This enables nft to display
frag frag-off 33
... by considering a mask during binop postprocess in case
the initial template lookup done when the exthdr expression was
created did not yield a match.
In the above example, kernel netlink data specifies 16bits,
but the frag field is only 13bits wide.
We use the implicit binop mask to re-do the template lookup with
corrected offset and size information.
Signed-off-by: Florian Westphal <fw@xxxxxxxxx>
---
include/exthdr.h | 2 ++
src/exthdr.c | 31 +++++++++++++++++++++++++++++++
src/netlink_delinearize.c | 12 ++++++++----
3 files changed, 41 insertions(+), 4 deletions(-)
diff --git a/include/exthdr.h b/include/exthdr.h
index 87c4285..d17841b 100644
--- a/include/exthdr.h
+++ b/include/exthdr.h
@@ -23,6 +23,8 @@ extern struct expr *exthdr_expr_alloc(const struct location *loc,
extern void exthdr_init_raw(struct expr *expr, uint8_t type,
unsigned int offset, unsigned int len);
+extern bool exthdr_find_template(struct expr *expr, const struct expr *mask,
+ unsigned int *shift);
enum hbh_hdr_fields {
HBHHDR_INVALID,
diff --git a/src/exthdr.c b/src/exthdr.c
index 512de0a..f392cff 100644
--- a/src/exthdr.c
+++ b/src/exthdr.c
@@ -102,6 +102,37 @@ void exthdr_init_raw(struct expr *expr, uint8_t type,
}
}
+static unsigned int mask_length(const struct expr *mask)
+{
+ unsigned long off = mpz_scan1(mask->value, 0);
+
+ return mpz_scan0(mask->value, off + 1);
+}
+
+bool exthdr_find_template(struct expr *expr, const struct expr *mask, unsigned int *shift)
+{
+ unsigned int off, mask_offset, mask_len;
+
+ if (expr->exthdr.tmpl != &exthdr_unknown_template)
+ return false;
+
+ mask_offset = mpz_scan1(mask->value, 0);
+ mask_len = mask_length(mask);
+
+ off = expr->exthdr.offset;
+ off += round_up(mask->len, BITS_PER_BYTE) - mask_len;
+
+ exthdr_init_raw(expr, expr->exthdr.desc->type,
+ off, mask_len - mask_offset);
+
+ /* still failed to find a template... Bug. */
+ if (expr->exthdr.tmpl == &exthdr_unknown_template)
+ return false;
+
+ *shift = mask_offset;
+ return true;
+}
+
#define HDR_TEMPLATE(__name, __dtype, __type, __member) \
PROTO_HDR_TEMPLATE(__name, __dtype, \
BYTEORDER_BIG_ENDIAN, \
diff --git a/src/netlink_delinearize.c b/src/netlink_delinearize.c
index 30c5f62..fae6e33 100644
--- a/src/netlink_delinearize.c
+++ b/src/netlink_delinearize.c
@@ -1218,7 +1218,9 @@ static void binop_postprocess(struct rule_pp_ctx *ctx, struct expr *expr)
unsigned int shift;
if ((left->ops->type == EXPR_PAYLOAD &&
- payload_expr_trim(left, mask, &ctx->pctx, &shift))) {
+ payload_expr_trim(left, mask, &ctx->pctx, &shift)) ||
+ (left->ops->type == EXPR_EXTHDR &&
+ exthdr_find_template(left, mask, &shift))) {
/* mask is implicit, binop needs to be removed.
*
* Fix all values of the expression according to the mask
@@ -1226,7 +1228,7 @@ static void binop_postprocess(struct rule_pp_ctx *ctx, struct expr *expr)
* sizes and offsets we're interested in.
*
* Finally, convert the expression to 1) by replacing
- * the binop with the binop payload expr.
+ * the binop with the binop payload/exthdr expression.
*/
if (value->ops->type == EXPR_VALUE) {
assert(value->len >= expr->left->right->len);
@@ -1238,8 +1240,10 @@ static void binop_postprocess(struct rule_pp_ctx *ctx, struct expr *expr)
assert(binop->left == left);
expr->left = expr_get(left);
expr_free(binop);
-
- payload_match_postprocess(ctx, expr, left);
+ if (left->ops->type == EXPR_PAYLOAD)
+ payload_match_postprocess(ctx, expr, left);
+ else if (left->ops->type == EXPR_EXTHDR)
+ expr_set_type(expr->right, left->dtype, left->byteorder);
}
}
--
2.4.10
--
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