Errors returned in errno:

- ESRCH (wrong read/write direction)
	- open(): _stat opened for write
	- write(): message needs to be routed to master but there is no master on the channel at the moment
	- write(): addressed client is dead (won't read)

- EIO (internal error)
	- _stat failed to generate content
	- impossible read() return (internal error)
	- (impossible write() rlist full condition)

- ENXIO (chan type)
	- open: invalid channel type (first char of the name)
	- remove/unlink: not a channel

- ESPIPE (invalid slave op: master required)
	- slave open refused: channel needs to be created by master

- EEXIST (invalid master op)
 - master open refused: channel already has a master
 - create with O_EXCL: channel already exist (doesn't matter if it has an active master)

- ENOMEM
	- failed to allocate memory (for internal/administrative purposes)

- ENODEV
	- internal error: bad channel:client address
	- addressed unicast message lost because there was no reader at that adddress
	

- EFAULT
	- write(): channel needs address prefix but message is without address
	- write(): invalid address prefix

- EBADFD
	- client not found (internal error)

- ESTALE
	- used in internal communication between futebus and fuse kernel side; shouldn't be sent to the client

- EPERM:
	- creat(): tried to create() _stat

- EISDIR:
	- creat(): tried to create . or ..