src: allow nat maps containing both ip(6) address and port

nft will now be able to handle
map destinations {
	type ipv4_addr . inet_service : ipv4_addr . inet_service
}

chain f {
	dnat to ip daddr . tcp dport map @destinations
}

Something like this won't work though:
 meta l4proto tcp dnat ip6 to numgen inc mod 4 map { 0 : dead::f001 . 8080, ..

as we lack the type info to properly dissect "dead::f001" as an ipv6
address.

For the named map case, this info is available in the map
definition, but for the anon case we'd need to resort to guesswork.

Support is added by peeking into the map definition when evaluating
a nat statement with a map.
Right now, when a map is provided as address, we will only check that
the mapped-to data type matches the expected size (of an ipv4 or ipv6
address).

After this patch, if the mapped-to type is a concatenation, it will
take a peek at the individual concat expressions.  If its a combination
of address and service, nft will translate this so that the kernel nat
expression looks at the returned register that would store the
inet_service part of the octet soup returned from the lookup expression.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

4 files changed, 123 insertions, 1 deletions

diff --git a/include/statement.h b/include/statement.h
index 585908de..8fb459ca 100644
--- a/include/statement.h
+++ b/include/statement.h
@@ -125,6 +125,7 @@ struct nat_stmt {
 	struct expr		*proto;
 	uint32_t		flags;
 	uint8_t			family;
+	bool			ipportmap;
 };
 
 extern struct stmt *nat_stmt_alloc(const struct location *loc,
diff --git a/src/evaluate.c b/src/evaluate.c
index ce1e65f4..0afd0403 100644
--- a/src/evaluate.c
+++ b/src/evaluate.c
@@ -2849,6 +2849,52 @@ static int stmt_evaluate_addr(struct eval_ctx *ctx, struct stmt *stmt,
 	return err;
 }
 
+static int stmt_evaluate_nat_map(struct eval_ctx *ctx, struct stmt *stmt)
+{
+	struct expr *one, *two, *data, *tmp;
+	const struct datatype *dtype;
+	int err;
+
+	dtype = get_addr_dtype(stmt->nat.family);
+
+	expr_set_context(&ctx->ectx, dtype, dtype->size);
+	if (expr_evaluate(ctx, &stmt->nat.addr))
+		return -1;
+
+	data = stmt->nat.addr->mappings->set->data;
+	if (expr_ops(data)->type != EXPR_CONCAT)
+		return __stmt_evaluate_arg(ctx, stmt, dtype, dtype->size,
+					   BYTEORDER_BIG_ENDIAN,
+					   &stmt->nat.addr);
+
+	one = list_first_entry(&data->expressions, struct expr, list);
+	two = list_entry(one->list.next, struct expr, list);
+
+	if (one == two || !list_is_last(&two->list, &data->expressions))
+		return __stmt_evaluate_arg(ctx, stmt, dtype, dtype->size,
+					   BYTEORDER_BIG_ENDIAN,
+					   &stmt->nat.addr);
+
+	tmp = one;
+	err = __stmt_evaluate_arg(ctx, stmt, dtype, dtype->size,
+				  BYTEORDER_BIG_ENDIAN,
+				  &tmp);
+	if (err < 0)
+		return err;
+	if (tmp != one)
+		BUG("Internal error: Unexpected alteration of l3 expression");
+
+	tmp = two;
+	err = nat_evaluate_transport(ctx, stmt, &tmp);
+	if (err < 0)
+		return err;
+	if (tmp != two)
+		BUG("Internal error: Unexpected alteration of l4 expression");
+
+	stmt->nat.ipportmap = true;
+	return err;
+}
+
 static int stmt_evaluate_nat(struct eval_ctx *ctx, struct stmt *stmt)
 {
 	int err;
@@ -2862,6 +2908,16 @@ static int stmt_evaluate_nat(struct eval_ctx *ctx, struct stmt *stmt)
 		if (err < 0)
 			return err;
 
+		if (stmt->nat.proto == NULL &&
+		    expr_ops(stmt->nat.addr)->type == EXPR_MAP) {
+			err = stmt_evaluate_nat_map(ctx, stmt);
+			if (err < 0)
+				return err;
+
+			stmt->flags |= STMT_F_TERMINAL;
+			return 0;
+		}
+
 		err = stmt_evaluate_addr(ctx, stmt, stmt->nat.family,
 					 &stmt->nat.addr);
 		if (err < 0)
diff --git a/src/netlink_delinearize.c b/src/netlink_delinearize.c
index 4f774fb9..6203a53c 100644
--- a/src/netlink_delinearize.c
+++ b/src/netlink_delinearize.c
@@ -978,6 +978,35 @@ static void netlink_parse_reject(struct netlink_parse_ctx *ctx,
 	ctx->stmt = stmt;
 }
 
