netfilter: nf_nat: move alloc_null_binding to nf_nat_core.c

Similar to nat_decode_session, alloc_null_binding is needed for both
ip_tables and nf_tables, so move it to nf_nat_core.c. This change
is required by nf_tables.

This is an adapted version of the original patch from Patrick McHardy.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

2 files changed, 23 insertions, 0 deletions

diff --git a/include/net/netfilter/nf_nat.h b/include/net/netfilter/nf_nat.h
index c29b4e545f87..07eaaf604092 100644
--- a/include/net/netfilter/nf_nat.h
+++ b/include/net/netfilter/nf_nat.h
@@ -45,6 +45,9 @@ unsigned int nf_nat_setup_info(struct nf_conn *ct,
                                const struct nf_nat_range *range,
                                enum nf_nat_manip_type maniptype);
 
+extern unsigned int nf_nat_alloc_null_binding(struct nf_conn *ct,
+                                              unsigned int hooknum);
+
 /* 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);
diff --git a/net/netfilter/nf_nat_core.c b/net/netfilter/nf_nat_core.c
index 6f0f4f7f68a5..63a815402211 100644
--- a/net/netfilter/nf_nat_core.c
+++ b/net/netfilter/nf_nat_core.c
@@ -432,6 +432,26 @@ nf_nat_setup_info(struct nf_conn *ct,
 }
 EXPORT_SYMBOL(nf_nat_setup_info);
 
+unsigned int
+nf_nat_alloc_null_binding(struct nf_conn *ct, unsigned int hooknum)
+{
+        /* Force range to this IP; let proto decide mapping for
+         * per-proto parts (hence not IP_NAT_RANGE_PROTO_SPECIFIED).
+         * Use reply in case it's already been mangled (eg local packet).
+         */
+        union nf_inet_addr ip =
+                (HOOK2MANIP(hooknum) == NF_NAT_MANIP_SRC ?
+                ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3 :
+                ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3);
+        struct nf_nat_range range = {
+                .flags          = NF_NAT_RANGE_MAP_IPS,
+                .min_addr       = ip,
+                .max_addr       = ip,
+        };
+        return nf_nat_setup_info(ct, &range, HOOK2MANIP(hooknum));
+}
+EXPORT_SYMBOL_GPL(nf_nat_alloc_null_binding);
+
 /* Do packet manipulations according to nf_nat_setup_info. */
 unsigned int nf_nat_packet(struct nf_conn *ct,
                            enum ip_conntrack_info ctinfo,