Merge pull request #47241 from oxij/pull/36261-fix-local-hostname-alternative

nixos/networking: add hostname to /etc/hosts by default, simplify

1 files changed, 39 insertions, 22 deletions

diff --git a/nixos/modules/config/networking.nix b/nixos/modules/config/networking.nix
index 1ef5313d3fdd..1eb6fb43604a 100644
--- a/nixos/modules/config/networking.nix
+++ b/nixos/modules/config/networking.nix
@@ -16,6 +16,13 @@ let
   resolvconfOptions = cfg.resolvconfOptions
     ++ optional cfg.dnsSingleRequest "single-request"
     ++ optional cfg.dnsExtensionMechanism "edns0";
+
+
+  localhostMapped4 = cfg.hosts ? "127.0.0.1" && elem "localhost" cfg.hosts."127.0.0.1";
+  localhostMapped6 = cfg.hosts ? "::1"       && elem "localhost" cfg.hosts."::1";
+
+  localhostMultiple = any (elem "localhost") (attrValues (removeAttrs cfg.hosts [ "127.0.0.1" "::1" ]));
+
 in
 
 {
@@ -23,8 +30,7 @@ in
   options = {
 
     networking.hosts = lib.mkOption {
-      type = types.attrsOf ( types.listOf types.str );
-      default = {};
+      type = types.attrsOf (types.listOf types.str);
       example = literalExample ''
         {
           "127.0.0.1" = [ "foo.bar.baz" ];
@@ -192,6 +198,29 @@ in
 
   config = {
 
+    assertions = [{
+      assertion = localhostMapped4;
+      message = ''`networking.hosts` doesn't map "127.0.0.1" to "localhost"'';
+    } {
+      assertion = !cfg.enableIPv6 || localhostMapped6;
+      message = ''`networking.hosts` doesn't map "::1" to "localhost"'';
+    } {
+      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.
+      '';
+    }];
+
+    networking.hosts = {
+      "127.0.0.1" = [ "localhost" ];
+    } // optionalAttrs (cfg.hostName != "") {
+      "127.0.1.1" = [ cfg.hostName ];
+    } // optionalAttrs cfg.enableIPv6 {
+      "::1" = [ "localhost" ];
+    };
+
     environment.etc =
       { # /etc/services: TCP/UDP port assignments.
         "services".source = pkgs.iana-etc + "/etc/services";
@@ -203,25 +232,13 @@ in
         "rpc".source = pkgs.glibc.out + "/etc/rpc";
 
         # /etc/hosts: Hostname-to-IP mappings.
-        "hosts".text =
-          let oneToString = set : ip : ip + " " + concatStringsSep " " ( getAttr ip set );
-              allToString = set : concatMapStringsSep "\n" ( oneToString set ) ( attrNames set );
-              userLocalHosts = optionalString
-                ( builtins.hasAttr "127.0.0.1" cfg.hosts )
-                ( concatStringsSep " " ( remove "localhost" cfg.hosts."127.0.0.1" ));
-              userLocalHosts6 = optionalString
-                ( builtins.hasAttr "::1" cfg.hosts )
-                ( concatStringsSep " " ( remove "localhost" cfg.hosts."::1" ));
-              otherHosts = allToString ( removeAttrs cfg.hosts [ "127.0.0.1" "::1" ]);
-          in
-          ''
-            127.0.0.1 ${userLocalHosts} localhost
-            ${optionalString cfg.enableIPv6 ''
-              ::1 ${userLocalHosts6} localhost
-            ''}
-            ${otherHosts}
-            ${cfg.extraHosts}
-          '';
+        "hosts".text = let
+          oneToString = set: ip: ip + " " + concatStringsSep " " set.${ip};
+          allToString = set: concatMapStringsSep "\n" (oneToString set) (attrNames set);
+        in ''
+          ${allToString cfg.hosts}
+          ${cfg.extraHosts}
+        '';
 
         # /etc/host.conf: resolver configuration file
         "host.conf".text = cfg.hostConf;
@@ -296,4 +313,4 @@ in
 
   };
 
-  }
+}