Fix some warnings reported by CODESonar (#2227)

Remove some unreached/duplicated code.

Add error checking for `atoi()` calls.

About `isdigit()` and similar functions. The warning reported is:
```
Negative Character Value help
isdigit() is invoked here with an argument of signed type char, but only
has defined behavior for int arguments that are either representable
as unsigned char or equal to the value of macro EOF(-1).
Casting the argument to unsigned char will avoid the undefined behavior.
In a number of libc implementations, isdigit() is implemented using lookup
tables (arrays): passing in a negative value can result in a read underrun.
```
Switching to our macros fix that.
Add a check to `check_symbols.sh` to avoid using the original functions
from libc.

1 files changed, 31 insertions, 35 deletions

diff --git a/src/lib/ndpi_main.c b/src/lib/ndpi_main.c
index d9ba5b952..d870ffe5c 100644
--- a/src/lib/ndpi_main.c
+++ b/src/lib/ndpi_main.c
@@ -4539,7 +4539,7 @@ int ndpi_load_categories_file(struct ndpi_detection_module_struct *ndpi_str,
 int load_categories_file_fd(struct ndpi_detection_module_struct *ndpi_str,
 			    FILE *fd, void *user_data) {
   char buffer[512], *line, *name, *category, *saveptr;
-  int len, num = 0;
+  int len, num = 0, cat_id;
 
   if(!ndpi_str || !fd)
     return(-1);
@@ -4562,12 +4562,17 @@ int load_categories_file_fd(struct ndpi_detection_module_struct *ndpi_str,
       category = strtok_r(NULL, "\t", &saveptr);
 
       if(category) {
-	int rc = ndpi_load_category(ndpi_str, name,
-				    (ndpi_protocol_category_t) atoi(category),
-				    user_data);
+        const char *errstrp;
+        cat_id = ndpi_strtonum(category, 1, NDPI_PROTOCOL_NUM_CATEGORIES - 1, &errstrp, 10);
+        if(errstrp == NULL) {
+
+          int rc = ndpi_load_category(ndpi_str, name,
+				      (ndpi_protocol_category_t)cat_id,
+				      user_data);
 
-	if(rc >= 0)
-	  num++;
+          if(rc >= 0)
+           num++;
+        }
       }
     }
   }
@@ -4634,7 +4639,7 @@ int ndpi_load_category_file(struct ndpi_detection_module_struct *ndpi_str,
         line[i] = '\0';
         break;
       }
-      if (line[i] != '-' && line[i] != '.' && isalnum(line[i]) == 0
+      if (line[i] != '-' && line[i] != '.' && ndpi_isalnum(line[i]) == 0
           /* non standard checks for the sake of compatibility */
           && line[i] != '_')
         break;
@@ -4689,19 +4694,19 @@ int ndpi_load_categories_dir(struct ndpi_detection_module_struct *ndpi_str,
 
     /* Check if the format is <proto it>_<string>.<extension> */
     if((underscore = strchr(dp->d_name, '_')) != NULL) {
-      ndpi_protocol_category_t proto_id;
+      int cat_id;
+      const char *errstrp;
 
       underscore[0] = '\0';
-      proto_id = (ndpi_protocol_category_t)atoi(dp->d_name);
-
-      if((proto_id > 0) && (proto_id < (u_int16_t)NDPI_LAST_IMPLEMENTED_PROTOCOL)) {
+      cat_id = ndpi_strtonum(dp->d_name, 1, NDPI_PROTOCOL_NUM_CATEGORIES - 1, &errstrp, 10);
+      if(errstrp == NULL) {
 	/* Valid file */
 	char path[512];
 
 	underscore[0] = '_';
 	snprintf(path, sizeof(path), "%s/%s", dir_path, dp->d_name);
 
-	if (ndpi_load_category_file(ndpi_str, path, proto_id) < 0) {
+	if (ndpi_load_category_file(ndpi_str, path, (ndpi_protocol_category_t)cat_id) < 0) {
 	  NDPI_LOG_ERR(ndpi_str, "Failed to load '%s'\n", path);
 	  failed_files++;
 	}else
@@ -5975,9 +5980,6 @@ int ndpi_handle_ipv6_extension_headers(u_int16_t l3len, const u_int8_t **l4ptr,
 
     *nxt_hdr = (*l4ptr)[0];
 
-    if(*l4len < ehdr_len)
-      return(1);
-
     *l4len -= ehdr_len;
     (*l4ptr) += ehdr_len;
   }
@@ -6033,8 +6035,7 @@ static u_int8_t ndpi_detection_get_l4_internal(struct ndpi_detection_module_stru
   if(l3 == NULL || l3_len < sizeof(struct ndpi_iphdr))
     return(1);
 
-  if((iph = (const struct ndpi_iphdr *) l3) == NULL)
-    return(1);
+  iph = (const struct ndpi_iphdr *) l3;
 
   if(iph->version == IPVERSION && iph->ihl >= 5) {
     NDPI_LOG_DBG2(ndpi_str, "ipv4 header\n");
@@ -6483,7 +6484,7 @@ void ndpi_connection_tracking(struct ndpi_detection_module_struct *ndpi_str,
 	for(i=0; (i<packet->payload_packet_len)
 	      && (flow->flow_payload_len < ndpi_str->max_payload_track_len); i++) {
 	  flow->flow_payload[flow->flow_payload_len++] =
-	    (isprint(packet->payload[i]) || isspace(packet->payload[i])) ? packet->payload[i] : '.';
+	    (ndpi_isprint(packet->payload[i]) || ndpi_isspace(packet->payload[i])) ? packet->payload[i] : '.';
 	}
       }
     }
@@ -7019,7 +7020,7 @@ static void ndpi_reconcile_protocols(struct ndpi_detection_module_struct *ndpi_s
       (MS Teams uses Skype as transport protocol for voice/video)
     */
   case NDPI_PROTOCOL_MSTEAMS:
-    if(flow && (flow->l4_proto == IPPROTO_TCP)) {
+    if(flow->l4_proto == IPPROTO_TCP) {
       // printf("====>> NDPI_PROTOCOL_MSTEAMS\n");
 
