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- /*
- * (C) 1999-2001 Paul `Rusty' Russell
- * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
- * (C) 2011 Patrick McHardy <kaber@trash.net>
- *
- * 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/types.h>
- #include <linux/module.h>
- #include <linux/skbuff.h>
- #include <linux/ip.h>
- #include <linux/icmp.h>
- #include <linux/netfilter.h>
- #include <linux/netfilter_ipv4.h>
- #include <net/secure_seq.h>
- #include <net/checksum.h>
- #include <net/route.h>
- #include <net/ip.h>
- #include <net/netfilter/nf_conntrack_core.h>
- #include <net/netfilter/nf_conntrack.h>
- #include <net/netfilter/nf_nat_core.h>
- #include <net/netfilter/nf_nat_l3proto.h>
- #include <net/netfilter/nf_nat_l4proto.h>
- static const struct nf_nat_l3proto nf_nat_l3proto_ipv4;
- #ifdef CONFIG_XFRM
- static void nf_nat_ipv4_decode_session(struct sk_buff *skb,
- const struct nf_conn *ct,
- enum ip_conntrack_dir dir,
- unsigned long statusbit,
- struct flowi *fl)
- {
- const struct nf_conntrack_tuple *t = &ct->tuplehash[dir].tuple;
- struct flowi4 *fl4 = &fl->u.ip4;
- if (ct->status & statusbit) {
- fl4->daddr = t->dst.u3.ip;
- if (t->dst.protonum == IPPROTO_TCP ||
- t->dst.protonum == IPPROTO_UDP ||
- t->dst.protonum == IPPROTO_UDPLITE ||
- t->dst.protonum == IPPROTO_DCCP ||
- t->dst.protonum == IPPROTO_SCTP)
- fl4->fl4_dport = t->dst.u.all;
- }
- statusbit ^= IPS_NAT_MASK;
- if (ct->status & statusbit) {
- fl4->saddr = t->src.u3.ip;
- if (t->dst.protonum == IPPROTO_TCP ||
- t->dst.protonum == IPPROTO_UDP ||
- t->dst.protonum == IPPROTO_UDPLITE ||
- t->dst.protonum == IPPROTO_DCCP ||
- t->dst.protonum == IPPROTO_SCTP)
- fl4->fl4_sport = t->src.u.all;
- }
- }
- #endif /* CONFIG_XFRM */
- static bool nf_nat_ipv4_in_range(const struct nf_conntrack_tuple *t,
- const struct nf_nat_range *range)
- {
- return ntohl(t->src.u3.ip) >= ntohl(range->min_addr.ip) &&
- ntohl(t->src.u3.ip) <= ntohl(range->max_addr.ip);
- }
- static u32 nf_nat_ipv4_secure_port(const struct nf_conntrack_tuple *t,
- __be16 dport)
- {
- return secure_ipv4_port_ephemeral(t->src.u3.ip, t->dst.u3.ip, dport);
- }
- static bool nf_nat_ipv4_manip_pkt(struct sk_buff *skb,
- unsigned int iphdroff,
- const struct nf_nat_l4proto *l4proto,
- const struct nf_conntrack_tuple *target,
- enum nf_nat_manip_type maniptype)
- {
- struct iphdr *iph;
- unsigned int hdroff;
- if (!skb_make_writable(skb, iphdroff + sizeof(*iph)))
- return false;
- iph = (void *)skb->data + iphdroff;
- hdroff = iphdroff + iph->ihl * 4;
- if (!l4proto->manip_pkt(skb, &nf_nat_l3proto_ipv4, iphdroff, hdroff,
- 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;
- }
- static void nf_nat_ipv4_csum_update(struct sk_buff *skb,
- unsigned int iphdroff, __sum16 *check,
- const struct nf_conntrack_tuple *t,
- enum nf_nat_manip_type maniptype)
- {
- struct iphdr *iph = (struct iphdr *)(skb->data + iphdroff);
- __be32 oldip, newip;
- if (maniptype == NF_NAT_MANIP_SRC) {
- oldip = iph->saddr;
- newip = t->src.u3.ip;
- } else {
- oldip = iph->daddr;
- newip = t->dst.u3.ip;
- }
