[ldns-users] ldns_resolver_set_ip6() and ldns_resolver_query() leads to SIGSEGV

[Zbynek Michl]

Hello,

when I read resolver addresses from /etc/resolv.conf where are only IPv4 
addresses and set IPv6 resolvers preference to LDNS_RESOLV_INET6, then 
ldns_resolver_query() calling causes a crash.

My /etc/resolv.conf:

nameserver 127.0.0.1
nameserver 172.20.20.40


Sample code:

/* create a new resolver from /etc/resolv.conf */
s = ldns_resolver_new_frm_file(&res, NULL);

if (s != LDNS_STATUS_OK) {
   exit(EXIT_FAILURE);
}

/* set IPv6 resolver preference */
ldns_resolver_set_ip6(res, LDNS_RESOLV_INET6);

/* use the resolver to send a query for the mx
  * records of the domain given on the command line
  */
p = ldns_resolver_query(res, domain, LDNS_RR_TYPE_MX, LDNS_RR_CLASS_IN,
                         LDNS_RD);


When I compile it and run, on ldns_resolver_query() calling program crashes 
(Segmentation fault).

The same failure occurs when I set IPv4 preference and resolv.conf contains only 
IPv6 addresses.


gdb backtrace:

Program received signal SIGSEGV, Segmentation fault.
ldns_pkt_tc (packet=0x0) at packet.c:58
58	{
(gdb) bt
#0  ldns_pkt_tc (packet=0x0) at packet.c:58
#1  0x00007ffff73d3072 in ldns_resolver_send_pkt (answer=0x7fffffffe200, 
r=0x602290, query_pkt=0x602070) at resolver.c:968
#2  0x00007ffff73d3246 in ldns_resolver_send (answer=0x7fffffffe268, r=0x602290, 
name=0x602010, t=LDNS_RR_TYPE_MX,
     c=LDNS_RR_CLASS_IN, flags=8) at resolver.c:1090
#3  0x00007ffff73d3308 in ldns_resolver_query (r=0x602290, name=0x602010, 
t=LDNS_RR_TYPE_MX, c=LDNS_RR_CLASS_IN, flags=8)
     at resolver.c:908


Regards,
Zbynek