[PATCH nft v2] evaluate: fix expr_set_context call for shift binops.

[Jeremy Sowden <jeremy@xxxxxxxxxx>]

expr_evaluate_binop calls expr_set_context for shift expressions to set
the context data-type to `integer`.  This clobbers the byte-order of the
context, resulting in unexpected conversions to NBO.  For example:

  $ sudo nft flush ruleset
  $ sudo nft add table t
  $ sudo nft add chain t c '{ type filter hook output priority mangle; }'
  $ sudo nft add rule t c oif lo tcp dport ssh ct mark set '0x10 | 0xe'
  $ sudo nft add rule t c oif lo tcp dport ssh ct mark set '0xf << 1'
  $ sudo nft list table t
  table ip t {
          chain c {
                  type filter hook output priority mangle; policy accept;
                  oif "lo" tcp dport 22 ct mark set 0x0000001e
                  oif "lo" tcp dport 22 ct mark set 0x1e000000
          }
  }

Replace it with a call to __expr_set_context in order to preserve host
endianness.

Signed-off-by: Jeremy Sowden <jeremy@xxxxxxxxxx>
---
 src/evaluate.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Change-log:

  In v1, I just dropped the expr_set_context call; however, it is needed
  to ensure that the right operand has integer type.  Instead, I now
  change it to __expr_set_context in order to ensure that the byte-order
  is correct.

diff --git a/src/evaluate.c b/src/evaluate.c
index a865902c0fc7..43637e1cf6c8 100644
--- a/src/evaluate.c
+++ b/src/evaluate.c
@@ -1145,7 +1145,8 @@ static int expr_evaluate_binop(struct eval_ctx *ctx, struct expr **expr)
 	left = op->left;
 
 	if (op->op == OP_LSHIFT || op->op == OP_RSHIFT)
-		expr_set_context(&ctx->ectx, &integer_type, ctx->ectx.len);
+		__expr_set_context(&ctx->ectx, &integer_type,
+				   BYTEORDER_HOST_ENDIAN, ctx->ectx.len, 0);
 	if (expr_evaluate(ctx, &op->right) < 0)
 		return -1;
 	right = op->right;
-- 
2.24.0