Package: libc-bin
Version: 2.30-7
Severity: important
Tags: ipv6

Dear Maintainer,

When attempting to follow the instructions for installing the latest version of 
Docker Engine at I noticed that 'apt-get update' 
and curl were both
failing to resolve  The error message from both ping and 
curl was 
"Temporary failure in name resolution"

However, running 'host' yielded the following results: is an alias for has address has address has address has address has IPv6 address 
2600:9000:2202:c00:3:db06:4200:93a1 has IPv6 address 
2600:9000:2202:5000:3:db06:4200:93a1 has IPv6 address 
2600:9000:2202:7a00:3:db06:4200:93a1 has IPv6 address 
2600:9000:2202:9200:3:db06:4200:93a1 has IPv6 address 
2600:9000:2202:9600:3:db06:4200:93a1 has IPv6 address 
2600:9000:2202:9c00:3:db06:4200:93a1 has IPv6 address 
2600:9000:2202:a200:3:db06:4200:93a1 has IPv6 address 

After examining the source code for iputils-ping, I was able to determine that 
the cause of the
error message was getaddrinfo() returning EAI_AGAIN

The following workarounds were effective:

* curl -4 (Forcing curl to use IPv4 only)
* ping -4 (Forcing IPv4 ping to use IPv4 only)
* Forcing apt to use IPv4 by adding 'Acquire::ForceIPv4 "true";' to apt.conf

It is also noteworthy that not all hostnames with both A and AAAA records 
trigger this bug. In fact,
hostnames with a low total record count like have no problem 

root@sandbox:~# host has address has IPv6 address 2607:f8b0:4005:809::2004
root@sandbox:~# ping
PING ( 56(84) bytes of data.
64 bytes from ( icmp_seq=1 ttl=63 
time=29.6 ms
--- ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2005ms
rtt min/avg/max/mdev = 29.572/37.733/42.045/5.774 ms

Please note that this bug also affects libc-bin 2.28-10 in buster.

-- System Information:
Debian Release: bullseye/sid
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: amd64 (x86_64)

Kernel: Linux 4.19.0-9-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), 
LANGUAGE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages libc-bin depends on:
ii  libc6  2.30-7

Versions of packages libc-bin recommends:
ii  manpages  5.06-1

libc-bin suggests no packages.

-- Configuration Files:
/etc/gai.conf changed [not included]

-- no debconf information

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