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// +build !go1.9
package journald
import (
"net"
"syscall"
"unsafe"
"golang.org/x/sys/unix"
)
// Go implementation of sendmsg (UnixConn.WriteMsgUnix) is not suitable
// for systemd's Journal in case of sending file descriptors. It always
// sends a dummy data byte, but journal does not expect to get it:
//
// n = recvmsg(fd, &msghdr, MSG_DONTWAIT|MSG_CMSG_CLOEXEC);
// ...
// if (n > 0 && n_fds == 0)
// server_process_native_message(...);
// else if (n == 0 && n_fds == 1)
// server_process_native_file(...);
// else if (n_fds > 0)
// log_warning("Got too many file descriptors via native socket. Ignoring.");
//
// So we get a warning message (the last line) instead of the new log
// entry.
//
func writeMsgUnix(c *net.UnixConn, oob []byte, addr *net.UnixAddr) (oobn int, err error) {
ptr, salen := sockaddr(addr)
var msg syscall.Msghdr
msg.Name = (*byte)(ptr)
msg.Namelen = uint32(salen)
msg.Control = (*byte)(unsafe.Pointer(&oob[0]))
msg.SetControllen(len(oob))
f, err := c.File()
if err != nil {
return 0, err
}
defer f.Close()
_, n, errno := syscall.Syscall(unix.SYS_SENDMSG, f.Fd(), uintptr(unsafe.Pointer(&msg)), 0)
if errno != 0 {
return int(n), errno
}
return int(n), nil
}
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