- inet_proto_csum_replace4(check, skb, oldip, newip, true);
- }
- static void nf_nat_ipv4_csum_recalc(struct sk_buff *skb,
- u8 proto, void *data, __sum16 *check,
- int datalen, int oldlen)
- {
- const struct iphdr *iph = ip_hdr(skb);
- struct rtable *rt = skb_rtable(skb);
- if (skb->ip_summed != CHECKSUM_PARTIAL) {
- if (!(rt->rt_flags & RTCF_LOCAL) &&
- (!skb->dev || skb->dev->features & NETIF_F_V4_CSUM)) {
- skb->ip_summed = CHECKSUM_PARTIAL;
- skb->csum_start = skb_headroom(skb) +
- skb_network_offset(skb) +
- ip_hdrlen(skb);
- skb->csum_offset = (void *)check - data;
- *check = ~csum_tcpudp_magic(iph->saddr, iph->daddr,
- datalen, proto, 0);
- } else {
- *check = 0;
- *check = csum_tcpudp_magic(iph->saddr, iph->daddr,
- datalen, proto,
- csum_partial(data, datalen,
- 0));
- if (proto == IPPROTO_UDP && !*check)
- *check = CSUM_MANGLED_0;
- }
- } else
- inet_proto_csum_replace2(check, skb,
- htons(oldlen), htons(datalen), true);
- }
- #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
- static int nf_nat_ipv4_nlattr_to_range(struct nlattr *tb[],
- struct nf_nat_range *range)
- {
- if (tb[CTA_NAT_V4_MINIP]) {
- range->min_addr.ip = nla_get_be32(tb[CTA_NAT_V4_MINIP]);
- range->flags |= NF_NAT_RANGE_MAP_IPS;
- }
- if (tb[CTA_NAT_V4_MAXIP])
- range->max_addr.ip = nla_get_be32(tb[CTA_NAT_V4_MAXIP]);
- else
- range->max_addr.ip = range->min_addr.ip;
- return 0;
- }
- #endif
- static const struct nf_nat_l3proto nf_nat_l3proto_ipv4 = {
- .l3proto = NFPROTO_IPV4,
- .in_range = nf_nat_ipv4_in_range,
- .secure_port = nf_nat_ipv4_secure_port,
- .manip_pkt = nf_nat_ipv4_manip_pkt,
- .csum_update = nf_nat_ipv4_csum_update,
- .csum_recalc = nf_nat_ipv4_csum_recalc,
- #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
- .nlattr_to_range = nf_nat_ipv4_nlattr_to_range,
- #endif
- #ifdef CONFIG_XFRM
- .decode_session = nf_nat_ipv4_decode_session,
- #endif
- };
- int nf_nat_icmp_reply_translation(struct sk_buff *skb,
- struct nf_conn *ct,
- enum ip_conntrack_info ctinfo,
- unsigned int hooknum)
- {
- struct {
- struct icmphdr icmp;
- struct iphdr ip;
- } *inside;
- enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
- enum nf_nat_manip_type manip = HOOK2MANIP(hooknum);
- unsigned int hdrlen = ip_hdrlen(skb);
- const struct nf_nat_l4proto *l4proto;
- struct nf_conntrack_tuple target;
- unsigned long statusbit;
- NF_CT_ASSERT(ctinfo == IP_CT_RELATED || ctinfo == IP_CT_RELATED_REPLY);
- if (!skb_make_writable(skb, hdrlen + sizeof(*inside)))
- return 0;
- if (nf_ip_checksum(skb, hooknum, hdrlen, 0))
- return 0;
- inside = (void *)skb->data + hdrlen;
- if (inside->icmp.type == ICMP_REDIRECT) {
- 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 direction */
- if (dir == IP_CT_DIR_REPLY)
- statusbit ^= IPS_NAT_MASK;
- if (!(ct->status & statusbit))
- return 1;
- l4proto = __nf_nat_l4proto_find(NFPROTO_IPV4, inside->ip.protocol);
- if (!nf_nat_ipv4_manip_pkt(skb, hdrlen + sizeof(inside->icmp),
- l4proto, &ct->tuplehash[!dir].tuple, !manip))
- return 0;
- if (skb->ip_summed != CHECKSUM_PARTIAL) {
- /* Reloading "inside" here since manip_pkt may reallocate */
