Extra hosts (`extra_hosts` in compose-file, or `--hosts` in services) adds
custom host/ip mappings to the container's `/etc/hosts`.
The current implementation used a `map[string]string{}` as intermediate
storage, and sorted the results alphabetically when converting to a service-spec.
As a result, duplicate hosts were removed, and order of host/ip mappings was not
preserved (in case the compose-file used a list instead of a map).
According to the **host.conf(5)** man page (http://man7.org/linux/man-pages/man5/host.conf.5.html)
multi Valid values are on and off. If set to on, the resolver
library will return all valid addresses for a host that
appears in the /etc/hosts file, instead of only the first.
This is off by default, as it may cause a substantial
performance loss at sites with large hosts files.
Multiple entries for a host are allowed, and even required for some situations,
for example, to add mappings for IPv4 and IPv6 addreses for a host, as illustrated
by the example hosts file in the **hosts(5)** man page (http://man7.org/linux/man-pages/man5/hosts.5.html):
# The following lines are desirable for IPv4 capable hosts
127.0.0.1 localhost
# 127.0.1.1 is often used for the FQDN of the machine
127.0.1.1 thishost.mydomain.org thishost
192.168.1.10 foo.mydomain.org foo
192.168.1.13 bar.mydomain.org bar
146.82.138.7 master.debian.org master
209.237.226.90 www.opensource.org
# The following lines are desirable for IPv6 capable hosts
::1 localhost ip6-localhost ip6-loopback
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
This patch changes the intermediate storage format to use a `[]string`, and only
sorts entries if the input format in the compose file is a mapping. If the input
format is a list, the original sort-order is preserved.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Renaud Gaubert
Simon Ferquel
Sebastiaan van Stijn
Daniel Nephin
Daniel Nephin