trafgen: parser: add possibility for negative numbers

The previous commit reduced it, so now we allow it within cX() containers
in order to negate a result, if someone needs that.

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/trafgen_parser.y b/trafgen_parser.y
index b0e7e33..37c9a15 100644
--- a/trafgen_parser.y
+++ b/trafgen_parser.y
@@ -431,6 +431,8 @@ expression
 		{ $$ = $1 << $4; }
 	| expression '>' '>' expression
 		{ $$ = $1 >> $4; }
+	| '-' expression
+		{ $$ = -1 * $2; }
 	| '(' expression ')'
 		{ $$ = $2;}
 	;