Add an SSL_has_pending() function

This is similar to SSL_pending() but just returns a 1 if there is data
pending in the internal OpenSSL buffers or 0 otherwise (as opposed to
SSL_pending() which returns the number of bytes available). Unlike
SSL_pending() this will work even if "read_ahead" is set (which is the
case if you are using read pipelining, or if you are doing DTLS). A 1
return value means that we have unprocessed data. It does *not* necessarily
indicate that there will be application data returned from a call to
SSL_read(). The unprocessed data may not be application data or there
could be errors when we attempt to parse the records.
Reviewed-by: NTim Hudson <tjh@openssl.org>

include/openssl/ssl.h

@@ -1408,6 +1408,7 @@ __owur const char *SSL_get_cipher_list(const SSL *s, int n);
 __owur char *SSL_get_shared_ciphers(const SSL *s, char *buf, int len);
 __owur int SSL_get_read_ahead(const SSL *s);
 __owur int SSL_pending(const SSL *s);
+__owur int SSL_has_pending(const SSL *s);
 # ifndef OPENSSL_NO_SOCK
 __owur int SSL_set_fd(SSL *s, int fd);
 __owur int SSL_set_rfd(SSL *s, int fd);

ssl/record/rec_layer_s3.c

@@ -186,12 +186,12 @@ void RECORD_LAYER_release(RECORD_LAYER *rl)
     SSL3_RECORD_release(rl->rrec, SSL_MAX_PIPELINES);
 }
 
-int RECORD_LAYER_read_pending(RECORD_LAYER *rl)
+int RECORD_LAYER_read_pending(const RECORD_LAYER *rl)
 {
     return SSL3_BUFFER_get_left(&rl->rbuf) != 0;
 }
 
-int RECORD_LAYER_write_pending(RECORD_LAYER *rl)
+int RECORD_LAYER_write_pending(const RECORD_LAYER *rl)
 {
     return (rl->numwpipes > 0)
             && SSL3_BUFFER_get_left(&rl->wbuf[rl->numwpipes-1]) != 0;

ssl/record/record.h

@@ -322,8 +322,8 @@ typedef struct record_layer_st {
 void RECORD_LAYER_init(RECORD_LAYER *rl, SSL *s);
 void RECORD_LAYER_clear(RECORD_LAYER *rl);
 void RECORD_LAYER_release(RECORD_LAYER *rl);
-int RECORD_LAYER_read_pending(RECORD_LAYER *rl);
-int RECORD_LAYER_write_pending(RECORD_LAYER *rl);
+int RECORD_LAYER_read_pending(const RECORD_LAYER *rl);
+int RECORD_LAYER_write_pending(const RECORD_LAYER *rl);
 int RECORD_LAYER_set_data(RECORD_LAYER *rl, const unsigned char *buf, int len);
 void RECORD_LAYER_reset_read_sequence(RECORD_LAYER *rl);
 void RECORD_LAYER_reset_write_sequence(RECORD_LAYER *rl);

ssl/ssl_lib.c

@@ -1310,6 +1310,22 @@ int SSL_pending(const SSL *s)
     return (s->method->ssl_pending(s));
 }
 
+int SSL_has_pending(const SSL *s)
+{
+    /*
+     * Similar to SSL_pending() but returns a 1 to indicate that we have
+     * unprocessed data available or 0 otherwise (as opposed to the number of
+     * bytes available). Unlike SSL_pending() this will take into account
+     * read_ahead data. A 1 return simply indicates that we have unprocessed
+     * data. That data may not result in any application data, or we may fail
+     * to parse the records for some reason.
+     */
+    if (SSL_pending(s))
+        return 1;
+
+    return RECORD_LAYER_read_pending(&s->rlayer);
+}
+
 X509 *SSL_get_peer_certificate(const SSL *s)
 {
     X509 *r;

util/libssl.num

@@ -383,3 +383,4 @@ SSL_CTX_set_ct_validation_callback      382	1_1_0	EXIST::FUNCTION:CT
 SSL_CTX_get_ct_validation_callback      383	1_1_0	EXIST::FUNCTION:CT
 SSL_set_default_read_buffer_len         384	1_1_0	EXIST::FUNCTION:
 SSL_CTX_set_default_read_buffer_len     385	1_1_0	EXIST::FUNCTION:
+SSL_has_pending                         386	1_1_0	EXIST::FUNCTION: