Conf: Allow keywords to be redefined by user symbols

Most syntactic constructs in BIRD configuration (e.g. protocol options)
are defined as keywords, which are distinct from symbols (user-defined
names for protocols, variables, ...). That may cause backwards
compatibility issue when a new feature is added, as it may collide with
existing user names.

We can allow keywords to be shadowed by symbols in almost all cases to
avoid this issue.

This replaces the previous mechanism, where shadowable symbols have to be
explictly added to kw_syms.

9 files changed, 20 insertions, 14 deletions

diff --git a/conf/confbase.Y b/conf/confbase.Y
index a6b4b1ee..a43a8cca 100644
--- a/conf/confbase.Y
+++ b/conf/confbase.Y
@@ -119,7 +119,6 @@ CF_DECLS
 %type <t> text opttext
 %type <bs> bytestring
 %type <s> symbol
-%type <kw> kw_sym
 
 %type <v> bytestring_text text_or_ipa
 %type <x> bytestring_expr
@@ -178,7 +177,7 @@ expr_us:
  | expr US { $$ = $1 US_; }
  ;
 
-symbol: CF_SYM_UNDEFINED | CF_SYM_KNOWN | kw_sym { $$ = cf_symbol_from_keyword($1); } ;
+symbol: CF_SYM_UNDEFINED | CF_SYM_KNOWN | KEYWORD { $$ = cf_symbol_from_keyword($1); } ;
 
 /* Switches */
 
diff --git a/conf/gen_keywords.m4 b/conf/gen_keywords.m4
index 0c1dc545..3206c186 100644
--- a/conf/gen_keywords.m4
+++ b/conf/gen_keywords.m4
@@ -28,6 +28,7 @@ m4_divert(-1)')
 m4_define(CF_keywd, `m4_ifdef([[CF_tok_$1]],,[[m4_define([[CF_tok_$1]],1)CF_handle_kw($1)]])')
 m4_define(CF_KEYWORDS, `m4_define([[CF_toks]],[[]])CF_iterate([[CF_keywd]], [[$@]])m4_ifelse(CF_toks,,,%token[[]]CF_toks
 )DNL')
+m4_define(CF_KEYWORDS_EXCLUSIVE, `CF_KEYWORDS($@)')
 
 # CLI commands generate keywords as well
 m4_define(CF_CLI, `CF_KEYWORDS(m4_translit($1, [[ ]], [[,]]))
diff --git a/conf/gen_parser.m4 b/conf/gen_parser.m4
index 7a2a9de4..a26af851 100644
--- a/conf/gen_parser.m4
+++ b/conf/gen_parser.m4
@@ -29,11 +29,17 @@ m4_define(CF_END, `m4_divert(-1)')
 m4_define(CF_itera, `m4_ifelse($#, 1, [[CF_iter($1)]], [[CF_iter($1)[[]]CF_itera(m4_shift($@))]])')
 m4_define(CF_iterate, `m4_define([[CF_iter]], m4_defn([[$1]]))CF_itera($2)')
 
+m4_define(CF_append, `m4_define([[$1]], m4_ifdef([[$1]], m4_defn([[$1]])[[$3]])[[$2]])')
+
 # Keywords act as %token<kw>
-m4_define(CF_keywd, `m4_ifdef([[CF_tok_$1]],,[[m4_define([[CF_tok_$1]],1)m4_define([[CF_toks]],CF_toks $1)]])')
+m4_define(CF_keywd, `m4_ifdef([[CF_tok_$1]],,[[m4_define([[CF_tok_$1]],1)CF_append([[CF_kw_rule]],$1,[[ | ]])m4_define([[CF_toks]],CF_toks $1)]])')
 m4_define(CF_KEYWORDS, `m4_define([[CF_toks]],[[]])CF_iterate([[CF_keywd]], [[$@]])m4_ifelse(CF_toks,,,%token<kw>[[]]CF_toks
 )DNL')
 
+m4_define(CF_keywd2, `m4_ifdef([[CF_tok_$1]],,[[m4_define([[CF_tok_$1]],1)m4_define([[CF_toks]],CF_toks $1)]])')
+m4_define(CF_KEYWORDS_EXCLUSIVE, `m4_define([[CF_toks]],[[]])CF_iterate([[CF_keywd2]], [[$@]])m4_ifelse(CF_toks,,,%token<kw>[[]]CF_toks
+)DNL')
+
 # CLI commands
 m4_define(CF_CLI, `m4_define([[CF_cmd]], cmd_[[]]m4_translit($1, [[ ]], _))DNL
 m4_divert(2)CF_KEYWORDS(m4_translit($1, [[ ]], [[,]]))
@@ -55,7 +61,11 @@ m4_undivert(1)DNL
 
 m4_undivert(2)DNL
 
+%type <kw> KEYWORD
+
 %%
+KEYWORD: CF_kw_rule;
+
 m4_undivert(3)DNL
 
 %%
diff --git a/filter/config.Y b/filter/config.Y
index e02af182..3bf3a2b6 100644
--- a/filter/config.Y
+++ b/filter/config.Y
@@ -298,12 +298,13 @@ assert_assign(struct f_lval *lval, struct f_inst *expr, const char *start, const
 
