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13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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15  * accompanied this code).
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25 
26 package sun.nio.ch;
27 
28 import java.lang.reflect.Constructor;
29 import java.io.FileDescriptor;
30 import java.io.IOException;
31 import java.net.InetAddress;
32 import java.net.InetSocketAddress;
33 import java.nio.channels.Channel;
34 import java.nio.channels.SocketChannel;
35 import java.nio.channels.ServerSocketChannel;
36 import java.nio.channels.DatagramChannel;
37 import java.nio.channels.spi.SelectorProvider;
38 
39 class InheritedChannel {
40 
41     // the "types" of socket returned by soType0
42     private static final int UNKNOWN            = -1;
43     private static final int SOCK_STREAM        = 1;
44     private static final int SOCK_DGRAM         = 2;
45 
46     // oflag values when opening a file
47     private static final int O_RDONLY           = 0;
48     private static final int O_WRONLY           = 1;
49     private static final int O_RDWR             = 2;
50 
51     /*
52      * In order to "detach" the standard streams we dup them to /dev/null.
53      * In order to reduce the possibility of an error at close time we
54      * open /dev/null early - that way we know we won't run out of file
55      * descriptors at close time. This makes the close operation a
56      * simple dup2 operation for each of the standard streams.
57      */
58     private static int devnull = -1;
59 
detachIOStreams()60     private static void detachIOStreams() {
61         try {
62             dup2(devnull, 0);
63             dup2(devnull, 1);
64             dup2(devnull, 2);
65         } catch (IOException ioe) {
66             // this shouldn't happen
67             throw new InternalError();
68         }
69     }
70 
71     /*
72      * Override the implCloseSelectableChannel for each channel type - this
73      * allows us to "detach" the standard streams after closing and ensures
74      * that the underlying socket really closes.
75      */
76     public static class InheritedSocketChannelImpl extends SocketChannelImpl {
77 
InheritedSocketChannelImpl(SelectorProvider sp, FileDescriptor fd, InetSocketAddress remote)78         InheritedSocketChannelImpl(SelectorProvider sp,
79                                    FileDescriptor fd,
80                                    InetSocketAddress remote)
81             throws IOException
82         {
83             super(sp, fd, remote);
84         }
85 
implCloseSelectableChannel()86         protected void implCloseSelectableChannel() throws IOException {
87             super.implCloseSelectableChannel();
88             detachIOStreams();
89         }
90     }
91 
92     public static class InheritedServerSocketChannelImpl extends
93         ServerSocketChannelImpl {
94 
InheritedServerSocketChannelImpl(SelectorProvider sp, FileDescriptor fd)95         InheritedServerSocketChannelImpl(SelectorProvider sp,
96                                          FileDescriptor fd)
97             throws IOException
98         {
99             super(sp, fd, true);
100         }
101 
implCloseSelectableChannel()102         protected void implCloseSelectableChannel() throws IOException {
103             super.implCloseSelectableChannel();
104             detachIOStreams();
105         }
106 
107     }
108 
109     public static class InheritedDatagramChannelImpl extends
110         DatagramChannelImpl {
111 
InheritedDatagramChannelImpl(SelectorProvider sp, FileDescriptor fd)112         InheritedDatagramChannelImpl(SelectorProvider sp,
113                                      FileDescriptor fd)
114             throws IOException
115         {
116             super(sp, fd);
117         }
118 
implCloseSelectableChannel()119         protected void implCloseSelectableChannel() throws IOException {
120             super.implCloseSelectableChannel();
121             detachIOStreams();
122         }
123     }
124 
125     /*
126      * If there's a SecurityManager then check for the appropriate
127      * RuntimePermission.
128      */
checkAccess(Channel c)129     private static void checkAccess(Channel c) {
130         SecurityManager sm = System.getSecurityManager();
131         if (sm != null) {
132             sm.checkPermission(
133                 new RuntimePermission("inheritedChannel")
134             );
135         }
136     }
137 
138 
139     /*
140      * If standard inherited channel is connected to a socket then return a Channel
141      * of the appropriate type based standard input.
142      */
createChannel()143     private static Channel createChannel() throws IOException {
144 
145         // dup the file descriptor - we do this so that for two reasons :-
146         // 1. Avoids any timing issues with FileDescriptor.in being closed
147         //    or redirected while we create the channel.
148         // 2. Allows streams based on file descriptor 0 to co-exist with
149         //    the channel (closing one doesn't impact the other)
150 
151         int fdVal = dup(0);
152 
153         // Examine the file descriptor - if it's not a socket then we don't
154         // create a channel so we release the file descriptor.
155 
156         int st;
157         st = soType0(fdVal);
158         if (st != SOCK_STREAM && st != SOCK_DGRAM) {
159             close0(fdVal);
160             return null;
161         }
162 
163 
164         // Next we create a FileDescriptor for the dup'ed file descriptor
165         // Have to use reflection and also make assumption on how FD
166         // is implemented.
167 
168         Class paramTypes[] = { int.class };
169         Constructor ctr = Reflect.lookupConstructor("java.io.FileDescriptor",
170                                                     paramTypes);
171         Object args[] = { new Integer(fdVal) };
172         FileDescriptor fd = (FileDescriptor)Reflect.invoke(ctr, args);
173 
174 
175         // Now create the channel. If the socket is a streams socket then
176         // we see if tthere is a peer (ie: connected). If so, then we
177         // create a SocketChannel, otherwise a ServerSocketChannel.
178         // If the socket is a datagram socket then create a DatagramChannel
179 
180         SelectorProvider provider = SelectorProvider.provider();
181         assert provider instanceof sun.nio.ch.SelectorProviderImpl;
182 
183         Channel c;
184         if (st == SOCK_STREAM) {
185             InetAddress ia = peerAddress0(fdVal);
186             if (ia == null) {
187                c = new InheritedServerSocketChannelImpl(provider, fd);
188             } else {
189                int port = peerPort0(fdVal);
190                assert port > 0;
191                InetSocketAddress isa = new InetSocketAddress(ia, port);
192                c = new InheritedSocketChannelImpl(provider, fd, isa);
193             }
194         } else {
195             c = new InheritedDatagramChannelImpl(provider, fd);
196         }
197         return c;
198     }
199 
200     private static boolean haveChannel = false;
201     private static Channel channel = null;
202 
203     /*
204      * Returns a Channel representing the inherited channel if the
205      * inherited channel is a stream connected to a network socket.
206      */
getChannel()207     public static synchronized Channel getChannel() throws IOException {
208         if (devnull < 0) {
209             devnull = open0("/dev/null", O_RDWR);
210         }
211 
212         // If we don't have the channel try to create it
213         if (!haveChannel) {
214             channel = createChannel();
215             haveChannel = true;
216         }
217 
218         // if there is a channel then do the security check before
219         // returning it.
220         if (channel != null) {
221             checkAccess(channel);
222         }
223         return channel;
224     }
225 
226 
227     // -- Native methods --
228 
dup(int fd)229     private static native int dup(int fd) throws IOException;
dup2(int fd, int fd2)230     private static native void dup2(int fd, int fd2) throws IOException;
open0(String path, int oflag)231     private static native int open0(String path, int oflag) throws IOException;
close0(int fd)232     private static native void close0(int fd) throws IOException;
soType0(int fd)233     private static native int soType0(int fd);
peerAddress0(int fd)234     private static native InetAddress peerAddress0(int fd);
peerPort0(int fd)235     private static native int peerPort0(int fd);
236 }
237