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       dns_name4 - IP address to host name


       #include <dns.h>

       dns_name4(&out, ip);
       dns_name_packet(&out, buf, len);
       dns_name4_domain(q, ip);
         stralloc out = {0};
         char ip[4];
         char q[DNS_NAME4_DOMAIN];
         char *buf;
         unsigned int len;


       dns_name4 looks up the domain name for the 4-byte IP address in ip.  It
       puts the (first) domain name into out and returns 0.  If  the  relevant  domain  does not exist in DNS, or has no PTR records, out
       will be empty.

       If dns_name4 has trouble with the DNS lookup or runs out of memory,  it
       returns -1, setting errno appropriately.  It may or may not change out.

       dns_name_packet is a low-level  component  of  dns_name4,  designed  to
       support  asynchronous  DNS lookups. It reads a DNS packet of length len
       from buf, extracts the first PTR record from the answer section of  the
       packet,  puts  the result into out, and returns 0 or -1 the same way as

       dns_name4_domain is  another  low-level  component  of  dns_name4.   It
       converts  an  IP  address  such  as into a domain name such as and places the packet-encoded domain name into  q.


       dns_domain(3),      dns_ip4(3),      dns_ip4_qualify(3),     dns_mx(3),
       dns_packet(3), dns_random(3), dns_transmit(3), dns_txt(3)