Original commit: https://github.com/DerpFest-11/packages_modules_NetworkStack/commit/22fd53a977eeaf4e36be7bf6358ecf2c2737fa5e

From 22fd53a977eeaf4e36be7bf6358ecf2c2737fa5e Mon Sep 17 00:00:00 2001
From: Bruno Martins <bgcngm@gmail.com>
Date: Wed, 14 Oct 2020 16:08:13 +0100
Subject: [PATCH] TcpSocketTracker: Opt-out for TCP info parsing on legacy
 kernels

This feature requires netlink features that are unsupported on
kernel versions lower than 4.4, therefore opt-out for it in such
cases and avoid constantly crashing TcpSocketTracker.

Change-Id: I128ed1d0dcb6ca07eef1179f1ef036ccaad64e52
---
 .../netlink/TcpSocketTracker.java             | 36 ++++++++++++++++++-
 1 file changed, 35 insertions(+), 1 deletion(-)

diff --git a/packages/modules/NetworkStack/src/com/android/networkstack/netlink/TcpSocketTracker.java b/packages/modules/NetworkStack/src/com/android/networkstack/netlink/TcpSocketTracker.java
index ef33f13..f39518f 100644
--- a/packages/modules/NetworkStack/src/com/android/networkstack/netlink/TcpSocketTracker.java
+++ b/packages/modules/NetworkStack/src/com/android/networkstack/netlink/TcpSocketTracker.java
@@ -57,8 +57,10 @@
 import android.system.ErrnoException;
 import android.system.Os;
 import android.system.StructTimeval;
+import android.text.TextUtils;
 import android.util.Log;
 import android.util.LongSparseArray;
+import android.util.Pair;
 import android.util.SparseArray;
 
 import androidx.annotation.NonNull;
@@ -77,6 +79,8 @@
 import java.util.ArrayList;
 import java.util.Base64;
 import java.util.List;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 
 /**
  * Class for NetworkStack to send a SockDiag request and parse the returned tcp info.
@@ -431,6 +435,35 @@ private void log(final String str) {
         if (DBG) Log.d(TAG, str);
     }
 
+    private static boolean isTcpInfoParsingSupportedByKernel() {
+        final String kVersionString = Os.uname().release;
+        return compareMajorMinorVersion(kVersionString, "4.4") >= 0;
+    }
+
+    private static int compareMajorMinorVersion(final String s1, final String s2) {
+        final Pair<Integer, Integer> v1 = getVersionFromString(s1);
+        final Pair<Integer, Integer> v2 = getVersionFromString(s2);
+
+        if (v1.first == v2.first) {
+            return Integer.compare(v1.second, v2.second);
+        } else {
+            return Integer.compare(v1.first, v2.first);
+        }
+    }
+
+    private static Pair<Integer, Integer> getVersionFromString(String version) {
+        // Only gets major and minor number of the version string.
+        final Pattern versionPattern = Pattern.compile("^(\\d+)(\\.(\\d+))?.*");
+        final Matcher m = versionPattern.matcher(version);
+        if (m.matches()) {
+            final int major = Integer.parseInt(m.group(1));
+            final int minor = TextUtils.isEmpty(m.group(3)) ? 0 : Integer.parseInt(m.group(3));
+            return new Pair<>(major, minor);
+        } else {
+            return new Pair<>(0, 0);
+        }
+    }
+
     /**
      * Corresponds to {@code struct rtattr} from bionic/libc/kernel/uapi/linux/rtnetlink.h
      *
@@ -578,7 +611,8 @@ public int getDeviceConfigPropertyInt(@NonNull final String namespace,
         public boolean isTcpInfoParsingSupported() {
             // Request tcp info from NetworkStack directly needs extra SELinux permission added
             // after Q release.
-            return ShimUtils.isReleaseOrDevelopmentApiAbove(Build.VERSION_CODES.Q);
+            return ShimUtils.isReleaseOrDevelopmentApiAbove(Build.VERSION_CODES.Q) &&
+                    isTcpInfoParsingSupportedByKernel();
         }
 
         /**