1. Optimization on TLS record size

The client can decipher the data only once it has received a full record over SSL. The record size can have significant impact on the page load time performance of the application. No limitation on record size means that clients might have to download up to 16KB of data before starting to process them, whereas very small records incur a larger overhead due to record framing. The suggestion is to configure the TLS record size to fit into a single TCP segment, this can improve page load times on browsers located over high latency or low bandwidth networks.
- ref: http://www.igvita.com/2013/10/24/optimizing-tls-record-size-and-buffering-latency/
Status: https://issues.apache.org/jira/browse/TS-2365

2. Configurable session time

Session size is configurable, whereas application can not specify a session time out threshold. The default is 300 seconds. In some cases, applications need to reduce or increase the caching time, it's good to be configurable.

3. Release memory for idle ssl connection

When we no longer need a read buffer or a write buffer for a given SSL, then release the memory we were using to hold it. Released memory is either appended to a list of unused RAM chunks on the SSL_CTX, or simply freed if the list of unused chunks would become longer than SSL_CTX->freelist_max_len, which defaults to 32. Using this flag can save around 34K per idle SSL connection. This flag has no effect on SSL v2 connections, or on DTLS connections.

ref: http://www.openssl.org/docs/ssl/SSL_CTX_set_mode.html

#ifdef SSL_MODE_RELEASE_BUFFERS
    SSL_CTX_set_mode(ctx, SSL_MODE_RELEASE_BUFFERS);
#endif

4. Expose API to extract peer certificate data

When verifying peer certificates, A few customers expect to obtain the specific cert data (i.e. subject, issuer info) and forward them to origin servers. It's better to expose API to extract peer certificate data.
Status: https://issues.apache.org/jira/browse/TS-2210

5. SSL_read size threshold

A few customers expect a size threshold for client request over ssl from protecting system perspective. If the max requested data exceed the threshold, server will reject the client connection.

6. Specific mode for verifying peer certificate

Current 'mode' for verifying peer certificate is a global option, it's good to have specific mode among different sites hosted on a same machine. If the mode is non-empty, it would be the preference when making the decision to verify peer or not. Otherwise, the global mode will take effect.

   # Client certification level should be:
   # 0 no client certificates
   # 1 client certificates optional
   # 2 client certificates required
   CONFIG proxy.config.ssl.client.certification_level INT 0