--- /dev/null
+/*
+ * (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, 1);
+}
+
+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), 1);
+}
+
+#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(const struct nf_hook_ops *ops, struct sk_buff *skb,
+ const struct nf_hook_state *state,
+ unsigned int (*do_chain)(const struct nf_hook_ops *ops,
+ 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(ops->hooknum);
+
+ /* We never see fragments: conntrack defrags on pre-routing
+ * and local-out, and nf_nat_out protects post-routing.
+ */
+ NF_CT_ASSERT(!ip_is_fragment(ip_hdr(skb)));
+
+ 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,
+ ops->hooknum))
+ 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(ops, skb, state, ct);
+ if (ret != NF_ACCEPT)
+ return ret;
+
+ if (nf_nat_initialized(ct, HOOK2MANIP(ops->hooknum)))
+ break;
+
+ ret = nf_nat_alloc_null_binding(ct, ops->hooknum);
+ 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(ops->hooknum, 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(ops->hooknum, ctinfo, nat, state->out))
+ goto oif_changed;
+ }
+
+ return nf_nat_packet(ct, ctinfo, ops->hooknum, 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(const struct nf_hook_ops *ops, struct sk_buff *skb,
+ const struct nf_hook_state *state,
+ unsigned int (*do_chain)(const struct nf_hook_ops *ops,
+ 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(ops, 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(const struct nf_hook_ops *ops, struct sk_buff *skb,
+ const struct nf_hook_state *state,
+ unsigned int (*do_chain)(const struct nf_hook_ops *ops,
+ 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(ops, 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(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(const struct nf_hook_ops *ops, struct sk_buff *skb,
+ const struct nf_hook_state *state,
+ unsigned int (*do_chain)(const struct nf_hook_ops *ops,
+ 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(ops, 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(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(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);
Code Review / kvmfornfv.git / blobdiff