nixpkgs/nixos/modules/config/networking.nix
Michael Weiss 234d95a6fc
nixos/networking: Add the FQDN and hostname to /etc/hosts
This fixes the output of "hostname --fqdn" (previously the domain name
was not appended). Additionally it's now possible to use the FQDN.

This works by unconditionally adding two entries to /etc/hosts:
127.0.0.1 localhost
::1 localhost

These are the first two entries and therefore gethostbyaddr() will
always resolve "127.0.0.1" and "::1" back to "localhost" [0].
This works because nscd (or rather the nss-files module) returns the
first matching row from /etc/hosts (and ignores the rest).

The FQDN and hostname entries are appended later to /etc/hosts, e.g.:
127.0.0.2 nixos-unstable.test.tld nixos-unstable
::1 nixos-unstable.test.tld nixos-unstable
Note: We use 127.0.0.2 here to follow nss-myhostname (systemd) as close
as possible. This has the advantage that 127.0.0.2 can be resolved back
to the FQDN but also the drawback that applications that only listen to
127.0.0.1 (and not additionally ::1) cannot be reached via the FQDN.
If you would like this to work you can use the following configuration:
```nix
networking.hosts."127.0.0.1" = [
  "${config.networking.hostName}.${config.networking.domain}"
  config.networking.hostName
];
```

Therefore gethostbyname() resolves "nixos-unstable" to the FQDN
(canonical name): "nixos-unstable.test.tld".

Advantages over the previous behaviour:
- The FQDN will now also be resolved correctly (the entry was missing).
- E.g. the command "hostname --fqdn" will now work as expected.
Drawbacks:
- Overrides entries form the DNS (an issue if e.g. $FQDN should resolve
  to the public IP address instead of 127.0.0.1)
  - Note: This was already partly an issue as there's an entry for
    $HOSTNAME (without the domain part) that resolves to
    127.0.1.1 (!= 127.0.0.1).
- Unknown (could potentially cause other unexpected issues, but special
  care was taken).

[0]: Some applications do apparently depend on this behaviour (see
c578924) and this is typically the expected behaviour.

