Re: [PATCH] usbip: tools: add --sockfd option to usbip attach

[Shuah Khan <skhan@linuxfoundation.org>]

On 10/21/26 15:48, Raul E Rangel wrote:
> 'usbip attach' always opens its own TCP connection to --remote. A client
> that reaches the USB/IP server some other way, for example over a UNIX
> domain socket or a channel forwarded by a multiplexed SSH connection,
> therefore has to expose a listening TCP port on the local host just so
> usbip can connect back to it. Any local user can connect to that port
> while it is open.
> 
> Add a '--sockfd <fd>' option (short option '-s') that attaches the
> device over an inherited, already-connected stream socket instead.
> '--sockfd' and '--remote' are mutually exclusive. Because sudo closes
> file descriptors >= 3 by default but preserves stdin, the typical
> invocation passes the socket as stdin:
> 
>    sudo usbip attach --sockfd 0 --busid <busid>
> 
> The descriptor must be a connected SOCK_STREAM socket: fstat() must
> report S_ISSOCK, getsockopt(SO_TYPE) must return SOCK_STREAM and
> getpeername() must succeed. Both AF_UNIX and AF_INET/AF_INET6 sockets
> are accepted, since vhci_hcd only requires a SOCK_STREAM socket. For
> AF_INET/AF_INET6 sockets, TCP_NODELAY and SO_KEEPALIVE are set as
> usbip_net_tcp_connect() does.
> 
> The connection recorded in /var/run/vhci_hcd/port<N> for 'usbip port'
> uses the numeric peer address and port for AF_INET/AF_INET6 sockets.
> UNIX sockets have no port, so 'unix' and '-' are recorded instead; this
> keeps read_record() working and 'usbip port' shows
> 'usbip://unix:-/<busid>'.
> 
> Update doc/usbip.8 and the usage text accordingly.

Does this patch fix a problem or does this add an enhancement?
What doesn't work without this patch?

thanks,
-- Shuah