ext/openssl/xp_ssl: eliminate poll() when MSG_DONTWAIT is available

If there is a zero timeout and MSG_DONTWAIT is available (or the
socket is non-blocking), the poll() call is not necessary, and we can
just call recv() right away.

Author: MaxKellermann

ext/openssl/xp_ssl.c

@@ -46,6 +46,10 @@
 #undef X509_EXTENSIONS
 #endif
 
+#ifndef MSG_DONTWAIT
+# define MSG_DONTWAIT 0
+#endif
+
 /* Flags for determining allowed stream crypto methods */
 #define STREAM_CRYPTO_IS_CLIENT            (1<<0)
 #define STREAM_CRYPTO_METHOD_SSLv2         (1<<1)
@@ -2395,7 +2399,10 @@ static int php_openssl_sockop_set_option(php_stream *stream, int option, int val
 
 				if (sslsock->s.socket == -1) {
 					alive = 0;
-				} else if (php_pollfd_for(sslsock->s.socket, PHP_POLLREADABLE|POLLPRI, &tv) > 0) {
+				} else if ((!sslsock->ssl_active && value == 0 && (MSG_DONTWAIT || !sslsock->s.is_blocked)) ||
+					   php_pollfd_for(sslsock->s.socket, PHP_POLLREADABLE|POLLPRI, &tv) > 0) {
+					/* the poll() call was skipped if the socket is non-blocking (or MSG_DONTWAIT is available) and if the timeout is zero */
+					/* additionally, we don't use this optimization if SSL is active because in that case, we're not using MSG_DONTWAIT */
 					if (sslsock->ssl_active) {
 						int n = SSL_peek(sslsock->ssl_handle, &buf, sizeof(buf));
 						if (n <= 0) {
@@ -2413,7 +2420,7 @@ static int php_openssl_sockop_set_option(php_stream *stream, int option, int val
 									alive = 0;
 							}
 						}
-					} else if (0 == recv(sslsock->s.socket, &buf, sizeof(buf), MSG_PEEK) && php_socket_errno() != EAGAIN) {
+					} else if (0 == recv(sslsock->s.socket, &buf, sizeof(buf), MSG_PEEK|MSG_DONTWAIT) && php_socket_errno() != EAGAIN) {
 						alive = 0;
 					}
 				}