fix several problems with config parser:

 a bug where it underflows the string
 a bug where it never frees parser_t struct
make read_config() return 0 if parser is NULL,
 make config_close() accept and ignore NULL parser -
 eliminates many if() blocks
reverse the sense of parser bit flags - negative flags
 are harder to grok.
hexdump: revert the change to use config parser, it is BIGGER
 and also requires additional quirks in parser
*: explicitly use PARSER_NORMAL instead of 0

function                                             old     new   delta
login_main                                          1575    1596     +21
config_close                                          18      29     +11
bbunpack                                             383     391      +8
qgravechar                                           106     109      +3
rtnl_tab_initialize                                  121     117      -4
expand                                              1697    1693      -4
man_main                                             717     712      -5
nameif_main                                          674     668      -6
hexdump_main                                         597     591      -6
read_config                                          217     209      -8
dnsd_main                                           1478    1470      -8
sysctl_main                                          203     189     -14
config_open2                                          44      25     -19
make_device                                         1177    1141     -36
config_read                                          597     549     -48
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 4/11 up/down: 43/-158)         Total: -115 bytes

5 files changed, 36 insertions, 45 deletions

diff --git a/networking/dnsd.c b/networking/dnsd.c
index efb5cfb..e8dcb40 100644
--- a/networking/dnsd.c
+++ b/networking/dnsd.c
@@ -106,43 +106,41 @@ static void undot(uint8_t * rip)
  */
 static void dnsentryinit(void)
 {
+	char *token[2];
 	parser_t *parser;
 	struct dns_entry *m, *prev;
 
 	prev = dnsentry = NULL;
 	parser = config_open(fileconf);
-	if (parser) {
-		char *token[2];
-		while (config_read(parser, token, 2, 2, "# \t", 0)) {
-			unsigned int a,b,c,d;
-			/*
-			 * Assumes all host names are lower case only
-			 * Hostnames with more than one label are not handled correctly.
-			 * Presently the dot is copied into name without
-			 * converting to a length/string substring for that label.
-			 */
-//			if (!token[1] || sscanf(token[1], ".%u.%u.%u.%u"+1, &a, &b, &c, &d) != 4)
-			if (sscanf(token[1], ".%u.%u.%u.%u"+1, &a, &b, &c, &d) != 4)
-				continue;
-
-			m = xzalloc(sizeof(*m));
-			/*m->next = NULL;*/
-			sprintf(m->ip, ".%u.%u.%u.%u"+1, a, b, c, d);
-			sprintf(m->rip, ".%u.%u.%u.%u", d, c, b, a);
-			undot((uint8_t*)m->rip);
-			convname(m->name, (uint8_t*)token[0]);
-
-			if (OPT_verbose)
-				fprintf(stderr, "\tname:%s, ip:%s\n", &(m->name[1]), m->ip);
-
-			if (prev == NULL)
-				dnsentry = m;
-			else
-				prev->next = m;
-			prev = m;
-		}
-		config_close(parser);
+	while (config_read(parser, token, 2, 2, "# \t", PARSE_NORMAL)) {
+		unsigned a, b, c, d;
+		/*
+		 * Assumes all host names are lower case only
+		 * Hostnames with more than one label are not handled correctly.
+		 * Presently the dot is copied into name without
+		 * converting to a length/string substring for that label.
+		 */
+//		if (!token[1] || sscanf(token[1], ".%u.%u.%u.%u"+1, &a, &b, &c, &d) != 4)
+		if (sscanf(token[1], ".%u.%u.%u.%u"+1, &a, &b, &c, &d) != 4)
+			continue;
+
+		m = xzalloc(sizeof(*m));
+		/*m->next = NULL;*/
+		sprintf(m->ip, ".%u.%u.%u.%u"+1, a, b, c, d);
+		sprintf(m->rip, ".%u.%u.%u.%u", d, c, b, a);
+		undot((uint8_t*)m->rip);
+		convname(m->name, (uint8_t*)token[0]);
+
+		if (OPT_verbose)
+			fprintf(stderr, "\tname:%s, ip:%s\n", &(m->name[1]), m->ip);
+
+		if (prev == NULL)
+			dnsentry = m;
+		else
+			prev->next = m;
+		prev = m;
 	}
+	config_close(parser);
 }
 
 /*
diff --git a/networking/hostname.c b/networking/hostname.c
index dd2a206..48e70db 100644
--- a/networking/hostname.c
+++ b/networking/hostname.c
@@ -20,7 +20,7 @@ static void do_sethostname(char *s, int isfile)
 		return;
 	if (isfile) {
 		parser_t *parser = config_open2(s, xfopen_for_read);
-		while (config_read(parser, &s, 1, 1, "# \t", 0)) {
+		while (config_read(parser, &s, 1, 1, "# \t", PARSE_NORMAL & ~PARSE_GREEDY)) {
 			do_sethostname(s, 0);
 		}
 		if (ENABLE_FEATURE_CLEAN_UP)
diff --git a/networking/libiproute/rt_names.c b/networking/libiproute/rt_names.c
index 1a2d52e..e4d1061 100644
--- a/networking/libiproute/rt_names.c
+++ b/networking/libiproute/rt_names.c
@@ -20,9 +20,7 @@ static void rtnl_tab_initialize(const char *file, const char **tab, int size)
 {
 	char *token[2];
 	parser_t *parser = config_open2(file, fopen_for_read);
-	if (!parser)
-		return;
-	while (config_read(parser, token, 2, 2, "# \t", 0)) {
+	while (config_read(parser, token, 2, 2, "# \t", PARSE_NORMAL)) {
 		int id = bb_strtou(token[0], NULL, 0);
 		if (id < 0 || id > size) {
 			bb_error_msg("database %s is corrupted at line %d",
diff --git a/networking/nameif.c b/networking/nameif.c
index 5a3bd60..12c08f1 100644
--- a/networking/nameif.c
+++ b/networking/nameif.c
@@ -160,13 +160,11 @@ int nameif_main(int argc, char **argv)
 			prepend_new_eth_table(&clist, ifname, *argv++);
 		}
 	} else {
+		char *tokens[2];
 		struct parser_t *parser = config_open(fname);
-		if (parser) {
-			char *tokens[2];
-			while (config_read(parser, tokens, 2, 2, "# \t", 0))
-				prepend_new_eth_table(&clist, tokens[0], tokens[1]);
-			config_close(parser);
-		}
+		while (config_read(parser, tokens, 2, 2, "# \t", PARSE_NORMAL))
+			prepend_new_eth_table(&clist, tokens[0], tokens[1]);
+		config_close(parser);
 	}
 
 	ctl_sk = xsocket(PF_INET, SOCK_DGRAM, 0);
diff --git a/networking/udhcp/files.c b/networking/udhcp/files.c
index 264a988..ff5847d 100644
--- a/networking/udhcp/files.c
+++ b/networking/udhcp/files.c
@@ -318,10 +318,7 @@ void read_config(const char *file)
 		keywords[i].handler(keywords[i].def, keywords[i].var);
 
 	parser = config_open(file);
-	if (!parser)
-		return;
-
-	while (config_read(parser, token, 2, 2, "# \t", PARSE_LAST_IS_GREEDY)) {
+	while (config_read(parser, token, 2, 2, "# \t", PARSE_NORMAL)) {
 		for (k = keywords, i = 0; i < ARRAY_SIZE(keywords); k++, i++) {
 			if (!strcasecmp(token[0], k->keyword)) {
 				if (!k->handler(token[1], k->var)) {