Co-authored-by: Florian Klink <flokli@flokli.de>
2020-05-25 14:06:25 +02:00

230 lines
7.3 KiB
Nix

# /etc files related to networking, such as /etc/services.
{ config, lib, pkgs, ... }:
with lib;
let
cfg = config.networking;
localhostMultiple = any (elem "localhost") (attrValues (removeAttrs cfg.hosts [ "127.0.0.1" "::1" ]));
in
{
imports = [
(mkRemovedOptionModule [ "networking" "hostConf" ] "Use environment.etc.\"host.conf\" instead.")
];
options = {
networking.hosts = lib.mkOption {
type = types.attrsOf (types.listOf types.str);
example = literalExample ''
{
"127.0.0.1" = [ "foo.bar.baz" ];
"192.168.0.2" = [ "fileserver.local" "nameserver.local" ];
};
'';
description = ''
Locally defined maps of hostnames to IP addresses.
'';
};
networking.hostFiles = lib.mkOption {
type = types.listOf types.path;
defaultText = lib.literalExample "Hosts from `networking.hosts` and `networking.extraHosts`";
example = lib.literalExample ''[ "''${pkgs.my-blocklist-package}/share/my-blocklist/hosts" ]'';
description = ''
Files that should be concatenated together to form <filename>/etc/hosts</filename>.
'';
};
networking.extraHosts = lib.mkOption {
type = types.lines;
default = "";
example = "192.168.0.1 lanlocalhost";
description = ''
Additional verbatim entries to be appended to <filename>/etc/hosts</filename>.
For adding hosts from derivation results, use <option>networking.hostFiles</option> instead.
'';
};
networking.timeServers = mkOption {
default = [
"0.nixos.pool.ntp.org"
"1.nixos.pool.ntp.org"
"2.nixos.pool.ntp.org"
"3.nixos.pool.ntp.org"
];
description = ''
The set of NTP servers from which to synchronise.
'';
};
networking.proxy = {
default = lib.mkOption {
type = types.nullOr types.str;
default = null;
description = ''
This option specifies the default value for httpProxy, httpsProxy, ftpProxy and rsyncProxy.
'';
example = "http://127.0.0.1:3128";
};
httpProxy = lib.mkOption {
type = types.nullOr types.str;
default = cfg.proxy.default;
description = ''
This option specifies the http_proxy environment variable.
'';
example = "http://127.0.0.1:3128";
};
httpsProxy = lib.mkOption {
type = types.nullOr types.str;
default = cfg.proxy.default;
description = ''
This option specifies the https_proxy environment variable.
'';
example = "http://127.0.0.1:3128";
};
ftpProxy = lib.mkOption {
type = types.nullOr types.str;
default = cfg.proxy.default;
description = ''
This option specifies the ftp_proxy environment variable.
'';
example = "http://127.0.0.1:3128";
};
rsyncProxy = lib.mkOption {
type = types.nullOr types.str;
default = cfg.proxy.default;
description = ''
This option specifies the rsync_proxy environment variable.
'';
example = "http://127.0.0.1:3128";
};
allProxy = lib.mkOption {
type = types.nullOr types.str;
default = cfg.proxy.default;
description = ''
This option specifies the all_proxy environment variable.
'';
example = "http://127.0.0.1:3128";
};
noProxy = lib.mkOption {
type = types.nullOr types.str;
default = null;
description = ''
This option specifies the no_proxy environment variable.
If a default proxy is used and noProxy is null,
then noProxy will be set to 127.0.0.1,localhost.
'';
example = "127.0.0.1,localhost,.localdomain";
};
envVars = lib.mkOption {
type = types.attrs;
internal = true;
default = {};
description = ''
Environment variables used for the network proxy.
'';
};
};
};
config = {
assertions = [{
assertion = !localhostMultiple;
message = ''
`networking.hosts` maps "localhost" to something other than "127.0.0.1"
or "::1". This will break some applications. Please use
`networking.extraHosts` if you really want to add such a mapping.
'';
}];
# These entries are required for "hostname -f" and to resolve both the
# hostname and FQDN correctly:
networking.hosts = let
hostnames = # Note: The FQDN (canonical hostname) has to come first:
optional (cfg.hostName != "" && cfg.domain != null) "${cfg.hostName}.${cfg.domain}"
++ optional (cfg.hostName != "") cfg.hostName; # Then the hostname (without the domain)
in {
"127.0.0.2" = hostnames;
} // optionalAttrs cfg.enableIPv6 {
"::1" = hostnames;
};
networking.hostFiles = let
# Note: localhostHosts has to appear first in /etc/hosts so that 127.0.0.1
# resolves back to "localhost" (as some applications assume) instead of
# the FQDN! By default "networking.hosts" also contains entries for the
# FQDN so that e.g. "hostname -f" works correctly.
localhostHosts = pkgs.writeText "localhost-hosts" ''
127.0.0.1 localhost
${optionalString cfg.enableIPv6 "::1 localhost"}
'';
stringHosts =
let
oneToString = set: ip: ip + " " + concatStringsSep " " set.${ip} + "\n";
allToString = set: concatMapStrings (oneToString set) (attrNames set);
in pkgs.writeText "string-hosts" (allToString (filterAttrs (_: v: v != []) cfg.hosts));
extraHosts = pkgs.writeText "extra-hosts" cfg.extraHosts;
in mkBefore [ localhostHosts stringHosts extraHosts ];
environment.etc =
{ # /etc/services: TCP/UDP port assignments.
services.source = pkgs.iana-etc + "/etc/services";
# /etc/protocols: IP protocol numbers.
protocols.source = pkgs.iana-etc + "/etc/protocols";
# /etc/hosts: Hostname-to-IP mappings.
hosts.source = pkgs.runCommandNoCC "hosts" {} ''
cat ${escapeShellArgs cfg.hostFiles} > $out
'';
# /etc/host.conf: resolver configuration file
"host.conf".text = ''
multi on
'';
} // optionalAttrs (pkgs.stdenv.hostPlatform.libc == "glibc") {
# /etc/rpc: RPC program numbers.
rpc.source = pkgs.stdenv.cc.libc.out + "/etc/rpc";
};
networking.proxy.envVars =
optionalAttrs (cfg.proxy.default != null) {
# other options already fallback to proxy.default
no_proxy = "127.0.0.1,localhost";
} // optionalAttrs (cfg.proxy.httpProxy != null) {
http_proxy = cfg.proxy.httpProxy;
} // optionalAttrs (cfg.proxy.httpsProxy != null) {
https_proxy = cfg.proxy.httpsProxy;
} // optionalAttrs (cfg.proxy.rsyncProxy != null) {
rsync_proxy = cfg.proxy.rsyncProxy;
} // optionalAttrs (cfg.proxy.ftpProxy != null) {
ftp_proxy = cfg.proxy.ftpProxy;
} // optionalAttrs (cfg.proxy.allProxy != null) {
all_proxy = cfg.proxy.allProxy;
} // optionalAttrs (cfg.proxy.noProxy != null) {
no_proxy = cfg.proxy.noProxy;
};
# Install the proxy environment variables
environment.sessionVariables = cfg.proxy.envVars;
};
}