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>

1 files changed, 30 insertions, 1 deletions

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) {