[GitHub] [spark] attilapiros commented on a diff in pull request #39728: [SPARK-42173][CORE] RpcAddress equality can fail

["attilapiros (via GitHub)" <gi...@apache.org>]

attilapiros commented on code in PR #39728:
URL: https://github.com/apache/spark/pull/39728#discussion_r1087190921


##########
core/src/main/scala/org/apache/spark/util/Utils.scala:
##########
@@ -1109,6 +1109,24 @@ private[spark] object Utils extends Logging {
     }
   }
 
+  /**
+   * Normalize IPv6 IPs and no-op on all other hosts.
+   */
+  private[spark] def normalizeIpIfNeeded(host: String): String = {
+    // Is this a v6 address. We ask users to add [] around v6 addresses as strs but
+    // there not always there. If it's just 0-9 and : and [] we treat it as a v6 address.
+    // This means some invalid addresses are treated as v6 addresses, but since they are
+    // not valid hostnames it doesn't matter.
+    // See https://www.rfc-editor.org/rfc/rfc1123#page-13 for context around valid hostnames.
+    val addressRe = """^\[{0,1}([0-9:]+?:[0-9]+)\]{0,1}$""".r

Review Comment:
   If the v6 address ends with 0's and it is shortened then the regexp will fail, isn't it?
   ```
   scala> "[2:7::]".matches("""^\[{0,1}([0-9:]+?:[0-9]+)\]{0,1}$""")
   res1: Boolean = false
   ```
   
   Or the example from [this comment](https://www.reddit.com/r/networking/comments/49eap8/comment/d0r42ww/?utm_source=reddit&utm_medium=web2x&context=3):
   
   ```
   scala> "[2600::]".matches("""^\[{0,1}([0-9:]+?:[0-9]+)\]{0,1}$""")
   res2: Boolean = false
   ```



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