SERVER-48466 Suppress tcp_fastopen test on hosts with blackhole events

2 files changed, 56 insertions, 1 deletions

diff --git a/jstests/core/tcp_fastopen.js b/jstests/core/tcp_fastopen.js
index ac45d2faa2d..d63a86c5c5e 100644
--- a/jstests/core/tcp_fastopen.js
+++ b/jstests/core/tcp_fastopen.js
@@ -4,6 +4,8 @@
 (function() {
 'use strict';
 
+load("jstests/libs/netstat.js");
+
 // Does it make sense to expect TFO support?
 try {
     // Both client and server bits must be set to run this test.
@@ -21,7 +23,15 @@ try {
 const initial = db.serverStatus().network.tcpFastOpen;
 printjson(initial);
 print("/proc/net/netstat:");
-print(cat("/proc/net/netstat"));
+const initialObj = getNetStatObj();
+printjson(initialObj);
+
+// If TCPFastOpenBlackhole is 0 or not present, try to run the test. Otherwise,
+// we've seen an event, and should skip the test.
+if (initialObj.TcpExt.TCPFastOpenBlackhole) {
+    print("==Skipping test, host OS has observed a TCPFastOpenBlackhole event");
+    return;
+}
 
 if (!initial.serverSupported || !initial.clientSupported) {
     print("==Skipping test, one or both setsockopt() calls failed");
diff --git a/jstests/libs/netstat.js b/jstests/libs/netstat.js
new file mode 100644
index 00000000000..0fe05922259
--- /dev/null
+++ b/jstests/libs/netstat.js
@@ -0,0 +1,45 @@
+'use strict';
+
+/* Read the contents of /proc/net/netstat, and transform the output into a JS object.
+ * Netstat contains sections of key/value pairs, for different metrics tracked by the
+ * Linux kernel. Sections are encoded as two lines, prefixed by the field name. The first
+ * line contains an ordered list of all key names. The second line contains the ordered
+ * list of values.
+ * The schema of resulting Javascript object is:
+ * {
+ *   "section1": {
+ *     "key1": value1,
+ *     "key2": value2,
+ *     ...
+ *   },
+ *   "section2": {
+ *     "key1": value1,
+ *     ...
+ *   },
+ *   ...
+ * }
+ */
+function getNetStatObj() {
+    return cat("/proc/net/netstat")
+        .split("\n")
+        .filter((item) => item.length)
+        .map(line => line.split(" "))
+        .reduce((acc, current) => {
+            const sectionName = current[0].slice(0, -1);
+            // If we're populating a subsection for the first time,
+            // just copy over the key names, resulting in:
+            // {..., "section": ["key1", "key2", ..., "keyN"] }
+            if (!acc[sectionName]) {
+                acc[sectionName] = current.slice(1);
+            } else {
+                // Merge the values into a subsection, resulting in:
+                // {..., "section": {"key1": value1, ..., "keyN", valueN} }
+                const populated = {};
+                acc[sectionName].forEach((item, index) => {
+                    populated[item] = current[index + 1];
+                });
+                acc[sectionName] = populated;
+            }
+            return acc;
+        }, {});
+}