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 efb5cfba7..e8dcb404b 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 dd2a20689..48e70db91 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 1a2d52e86..e4d10613b 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 5a3bd606f..12c08f13b 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 264a98899..ff5847d25 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)) {