res_nquery for ipv6 DNS server issue on libc2-27.

[Vishnu Prasad S K (Nokia)]

Hi Florian,
Thanks for your attention to this.

>>>> Are the IPv6 addresses that are incorrectly contacted listed in /etc/resolv.conf?
Yes the ip's are picked randomly from /etc/resolv.conf.
How to force res_nquery to use only the IP's we fill in _res._u._ext.nsaddrs??



Pasting the query again by removing hyperlinks.

We are using the below code to send DNS TXT query to specific ipv6 DNS server IP in "bootstrapDNS".
In libc2-21.so this piece of code is working fine TXT query would always go to bootstrapDNS server.
 
We upgraded to libc2-27, on top of this the below code is not working, res_nquery() is sending query to random IP's and not to bootstrapDNS server IP.
Is there any change in libc2-27 on using
We are using the below code to send DNS TXT query to specific ipv6 DNS server IP in "bootstrapDNS".
In libc2-21.so this piece of code is working fine TXT query would always go to bootstrapDNS server.

We upgraded to libc2-27, on top of this the below code is not working, res_nquery() is sending query to random IP's and not to bootstrapDNS server IP.
Is there any change in libc2-27 on using _res._u._ext.nsaddrs fields??

How to make our TXT query go to bootstrapDNS server on libc2-27? 


    _res._u._ext.nscount6 = 0;
    _res.nscount = 0;
    _res._u._ext.nsaddrs[0] = NULL;
    res_init();
        _res.options|=RES_ROTATE;
        bootIn6->sin6_family = AF_INET6;
        bootIn6->sin6_port = htons(53);
        int ret = inet_pton(AF_INET6, bootstrapDNS.c_str(), bootIn6->sin6_addr.s6_addr);
        OUTLOG_LEVEL(IKEMLOG_DETAIL, 7, "Boot DNS is IPv6, ret is %d",ret);
      #if defined(HW_FAMILY_fsm9xxx)
        _res.nscount = 3;
        _res._u._ext.nscount6 = 3;
        _res._u._ext.nscount = 0;
        _res._u._ext.nsaddrs[0] = bootIn6;
        _res._u._ext.nsaddrs[1] = bootIn6;
        _res._u._ext.nsaddrs[2] = bootIn6;

        _res._u._ext.nsmap[0] = MAXNS + 1;
        _res._u._ext.nsmap[1] = MAXNS + 1;
        _res._u._ext.nsmap[2] = MAXNS + 1;

res_nquery(&_res,fqdn, C_IN, T_TXT, answer, sizeof(answer));


Regards,
Vishnu.

-----Original Message-----
From: Florian Weimer <fweimer@redhat.com> 
Sent: Monday, August 28, 2023 5:15 PM
To: Vishnu Prasad S K (Nokia) via Libc-alpha <libc-alpha@sourceware.org>
Cc: Vishnu Prasad S K (Nokia) <vishnu.prasad_s_k@nokia.com>
Subject: Re: res_nquery for ipv6 DNS server issue on libc2-27.

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Vishnu,

your message is full of internal alcatel-lucent.com URLs and is therefore unreadable.

What you are seeing might be a side effect of /etc/resolv.conf auto-reloading.  Are the IPv6 addresses that are incorrectly contacted listed in /etc/resolv.conf?

Thanks,
Florian