netlink: split generic part of netlink_gen_payload_mask into helper

netlink_gen_payload_mask assumes expr is a payload expression,
but most of this function would work fine with exthdr too.

So split the gernic part into a helper, followup patch will
add netlink_gen_exthdr_mask.

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

diff --git a/src/netlink_linearize.c b/src/netlink_linearize.c
index 86b49c641784030d285eba29475e3d3ccc1fe9a9..7715a287d4b02296f954a001e75415ca70b3523a 100644 (file)
--- a/src/netlink_linearize.c
+++ b/src/netlink_linearize.c
@@ -103,12 +103,13 @@ static void netlink_gen_concat(struct netlink_linearize_ctx *ctx,
        }
 }
 
-static unsigned int payload_shift_calc(const struct expr *expr)
+static unsigned int payload_shift_calc(const struct expr *expr,
+                                      unsigned int offset)
 {
-       unsigned int offset, len;
+       unsigned int len;
        int shift;
 
-       offset = expr->payload.offset % BITS_PER_BYTE;
+       offset %= BITS_PER_BYTE;
        len = round_up(expr->len, BITS_PER_BYTE);
        shift = len - (offset + expr->len);
        assert(shift >= 0);
@@ -116,19 +117,16 @@ static unsigned int payload_shift_calc(const struct expr *expr)
        return shift;
 }
 
-static void netlink_gen_payload_mask(struct netlink_linearize_ctx *ctx,
-                                    const struct expr *expr,
-                                    enum nft_registers dreg)
+static void netlink_gen_mask(struct netlink_linearize_ctx *ctx,
+                            const struct expr *expr,
+                            unsigned int shift,
+                            enum nft_registers dreg)
 {
        struct nft_data_linearize nld, zero = {};
-       unsigned int shift, len, masklen;
+       unsigned int len, masklen;
        struct nftnl_expr *nle;
        mpz_t mask;
 
-       shift = payload_shift_calc(expr);
-       if (!shift && expr->payload.offset % BITS_PER_BYTE == 0)
-               return;
-
        masklen = expr->len + shift;
        assert(masklen <= NFT_REG_SIZE * BITS_PER_BYTE);
        mpz_init2(mask, masklen);
@@ -151,6 +149,18 @@ static void netlink_gen_payload_mask(struct netlink_linearize_ctx *ctx,
        nftnl_rule_add_expr(ctx->nlr, nle);
 }
 
+static void netlink_gen_payload_mask(struct netlink_linearize_ctx *ctx,
+                                    const struct expr *expr,
+                                    enum nft_registers dreg)
+{
+       unsigned int shift, offset;
+
+       offset = expr->payload.offset % BITS_PER_BYTE;
+       shift = payload_shift_calc(expr, offset);
+       if (shift || offset)
+               netlink_gen_mask(ctx, expr, shift, dreg);
+}
+
 static void netlink_gen_payload(struct netlink_linearize_ctx *ctx,
                                const struct expr *expr,
                                enum nft_registers dreg)
@@ -300,7 +310,8 @@ static void payload_shift_value(const struct expr *left, struct expr *right)
            left->ops->type != EXPR_PAYLOAD)
                return;
 
-       mpz_lshift_ui(right->value, payload_shift_calc(left));
+       mpz_lshift_ui(right->value,
+                       payload_shift_calc(left, left->payload.offset));
 }
 
 static struct expr *netlink_gen_prefix(struct netlink_linearize_ctx *ctx,