src: add offset attribute for numgen expression

Add support to add an offset to the numgen generated value.

Example:

 ct mark set numgen inc mod 2 offset 100

This will generate marks with serie like 100, 101, 100, ...

Signed-off-by: Laura Garcia Liebana <nevola@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

4 files changed, 14 insertions, 6 deletions

diff --git a/src/netlink_delinearize.c b/src/netlink_delinearize.c
index d8d1d7d7..c3b0b278 100644
--- a/src/netlink_delinearize.c
+++ b/src/netlink_delinearize.c
@@ -590,13 +590,14 @@ static void netlink_parse_numgen(struct netlink_parse_ctx *ctx,
 				 const struct nftnl_expr *nle)
 {
 	enum nft_registers dreg;
-	uint32_t type, until;
+	uint32_t type, until, offset;
 	struct expr *expr;
 
 	type  = nftnl_expr_get_u32(nle, NFTNL_EXPR_NG_TYPE);
 	until = nftnl_expr_get_u32(nle, NFTNL_EXPR_NG_MODULUS);
+	offset = nftnl_expr_get_u32(nle, NFTNL_EXPR_NG_OFFSET);
 
-	expr = numgen_expr_alloc(loc, type, until);
+	expr = numgen_expr_alloc(loc, type, until, offset);
 	dreg = netlink_parse_register(nle, NFTNL_EXPR_NG_DREG);
 	netlink_set_register(ctx, dreg, expr);
 }
diff --git a/src/netlink_linearize.c b/src/netlink_linearize.c
index 0072dca0..80199318 100644
--- a/src/netlink_linearize.c
+++ b/src/netlink_linearize.c
@@ -182,6 +182,7 @@ static void netlink_gen_numgen(struct netlink_linearize_ctx *ctx,
 	netlink_put_register(nle, NFTNL_EXPR_NG_DREG, dreg);
 	netlink_put_register(nle, NFTNL_EXPR_NG_TYPE, expr->numgen.type);
 	nftnl_expr_set_u32(nle, NFTNL_EXPR_NG_MODULUS, expr->numgen.mod);
+	nftnl_expr_set_u32(nle, NFTNL_EXPR_NG_OFFSET, expr->numgen.offset);
 	nftnl_rule_add_expr(ctx->nlr, nle);
 }
 
diff --git a/src/numgen.c b/src/numgen.c
index d9a43aa0..5c1d00a0 100644
--- a/src/numgen.c
+++ b/src/numgen.c
@@ -32,18 +32,22 @@ static void numgen_expr_print(const struct expr *expr)
 {
 	printf("numgen %s mod %u", numgen_type_str(expr->numgen.type),
 	       expr->numgen.mod);
+	if (expr->numgen.offset)
+		printf(" offset %u", expr->numgen.offset);
 }
 
 static bool numgen_expr_cmp(const struct expr *e1, const struct expr *e2)
 {
 	return e1->numgen.type == e2->numgen.type &&
-	       e1->numgen.mod == e2->numgen.mod;
+	       e1->numgen.mod == e2->numgen.mod &&
+	       e1->numgen.offset == e2->numgen.offset;
 }
 
 static void numgen_expr_clone(struct expr *new, const struct expr *expr)
 {
 	new->numgen.type = expr->numgen.type;
 	new->numgen.mod = expr->numgen.mod;
+	new->numgen.offset = expr->numgen.offset;
 }
 
 static const struct expr_ops numgen_expr_ops = {
@@ -55,7 +59,8 @@ static const struct expr_ops numgen_expr_ops = {
 };
 
 struct expr *numgen_expr_alloc(const struct location *loc,
-			       enum nft_ng_types type, uint32_t mod)
+			       enum nft_ng_types type, uint32_t mod,
+			       uint32_t offset)
 {
 	struct expr *expr;
 
@@ -63,6 +68,7 @@ struct expr *numgen_expr_alloc(const struct location *loc,
 			  BYTEORDER_HOST_ENDIAN, 4 * BITS_PER_BYTE);
 	expr->numgen.type  = type;
 	expr->numgen.mod   = mod;
+	expr->numgen.offset = offset;
 
 	return expr;
 }
diff --git a/src/parser_bison.y b/src/parser_bison.y
index f582221a..7377492b 100644
--- a/src/parser_bison.y
+++ b/src/parser_bison.y
@@ -2490,9 +2490,9 @@ numgen_type		:	INC		{ $$ = NFT_NG_INCREMENTAL; }
 			|	RANDOM		{ $$ = NFT_NG_RANDOM; }
 			;
 
-numgen_expr		:	NUMGEN	numgen_type	MOD	NUM
+numgen_expr		:	NUMGEN	numgen_type	MOD	NUM	offset_opt
 			{
-				$$ = numgen_expr_alloc(&@$, $2, $4);
+				$$ = numgen_expr_alloc(&@$, $2, $4, $5);
 			}
 			;