Both SNAT and DNAT (and the upcoming masquerade) can have additional
configuration parameters, such as port randomization or NAT addressing
persistence.
We can cover these scenarios by simply adding a flag attribute for
userspace to fill when needed.
The flags to use are defined in include/uapi/linux/netfilter/nf_nat.h,
NF_NAT_RANGE_MAP_IPS
NF_NAT_RANGE_PROTO_SPECIFIED
NF_NAT_RANGE_PROTO_RANDOM
NF_NAT_RANGE_PERSISTENT
NF_NAT_RANGE_PROTO_RANDOM_FULLY
NF_NAT_RANGE_PROTO_RANDOM_ALL
The caller must take care of not messing up with the flags, as they are
added unconditionally to the final resulting nf_nat_range.
Signed-off-by: Arturo Borrero Gonzalez <arturo.borrero.glez@xxxxxxxxx>
---
v2: address Florian Westphal's comments: check all flag bits to be known.
v3: style cleanup requested by Pablo Neira. Mask name shortened.
include/uapi/linux/netfilter/nf_nat.h | 5 +++++
include/uapi/linux/netfilter/nf_tables.h | 2 ++
net/netfilter/nft_nat.c | 16 ++++++++++++++++
3 files changed, 23 insertions(+)
diff --git a/include/uapi/linux/netfilter/nf_nat.h b/include/uapi/linux/netfilter/nf_nat.h
index 1ad3659..898db2d 100644
--- a/include/uapi/linux/netfilter/nf_nat.h
+++ b/include/uapi/linux/netfilter/nf_nat.h
@@ -13,6 +13,11 @@
#define NF_NAT_RANGE_PROTO_RANDOM_ALL \
(NF_NAT_RANGE_PROTO_RANDOM | NF_NAT_RANGE_PROTO_RANDOM_FULLY)
+#define NF_NAT_RANGE_MASK \
+ (NF_NAT_RANGE_MAP_IPS|NF_NAT_RANGE_PROTO_SPECIFIED \
+ |NF_NAT_RANGE_PROTO_RANDOM|NF_NAT_RANGE_PERSISTENT \
+ |NF_NAT_RANGE_PROTO_RANDOM_FULLY)
+
struct nf_nat_ipv4_range {
unsigned int flags;
__be32 min_ip;
diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
index 2a88f64..92c211b 100644
--- a/include/uapi/linux/netfilter/nf_tables.h
+++ b/include/uapi/linux/netfilter/nf_tables.h
@@ -773,6 +773,7 @@ enum nft_nat_types {
* @NFTA_NAT_REG_ADDR_MAX: source register of address range end (NLA_U32: nft_registers)
* @NFTA_NAT_REG_PROTO_MIN: source register of proto range start (NLA_U32: nft_registers)
* @NFTA_NAT_REG_PROTO_MAX: source register of proto range end (NLA_U32: nft_registers)
+ * @NFTA_NAT_FLAGS: additional NAT configuration (NF_NAT_RANGE_*) (NLA_U32)
*/
enum nft_nat_attributes {
NFTA_NAT_UNSPEC,
@@ -782,6 +783,7 @@ enum nft_nat_attributes {
NFTA_NAT_REG_ADDR_MAX,
NFTA_NAT_REG_PROTO_MIN,
NFTA_NAT_REG_PROTO_MAX,
+ NFTA_NAT_FLAGS,
__NFTA_NAT_MAX
};
#define NFTA_NAT_MAX (__NFTA_NAT_MAX - 1)
diff --git a/net/netfilter/nft_nat.c b/net/netfilter/nft_nat.c
index 79ff58c..799550b 100644
--- a/net/netfilter/nft_nat.c
+++ b/net/netfilter/nft_nat.c
@@ -33,6 +33,7 @@ struct nft_nat {
enum nft_registers sreg_proto_max:8;
enum nf_nat_manip_type type:8;
u8 family;
+ u16 flags;
};
static void nft_nat_eval(const struct nft_expr *expr,
@@ -71,6 +72,8 @@ static void nft_nat_eval(const struct nft_expr *expr,
range.flags |= NF_NAT_RANGE_PROTO_SPECIFIED;
}
+ range.flags |= priv->flags;
+
data[NFT_REG_VERDICT].verdict =
nf_nat_setup_info(ct, &range, priv->type);
}
@@ -82,6 +85,7 @@ static const struct nla_policy nft_nat_policy[NFTA_NAT_MAX + 1] = {
[NFTA_NAT_REG_ADDR_MAX] = { .type = NLA_U32 },
[NFTA_NAT_REG_PROTO_MIN] = { .type = NLA_U32 },
[NFTA_NAT_REG_PROTO_MAX] = { .type = NLA_U32 },
+ [NFTA_NAT_FLAGS] = { .type = NLA_U32 },
};
static int nft_nat_init(const struct nft_ctx *ctx, const struct nft_expr *expr,
@@ -149,6 +153,12 @@ static int nft_nat_init(const struct nft_ctx *ctx, const struct nft_expr *expr,
} else
priv->sreg_proto_max = priv->sreg_proto_min;
+ if (tb[NFTA_NAT_FLAGS]) {
+ priv->flags = ntohl(nla_get_be32(tb[NFTA_NAT_FLAGS]));
+ if (priv->flags & ~NF_NAT_RANGE_MASK)
+ return -EINVAL;
+ }
+
return 0;
}
@@ -183,6 +193,12 @@ static int nft_nat_dump(struct sk_buff *skb, const struct nft_expr *expr)
htonl(priv->sreg_proto_max)))
goto nla_put_failure;
}
+
+ if (priv->flags != 0) {
+ if (nla_put_be32(skb, NFTA_NAT_FLAGS, htonl(priv->flags)))
+ goto nla_put_failure;
+ }
+
return 0;
nla_put_failure:
--
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