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/*++
/* NAME
/* unix_recv_fd 3
/* SUMMARY
/* receive file descriptor
/* SYNOPSIS
/* #include <iostuff.h>
/*
/* int unix_recv_fd(fd)
/* int fd;
/* DESCRIPTION
/* unix_recv_fd() receives a file descriptor via the specified
/* UNIX-domain socket. The result value is the received descriptor.
/*
/* Arguments:
/* .IP fd
/* File descriptor that connects the sending and receiving processes.
/* DIAGNOSTICS
/* unix_recv_fd() returns -1 upon failure.
/* LICENSE
/* .ad
/* .fi
/* The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/* Wietse Venema
/* IBM T.J. Watson Research
/* P.O. Box 704
/* Yorktown Heights, NY 10598, USA
/*--*/
/* System library. */
#include <sys_defs.h> /* includes <sys/types.h> */
#include <sys/socket.h>
#include <sys/uio.h>
#include <string.h>
/* Utility library. */
#include <msg.h>
#include <iostuff.h>
/* unix_recv_fd - receive file descriptor */
int unix_recv_fd(int fd)
{
const char *myname = "unix_recv_fd";
/*
* This code does not work with version <2.2 Linux kernels, and it does
* not compile with version <2 Linux libraries.
*/
#ifdef CANT_USE_SEND_RECV_MSG
msg_warn("%s: your system has no support for file descriptor passing",
myname);
return (-1);
#else
struct msghdr msg;
int newfd;
struct iovec iov[1];
char buf[1];
/*
* Adapted from: W. Richard Stevens, UNIX Network Programming, Volume 1,
* Second edition. Except that we use CMSG_LEN instead of CMSG_SPACE, for
* portability to some LP64 environments. See also unix_send_fd.c.
*/
#if defined(CMSG_SPACE) && !defined(NO_MSGHDR_MSG_CONTROL)
union {
struct cmsghdr just_for_alignment;
char control[CMSG_SPACE(sizeof(newfd))];
} control_un;
struct cmsghdr *cmptr;
memset((void *) &msg, 0, sizeof(msg)); /* Fix 200512 */
msg.msg_control = control_un.control;
if (unix_pass_fd_fix & UNIX_PASS_FD_FIX_CMSG_LEN) {
msg.msg_controllen = CMSG_LEN(sizeof(newfd)); /* Fix 200506 */
} else {
msg.msg_controllen = sizeof(control_un.control); /* normal */
}
#else
msg.msg_accrights = (char *) &newfd;
msg.msg_accrightslen = sizeof(newfd);
#endif
msg.msg_name = 0;
msg.msg_namelen = 0;
/*
* XXX We don't want to pass any data, just a file descriptor. However,
* setting msg.msg_iov = 0 and msg.msg_iovlen = 0 causes trouble: we need
* to read_wait() before we can receive the descriptor, and the code
* fails after the first descriptor when we attempt to receive a sequence
* of descriptors.
*/
iov->iov_base = buf;
iov->iov_len = sizeof(buf);
msg.msg_iov = iov;
msg.msg_iovlen = 1;
if (recvmsg(fd, &msg, 0) < 0)
return (-1);
#if defined(CMSG_SPACE) && !defined(NO_MSGHDR_MSG_CONTROL)
if ((cmptr = CMSG_FIRSTHDR(&msg)) != 0
&& cmptr->cmsg_len == CMSG_LEN(sizeof(newfd))) {
if (cmptr->cmsg_level != SOL_SOCKET)
msg_fatal("%s: control level %d != SOL_SOCKET",
myname, cmptr->cmsg_level);
if (cmptr->cmsg_type != SCM_RIGHTS)
msg_fatal("%s: control type %d != SCM_RIGHTS",
myname, cmptr->cmsg_type);
return (*(int *) CMSG_DATA(cmptr));
} else
return (-1);
#else
if (msg.msg_accrightslen == sizeof(newfd))
return (newfd);
else
return (-1);
#endif
#endif
}
#ifdef TEST
/*
* Proof-of-concept program. Receive a descriptor (presumably from the
* unix_send_fd test program) and copy its content until EOF.
*/
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <split_at.h>
#include <listen.h>
int main(int argc, char **argv)
{
char *transport;
char *endpoint;
int listen_sock;
int client_sock;
int client_fd;
ssize_t read_count;
char buf[1024];
if (argc < 2 || argc > 3
|| (endpoint = split_at(transport = argv[1], ':')) == 0
|| *endpoint == 0 || *transport == 0)
msg_fatal("usage: %s transport:endpoint [workaround]", argv[0]);
if (strcmp(transport, "unix") == 0) {
listen_sock = unix_listen(endpoint, 10, BLOCKING);
} else {
msg_fatal("invalid transport name: %s", transport);
}
if (listen_sock < 0)
msg_fatal("listen %s:%s: %m", transport, endpoint);
client_sock = accept(listen_sock, (struct sockaddr *) 0, (SOCKADDR_SIZE) 0);
if (client_sock < 0)
msg_fatal("accept: %m");
set_unix_pass_fd_fix(argv[2] ? argv[2] : "");
while ((client_fd = unix_recv_fd(client_sock)) >= 0) {
msg_info("client_fd = %d, fix=%d", client_fd, unix_pass_fd_fix);
while ((read_count = read(client_fd, buf, sizeof(buf))) > 0)
write(1, buf, read_count);
if (read_count < 0)
msg_fatal("read: %m");
close(client_fd);
}
exit(0);
}
#endif
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