Implement Maximum Fragment Length TLS extension.

Based on patch from Tomasz Moń:
https://groups.google.com/forum/#!topic/mailing.openssl.dev/fQxXvCg1uQY

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
(Merged from https://github.com/openssl/openssl/pull/1008)

1 files changed, 27 insertions, 0 deletions

diff --git a/ssl/ssl_lib.c b/ssl/ssl_lib.c
index c151e7e27e..b1173f0c02 100644
--- a/ssl/ssl_lib.c
+++ b/ssl/ssl_lib.c
@@ -688,6 +688,8 @@ SSL *SSL_new(SSL_CTX *ctx)
         goto err;
     X509_VERIFY_PARAM_inherit(s->param, ctx->param);
     s->quiet_shutdown = ctx->quiet_shutdown;
+
+    s->ext.max_fragment_len_mode = ctx->ext.max_fragment_len_mode;
     s->max_send_fragment = ctx->max_send_fragment;
     s->split_send_fragment = ctx->split_send_fragment;
     s->max_pipelines = ctx->max_pipelines;
@@ -5160,3 +5162,28 @@ int ssl_randbytes(SSL *s, unsigned char *rnd, size_t size)
     }
     return RAND_bytes(rnd, (int)size);
 }
+
+__owur unsigned int ssl_get_max_send_fragment(const SSL *ssl)
+{
+    /* Return any active Max Fragment Len extension */
+    if (ssl->session != NULL && USE_MAX_FRAGMENT_LENGTH_EXT(ssl->session))
+        return GET_MAX_FRAGMENT_LENGTH(ssl->session);
+
+    /* return current SSL connection setting */
+    return ssl->max_send_fragment;
+}
+
+__owur unsigned int ssl_get_split_send_fragment(const SSL *ssl)
+{
+    /* Return a value regarding an active Max Fragment Len extension */
+    if (ssl->session != NULL && USE_MAX_FRAGMENT_LENGTH_EXT(ssl->session)
+        && ssl->split_send_fragment > GET_MAX_FRAGMENT_LENGTH(ssl->session))
+        return GET_MAX_FRAGMENT_LENGTH(ssl->session);
+
+    /* else limit |split_send_fragment| to current |max_send_fragment| */
+    if (ssl->split_send_fragment > ssl->max_send_fragment)
+        return ssl->max_send_fragment;
+
+    /* return current SSL connection setting */
+    return ssl->split_send_fragment;
+}