[Bug libc/26977] New: getaddrinfo does not handle the hosts file correctly

[Bug libc/26977] New: getaddrinfo does not handle the hosts file correctly

[bugs at jth dot net]

https://sourceware.org/bugzilla/show_bug.cgi?id=26977

            Bug ID: 26977
           Summary: getaddrinfo does not handle the hosts file correctly
           Product: glibc
           Version: 2.32
            Status: UNCONFIRMED
          Keywords: glibc_2.32
          Severity: normal
          Priority: P2
         Component: libc
          Assignee: unassigned at sourceware dot org
          Reporter: bugs at jth dot net
                CC: drepper.fsp at gmail dot com
  Target Milestone: 2.32

Host: Linux Fedora 33
On a dual stack IP4 + IP6 server the 2.32 release has introduced a problem of
getaddrinfo omitting looking up the IP6 address in the DNS in case the IP4
address is found in the hosts file or vice versa.

After upgrading 'ping -6 IP6.HOST' suddenly failed by "Address family for
hostname not supported" and the monitoring software reported downtime.
Similarly for the dig command.
A test program for getaddrinfo verified the changed behaviour. 

Only after entering the IP6 address into or deleting the IP4 address from the
hosts file the old behaviour was restored.

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[Bug libc/26977] getaddrinfo does not handle the hosts file correctly

[bugs at jth dot net]

https://sourceware.org/bugzilla/show_bug.cgi?id=26977

Joergen Thomsen <bugs at jth dot net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bugs at jth dot net

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[Bug libc/26977] getaddrinfo does not handle the hosts file correctly

[bugs at jth dot net]

https://sourceware.org/bugzilla/show_bug.cgi?id=26977

--- Comment #1 from Joergen Thomsen <bugs at jth dot net> ---
This is probably not related to the AI_ADDRCONFIG flag as the test program 
used these parameters

  hints.ai_family = PF_UNSPEC;
  hints.ai_socktype = SOCK_STREAM;
  hints.ai_flags = AI_CANONNAME;

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[Bug libc/26977] getaddrinfo does not handle the hosts file correctly

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26977

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |fweimer at redhat dot com
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2020-11-30
             Status|UNCONFIRMED                 |WAITING

--- Comment #2 from Florian Weimer <fweimer at redhat dot com> ---
Do you use systemd-resolved? Thanks.

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[Bug libc/26977] getaddrinfo does not handle the hosts file correctly

[bugs at jth dot net]

https://sourceware.org/bugzilla/show_bug.cgi?id=26977

--- Comment #3 from Joergen Thomsen <bugs at jth dot net> ---
(In reply to Florian Weimer from comment #2)
> Do you use systemd-resolved? Thanks.

Apparently as the systemd-resolved service is running, but after stopping the
service no change in behaviour was observed.

Only by changing /etc/nsswitch.conf between the two lines below I observed a
change

hosts:      files dns    incorrect behaviour
hosts:       dns         correct

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[Bug libc/26977] getaddrinfo does not handle the hosts file correctly

[bugs at jth dot net]

https://sourceware.org/bugzilla/show_bug.cgi?id=26977

--- Comment #4 from Joergen Thomsen <bugs at jth dot net> ---
My usage case is this:

In some cases it is important to overrule the DNS IP address by a temporary
address in the /etc/hosts file without changing the DNS. 
This should not need any other entries in the /etc/hosts file than the
temporary ones.

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[Bug libc/26977] getaddrinfo does not handle the hosts file correctly

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26977

--- Comment #5 from Florian Weimer <fweimer at redhat dot com> ---
I would like to see your test program for getaddrinfo. Thanks.

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[Bug network/26977] getaddrinfo does not handle the hosts file correctly

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26977

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|libc                        |network

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[Bug network/26977] getaddrinfo does not handle the hosts file correctly

[bugs at jth dot net]

https://sourceware.org/bugzilla/show_bug.cgi?id=26977

--- Comment #6 from Joergen Thomsen <bugs at jth dot net> ---
Created attachment 13009
  --> https://sourceware.org/bugzilla/attachment.cgi?id=13009&action=edit
getaddrinfo test program

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