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/*++
/* NAME
/* unix_send_fd 3
/* SUMMARY
/* send file descriptor
/* SYNOPSIS
/* #include <iostuff.h>
/*
/* int unix_send_fd(fd, sendfd)
/* int fd;
/* int sendfd;
/* DESCRIPTION
/* unix_send_fd() sends a file descriptor over the specified
/* UNIX-domain socket.
/*
/* Arguments:
/* .IP fd
/* File descriptor that connects the sending and receiving processes.
/* .IP sendfd
/* The file descriptor to be sent.
/* DIAGNOSTICS
/* unix_send_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_send_fd - send file descriptor */
int unix_send_fd(int fd, int sendfd)
{
/*
* 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
const char *myname = "unix_send_fd";
msg_warn("%s: your system has no support for file descriptor passing",
myname);
return (-1);
#else
struct msghdr msg;
struct iovec iov[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_recv_fd.c.
*/
#if defined(CMSG_SPACE) && !defined(NO_MSGHDR_MSG_CONTROL)
union {
struct cmsghdr just_for_alignment;
char control[CMSG_SPACE(sizeof(sendfd))];
} 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(sendfd)); /* Fix 200506 */
} else {
msg.msg_controllen = sizeof(control_un.control); /* normal */
}
cmptr = CMSG_FIRSTHDR(&msg);
cmptr->cmsg_len = CMSG_LEN(sizeof(sendfd));
cmptr->cmsg_level = SOL_SOCKET;
cmptr->cmsg_type = SCM_RIGHTS;
*(int *) CMSG_DATA(cmptr) = sendfd;
#else
msg.msg_accrights = (char *) &sendfd;
msg.msg_accrightslen = sizeof(sendfd);
#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. See the
* comments in the unix_recv_fd() routine.
*/
iov->iov_base = "";
iov->iov_len = 1;
msg.msg_iov = iov;
msg.msg_iovlen = 1;
/*
* The CMSG_LEN send/receive workaround was originally developed for
* OpenBSD 3.6 on SPARC64. After the workaround was verified to not break
* Solaris 8 on SPARC64, it was hard-coded with Postfix 2.3 for all
* platforms because of increasing pressure to work on other things. The
* workaround does nothing for 32-bit systems.
*
* The investigation was reopened with Postfix 2.7 because the workaround
* broke with NetBSD 5.0 on 64-bit architectures. This time it was found
* that OpenBSD <= 4.3 on AMD64 and SPARC64 needed the workaround for
* sending only. The following platforms worked with and without the
* workaround: OpenBSD 4.5 on AMD64 and SPARC64, FreeBSD 7.2 on AMD64,
* Solaris 8 on SPARC64, and Linux 2.6-11 on x86_64.
*
* As this appears to have been an OpenBSD-specific problem, we revert to
* the Postfix 2.2 behavior. Instead of hard-coding the workaround for
* all platforms, we now detect sendmsg() errors at run time and turn on
* the workaround dynamically.
*
* The workaround was made run-time configurable to investigate the problem
* on multiple platforms. Though set_unix_pass_fd_fix() is over-kill for
* this specific problem, it is left in place so that it can serve as an
* example of how to add run-time configurable workarounds to Postfix.
*/
if (sendmsg(fd, &msg, 0) >= 0)
return (0);
if (unix_pass_fd_fix == 0) {
if (msg_verbose)
msg_info("sendmsg error (%m). Trying CMSG_LEN workaround.");
unix_pass_fd_fix = UNIX_PASS_FD_FIX_CMSG_LEN;
return (unix_send_fd(fd, sendfd));
} else {
return (-1);
}
#endif
}
#ifdef TEST
/*
* Proof-of-concept program. Open a file and send the descriptor, presumably
* to the unix_recv_fd test program.
*/
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <fcntl.h>
#include <split_at.h>
#include <connect.h>
int main(int argc, char **argv)
{
char *transport;
char *endpoint;
char *path;
int server_sock;
int client_fd;
msg_verbose = 1;
if (argc < 3
|| (endpoint = split_at(transport = argv[1], ':')) == 0
|| *endpoint == 0 || *transport == 0)
msg_fatal("usage: %s transport:endpoint file...", argv[0]);
if (strcmp(transport, "unix") == 0) {
server_sock = unix_connect(endpoint, BLOCKING, 0);
} else {
msg_fatal("invalid transport name: %s", transport);
}
if (server_sock < 0)
msg_fatal("connect %s:%s: %m", transport, endpoint);
argv += 2;
while ((path = *argv++) != 0) {
if ((client_fd = open(path, O_RDONLY, 0)) < 0)
msg_fatal("open %s: %m", path);
msg_info("path=%s fd=%d", path, client_fd);
if (unix_send_fd(server_sock, client_fd) < 0)
msg_fatal("send file descriptor: %m");
if (close(client_fd) != 0)
msg_fatal("close(%d): %m", client_fd);
}
exit(0);
}
#endif
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