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junixsocket is a Java/JNI library that allows the use of Unix Domain Sockets (AF_UNIX sockets) and other socket types, such as AF_TIPC and AF_VSOCK, from Java, using the standard Socket API
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/*
* junixsocket
*
* Copyright 2009-2024 Christian Kohlschütter
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.newsclub.net.unix;
import java.lang.ProcessBuilder.Redirect;
/**
* Describes junixsocket capabilities the current environment (system platform, native library,
* etc.) may or may not support.
*
* You can check whether your environment supports a given capability by calling
* {@link AFSocket#supports(AFSocketCapability)}.
*
* You can also manually disable a given capability by specifying a System property of the form
* org.newsclub.net.unix.library.disable.CAPABILITY_SOMETHING_SOMETHING=true
* when invoking the JVM (make sure this property is set before junixsocket is accessed).
*
* A simple way to check which capabilities are supported in an environment is to run the
* `junixsocket-selftest` jar.
*/
public enum AFSocketCapability {
// see org_newsclub_net_unix_NativeUnixSocket.c in junixsocket-native
/** Socket supports retrieving peer credentials. */
CAPABILITY_PEER_CREDENTIALS(0),
/** Socket supports sending and receiving ancillary messages. */
CAPABILITY_ANCILLARY_MESSAGES(1),
/** Socket supports passing file descriptors via ancillary messages. */
CAPABILITY_FILE_DESCRIPTORS(2),
/** Socket addressing supports the abstract namespace (Linux). */
CAPABILITY_ABSTRACT_NAMESPACE(3),
/** Support for AF_UNIX datagrams. */
CAPABILITY_UNIX_DATAGRAMS(4),
/**
* A pair of interconnected sockets can be created natively as AF_UNIX sockets.
*
* This currently not possible on Windows, but instead emulated via anonymous AF_INET ports when
* you use {@link AFSocketPair}. Other systems may provide partial implementations of pipe-based
* (i.e., non-socket) pairs.
*
* This capability is specific to AF_UNIX sockets. Other sockets, such as AF_VSOCK, may not
* implement socketpair natively even if this capability is set, but would work-around that
* limitation in a similar fashion but maybe without resorting to AF_INET.
*/
CAPABILITY_NATIVE_SOCKETPAIR(5),
/**
* A file descriptor can be converted to {@link Redirect}.
*
* This feature currently uses Java SDK internals that may change/disappear.
*/
CAPABILITY_FD_AS_REDIRECT(6),
/**
* Support for AF_TIPC.
*
* Availability of this feature is checked upon launch and therefore loading the "tipc" kernel
* module at a later point may not be properly reflected.
*/
CAPABILITY_TIPC(7),
/**
* Support for AF_UNIX.
*
* Availability of this feature is checked upon launch and therefore, on systems adding support at
* a later point, may not be properly reflected when checking at a later point.
*
* NOTE: While this capability is typically supported on most systems that can actually load a
* junixsocket JNI library, it is unavailable for older Windows versions (such as 8.1, 10 before
* AFUNIX.SYS was included, etc.) and on systems where support for UNIX domain sockets is actively
* disabled. Therefore, it is still recommended to check for this capability.
*/
CAPABILITY_UNIX_DOMAIN(8),
/**
* Support for AF_VSOCK.
*
* Availability of this feature is checked upon launch and therefore enabling vsock at a later
* point may not be properly reflected.
*
* @see #CAPABILITY_VSOCK_DGRAM
*/
CAPABILITY_VSOCK(9),
/**
* Support for AF_VSOCK datagrams (not all platforms/kernel versions or configurations support
* this).
*
* Availability of this feature is checked upon launch and therefore enabling vsock at a later
* point may not be properly reflected.
*/
CAPABILITY_VSOCK_DGRAM(10),
/**
* Support for zero-length send(2).
*
* This can be used to perform a connection check, but not all operating systems support this or
* behave correctly (particularly, IBM AIX, IBM i, and IBM z/OS) at the moment.
*
* If not supported, junixsocket will simply ignore writes of zero-length, and connection checking
* with {@link AFSocket#checkConnectionClosed()} may return {@code false} regardless of the actual
* condition.
*/
CAPABILITY_ZERO_LENGTH_SEND(11),
/**
* Support for "unsafe" operations.
*
* Trading-in safety for speed or simplicity may be justified sometimes.
*
* @see Unsafe
* @see AFSocket#ensureUnsafeSupported()
*/
CAPABILITY_UNSAFE(12),
/**
* Support for port numbers larger than 65535 (0xffff).
*
* Not all systems allow setting port numbers beyond the default TCP range (we use JNI tricks for
* that). This capability is required for RMI support.
*/
CAPABILITY_LARGE_PORTS(13),
/**
* Support for certain Darwin (macOS Kernel)-specific features, such as the AF_SYSTEM domain.
*/
CAPABILITY_DARWIN(14),
; // end of list
private final int bitmask;
AFSocketCapability(int bit) {
this.bitmask = 1 << bit;
}
int getBitmask() {
return bitmask;
}
}
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