/*
* Utility to send fds via Unix domain socket
*
* Copyright 2011, 2018 Yuya Nishihara <yuya@tcha.org>
*
* This software may be used and distributed according to the terms of the
* GNU General Public License version 2 or any later version.
*/
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#define MAX_FD_LEN 10
/*
* Sends the given fds with 1-byte dummy payload.
*
* Returns the number of bytes sent on success, -1 on error and errno is set
* appropriately.
*/
ssize_t sendfds(int sockfd, const int *fds, size_t fdlen)
{
char dummy[1] = {0};
struct iovec iov = {dummy, sizeof(dummy)};
char fdbuf[CMSG_SPACE(sizeof(fds[0]) * MAX_FD_LEN)];
struct msghdr msgh;
struct cmsghdr *cmsg;
/* just use a fixed-size buffer since we'll never send tons of fds */
if (fdlen > MAX_FD_LEN) {
errno = EINVAL;
return -1;
}
memset(&msgh, 0, sizeof(msgh));
msgh.msg_iov = &iov;
msgh.msg_iovlen = 1;
msgh.msg_control = fdbuf;
msgh.msg_controllen = CMSG_SPACE(sizeof(fds[0]) * fdlen);
cmsg = CMSG_FIRSTHDR(&msgh);
cmsg->cmsg_level = SOL_SOCKET;
cmsg->cmsg_type = SCM_RIGHTS;
cmsg->cmsg_len = CMSG_LEN(sizeof(fds[0]) * fdlen);
memcpy(CMSG_DATA(cmsg), fds, sizeof(fds[0]) * fdlen);
msgh.msg_controllen = cmsg->cmsg_len;
return sendmsg(sockfd, &msgh, 0);
}