Red Hat Bugzilla – Bug 1015851
gethostbyname failed to retrieve IPv6 address in /etc/hosts
Last modified: 2017-11-08 05:43:28 EST
Description of problem: the IPv6 address put in /etc/hosts with a special and unique name for it doesn't get returned by gethostbyname using that name.
Version-Release number of selected component (if applicable):
Just put an IPv6 address in /etc/hosts, and give it a name. Then in a C program call gethostbyname("thename"); even when the /etc/nsswitch.conf has "files dns" for hosts, but the return result is not the IPv6 address in the /etc/hosts for that name. You may need to select a name that your DNS server can resolve.
Steps to Reproduce:
the returned address is from DNS, not the one in /etc/hosts.
the returned address should be from /etc/hosts when "files dns" is used for hosts in nsswitch.conf.
only after add "options inet6", now it works.
But then the IPv4 address in /etc/hosts fail to work.
This request was not resolved in time for the current release.
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the next release of Red Hat Enterprise Linux.
Moving to rhel-6.6 for scoping.
(In reply to wzis from comment #0)
> Description of problem: the IPv6 address put in /etc/hosts with a special
> and unique name for it doesn't get returned by gethostbyname using that name.
gethostbyname only returns IPv4 addresses, by design. Please provide more details what you are doing.
"gethostbyname only returns IPv4 addresses"? then why after adding "options inet6" to resolve.conf, it can return IPv6 address? Also the man page says
"The gethostbyname() function returns a structure of type hostent for the given host name. Here name is either a hostname, or an IPv4 address in standard dot notation (as for inet_addr(3)), or an IPv6 address in colon (and possibly dot) notation."
The gethostbyname does handle IPv6 address. So why without using the options, it can't return the IPv6 addr specified in the /etc/hosts?
I cannot reproduce this issue with glibc-2.12-1.209.el6.x86_64. With “options inet6”, gethostbyname returns IPv6 addresses mapped IPv4, as expected.
Note that “options inet6” has been deprecated in upstream glibc.