https://github.com/zenhack/fdmsg
Helpers for sending file descriptors down sockets
https://github.com/zenhack/fdmsg
Last synced: about 2 months ago
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Helpers for sending file descriptors down sockets
- Host: GitHub
- URL: https://github.com/zenhack/fdmsg
- Owner: zenhack
- License: isc
- Created: 2016-07-24T03:31:07.000Z (almost 9 years ago)
- Default Branch: master
- Last Pushed: 2016-07-24T03:59:02.000Z (almost 9 years ago)
- Last Synced: 2025-02-03T13:45:07.196Z (3 months ago)
- Language: C
- Size: 13.7 KB
- Stars: 0
- Watchers: 2
- Forks: 1
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: COPYING
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README
Simple library for sending file descriptors to other processes over
sockets.
# Introduction
The Unix socket API provides facilities for sending file descriptors
over domain sockets. This allows for some interesting possibilities, but
like much of the sockets API, the interface to this functionality is...
arcane.
This library provides a wrapper around this feature that makes it
simpler to work with. It doesn't provide the full range of options; you
can only do stream-oriented connections, for example.
# Examples
```c
/* client.c */
#include
#include
#include
int main(void) {
/* create an FD buffer big enough for one fd, and put our
* stdout in it. The FDMSG_* macros are necessary due to
* an implementation detail; see the comments in the header
* file for a full explanation: */
char fdbuf[FDMSG_BUFSZ(1)];
int *fds = FDMSG_BUFDATA(&fdbuf[0]);
char *data = "Have fun with my stdout!";
int sock;
fds[0] = 1;
/* create the socket and connect: */
sock = fdmsg_socket();
if(sock < 0) {
perror("fdmsg_socket()");
return 1;
}
if(fdmsg_connect(sock, "/tmp/my-socket") < 0) {
perror("fdmsg_connect()");
return 1;
}
/* send some bytes and the file descriptor(s): */
fdmsg_send(sock, data, strlen(data), fdbuf, 1);
/* We don't even have to wait for the server; it's got a direct
* connection to our stdout now. */
return 0;
}
```
```c
/* server.c */
#include
#include
#include
int main(void) {
char fdbuf[FDMSG_BUFSZ(1)];
char data[4096];
int sock;
int connfd;
ssize_t data_count;
/* create the socket and bind: */
sock = fdmsg_socket();
if(sock < 0) {
perror("fdmsg_socket()");
return 1;
}
if(fdmsg_bind(sock, "/tmp/my-socket") < 0) {
perror("fdmsg_bind()");
return 1;
}
/* This is standard socket API stuff; listen and accept: */
if(listen(sock, SOMAXCONN) < 0) {
perror("listen()");
return 1;
}
connfd = accept(sock, NULL, NULL);
if(connfd < 0) {
perror("accept()");
return 1;
}
/* recieve some bytes and file descriptors(s): */
data_count = fdmsg_recv(connfd, data, sizeof data, fdbuf, 1);
/* send the data down the recieved file descriptor: */
write(FDMSG_BUFDATA(fdbuf)[0], data, data_count);
return 0;
}
```
# Building & Installing
## Building the library
make
## Building the examples
make examples
## Installing
To install the shared and static libraries:
make install
For just the shared, or just the static, you can do:
make install-shared
or
make install-static
respectively.
The library is installed into `/usr/local` by default. To install it
somewhere else use the `PREFIX` variable. E.g. to install into `/usr`:
make PREFIX=/usr install
Note: providing `PREFIX` during the build step will have no effect; it
must be supplied during `make install`.
The makefile also supports `DESTDIR` with the usual meaning, which is
useful for distro packagers:
make DESTDIR=${tmp_root_dir} PREFIX=/usr install
# License
ISC (simple permissive); see COPYING.
# TODOS
There are still a few things that need to be done before calling this
"ready":
* Tests. I've done some light manual testing, and run the examples, but
we should have a proper/thorough test suite.
* We need to report the number of file descriptors read/written. Right
now we only report the number of bytes. This is a huge API flaw.