| 1 | /* |
| 2 | * Copyright 2009, The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://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, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | /* Helper to perform abortable blocking operations on a socket: |
| 18 | * asocket_connect() |
| 19 | * asocket_accept() |
| 20 | * asocket_read() |
| 21 | * asocket_write() |
| 22 | * These calls are similar to the regular syscalls, but can be aborted with: |
| 23 | * asocket_abort() |
| 24 | * |
| 25 | * Calling close() on a regular POSIX socket does not abort blocked syscalls on |
| 26 | * that socket in other threads. |
| 27 | * |
| 28 | * After calling asocket_abort() the socket cannot be reused. |
| 29 | * |
| 30 | * Call asocket_destory() *after* all threads have finished with the socket to |
| 31 | * finish closing the socket and free the asocket structure. |
| 32 | * |
| 33 | * The helper is implemented by setting the socket non-blocking to initiate |
| 34 | * syscalls connect(), accept(), read(), write(), then using a blocking poll() |
| 35 | * on both the primary socket and a local pipe. This makes the poll() abortable |
| 36 | * by writing a byte to the local pipe in asocket_abort(). |
| 37 | * |
| 38 | * asocket_create() sets the fd to non-blocking mode. It must not be changed to |
| 39 | * blocking mode. |
| 40 | * |
| 41 | * Using asocket will triple the number of file descriptors required per |
| 42 | * socket, due to the local pipe. It may be possible to use a global pipe per |
| 43 | * process rather than per socket, but we have not been able to come up with a |
| 44 | * race-free implementation yet. |
| 45 | * |
| 46 | * All functions except asocket_init() and asocket_destroy() are thread safe. |
| 47 | */ |
| 48 | |
| 49 | #include <stdlib.h> |
| 50 | #include <sys/socket.h> |
| 51 | |
| 52 | #ifndef __CUTILS_ABORT_SOCKET_H__ |
| 53 | #define __CUTILS_ABORT_SOCKET_H__ |
| 54 | #ifdef __cplusplus |
| 55 | extern "C" { |
| 56 | #endif |
| 57 | |
| 58 | struct asocket { |
| 59 | int fd; /* primary socket fd */ |
| 60 | int abort_fd[2]; /* pipe used to abort */ |
| 61 | }; |
| 62 | |
| 63 | /* Create an asocket from fd. |
| 64 | * Sets the socket to non-blocking mode. |
| 65 | * Returns NULL on error with errno set. |
| 66 | */ |
| 67 | struct asocket *asocket_init(int fd); |
| 68 | |
| 69 | /* Blocking socket I/O with timeout. |
| 70 | * Calling asocket_abort() from another thread will cause each of these |
| 71 | * functions to immediately return with value -1 and errno ECANCELED. |
| 72 | * timeout is in ms, use -1 to indicate no timeout. On timeout -1 is returned |
| 73 | * with errno ETIMEDOUT. |
| 74 | * EINTR is handled in-call. |
| 75 | * Other semantics are identical to the regular syscalls. |
| 76 | */ |
| 77 | int asocket_connect(struct asocket *s, const struct sockaddr *addr, |
| 78 | socklen_t addrlen, int timeout); |
| 79 | |
| 80 | int asocket_accept(struct asocket *s, struct sockaddr *addr, |
| 81 | socklen_t *addrlen, int timeout); |
| 82 | |
| 83 | int asocket_read(struct asocket *s, void *buf, size_t count, int timeout); |
| 84 | |
| 85 | int asocket_write(struct asocket *s, const void *buf, size_t count, |
| 86 | int timeout); |
| 87 | |
| 88 | /* Abort above calls and shutdown socket. |
| 89 | * Further I/O operations on this socket will immediately fail after this call. |
| 90 | * asocket_destroy() should be used to release resources once all threads |
| 91 | * have returned from blocking calls on the socket. |
| 92 | */ |
| 93 | void asocket_abort(struct asocket *s); |
| 94 | |
| 95 | /* Close socket and free asocket structure. |
| 96 | * Must not be called until all calls on this structure have completed. |
| 97 | */ |
| 98 | void asocket_destroy(struct asocket *s); |
| 99 | |
| 100 | #ifdef __cplusplus |
| 101 | } |
| 102 | #endif |
| 103 | #endif //__CUTILS_ABORT_SOCKET__H__ |