       if(ndpi_str->msteams_cache)
@@ -7031,7 +7032,7 @@ static void ndpi_reconcile_protocols(struct ndpi_detection_module_struct *ndpi_s
     break;
 
   case NDPI_PROTOCOL_STUN:
-    if(flow && (flow->guessed_protocol_id_by_ip == NDPI_PROTOCOL_MICROSOFT_AZURE))
+    if(flow->guessed_protocol_id_by_ip == NDPI_PROTOCOL_MICROSOFT_AZURE)
       ndpi_reconcile_msteams_udp(ndpi_str, flow, NDPI_PROTOCOL_STUN);
     break;
 
@@ -7054,8 +7055,7 @@ static void ndpi_reconcile_protocols(struct ndpi_detection_module_struct *ndpi_s
       When Teams is unable to communicate via UDP
       it switches to TLS.TCP. Let's try to catch it
     */
-    if(flow
-       && (flow->guessed_protocol_id_by_ip == NDPI_PROTOCOL_MICROSOFT_AZURE)
+    if((flow->guessed_protocol_id_by_ip == NDPI_PROTOCOL_MICROSOFT_AZURE)
        && (ret->master_protocol == NDPI_PROTOCOL_UNKNOWN)
        && ndpi_str->msteams_cache
       ) {
@@ -9081,7 +9081,7 @@ const char *ndpi_category_get_name(struct ndpi_detection_module_struct *ndpi_str
   }
 
   if((category >= NDPI_PROTOCOL_CATEGORY_CUSTOM_1) && (category <= NDPI_PROTOCOL_CATEGORY_CUSTOM_5)) {
-    switch(category) {
+    switch((int)category) {
     case NDPI_PROTOCOL_CATEGORY_CUSTOM_1:
       return(ndpi_str->custom_category_labels[0]);
     case NDPI_PROTOCOL_CATEGORY_CUSTOM_2:
@@ -9092,13 +9092,9 @@ const char *ndpi_category_get_name(struct ndpi_detection_module_struct *ndpi_str
       return(ndpi_str->custom_category_labels[3]);
     case NDPI_PROTOCOL_CATEGORY_CUSTOM_5:
       return(ndpi_str->custom_category_labels[4]);
-    case NDPI_PROTOCOL_NUM_CATEGORIES:
-      return("Code should not use this internal constant");
-    default:
-      return("Unspecified");
     }
-  } else
-    return(categories[category]);
+  }
+  return(categories[category]);
 }
 
 /* ****************************************************** */
@@ -10178,7 +10174,7 @@ u_int8_t ends_with(struct ndpi_detection_module_struct *ndpi_struct,
 /* ******************************************************************** */
 
 static int ndpi_is_trigram_char(char c) {
-  if(isdigit(c) || (c == '.') || (c == '-'))
+  if(ndpi_isdigit(c) || (c == '.') || (c == '-'))
     return(0);
   else
     return(1);
@@ -10242,7 +10238,7 @@ int ndpi_check_dga_name(struct ndpi_detection_module_struct *ndpi_str,
        ndpi_match_string_subprotocol(ndpi_str, name, strlen(name), &ret_match) > 0)
       return(0); /* Ignore DGA for known domain names */
 
-    if(isdigit((int)name[0])) {
+    if(ndpi_isdigit(name[0])) {
       struct in_addr ip_addr;
 
       ip_addr.s_addr = inet_addr(name);
@@ -10278,7 +10274,7 @@ int ndpi_check_dga_name(struct ndpi_detection_module_struct *ndpi_str,
 	if(tmp[j] == '.') {
 	  num_dots++;
 	} else if(num_dots == 0) {
-	  if(!isdigit((int)tmp[j]))
+	  if(!ndpi_isdigit(tmp[j]))
 	    first_element_is_numeric = 0;
 	}
 
@@ -10291,10 +10287,10 @@ int ndpi_check_dga_name(struct ndpi_detection_module_struct *ndpi_str,
 	} else
 	  num_char_repetitions = 1, last_char = tmp[j];
 
-	if(isdigit((int)tmp[j])) {
+	if(ndpi_isdigit(tmp[j])) {
 	  num_digits++;
 
-	  if(((j+2)<(u_int)len) && isdigit((int)tmp[j+1]) && (tmp[j+2] == '.')) {
+	  if(((j+2)<(u_int)len) && ndpi_isdigit(tmp[j+1]) && (tmp[j+2] == '.')) {
 	    /* Check if there are too many digits */
 	    if(num_digits < 4)
 	      return(0); /* Double digits */
@@ -10393,7 +10389,7 @@ int ndpi_check_dga_name(struct ndpi_detection_module_struct *ndpi_str,
 	trigram_char_skip = 0;
 
 	for(i = 0; word[i+1] != '\0'; i++) {
-	  if(isdigit((int)word[i]))
+	  if(ndpi_isdigit(word[i]))
 	    num_consecutive_digits++;
 	  else {
 	    if((num_word == 1) && (num_consecutive_digits > max_num_consecutive_digits_first_word))