[nft PATCH 2/2] payload: generate dependency with wrong byteorder value format

[Alvaro Neira Ayuso <alvaroneay@gmail.com>]

From: Álvaro Neira Ayuso <alvaroneay@gmail.com>

In all case that we have added a payload dependency, we have supposed
that the byteorder must to be BYTEORDER_HOST_ENDIAN, the problem is
when we want to add a dependency that the value has another byteorder.
For example, if we try to add a new payload dependency in a bridge table
and we use ether type, the byteorder is BYTEORDER_BIG_ENDIAN. The value
of the type ip is 0x0800 in ether but when we add the payload dependency
for this specific protocol, we will have a payload like this:

[ payload load 2b @ link header + 12 => reg 1 ]
  [ cmp eq reg 1 0x00000008 ]

This patch allows to create payload dependency with the byteorder of the
template. For that I have updated the function for updating the context for
using the byteorder of the template too. With this changes we have a payload
with the correct format:

[ payload load 2b @ link header + 12 => reg 1 ]
  [ cmp eq reg 1 0x00000800 ]

Signed-off-by: Alvaro Neira Ayuso <alvaroneay@gmail.com>
---
[tested with the rules]

nft add rule filter input ip protocol tcp counter
nft add rule filter input ip protocol udp counter
nft add rule filter input tcp dport 22 counter

 src/payload.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/payload.c b/src/payload.c
index a1785a5..fb78ba5 100644
--- a/src/payload.c
+++ b/src/payload.c
@@ -69,13 +69,18 @@ static void payload_expr_pctx_update(struct proto_ctx *ctx,
 {
 	const struct expr *left = expr->left, *right = expr->right;
 	const struct proto_desc *base, *desc;
+	const struct proto_hdr_template *tmpl;
+	uint32_t value = 0;
 
 	if (!(left->flags & EXPR_F_PROTOCOL))
 		return;
 
 	assert(expr->op == OP_EQ);
 	base = ctx->protocol[left->payload.base].desc;
-	desc = proto_find_upper(base, mpz_get_uint32(right->value));
+	tmpl = &base->templates[base->protocol_key];
+	mpz_export_data(&value, right->value, tmpl->dtype->byteorder,
+			div_round_up(tmpl->len, BITS_PER_BYTE));
+	desc = proto_find_upper(base, value);
 
 	proto_ctx_update(ctx, left->payload.base + 1, &expr->location, desc);
 }
@@ -208,7 +213,7 @@ int payload_gen_dependency(struct eval_ctx *ctx, const struct expr *expr,
 		left = payload_expr_alloc(&expr->location, desc, desc->protocol_key);
 
 	right = constant_expr_alloc(&expr->location, tmpl->dtype,
-				    BYTEORDER_HOST_ENDIAN,
+				    tmpl->dtype->byteorder,
 				    tmpl->len,
 				    constant_data_ptr(protocol, tmpl->len));
 
-- 
1.7.10.4

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