ares_init_options() with invalid options values should unset the option

Apparently nodejs is relying on the above behavior for legacy reasons.  Add
sanity checks to the various optmask parameters where it makes sense.

See nodejs/node#50800

Fix By: Brad House (@bradh352)

Author: bradh352

src/lib/ares_options.c

@@ -272,24 +272,46 @@ ares_status_t ares__init_by_options(ares_channel_t            *channel,
   }
 
   if (optmask & ARES_OPT_TIMEOUTMS) {
-    channel->timeout = (unsigned int)options->timeout;
+    /* Apparently some integrations were passing -1 to tell c-ares to use
+     * the default instead of just omitting the optmask */
+    if (options->timeout <= 0) {
+      optmask &= ~(ARES_OPT_TIMEOUTMS);
+    } else {
+      channel->timeout = (unsigned int)options->timeout;
+    }
   } else if (optmask & ARES_OPT_TIMEOUT) {
-    /* Convert to milliseconds */
-    optmask          |= ARES_OPT_TIMEOUTMS;
-    optmask          &= ~(ARES_OPT_TIMEOUT);
-    channel->timeout  = (unsigned int)options->timeout * 1000;
+    optmask &= ~(ARES_OPT_TIMEOUT);
+    /* Apparently some integrations were passing -1 to tell c-ares to use
+     * the default instead of just omitting the optmask */
+    if (options->timeout > 0) {
+      /* Convert to milliseconds */
+      optmask          |= ARES_OPT_TIMEOUTMS;
+      channel->timeout  = (unsigned int)options->timeout * 1000;
+    }
   }
 
   if (optmask & ARES_OPT_TRIES) {
-    channel->tries = (size_t)options->tries;
+    if (options->tries <= 0) {
+      optmask &= ~(ARES_OPT_TRIES);
+    } else {
+      channel->tries = (size_t)options->tries;
+    }
   }
 
   if (optmask & ARES_OPT_NDOTS) {
-    channel->ndots = (size_t)options->ndots;
+    if (options->ndots <= 0) {
+      optmask &= ~(ARES_OPT_NDOTS);
+    } else {
+      channel->ndots = (size_t)options->ndots;
+    }
   }
 
   if (optmask & ARES_OPT_MAXTIMEOUTMS) {
-    channel->maxtimeout = (size_t)options->maxtimeout;
+    if (options->maxtimeout <= 0) {
+      optmask &= ~(ARES_OPT_MAXTIMEOUTMS);
+    } else {
+      channel->maxtimeout = (size_t)options->maxtimeout;
+    }
   }
 
   if (optmask & ARES_OPT_ROTATE) {
@@ -313,17 +335,28 @@ ares_status_t ares__init_by_options(ares_channel_t            *channel,
     channel->sock_state_cb_data = options->sock_state_cb_data;
   }
 
-  if (optmask & ARES_OPT_SOCK_SNDBUF && options->socket_send_buffer_size > 0) {
-    channel->socket_send_buffer_size = options->socket_send_buffer_size;
+  if (optmask & ARES_OPT_SOCK_SNDBUF) {
+    if (options->socket_send_buffer_size <= 0) {
+      optmask &= ~(ARES_OPT_SOCK_SNDBUF);
+    } else {
+      channel->socket_send_buffer_size = options->socket_send_buffer_size;
+    }
   }
 
-  if (optmask & ARES_OPT_SOCK_RCVBUF &&
-      options->socket_receive_buffer_size > 0) {
-    channel->socket_receive_buffer_size = options->socket_receive_buffer_size;
+  if (optmask & ARES_OPT_SOCK_RCVBUF) {
+    if (options->socket_receive_buffer_size <= 0) {
+      optmask &= ~(ARES_OPT_SOCK_RCVBUF);
+    } else {
+      channel->socket_receive_buffer_size = options->socket_receive_buffer_size;
+    }
   }
 
   if (optmask & ARES_OPT_EDNSPSZ) {
-    channel->ednspsz = (size_t)options->ednspsz;
+    if (options->ednspsz <= 0) {
+      optmask &= ~(ARES_OPT_EDNSPSZ);
+    } else {
+      channel->ednspsz = (size_t)options->ednspsz;
+    }
   }
 
