Helper to perform abortable blocking operations on a socket:

   asocket_connect()
   asocket_accept()
   asocket_read()
   asocket_write()
 These calls are similar to the regular syscalls, but can be aborted with:
   asocket_abort()

Calling close() on a regular POSIX socket does not abort blocked syscalls on
that socket in other threads.

After calling asocket_abort() the socket cannot be reused.

Call asocket_destory() *after* all threads have finished with the socket to
finish closing the socket and free the asocket structure.

The helper is implemented by setting the socket non-blocking to initiate
syscalls connect(), accept(), read(), write(), then using a blocking poll()
on both the primary socket and a local pipe. This makes the poll() abortable
by writing a byte to the local pipe in asocket_abort().

asocket_create() sets the fd to non-blocking mode. It must not be changed to
blocking mode.

Using asocket will triple the number of file descriptors required per
socket, due to the local pipe. It may be possible to use a global pipe per
process rather than per socket, but we have not been able to come up with a
race-free implementation yet.

All functions except asocket_init() and asocket_destroy() are thread safe.

1 files changed, 103 insertions, 0 deletions

diff --git a/include/cutils/abort_socket.h b/include/cutils/abort_socket.h
new file mode 100644
index 000000000..fbb1112fa
--- /dev/null
+++ b/include/cutils/abort_socket.h
@@ -0,0 +1,103 @@
+/*
+ * Copyright 2009, The Android Open Source Project
+ *
+ * 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.
+ */
+
+/* Helper to perform abortable blocking operations on a socket:
+ *   asocket_connect()
+ *   asocket_accept()
+ *   asocket_read()
+ *   asocket_write()
+ * These calls are similar to the regular syscalls, but can be aborted with:
+ *   asocket_abort()
+ *
+ * Calling close() on a regular POSIX socket does not abort blocked syscalls on
+ * that socket in other threads.
+ *
+ * After calling asocket_abort() the socket cannot be reused.
+ *
+ * Call asocket_destory() *after* all threads have finished with the socket to
+ * finish closing the socket and free the asocket structure.
+ *
+ * The helper is implemented by setting the socket non-blocking to initiate
+ * syscalls connect(), accept(), read(), write(), then using a blocking poll()
+ * on both the primary socket and a local pipe. This makes the poll() abortable
+ * by writing a byte to the local pipe in asocket_abort().
+ *
+ * asocket_create() sets the fd to non-blocking mode. It must not be changed to
+ * blocking mode.
+ *
+ * Using asocket will triple the number of file descriptors required per
+ * socket, due to the local pipe. It may be possible to use a global pipe per
+ * process rather than per socket, but we have not been able to come up with a
+ * race-free implementation yet.
+ *
+ * All functions except asocket_init() and asocket_destroy() are thread safe.
+ */
+
+#include <stdlib.h>
+#include <sys/socket.h>
+
+#ifndef __CUTILS_ABORT_SOCKET_H__
+#define __CUTILS_ABORT_SOCKET_H__
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+struct asocket {
+    int fd;           /* primary socket fd */
+    int abort_fd[2];  /* pipe used to abort */
+};
+
+/* Create an asocket from fd.
+ * Sets the socket to non-blocking mode.
+ * Returns NULL on error with errno set.
+ */
+struct asocket *asocket_init(int fd);
+
+/* Blocking socket I/O with timeout.
+ * Calling asocket_abort() from another thread will cause each of these
+ * functions to immediately return with value -1 and errno ECANCELED.
+ * timeout is in ms, use -1 to indicate no timeout. On timeout -1 is returned
+ * with errno ETIMEDOUT.
+ * EINTR is handled in-call.
+ * Other semantics are identical to the regular syscalls.
+ */
+int asocket_connect(struct asocket *s, const struct sockaddr *addr,
+        socklen_t addrlen, int timeout);
+
+int asocket_accept(struct asocket *s, struct sockaddr *addr,
+        socklen_t *addrlen, int timeout);
+
+int asocket_read(struct asocket *s, void *buf, size_t count, int timeout);
+
+int asocket_write(struct asocket *s, const void *buf, size_t count,
+        int timeout);
+
+/* Abort above calls and shutdown socket.
+ * Further I/O operations on this socket will immediately fail after this call.
+ * asocket_destroy() should be used to release resources once all threads
+ * have returned from blocking calls on the socket.
+ */
+void asocket_abort(struct asocket *s);
+
+/* Close socket and free asocket structure.
+ * Must not be called until all calls on this structure have completed.
+ */
+void asocket_destroy(struct asocket *s);
+
+#ifdef __cplusplus
+}
+#endif
+#endif //__CUTILS_ABORT_SOCKET__H__