fix: don't split a bracketed IPv6 host in req.subdomains

lib/request.js

@@ -386,9 +386,14 @@ defineGetter(req, 'subdomains', function subdomains() {
   if (!hostname) return [];
 
   var offset = this.app.get('subdomain offset');
-  var subdomains = !isIP(hostname)
-    ? hostname.split('.').reverse()
-    : [hostname];
+  // An IPv6 literal keeps its brackets (e.g. "[::ffff:127.0.0.1]"), which
+  // net.isIP() rejects, so detect it by the brackets and keep it as a single
+  // unit instead of splitting it on its dots.
+  var subdomains = hostname[0] === '[' && hostname[hostname.length - 1] === ']'
+    ? [hostname]
+    : !isIP(hostname)
+      ? hostname.split('.').reverse()
+      : [hostname];
 
   return subdomains.slice(offset);
 });

test/req.subdomains.js

@@ -44,6 +44,19 @@ describe('req', function(){
         .set('Host', '[::1]')
         .expect(200, [], done);
       })
+
+      it('should work with a dotted IPv6 address', function(done){
+        var app = express();
+
+        app.use(function(req, res){
+          res.send(req.subdomains);
+        });
+
+        request(app)
+        .get('/')
+        .set('Host', '[::ffff:127.0.0.1]')
+        .expect(200, [], done);
+      })
     })
 
     describe('otherwise', function(){
@@ -135,6 +148,20 @@ describe('req', function(){
           .set('Host', '[::1]')
           .expect(200, ['[::1]'], done);
         })
+
+        it('should return an array with the whole dotted IPv6', function (done) {
+          var app = express();
+          app.set('subdomain offset', 0);
+
+          app.use(function(req, res){
+            res.send(req.subdomains);
+          });
+
+          request(app)
+          .get('/')
+          .set('Host', '[::ffff:127.0.0.1]')
+          .expect(200, ['[::ffff:127.0.0.1]'], done);
+        })
       })
 
       describe('when present', function(){