Make low-level record errors idempotent.

Enough were to make record processing idempotent (we either consume a
record or we don't), but some errors would cause us to keep processing
records when we should get stuck.

This leaves errors in the layer between the record bits and the
handshake. I'm hoping that will be easier to resolve once they do not
depend on BIO, at which point the checks added in this CL may move
around.

Bug: 206
Change-Id: I6b177079388820335e25947c5bd736451780ab8f
Reviewed-on: https://boringssl-review.googlesource.com/21366
Commit-Queue: Steven Valdez <svaldez@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
Reviewed-by: Steven Valdez <svaldez@google.com>

ssl/ssl_lib.cc

diff --git a/ssl/ssl_lib.cc b/ssl/ssl_lib.cc
index c975337..2f5374b 100644
--- a/ssl/ssl_lib.cc
+++ b/ssl/ssl_lib.cc
@@ -206,6 +206,12 @@
   ERR_clear_system_error();
 }
 
+void ssl_set_read_error(SSL* ssl) {
+  ssl->s3->read_shutdown = ssl_shutdown_error;
+  ERR_SAVE_STATE_free(ssl->s3->read_error);
+  ssl->s3->read_error = ERR_save_state();
+}
+
 int ssl_can_write(const SSL *ssl) {
   return !SSL_in_init(ssl) || ssl->s3->hs->can_early_write;
 }