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diff --git a/Documentation/filesystems/cifs/ksmbd.rst b/Documentation/filesystems/cifs/ksmbd.rst new file mode 100644 index 000000000..7bed96d79 --- /dev/null +++ b/Documentation/filesystems/cifs/ksmbd.rst @@ -0,0 +1,183 @@ +.. SPDX-License-Identifier: GPL-2.0 + +========================== +KSMBD - SMB3 Kernel Server +========================== + +KSMBD is a linux kernel server which implements SMB3 protocol in kernel space +for sharing files over network. + +KSMBD architecture +================== + +The subset of performance related operations belong in kernelspace and +the other subset which belong to operations which are not really related with +performance in userspace. So, DCE/RPC management that has historically resulted +into number of buffer overflow issues and dangerous security bugs and user +account management are implemented in user space as ksmbd.mountd. +File operations that are related with performance (open/read/write/close etc.) +in kernel space (ksmbd). This also allows for easier integration with VFS +interface for all file operations. + +ksmbd (kernel daemon) +--------------------- + +When the server daemon is started, It starts up a forker thread +(ksmbd/interface name) at initialization time and open a dedicated port 445 +for listening to SMB requests. Whenever new clients make request, Forker +thread will accept the client connection and fork a new thread for dedicated +communication channel between the client and the server. It allows for parallel +processing of SMB requests(commands) from clients as well as allowing for new +clients to make new connections. Each instance is named ksmbd/1~n(port number) +to indicate connected clients. Depending on the SMB request types, each new +thread can decide to pass through the commands to the user space (ksmbd.mountd), +currently DCE/RPC commands are identified to be handled through the user space. +To further utilize the linux kernel, it has been chosen to process the commands +as workitems and to be executed in the handlers of the ksmbd-io kworker threads. +It allows for multiplexing of the handlers as the kernel take care of initiating +extra worker threads if the load is increased and vice versa, if the load is +decreased it destroys the extra worker threads. So, after connection is +established with client. Dedicated ksmbd/1..n(port number) takes complete +ownership of receiving/parsing of SMB commands. Each received command is worked +in parallel i.e., There can be multiple clients commands which are worked in +parallel. After receiving each command a separated kernel workitem is prepared +for each command which is further queued to be handled by ksmbd-io kworkers. +So, each SMB workitem is queued to the kworkers. This allows the benefit of load +sharing to be managed optimally by the default kernel and optimizing client +performance by handling client commands in parallel. + +ksmbd.mountd (user space daemon) +-------------------------------- + +ksmbd.mountd is userspace process to, transfer user account and password that +are registered using ksmbd.adduser (part of utils for user space). Further it +allows sharing information parameters that parsed from smb.conf to ksmbd in +kernel. For the execution part it has a daemon which is continuously running +and connected to the kernel interface using netlink socket, it waits for the +requests (dcerpc and share/user info). It handles RPC calls (at a minimum few +dozen) that are most important for file server from NetShareEnum and +NetServerGetInfo. Complete DCE/RPC response is prepared from the user space +and passed over to the associated kernel thread for the client. + + +KSMBD Feature Status +==================== + +============================== ================================================= +Feature name Status +============================== ================================================= +Dialects Supported. SMB2.1 SMB3.0, SMB3.1.1 dialects + (intentionally excludes security vulnerable SMB1 + dialect). +Auto Negotiation Supported. +Compound Request Supported. +Oplock Cache Mechanism Supported. +SMB2 leases(v1 lease) Supported. +Directory leases(v2 lease) Planned for future. +Multi-credits Supported. +NTLM/NTLMv2 Supported. +HMAC-SHA256 Signing Supported. +Secure negotiate Supported. +Signing Update Supported. +Pre-authentication integrity Supported. +SMB3 encryption(CCM, GCM) Supported. (CCM and GCM128 supported, GCM256 in + progress) +SMB direct(RDMA) Supported. +SMB3 Multi-channel Partially Supported. Planned to implement + replay/retry mechanisms for future. +Receive Side Scaling mode Supported. +SMB3.1.1 POSIX extension Supported. +ACLs Partially Supported. only DACLs available, SACLs + (auditing) is planned for the future. For + ownership (SIDs) ksmbd generates random subauth + values(then store it to disk) and use uid/gid + get from inode as RID for local domain SID. + The current acl implementation is limited to + standalone server, not a domain member. + Integration with Samba tools is being worked on + to allow future support for running as a domain + member. +Kerberos Supported. +Durable handle v1,v2 Planned for future. +Persistent handle Planned for future. +SMB2 notify Planned for future. +Sparse file support Supported. +DCE/RPC support Partially Supported. a few calls(NetShareEnumAll, + NetServerGetInfo, SAMR, LSARPC) that are needed + for file server handled via netlink interface + from ksmbd.mountd. Additional integration with + Samba tools and libraries via upcall is being + investigated to allow support for additional + DCE/RPC management calls (and future support + for Witness protocol e.g.) +ksmbd/nfsd interoperability Planned for future. The features that ksmbd + support are Leases, Notify, ACLs and Share modes. +============================== ================================================= + + +How to run +========== + +1. Download ksmbd-tools(https://github.com/cifsd-team/ksmbd-tools/releases) and + compile them. + + - Refer README(https://github.com/cifsd-team/ksmbd-tools/blob/master/README.md) + to know how to use ksmbd.mountd/adduser/addshare/control utils + + $ ./autogen.sh + $ ./configure --with-rundir=/run + $ make && sudo make install + +2. Create /usr/local/etc/ksmbd/ksmbd.conf file, add SMB share in ksmbd.conf file. + + - Refer ksmbd.conf.example in ksmbd-utils, See ksmbd.conf manpage + for details to configure shares. + + $ man ksmbd.conf + +3. Create user/password for SMB share. + + - See ksmbd.adduser manpage. + + $ man ksmbd.adduser + $ sudo ksmbd.adduser -a <Enter USERNAME for SMB share access> + +4. Insert ksmbd.ko module after build your kernel. No need to load module + if ksmbd is built into the kernel. + + - Set ksmbd in menuconfig(e.g. $ make menuconfig) + [*] Network File Systems ---> + <M> SMB3 server support (EXPERIMENTAL) + + $ sudo modprobe ksmbd.ko + +5. Start ksmbd user space daemon + + $ sudo ksmbd.mountd + +6. Access share from Windows or Linux using SMB3 client (cifs.ko or smbclient of samba) + +Shutdown KSMBD +============== + +1. kill user and kernel space daemon + # sudo ksmbd.control -s + +How to turn debug print on +========================== + +Each layer +/sys/class/ksmbd-control/debug + +1. Enable all component prints + # sudo ksmbd.control -d "all" + +2. Enable one of components (smb, auth, vfs, oplock, ipc, conn, rdma) + # sudo ksmbd.control -d "smb" + +3. Show what prints are enabled. + # cat /sys/class/ksmbd-control/debug + [smb] auth vfs oplock ipc conn [rdma] + +4. Disable prints: + If you try the selected component once more, It is disabled without brackets. |