- 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 like the reply to an incoming packet */
- nf_ct_invert_tuplepr(&target, &ct->tuplehash[!dir].tuple);
- l4proto = __nf_nat_l4proto_find(NFPROTO_IPV4, 0);
- if (!nf_nat_ipv4_manip_pkt(skb, 0, l4proto, &target, manip))
- return 0;
- return 1;
- }
- EXPORT_SYMBOL_GPL(nf_nat_icmp_reply_translation);
- unsigned int
- nf_nat_ipv4_fn(void *priv, struct sk_buff *skb,
- const struct nf_hook_state *state,
- unsigned int (*do_chain)(void *priv,
- struct sk_buff *skb,
- const struct nf_hook_state *state,
- struct nf_conn *ct))
- {
- struct nf_conn *ct;
- enum ip_conntrack_info ctinfo;
- struct nf_conn_nat *nat;
- /* maniptype == SRC for postrouting. */
- enum nf_nat_manip_type maniptype = HOOK2MANIP(state->hook);
- ct = nf_ct_get(skb, &ctinfo);
- /* Can't track? It's not due to stress, or conntrack would
- * have dropped it. Hence it's the user's responsibilty to
- * packet filter it out, or implement conntrack/NAT for that
- * protocol. 8) --RR
- */
- if (!ct)
- return NF_ACCEPT;
- /* Don't try to NAT if this packet is not conntracked */
- if (nf_ct_is_untracked(ct))
- return NF_ACCEPT;
- nat = nf_ct_nat_ext_add(ct);
- if (nat == NULL)
- return NF_ACCEPT;
- switch (ctinfo) {
- case IP_CT_RELATED:
- case IP_CT_RELATED_REPLY:
- if (ip_hdr(skb)->protocol == IPPROTO_ICMP) {
- if (!nf_nat_icmp_reply_translation(skb, ct, ctinfo,
- state->hook))
- return NF_DROP;
- else
- return NF_ACCEPT;
- }
- /* Fall thru... (Only ICMPs can be IP_CT_IS_REPLY) */
- case IP_CT_NEW:
- /* Seen it before? This can happen for loopback, retrans,
- * or local packets.
- */
- if (!nf_nat_initialized(ct, maniptype)) {
- unsigned int ret;
- ret = do_chain(priv, skb, state, ct);
- if (ret != NF_ACCEPT)
- return ret;
- if (nf_nat_initialized(ct, HOOK2MANIP(state->hook)))
- break;
- ret = nf_nat_alloc_null_binding(ct, state->hook);
- if (ret != NF_ACCEPT)
- return ret;
- } else {
- pr_debug("Already setup manip %s for ct %p\n",
- maniptype == NF_NAT_MANIP_SRC ? "SRC" : "DST",
- ct);
- if (nf_nat_oif_changed(state->hook, ctinfo, nat,
- state->out))
- goto oif_changed;
- }
- break;
- default:
- /* ESTABLISHED */
- NF_CT_ASSERT(ctinfo == IP_CT_ESTABLISHED ||
- ctinfo == IP_CT_ESTABLISHED_REPLY);
- if (nf_nat_oif_changed(state->hook, ctinfo, nat, state->out))
- goto oif_changed;
- }
- return nf_nat_packet(ct, ctinfo, state->hook, skb);
- oif_changed:
- nf_ct_kill_acct(ct, ctinfo, skb);
- return NF_DROP;
- }
- EXPORT_SYMBOL_GPL(nf_nat_ipv4_fn);
- unsigned int
- nf_nat_ipv4_in(void *priv, struct sk_buff *skb,
- const struct nf_hook_state *state,
- unsigned int (*do_chain)(void *priv,
- struct sk_buff *skb,
- const struct nf_hook_state *state,
- struct nf_conn *ct))
- {
- unsigned int ret;
- __be32 daddr = ip_hdr(skb)->daddr;
- ret = nf_nat_ipv4_fn(priv, skb, state, do_chain);
- if (ret != NF_DROP && ret != NF_STOLEN &&
- daddr != ip_hdr(skb)->daddr)
- skb_dst_drop(skb);
- return ret;
- }
- EXPORT_SYMBOL_GPL(nf_nat_ipv4_in);
- unsigned int
- nf_nat_ipv4_out(void *priv, struct sk_buff *skb,
