RFR: 8328608: Multiple NewSessionTicket support for TLS

[John Jiang]

On Wed, 29 May 2024 18:53:55 GMT, Anthony Scarpino <ascarpino at openjdk.org> wrote:

> Hi
> 
> This change is to improve TLS 1.3 session resumption by allowing a TLS server to send more than one resumption ticket per connection and clients to store more.  Resumption is a quick way to use an existing TLS session to establish another session by avoiding the long TLS full handshake process.  In TLS 1.2 and below, clients can repeatedly resume a session by using the session ID from an established connection.  In TLS 1.3, a one-time "resumption ticket" is sent by the server after the TLS connection has been established.  The server may send multiple resumption tickets to help clients that rapidly resume connections.  If the client does not have another resumption ticket, it must go through the full TLS handshake again.  The current implementation in JDK 23 and below, only sends and store one resumption ticket.
> 
> The number of resumption tickets a server can send should be configurable by the application developer or administrator. [RFC 8446](https://www.rfc-editor.org/rfc/rfc8446) does not specify a default value.  A system property called `jdk.tls.server.newSessionTicketCount` allows the user to change the number of resumption tickets sent by the server.  If this property is not set or given an invalid value, the default value of 3 is used. Further details are in the CSR.
> 
> A large portion of the changeset is on the client side by changing the caching system used by TLS.  It creates a new `CacheEntry<>` type called `QueueCacheEntry<>` that will store multiple values for a Map entry.

src/java.base/share/classes/sun/security/util/Cache.java line 417:

> 415:      * @param canQueue can the value be put into a QueueCacheEntry
> 416:      */
> 417:     public synchronized void put(K key, V value, boolean canQueue) {

In practice, can `QueueCacheEntry` and other `CacheEntry` instances be stored in a single cache?
If not, the argument `canQueue` in this method could be moved to class `MemoryCache` as a field.
Then, if `canQueue` is true, the `put` method always adds the value into the `QueueCacheEntry` associated with the `key`; otherwise, this method just uses other `CacheEntry` types.

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PR Review Comment: https://git.openjdk.org/jdk/pull/19465#discussion_r1646354546