+static bool is_nat_proto_map(const struct expr *addr, uint8_t family)
+{
+	const struct expr *mappings, *data;
+	const struct set *set;
+
+	if (!addr ||
+	    expr_ops(addr)->type != EXPR_MAP)
+		return false;
+
+	mappings = addr->right;
+	if (expr_ops(mappings)->type != EXPR_SET_REF)
+		return false;
+
+	set = mappings->set;
+	data = set->data;
+
+	/* if we're dealing with an address:inet_service map,
+	 * the length will be bit_sizeof(addr) + 32 (one register).
+	 */
+	switch (family) {
+	case NFPROTO_IPV4:
+		return data->len == 32 + 32;
+	case NFPROTO_IPV6:
+		return data->len == 128 + 32;
+	}
+
+	return false;
+}
+
 static void netlink_parse_nat(struct netlink_parse_ctx *ctx,
 			      const struct location *loc,
 			      const struct nftnl_expr *nle)
@@ -998,6 +1027,7 @@ static void netlink_parse_nat(struct netlink_parse_ctx *ctx,
 	if (nftnl_expr_is_set(nle, NFTNL_EXPR_NAT_FLAGS))
 		stmt->nat.flags = nftnl_expr_get_u32(nle, NFTNL_EXPR_NAT_FLAGS);
 
+	addr = NULL;
 	reg1 = netlink_parse_register(nle, NFTNL_EXPR_NAT_REG_ADDR_MIN);
 	if (reg1) {
 		addr = netlink_get_register(ctx, loc, reg1);
@@ -1034,6 +1064,12 @@ static void netlink_parse_nat(struct netlink_parse_ctx *ctx,
 		stmt->nat.addr = addr;
 	}
 
+	if (is_nat_proto_map(addr, family)) {
+		stmt->nat.ipportmap = true;
+		ctx->stmt = stmt;
+		return;
+	}
+
 	reg1 = netlink_parse_register(nle, NFTNL_EXPR_NAT_REG_PROTO_MIN);
 	if (reg1) {
 		proto = netlink_get_register(ctx, loc, reg1);
diff --git a/src/netlink_linearize.c b/src/netlink_linearize.c
index b542aa3b..de461775 100644
--- a/src/netlink_linearize.c
+++ b/src/netlink_linearize.c
@@ -1052,14 +1052,25 @@ static void netlink_gen_reject_stmt(struct netlink_linearize_ctx *ctx,
 	nftnl_rule_add_expr(ctx->nlr, nle);
 }
 
+static unsigned int nat_addrlen(uint8_t family)
+{
+	switch (family) {
+	case NFPROTO_IPV4: return 32;
+	case NFPROTO_IPV6: return 128;
+	}
+
+	BUG("invalid nat family %u\n", family);
+	return 0;
+}
+
 static void netlink_gen_nat_stmt(struct netlink_linearize_ctx *ctx,
 				 const struct stmt *stmt)
 {
 	struct nftnl_expr *nle;
 	enum nft_registers amin_reg, amax_reg;
 	enum nft_registers pmin_reg, pmax_reg;
+	uint8_t family = 0;
 	int registers = 0;
-	int family;
 	int nftnl_flag_attr;
 	int nftnl_reg_pmin, nftnl_reg_pmax;
 
@@ -1118,6 +1129,24 @@ static void netlink_gen_nat_stmt(struct netlink_linearize_ctx *ctx,
 					     amin_reg);
 		}
 
+		if (stmt->nat.ipportmap) {
+			/* nat_stmt evaluation step doesn't allow
+			 * stmt->nat.ipportmap && stmt->nat.proto.
+			 */
+			assert(stmt->nat.proto == NULL);
+
+			pmin_reg = amin_reg;
+
+			/* if ipportmap is set, the mapped type is a
+			 * concatenation of 'addr . inet_service'.
+			 * The map lookup will then return the
+			 * concatenated value, so we need to skip
+			 * the address and use the register that
+			 * will hold the inet_service part.
+			 */
+			pmin_reg += netlink_register_space(nat_addrlen(family));
+			netlink_put_register(nle, nftnl_reg_pmin, pmin_reg);
+		}
 	}
 
 	if (stmt->nat.proto) {