 CF_DECLS
 
+CF_KEYWORDS_EXCLUSIVE(IN)
 CF_KEYWORDS(FUNCTION, PRINT, PRINTN, UNSET, RETURN,
 	ACCEPT, REJECT, ERROR,
 	INT, BOOL, IP, TYPE, PREFIX, RD, PAIR, QUAD, EC, LC,
 	SET, STRING, BYTESTRING, BGPMASK, BGPPATH, CLIST, ECLIST, LCLIST,
 	IF, THEN, ELSE, CASE,
-	FOR, IN, DO,
+	FOR, DO,
 	TRUE, FALSE, RT, RO, UNKNOWN, GENERIC,
 	FROM, GW, NET, MASK, PROTO, SOURCE, SCOPE, DEST, IFNAME, IFINDEX, WEIGHT, GW_MPLS, ONLINK,
 	PREFERENCE,
diff --git a/nest/config.Y b/nest/config.Y
index ce45d98d..c583dc7f 100644
--- a/nest/config.Y
+++ b/nest/config.Y
@@ -154,8 +154,6 @@ CF_ENUM_PX(T_ENUM_AF, AF_, AFI_, IPV4, IPV6)
 
 CF_GRAMMAR
 
-kw_sym: MIN | MAX ;
-
 /* Setting of router ID */
 
 conf: rtrid ;
@@ -842,7 +840,7 @@ sym_args:
  | sym_args FILTER { $$ = $1; $$->type = SYM_FILTER; }
  | sym_args PROTOCOL { $$ = $1; $$->type = SYM_PROTO; }
  | sym_args TEMPLATE { $$ = $1; $$->type = SYM_TEMPLATE; }
- | sym_args symbol { $$ = $1; $$->sym = $2; }
+ | sym_args CF_SYM_KNOWN { $$ = $1; $$->sym = $2; }
  ;
 
 
diff --git a/proto/bgp/config.Y b/proto/bgp/config.Y
index 218e0d04..ba50446a 100644
--- a/proto/bgp/config.Y
+++ b/proto/bgp/config.Y
@@ -45,9 +45,6 @@ CF_KEYWORDS(CEASE, PREFIX, LIMIT, HIT, ADMINISTRATIVE, SHUTDOWN, RESET, PEER,
 
 CF_GRAMMAR
 
-/* Workaround for collisions between keywords and symbols */
-kw_sym: ROLE | PEER | PROVIDER | CUSTOMER | RS_SERVER | RS_CLIENT ;
-
 proto: bgp_proto '}'  ;
 
 bgp_proto_start: proto_start BGP {
diff --git a/proto/ospf/config.Y b/proto/ospf/config.Y
index 4b7d5a36..cfde3a5d 100644
--- a/proto/ospf/config.Y
+++ b/proto/ospf/config.Y
@@ -190,7 +190,8 @@ ospf_check_auth(void)
 
 CF_DECLS
 
-CF_KEYWORDS(OSPF, V2, V3, OSPF_METRIC1, OSPF_METRIC2, OSPF_TAG, OSPF_ROUTER_ID)
+CF_KEYWORDS_EXCLUSIVE(V2, V3)
+CF_KEYWORDS(OSPF, OSPF_METRIC1, OSPF_METRIC2, OSPF_TAG, OSPF_ROUTER_ID)
 CF_KEYWORDS(AREA, NEIGHBORS, RFC1583COMPAT, STUB, TICK, COST, COST2, RETRANSMIT)
 CF_KEYWORDS(HELLO, TRANSMIT, PRIORITY, DEAD, TYPE, BROADCAST, BCAST, DEFAULT)
 CF_KEYWORDS(NONBROADCAST, NBMA, POINTOPOINT, PTP, POINTOMULTIPOINT, PTMP)
diff --git a/proto/radv/config.Y b/proto/radv/config.Y
index 9c5e1761..c57752d9 100644
--- a/proto/radv/config.Y
+++ b/proto/radv/config.Y
@@ -50,8 +50,6 @@ CF_ENUM(T_ENUM_RA_PREFERENCE, RA_PREF_, LOW, MEDIUM, HIGH)
 
 CF_GRAMMAR
 
-kw_sym: CUSTOM | OPTION | VALUE ;
-
 proto: radv_proto ;
 
 radv_proto_start: proto_start RADV
diff --git a/proto/rip/config.Y b/proto/rip/config.Y
index 28ee9609..1fab4527 100644
--- a/proto/rip/config.Y
+++ b/proto/rip/config.Y
@@ -32,7 +32,8 @@ rip_check_auth(void)
 
 CF_DECLS
 
-CF_KEYWORDS(RIP, NG, ECMP, LIMIT, WEIGHT, INFINITY, METRIC, UPDATE, TIMEOUT,
+CF_KEYWORDS_EXCLUSIVE(NG)
+CF_KEYWORDS(RIP, ECMP, LIMIT, WEIGHT, INFINITY, METRIC, UPDATE, TIMEOUT,
 	    GARBAGE, RETRANSMIT, PORT, ADDRESS, MODE, BROADCAST, MULTICAST,
 	    PASSIVE, VERSION, SPLIT, HORIZON, POISON, REVERSE, CHECK, ZERO,
 	    TIME, BFD, AUTHENTICATION, NONE, PLAINTEXT, CRYPTOGRAPHIC, MD5,