scanner: introduce start condition stack

Add a small initial chunk of flex start conditionals.

This starts with two low-hanging fruits, numgen and j/symhash.

NUMGEN and HASH start conditions are entered from flex when
the corresponding expression token is encountered.

Flex returns to the INIT condition when the bison parser
has seen a complete numgen/hash statement.

This intentionally uses a stack rather than BEGIN()
to eventually support nested states.

The scanner_pop_start_cond() function argument is not used yet, but
will need to be used later to deal with nesting.

Signed-off-by: Florian Westphal <fw@strlen.de>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/parser.h b/include/parser.h
index 9baa3a4d..b2ebd7aa 100644
--- a/include/parser.h
+++ b/include/parser.h
@@ -26,6 +26,12 @@ struct parser_state {
 	struct list_head		*cmds;
 };
 
+enum startcond_type {
+	PARSER_SC_BEGIN,
+	PARSER_SC_EXPR_HASH,
+	PARSER_SC_EXPR_NUMGEN,
+};
+
 struct mnl_socket;
 
 extern void parser_init(struct nft_ctx *nft, struct parser_state *state,
@@ -45,4 +51,6 @@ extern void scanner_push_buffer(void *scanner,
 				const struct input_descriptor *indesc,
 				const char *buffer);
 
+extern void scanner_pop_start_cond(void *scanner, enum startcond_type sc);
+
 #endif /* NFTABLES_PARSER_H */