[Bug network/19369] New: Default domain name not reset by res_ninit when "search" / "domain" entry is removed from resolv.conf

["rob at robwu dot nl" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=19369

            Bug ID: 19369
           Summary: Default domain name not reset by res_ninit when
                    "search" / "domain" entry is removed from resolv.conf
           Product: glibc
           Version: 2.24
            Status: NEW
          Severity: normal
          Priority: P2
         Component: network
          Assignee: rob at robwu dot nl
          Reporter: rob at robwu dot nl
  Target Milestone: ---

Created attachment 8850
  --> https://sourceware.org/bugzilla/attachment.cgi?id=8850&action=edit
Repeatedly uses res_ninit, getaddrinfo, res_nclose.

When I call res_ninit(&_res), I expect resolver functions such as getaddrinfo
to use exactly the same configuration as if the program was run for the first
time (which then uses /etc/resolv.conf).

This is not the case for the "search" (or "domain") entries. When the "domain"
entry is removed, the resolver still uses the previously configured domain
name.

Steps to reproduce:
1. Compile the attached program (gcc -Wall getaddr.c). This program repeatedly
calls res_ninit, getaddrinfo("www", ...), res_nclose.
2. Edit /etc/resolv.conf, add "search example.com"
3. Run ./a.out www
4. Edit /etc/resolv.conf, remove "search example.com"
5. Run ./a.out www

Expected results:
At step 3, the following is output (because "www" -> "www.example.com", which
exists).
   getaddrinfo("www") = 0
   93.184.216.34:0

At step 5, the following should be output (or anything else that is not
"www.example.com", -2 = EAI_NONAME):
   getaddrinfo("www") = -2

Actual results:
At step 5, the same result as step 3 is shown, which indicates that the default
domain suffix is not reset.

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