1 /*
2 * Copyright 2014 The Netty Project
3 *
4 * The Netty Project licenses this file to you under the Apache License,
5 * version 2.0 (the "License"); you may not use this file except in compliance
6 * with the License. You may obtain a copy of the License at:
7 *
8 * https://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13 * License for the specific language governing permissions and limitations
14 * under the License.
15 */
16 package io.netty.channel.epoll;
17
18 import io.netty.channel.ChannelOption;
19 import io.netty.channel.unix.FileDescriptor;
20 import io.netty.util.internal.SystemPropertyUtil;
21 import io.netty.util.internal.logging.InternalLogger;
22 import io.netty.util.internal.logging.InternalLoggerFactory;
23
24 /**
25 * Tells if <a href="https://netty.io/wiki/native-transports.html">{@code netty-transport-native-epoll}</a> is
26 * supported.
27 */
28 public final class Epoll {
29
30 private static final Throwable UNAVAILABILITY_CAUSE;
31
32 static {
33 Throwable cause = null;
34
35 if (SystemPropertyUtil.getBoolean("io.netty.transport.noNative", false)) {
36 cause = new UnsupportedOperationException(
37 "Native transport was explicit disabled with -Dio.netty.transport.noNative=true");
38 } else {
39 FileDescriptor epollFd = null;
40 FileDescriptor eventFd = null;
41 try {
42 epollFd = Native.newEpollCreate();
43 eventFd = Native.newEventFd();
44 } catch (Throwable t) {
45 cause = t;
46 } finally {
47 if (epollFd != null) {
48 try {
49 epollFd.close();
50 } catch (Exception ignore) {
51 // ignore
52 }
53 }
54 if (eventFd != null) {
55 try {
56 eventFd.close();
57 } catch (Exception ignore) {
58 // ignore
59 }
60 }
61 }
62 }
63 if (cause != null) {
64 InternalLogger logger = InternalLoggerFactory.getInstance(Epoll.class);
65 if (logger.isTraceEnabled()) {
66 logger.debug("Epoll support is not available", cause);
67 } else if (logger.isDebugEnabled()) {
68 logger.debug("Epoll support is not available: {}", cause.getMessage());
69 }
70 }
71 UNAVAILABILITY_CAUSE = cause;
72 }
73
74 /**
75 * Returns {@code true} if and only if the <a href="https://netty.io/wiki/native-transports.html">{@code
76 * netty-transport-native-epoll}</a> is available.
77 */
78 public static boolean isAvailable() {
79 return UNAVAILABILITY_CAUSE == null;
80 }
81
82 /**
83 * Ensure that <a href="https://netty.io/wiki/native-transports.html">{@code netty-transport-native-epoll}</a> is
84 * available.
85 *
86 * @throws UnsatisfiedLinkError if unavailable
87 */
88 public static void ensureAvailability() {
89 if (UNAVAILABILITY_CAUSE != null) {
90 throw (Error) new UnsatisfiedLinkError(
91 "failed to load the required native library").initCause(UNAVAILABILITY_CAUSE);
92 }
93 }
94
95 /**
96 * Returns the cause of unavailability of <a href="https://netty.io/wiki/native-transports.html">
97 * {@code netty-transport-native-epoll}</a>.
98 *
99 * @return the cause if unavailable. {@code null} if available.
100 */
101 public static Throwable unavailabilityCause() {
102 return UNAVAILABILITY_CAUSE;
103 }
104
105 /**
106 * Returns {@code true} if the epoll native transport is both {@linkplain #isAvailable() available} and supports
107 * {@linkplain ChannelOption#TCP_FASTOPEN_CONNECT client-side TCP FastOpen}.
108 *
109 * @return {@code true} if it's possible to use client-side TCP FastOpen via epoll, otherwise {@code false}.
110 */
111 public static boolean isTcpFastOpenClientSideAvailable() {
112 return isAvailable() && Native.IS_SUPPORTING_TCP_FASTOPEN_CLIENT;
113 }
114
115 /**
116 * Returns {@code true} if the epoll native transport is both {@linkplain #isAvailable() available} and supports
117 * {@linkplain ChannelOption#TCP_FASTOPEN server-side TCP FastOpen}.
118 *
119 * @return {@code true} if it's possible to use server-side TCP FastOpen via epoll, otherwise {@code false}.
120 */
121 public static boolean isTcpFastOpenServerSideAvailable() {
122 return isAvailable() && Native.IS_SUPPORTING_TCP_FASTOPEN_SERVER;
123 }
124
125 private Epoll() {
126 }
127 }