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
22 /**
23 * Tells if <a href="https://netty.io/wiki/native-transports.html">{@code netty-transport-native-epoll}</a> is
24 * supported.
25 */
26 public final class Epoll {
27
28 private static final Throwable UNAVAILABILITY_CAUSE;
29
30 static {
31 Throwable cause = null;
32
33 if (SystemPropertyUtil.getBoolean("io.netty.transport.noNative", false)) {
34 cause = new UnsupportedOperationException(
35 "Native transport was explicit disabled with -Dio.netty.transport.noNative=true");
36 } else {
37 FileDescriptor epollFd = null;
38 FileDescriptor eventFd = null;
39 try {
40 epollFd = Native.newEpollCreate();
41 eventFd = Native.newEventFd();
42 } catch (Throwable t) {
43 cause = t;
44 } finally {
45 if (epollFd != null) {
46 try {
47 epollFd.close();
48 } catch (Exception ignore) {
49 // ignore
50 }
51 }
52 if (eventFd != null) {
53 try {
54 eventFd.close();
55 } catch (Exception ignore) {
56 // ignore
57 }
58 }
59 }
60 }
61
62 UNAVAILABILITY_CAUSE = cause;
63 }
64
65 /**
66 * Returns {@code true} if and only if the <a href="https://netty.io/wiki/native-transports.html">{@code
67 * netty-transport-native-epoll}</a> is available.
68 */
69 public static boolean isAvailable() {
70 return UNAVAILABILITY_CAUSE == null;
71 }
72
73 /**
74 * Ensure that <a href="https://netty.io/wiki/native-transports.html">{@code netty-transport-native-epoll}</a> is
75 * available.
76 *
77 * @throws UnsatisfiedLinkError if unavailable
78 */
79 public static void ensureAvailability() {
80 if (UNAVAILABILITY_CAUSE != null) {
81 throw (Error) new UnsatisfiedLinkError(
82 "failed to load the required native library").initCause(UNAVAILABILITY_CAUSE);
83 }
84 }
85
86 /**
87 * Returns the cause of unavailability of <a href="https://netty.io/wiki/native-transports.html">
88 * {@code netty-transport-native-epoll}</a>.
89 *
90 * @return the cause if unavailable. {@code null} if available.
91 */
92 public static Throwable unavailabilityCause() {
93 return UNAVAILABILITY_CAUSE;
94 }
95
96 /**
97 * Returns {@code true} if the epoll native transport is both {@linkplain #isAvailable() available} and supports
98 * {@linkplain ChannelOption#TCP_FASTOPEN_CONNECT client-side TCP FastOpen}.
99 *
100 * @return {@code true} if it's possible to use client-side TCP FastOpen via epoll, otherwise {@code false}.
101 */
102 public static boolean isTcpFastOpenClientSideAvailable() {
103 return isAvailable() && Native.IS_SUPPORTING_TCP_FASTOPEN_CLIENT;
104 }
105
106 /**
107 * Returns {@code true} if the epoll native transport is both {@linkplain #isAvailable() available} and supports
108 * {@linkplain ChannelOption#TCP_FASTOPEN server-side TCP FastOpen}.
109 *
110 * @return {@code true} if it's possible to use server-side TCP FastOpen via epoll, otherwise {@code false}.
111 */
112 public static boolean isTcpFastOpenServerSideAvailable() {
113 return isAvailable() && Native.IS_SUPPORTING_TCP_FASTOPEN_SERVER;
114 }
115
116 private Epoll() {
117 }
118 }
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