GPL(ip_nat_port_range_to_nfattr); #endif static int __init ip_nat_init(void) { size_t i; /* Leave them the same for the moment. */ ip_nat_htable_size = ip_conntrack_htable_size; /* One vmalloc for both hash tables */ bysource = vmalloc(sizeof(struct list_head) * ip_nat_htable_size); if (!bysource) return -ENOMEM; /* Sew in builtin protocols. */ write_lock_bh(&ip_nat_lock); for (i = 0; i < MAX_IP_NAT_PROTO; i++) ip_nat_protos[i] = &ip_nat_unknown_protocol; ip_nat_protos[IPPROTO_TCP] = &ip_nat_protocol_tcp; ip_nat_protos[IPPROTO_UDP] = &ip_nat_protocol_udp; ip_nat_protos[IPPROTO_ICMP] = &ip_nat_protocol_icmp; write_unlock_bh(&ip_nat_lock); for (i = 0; i < ip_nat_htable_size; i++) { INIT_LIST_HEAD(&bysource[i]); } /* FIXME: Man, this is a hack. */ IP_NF_ASSERT(ip_conntrack_destroyed == NULL); ip_conntrack_destroyed = &ip_nat_cleanup_conntrack; /* Initialize fake conntrack so that NAT will skip it */ ip_conntrack_untracked.status |= IPS_NAT_DONE_MASK; return 0; } /* Clear NAT section of all conntracks, in case we're loaded again. */ static int clean_nat(struct ip_conntrack *i, void *data) { memset(&i->nat, 0, sizeof(i->nat)); i->status &= ~(IPS_NAT_MASK | IPS_NAT_DONE_MASK | IPS_SEQ_ADJUST); return 0; } static void __exit ip_nat_cleanup(void) { ip_ct_iterate_cleanup(&clean_nat, NULL); ip_conntrack_destroyed = NULL; vfree(bysource); } MODULE_LICENSE("GPL"); module_init(ip_nat_init); module_exit(ip_nat_cleanup);