   /* Copy the domains, if given.  Keep channel->ndomains consistent so
@@ -346,9 +379,13 @@ ares_status_t ares__init_by_options(ares_channel_t            *channel,
 
   /* Set lookups, if given. */
   if (optmask & ARES_OPT_LOOKUPS) {
-    channel->lookups = ares_strdup(options->lookups);
-    if (!channel->lookups) {
-      return ARES_ENOMEM;
+    if (options->lookups == NULL) {
+      optmask &= ~(ARES_OPT_LOOKUPS);
+    } else {
+      channel->lookups = ares_strdup(options->lookups);
+      if (!channel->lookups) {
+        return ARES_ENOMEM;
+      }
     }
   }
 
@@ -367,35 +404,55 @@ ares_status_t ares__init_by_options(ares_channel_t            *channel,
 
   /* Set path for resolv.conf file, if given. */
   if (optmask & ARES_OPT_RESOLVCONF) {
-    channel->resolvconf_path = ares_strdup(options->resolvconf_path);
-    if (!channel->resolvconf_path && options->resolvconf_path) {
-      return ARES_ENOMEM;
+    if (options->resolvconf_path == NULL) {
+      optmask &= ~(ARES_OPT_RESOLVCONF);
+    } else {
+      channel->resolvconf_path = ares_strdup(options->resolvconf_path);
+      if (channel->resolvconf_path == NULL) {
+        return ARES_ENOMEM;
+      }
     }
   }
 
   /* Set path for hosts file, if given. */
   if (optmask & ARES_OPT_HOSTS_FILE) {
-    channel->hosts_path = ares_strdup(options->hosts_path);
-    if (!channel->hosts_path && options->hosts_path) {
-      return ARES_ENOMEM;
+    if (options->hosts_path == NULL) {
+      optmask &= ~(ARES_OPT_HOSTS_FILE);
+    } else {
+      channel->hosts_path = ares_strdup(options->hosts_path);
+      if (channel->hosts_path == NULL) {
+        return ARES_ENOMEM;
+      }
     }
   }
 
   if (optmask & ARES_OPT_UDP_MAX_QUERIES) {
-    channel->udp_max_queries = (size_t)options->udp_max_queries;
+    if (options->udp_max_queries <= 0) {
+      optmask &= ~(ARES_OPT_UDP_MAX_QUERIES);
+    } else {
+      channel->udp_max_queries = (size_t)options->udp_max_queries;
+    }
   }
 
   if (optmask & ARES_OPT_QUERY_CACHE) {
-    channel->qcache_max_ttl = options->qcache_max_ttl;
+    if (options->qcache_max_ttl <= 0) {
+      optmask &= ~(ARES_OPT_QUERY_CACHE);
+    } else {
+      channel->qcache_max_ttl = options->qcache_max_ttl;
+    }
   }
 
   /* Initialize the ipv4 servers if provided */
-  if (optmask & ARES_OPT_SERVERS && options->nservers > 0) {
-    ares_status_t status;
-    status = ares__init_options_servers(channel, options->servers,
-                                        (size_t)options->nservers);
-    if (status != ARES_SUCCESS) {
-      return status;
+  if (optmask & ARES_OPT_SERVERS) {
+    if (options->nservers <= 0) {
+      optmask &= ~(ARES_OPT_SERVERS);
+    } else {
+      ares_status_t status;
+      status = ares__init_options_servers(channel, options->servers,
+                                          (size_t)options->nservers);
+      if (status != ARES_SUCCESS) {
+        return status;
+      }
     }
   }