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Diffstat (limited to 'Documentation/filesystems/cifs')
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diff --git a/Documentation/filesystems/cifs/cifsd.rst b/Documentation/filesystems/cifs/cifsd.rst new file mode 100644 index 000000000000..e0c33d03f290 --- /dev/null +++ b/Documentation/filesystems/cifs/cifsd.rst @@ -0,0 +1,136 @@ +.. SPDX-License-Identifier: GPL-2.0 + +========================= +CIFSD - SMB3 Kernel Server +========================= + +CIFSD is a linux kernel server which implements SMB3 protocol in kernel space +for sharing files over network. + +CIFSD 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. + +Key Features +============ + +The supported features are: + * SMB3 protocols for basic file sharing + * Auto negotiation + * Compound requests + * Oplock/Lease + * Large MTU + * NTLM/NTLMv2 + * HMAC-SHA256 Signing + * Secure negotiate + * Signing Update + * Pre-authentication integrity(SMB 3.1.1) + * SMB3 encryption(CCM, GCM) + * SMB direct(RDMA) + * SMB3.1.1 POSIX extension support + * ACLs + * Kerberos + +The features that are planned or not supported: + * SMB3 Multi-channel + * Durable handle v1,v2 + * Persistent handles + * Directory lease + * SMB2 notify + +How to run +========== + +1. Download ksmbd-tools and compile them. + - https://github.com/cifsd-team/ksmbd-tools + +2. Create user/password for SMB share. + + # mkdir /etc/ksmbd/ + # ksmbd.adduser -a <Enter USERNAME for SMB share access> + +3. Create /etc/ksmbd/smb.conf file, add SMB share in smb.conf file + - Refer smb.conf.example and Documentation/configuration.txt + in ksmbd-tools + +4. Insert ksmbd.ko module + + # insmod ksmbd.ko + +5. Start ksmbd user space daemon + # ksmbd.mountd + +6. Access share from Windows or Linux using CIFS + +Shutdown CIFSD +============== + +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 enable. + # 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. |