This library provide an easy interface to the black magic that can be done on Unix domain sockets, like passing file descriptors from one process to another. It is supposed to be 100% conform to the Single Unix Specification v3 and has been tested under Linux (2.4), Solaris (8), OpenBSD (2.7) and FreeBSD (4.2). The license is a BSD style one.
The latest version of libancillary is available on Gitorious. You can clone the repository using the following command:
git clone git://gitorious.org/libancillary/libancillary.git
libancillary-0.9.1.tar.gz (4.6 ko)This library provide an easy interface to the black magic that can be done on Unix domain sockets, like passing file descriptors from one process to another. Programs that uses this library should include the ancillary.h header file. Nothing else is required. All functions of this library require the following header: #include <ancillary.h> At this time, the only ancillary data defined by the Single Unix Specification (v3) is file descriptors. Passing file descriptors int ancil_send_fd(socket, file_descriptor) int socket: the Unix socket int file_descriptor: the file descriptor Return value: 0 for success, -1 for failure. Sends one file descriptor on a socket. In case of failure, errno is set; the possible values are the ones of the sendmsg(2) system call. int ancil_recv_fd(socket, file_descriptor) int socket: the Unix socket int *file_descriptor: pointer to the returned file descriptor Return value: 0 for success, -1 for failure Receives one file descriptor from a socket. In case of success, the file descriptor is stored in the integer pointed to by file_descriptor. In case of failure, errno is set; the possible values are the ones of the recvmsg(2) system call. The behavior is undefined if the recv_fd does not match a send_fd* on the other side. int ancil_send_fds(socket, file_descriptors, num_file_descriptors) int socket: the Unix socket const int *file_descriptors: array of file descriptors unsigned num_file_descriptors: number of file descriptors Return value: 0 for success, -1 for failure Sends several file descriptors on a socket. In case of failure, errno is set; the possible values are the ones of the sendmsg(2) system call. The maximum number of file descriptors that can be sent using this function is ANCIL_MAX_N_FDS; the behavior is undefined in case of overflow, probably a stack corruption. int ancil_recv_fds(socket, file_descriptors, num_file_descriptors) int socket: the Unix socket int *file_descriptors: return array of file descriptors unsigned num_file_descriptors: number of file descriptors Return value: number of received fd for success, -1 for failure Receives several file descriptors from a socket, no more than num_file_descriptors. In case of success, the received file descriptors are stored in the array pointed to by file_descriptors. In case of failure, errno is set; the possible values are the ones of the recvmsg(2) system call. The maximum number of file descriptors that can be received using this function is ANCIL_MAX_N_FDS; the behavior is undefined in case of overflow, probably a stack corruption. The behavior is undefined if the recv_fds does not match a send_fd* on the other side, or if the number of received file descriptors is more than num_file_descriptors. int ancil_send_fds_with_buffer(socket, fds, num, buffer) int socket: the Unix socket const int *fds: array of file descriptors unsigned num: number of file descriptors void *buffer: buffer to hold the system data structures Return value: 0 for success, -1 for failure Sends several file descriptors on a socket. In case of failure, errno is set; the possible values are the ones of the sendmsg(2) system call. The buffer argument must point to a memory area large enough to hold the system data structures, see ANCIL_FD_BUFFER. int ancil_recv_fds_with_buffer(socket, fds, num, buffer) int socket: the Unix socket int *fds: return array of file descriptors unsigned num: number of file descriptors void *buffer: buffer to hold the system data structures Return value: number of received fd for success, -1 for failure Receives several file descriptors from a socket, no more than num_file_descriptors. In case of success, the received file descriptors are stored in the array pointed to by file_descriptors. In case of failure, errno is set; the possible values are the ones of the recvmsg(2) system call. The behavior is undefined if the recv_fds does not match a send_fd* on the other side, or if the number of received file descriptors is more than num_file_descriptors. The buffer argument must point to a memory area large enough to hold the system data structures, see ANCIL_FD_BUFFER. ANCIL_MAX_N_FDS Maximum number of file descriptors that can be sent with the sent_fds and recv_fds functions. If you have to send more at once, use the *_with_buffer versions. The value is enough to send "quite a few" file descriptors. ANCIL_FD_BUFFER(n) int n: number of file descriptors Expands to a structure data type large enough to hold the system data structures for n file descriptors. So the address of a variable declared of type ANCIL_FD_BUFFER(n) is suitable as the buffer argument for *_with_buffer on n file descriptors. To use this macro, you need <sys/types.h> and <sys/socket.h>. Bevare: with Solaris, the _XPG4_2 macro must be defined before sys/socket is included. Tuning the compilation This library is designed to be included in projects, not installed in /usr/lib. If your project does not use some of the functions, the TUNE_OPTS variable in the Makefile allows not to build them. It is a list of proprocessor options: -DNDEBUG: turn assertions off (see assert(3)) -DSPARE_SEND_FDS: do not build ancil_send_fds -DSPARE_SEND_FD: do not build ancil_send_fd -DSPARE_RECV_FDS: do not build ancil_recv_fds -DSPARE_RECV_FD: do not build ancil_recv_fd
libancillary - black magic on Unix domain sockets
(C) Nicolas George
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