- const struct nf_hook_state *state,
- unsigned int (*do_chain)(void *priv,
- struct sk_buff *skb,
- const struct nf_hook_state *state,
- struct nf_conn *ct))
- {
- #ifdef CONFIG_XFRM
- const struct nf_conn *ct;
- enum ip_conntrack_info ctinfo;
- int err;
- #endif
- unsigned int ret;
- /* root is playing with raw sockets. */
- if (skb->len < sizeof(struct iphdr) ||
- ip_hdrlen(skb) < sizeof(struct iphdr))
- return NF_ACCEPT;
- ret = nf_nat_ipv4_fn(priv, skb, state, do_chain);
- #ifdef CONFIG_XFRM
- if (ret != NF_DROP && ret != NF_STOLEN &&
- !(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&
- (ct = nf_ct_get(skb, &ctinfo)) != NULL) {
- enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
- if ((ct->tuplehash[dir].tuple.src.u3.ip !=
- ct->tuplehash[!dir].tuple.dst.u3.ip) ||
- (ct->tuplehash[dir].tuple.dst.protonum != IPPROTO_ICMP &&
- ct->tuplehash[dir].tuple.src.u.all !=
- ct->tuplehash[!dir].tuple.dst.u.all)) {
- err = nf_xfrm_me_harder(state->net, skb, AF_INET);
- if (err < 0)
- ret = NF_DROP_ERR(err);
- }
- }
- #endif
- return ret;
- }
- EXPORT_SYMBOL_GPL(nf_nat_ipv4_out);
- unsigned int
- nf_nat_ipv4_local_fn(void *priv, struct sk_buff *skb,
- const struct nf_hook_state *state,
- unsigned int (*do_chain)(void *priv,
- struct sk_buff *skb,
- const struct nf_hook_state *state,
- struct nf_conn *ct))
- {
- const struct nf_conn *ct;
- enum ip_conntrack_info ctinfo;
- unsigned int ret;
- int err;
- /* root is playing with raw sockets. */
- if (skb->len < sizeof(struct iphdr) ||
- ip_hdrlen(skb) < sizeof(struct iphdr))
- return NF_ACCEPT;
- ret = nf_nat_ipv4_fn(priv, skb, state, do_chain);
- if (ret != NF_DROP && ret != NF_STOLEN &&
- (ct = nf_ct_get(skb, &ctinfo)) != NULL) {
- enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
- if (ct->tuplehash[dir].tuple.dst.u3.ip !=
- ct->tuplehash[!dir].tuple.src.u3.ip) {
- err = ip_route_me_harder(state->net, skb, RTN_UNSPEC);
- if (err < 0)
- ret = NF_DROP_ERR(err);
- }
- #ifdef CONFIG_XFRM
- else if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&
- ct->tuplehash[dir].tuple.dst.protonum != IPPROTO_ICMP &&
- ct->tuplehash[dir].tuple.dst.u.all !=
- ct->tuplehash[!dir].tuple.src.u.all) {
- err = nf_xfrm_me_harder(state->net, skb, AF_INET);
- if (err < 0)
- ret = NF_DROP_ERR(err);
- }
- #endif
- }
- return ret;
- }
- EXPORT_SYMBOL_GPL(nf_nat_ipv4_local_fn);
- static int __init nf_nat_l3proto_ipv4_init(void)
- {
- int err;
- err = nf_nat_l4proto_register(NFPROTO_IPV4, &nf_nat_l4proto_icmp);
- if (err < 0)
- goto err1;
- err = nf_nat_l3proto_register(&nf_nat_l3proto_ipv4);
- if (err < 0)
- goto err2;
- return err;
- err2:
- nf_nat_l4proto_unregister(NFPROTO_IPV4, &nf_nat_l4proto_icmp);
- err1:
- return err;
- }
- static void __exit nf_nat_l3proto_ipv4_exit(void)
- {
- nf_nat_l3proto_unregister(&nf_nat_l3proto_ipv4);
- nf_nat_l4proto_unregister(NFPROTO_IPV4, &nf_nat_l4proto_icmp);
- }
- MODULE_LICENSE("GPL");
- MODULE_ALIAS("nf-nat-" __stringify(AF_INET));
- module_init(nf_nat_l3proto_ipv4_init);
- module_exit(nf_nat_l3proto_ipv4_exit);
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