From dc15397590d2240b9204e88bde146920ecc38e77 Mon Sep 17 00:00:00 2001
From: George Hertz <hertzg@users.noreply.github.com>
Date: Sat, 3 Jul 2021 17:22:13 +0200
Subject: [PATCH] feat(user-timeout): use TCP_RXT_CONNDROPTIME on darwin (#263)

---
 README.md                 | 17 ++++++++++++++++-
 lib/constants.js          |  4 ++++
 lib/index.js              |  4 ++--
 test/unit/test-timeout.js |  8 ++++----
 4 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/README.md b/README.md
index ffad49aa..a0e7ece3 100644
--- a/README.md
+++ b/README.md
@@ -34,7 +34,22 @@ The Missing (`TCP_KEEPINTVL` and `TCP_KEEPCNT`) `SO_KEEPALIVE` socket option set
 
 Tested on 🐧 `linux` & 🍏 `osx` (both `amd64` and `arm64`), should work on 😈 `freebsd` and others. Does not work on 🐄 `win32` (pull requests welcome).
 
-There's also support for getting & setting the `TCP_USER_TIMEOUT` (linux 🐧 only) option, which is closely related to keep-alive.
+There's also support for getting & setting the `TCP_USER_TIMEOUT` (🐧 `linux`  and 🍏 `osx` only) option, which is closely related to keep-alive.
+
+
+## Platform support
+
+| Platform     | TCP_KEEPINTVL | TCP_KEEPCNT | TCP_USER_TIMEOUT            |
+| ------------ | ------------- | ----------- | --------------------------- |
+| 🐧 `linux`   | ✅            | ✅          | ✅                          |
+| 🍏 `osx`     | ✅            | ✅          | ✅ (`TCP_RXT_CONNDROPTIME`) |
+| 😈 `freebsd` | ✅            | ✅          | ❌                          |
+| 🐄 `win32`   | ❌            | ❌          | ❌                          |
+
+Legend:
+
+- ✅ - Supported
+- ❌ - Unsupported (throws)
 
 ## Install
 
diff --git a/lib/constants.js b/lib/constants.js
index 18df9454..d5317cb7 100644
--- a/lib/constants.js
+++ b/lib/constants.js
@@ -13,6 +13,10 @@ switch (OS.platform()) {
   case 'darwin':
     Constants.TCP_KEEPINTVL = 0x101
     Constants.TCP_KEEPCNT = 0x102
+
+    // Alias for TCP_RXT_CONNDROPTIME
+    // Source https://github.com/apple/darwin-xnu/blob/a1babec6b135d1f35b2590a1990af3c5c5393479/bsd/netinet/tcp.h#L221
+    Constants.TCP_USER_TIMEOUT = 0x80
     break
 
   case 'freebsd':
diff --git a/lib/index.js b/lib/index.js
index 09a584b6..3f21fc56 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -215,10 +215,10 @@ module.exports.getKeepAliveProbes = function getKeepAliveProbes(socket) {
 }
 
 /**
- * Sets the TCP_USER_TIMEOUT value for specified socket.
+ * Sets the TCP_USER_TIMEOUT (TCP_RXT_CONNDROPTIME on `darwin`) value for specified socket.
  *
  * Notes:
- * * This method is only supported on `linux`, will throw on `darwin` and `freebsd`.
+ * * This method is only supported on `linux` and `darwin`, will throw on `freebsd`.
  * * The msec will be rounded towards the closest integer.
  * * When used with the TCP keepalive options, will override them.
  *
diff --git a/test/unit/test-timeout.js b/test/unit/test-timeout.js
index e4106820..9ce56a6e 100644
--- a/test/unit/test-timeout.js
+++ b/test/unit/test-timeout.js
@@ -13,7 +13,7 @@ describe('TCP User Timeout', () => {
   })
 
   itSkipOS(
-    ['darwin', 'freebsd'],'should validate passed arguments', function () {
+    ['freebsd'],'should validate passed arguments', function () {
     ;(() => Lib.setUserTimeout()).should.throw(
       'setUserTimeout requires two arguments'
     )
@@ -52,7 +52,7 @@ describe('TCP User Timeout', () => {
   })
 
   itSkipOS(
-    ['darwin', 'freebsd'],
+    ['freebsd'],
     'should throw when setsockopt returns -1',
     (done) => {
       const srv = Net.createServer()
@@ -68,7 +68,7 @@ describe('TCP User Timeout', () => {
     }
   )
 
-  itSkipOS(['darwin', 'freebsd'], 'should be able to set and get 4 second value', (done) => {
+  itSkipOS(['freebsd'], 'should be able to set and get 4 second value', (done) => {
     const srv = Net.createServer()
     srv.listen(0, () => {
       const expected = 4000
@@ -91,7 +91,7 @@ describe('TCP User Timeout', () => {
     })
   })
 
-  itSkipOS(['darwin', 'freebsd'], 'should throw when trying to get using invalid fd', (done) => {
+  itSkipOS(['freebsd'], 'should throw when trying to get using invalid fd', (done) => {
     ;(() => Lib.setUserTimeout(new Net.Socket(), 1)).should.throw(
       'Unable to get socket fd'
     )