lib: fix validatePort to reject string '0' when allowZero is false

The `port === 0 && !allowZero` check used strict equality, so the
string `'0'` (and other numeric-zero string forms like `'0x0'`) slipped
through because `'0' === 0` is `false`. As a result,
`validatePort('0', name, false)` returned `0`, contradicting the
`allowZero=false` contract and letting callers such as
`dgram.Socket#connect('0', ...)` proceed past the validator and fail
deep in the stack with `EADDRNOTAVAIL` while leaking the handle.

Compare the numeric coercion (`+port === 0`) so all numeric-zero forms
are rejected consistently.

Co-Authored-By: Claude <[email protected]>
Co-Authored-By: DeepView Autofix <[email protected]>
Co-Authored-By: Nikita Skovoroda <[email protected]>
Signed-off-by: Nikita Skovoroda <[email protected]>

Author: 3 people

lib/internal/validators.js

@@ -428,7 +428,7 @@ const validatePort = hideStackFrames((port, name = 'Port', allowZero = true) =>
       (typeof port === 'string' && StringPrototypeTrim(port).length === 0) ||
       +port !== (+port >>> 0) ||
       port > 0xFFFF ||
-      (port === 0 && !allowZero)) {
+      (+port === 0 && !allowZero)) {
     throw new ERR_SOCKET_BAD_PORT(name, port, allowZero);
   }
   return port | 0;

test/parallel/test-dgram-connect.js

@@ -55,7 +55,7 @@ assert.throws(() => {
   code: 'ERR_SOCKET_DGRAM_NOT_CONNECTED'
 });
 
-[ 0, null, 78960, undefined ].forEach((port) => {
+[ 0, '0', null, 78960, undefined ].forEach((port) => {
   assert.throws(() => {
     client.connect(port);
   }, {

test/parallel/test-internal-validators-validateport.js

@@ -21,3 +21,10 @@ for (let n = 0; n <= 0xFFFF; n++) {
 ].forEach((i) => assert.throws(() => validatePort(i), {
   code: 'ERR_SOCKET_BAD_PORT'
 }));
+
+// When `allowZero` is false, both the number `0` and the string `'0'` (and
+// other numeric-zero string forms) must be rejected.
+[0, '0', '0x0', '0o0', '0b0'].forEach((i) => assert.throws(
+  () => validatePort(i, 'Port', false),
+  { code: 'ERR_SOCKET_BAD_PORT' },
+));