[PATCH nftables 6/9] segtree: add string "range" reversal support

[Florian Westphal <fw@strlen.de>]

Previous commits allows to use set key as a range, i.e.

	key ifname
	flags interval
	elements = { eth* }

and then have it match on any interface starting with 'eth'.

Listing is broken however, we need to reverse-translate the (128bit)
number back to a string.

'eth*' is stored as interval
00687465 0000000 ..  00697465 0000000, i.e. "eth-eti",
this adds the needed endianess fixups.

Signed-off-by: Florian Westphal <fw@strlen.de>
---
 src/segtree.c | 47 +++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 41 insertions(+), 6 deletions(-)

diff --git a/src/segtree.c b/src/segtree.c
index b4e76bf530d6..bed8bbcf0c8e 100644
--- a/src/segtree.c
+++ b/src/segtree.c
@@ -1032,6 +1032,33 @@ static struct expr *interval_to_prefix(struct expr *low, struct expr *i, const m
 	return __expr_to_set_elem(low, prefix);
 }
 
+static struct expr *interval_to_string(struct expr *low, struct expr *i, const mpz_t range)
+{
+	unsigned int len = div_round_up(i->len, BITS_PER_BYTE);
+	unsigned int prefix_len, str_len;
+	char data[len + 2];
+	struct expr *expr;
+
+	prefix_len = expr_value(i)->len - mpz_scan0(range, 0);
+
+	if (prefix_len > i->len || prefix_len % BITS_PER_BYTE)
+		return interval_to_prefix(low, i, range);
+
+	mpz_export_data(data, expr_value(low)->value, BYTEORDER_BIG_ENDIAN, len);
+
+	str_len = strnlen(data, len);
+	if (str_len >= len || str_len == 0)
+		return interval_to_prefix(low, i, range);
+
+	data[str_len] = '*';
+
+	expr = constant_expr_alloc(&low->location, low->dtype,
+				   BYTEORDER_HOST_ENDIAN,
+				   (str_len + 1) * BITS_PER_BYTE, data);
+
+	return __expr_to_set_elem(low, expr);
+}
+
 static struct expr *interval_to_range(struct expr *low, struct expr *i, mpz_t range)
 {
 	struct expr *tmp;
@@ -1130,16 +1157,24 @@ void interval_map_decompose(struct expr *set)
 
 		mpz_and(p, expr_value(low)->value, range);
 
-		if (!mpz_cmp_ui(range, 0))
+		if (!mpz_cmp_ui(range, 0)) {
+			if (expr_basetype(low)->type == TYPE_STRING)
+				mpz_switch_byteorder(expr_value(low)->value, low->len / BITS_PER_BYTE);
+
 			compound_expr_add(set, expr_get(low));
-		else if ((!range_is_prefix(range) ||
-			  !(i->dtype->flags & DTYPE_F_PREFIX)) ||
-			 mpz_cmp_ui(p, 0)) {
-			struct expr *expr = interval_to_range(low, i, range);
+		} else if (range_is_prefix(range) && !mpz_cmp_ui(p, 0)) {
+			struct expr *expr;
+
+			if (i->dtype->flags & DTYPE_F_PREFIX)
+				expr = interval_to_prefix(low, i, range);
+			else if (expr_basetype(i)->type == TYPE_STRING)
+				expr = interval_to_string(low, i, range);
+			else
+				expr = interval_to_range(low, i, range);
 
 			compound_expr_add(set, expr);
 		} else {
-			struct expr *expr = interval_to_prefix(low, i, range);
+			struct expr *expr = interval_to_range(low, i, range);
 
 			compound_expr_add(set, expr);
 		}
-- 
2.35.1