[GitHub] [incubator-nuttx] xiaoxiang781216 commented on a change in pull request #892: Netdb multiple dns servers

[GitBox <gi...@apache.org>]

xiaoxiang781216 commented on a change in pull request #892:
URL: https://github.com/apache/incubator-nuttx/pull/892#discussion_r415608827



##########
File path: libs/libc/netdb/lib_dnsaddserver.c
##########
@@ -198,10 +198,24 @@ int dns_add_nameserver(FAR const struct sockaddr *addr, socklen_t addrlen)
 {
   FAR uint16_t *pport;
   size_t copylen;
+  int nservers;
+  int idx;
 
   DEBUGASSERT(addr != NULL);
 
-  /* Copy the new server IP address into our private global data structure */
+  /* Get the index of the next free nameserver slot. */
+
+  dns_semtake();
+  if (g_dns_nservers == CONFIG_NETDB_DNSSERVER_NAMESERVERS)

Review comment:
       > Perhaps, but note that the resolv.conf version of the function appends the new nameserver at the end of the file. It should be changed to match for consistency. I would leave that to some future PR.
   > 
   
   If so, it is better to append the new server to the end of list and iterate through the server backward.
   
   > I think the most common use case is to get DNS1, DNS2,... IPs from operator and then add entire list by first calling dns_default_nameserver() and then add the DNS1, DNS2, DNS3... and maybe add some generic fallback server like Google's 8.8.8.8 as _last_ in case operator's preferred servers are down.
   
   




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