1.. SPDX-License-Identifier: GPL-2.0 2 3========================== 4KSMBD - SMB3 Kernel Server 5========================== 6 7KSMBD is a linux kernel server which implements SMB3 protocol in kernel space 8for sharing files over network. 9 10KSMBD architecture 11================== 12 13The subset of performance related operations belong in kernelspace and 14the other subset which belong to operations which are not really related with 15performance in userspace. So, DCE/RPC management that has historically resulted 16into number of buffer overflow issues and dangerous security bugs and user 17account management are implemented in user space as ksmbd.mountd. 18File operations that are related with performance (open/read/write/close etc.) 19in kernel space (ksmbd). This also allows for easier integration with VFS 20interface for all file operations. 21 22ksmbd (kernel daemon) 23--------------------- 24 25When the server daemon is started, It starts up a forker thread 26(ksmbd/interface name) at initialization time and open a dedicated port 445 27for listening to SMB requests. Whenever new clients make request, Forker 28thread will accept the client connection and fork a new thread for dedicated 29communication channel between the client and the server. It allows for parallel 30processing of SMB requests(commands) from clients as well as allowing for new 31clients to make new connections. Each instance is named ksmbd/1~n(port number) 32to indicate connected clients. Depending on the SMB request types, each new 33thread can decide to pass through the commands to the user space (ksmbd.mountd), 34currently DCE/RPC commands are identified to be handled through the user space. 35To further utilize the linux kernel, it has been chosen to process the commands 36as workitems and to be executed in the handlers of the ksmbd-io kworker threads. 37It allows for multiplexing of the handlers as the kernel take care of initiating 38extra worker threads if the load is increased and vice versa, if the load is 39decreased it destroys the extra worker threads. So, after connection is 40established with client. Dedicated ksmbd/1..n(port number) takes complete 41ownership of receiving/parsing of SMB commands. Each received command is worked 42in parallel i.e., There can be multiple clients commands which are worked in 43parallel. After receiving each command a separated kernel workitem is prepared 44for each command which is further queued to be handled by ksmbd-io kworkers. 45So, each SMB workitem is queued to the kworkers. This allows the benefit of load 46sharing to be managed optimally by the default kernel and optimizing client 47performance by handling client commands in parallel. 48 49ksmbd.mountd (user space daemon) 50-------------------------------- 51 52ksmbd.mountd is userspace process to, transfer user account and password that 53are registered using ksmbd.adduser (part of utils for user space). Further it 54allows sharing information parameters that parsed from smb.conf to ksmbd in 55kernel. For the execution part it has a daemon which is continuously running 56and connected to the kernel interface using netlink socket, it waits for the 57requests (dcerpc and share/user info). It handles RPC calls (at a minimum few 58dozen) that are most important for file server from NetShareEnum and 59NetServerGetInfo. Complete DCE/RPC response is prepared from the user space 60and passed over to the associated kernel thread for the client. 61 62 63KSMBD Feature Status 64==================== 65 66============================== ================================================= 67Feature name Status 68============================== ================================================= 69Dialects Supported. SMB2.1 SMB3.0, SMB3.1.1 dialects 70 (intentionally excludes security vulnerable SMB1 71 dialect). 72Auto Negotiation Supported. 73Compound Request Supported. 74Oplock Cache Mechanism Supported. 75SMB2 leases(v1 lease) Supported. 76Directory leases(v2 lease) Supported. 77Multi-credits Supported. 78NTLM/NTLMv2 Supported. 79HMAC-SHA256 Signing Supported. 80Secure negotiate Supported. 81Signing Update Supported. 82Pre-authentication integrity Supported. 83SMB3 encryption(CCM, GCM) Supported. (CCM/GCM128 and CCM/GCM256 supported) 84SMB direct(RDMA) Supported. 85SMB3 Multi-channel Partially Supported. Planned to implement 86 replay/retry mechanisms for future. 87Receive Side Scaling mode Supported. 88SMB3.1.1 POSIX extension Supported. 89ACLs Partially Supported. only DACLs available, SACLs 90 (auditing) is planned for the future. For 91 ownership (SIDs) ksmbd generates random subauth 92 values(then store it to disk) and use uid/gid 93 get from inode as RID for local domain SID. 94 The current acl implementation is limited to 95 standalone server, not a domain member. 96 Integration with Samba tools is being worked on 97 to allow future support for running as a domain 98 member. 99Kerberos Supported. 100Durable handle v1,v2 Planned for future. 101Persistent handle Planned for future. 102SMB2 notify Planned for future. 103Sparse file support Supported. 104DCE/RPC support Partially Supported. a few calls(NetShareEnumAll, 105 NetServerGetInfo, SAMR, LSARPC) that are needed 106 for file server handled via netlink interface 107 from ksmbd.mountd. Additional integration with 108 Samba tools and libraries via upcall is being 109 investigated to allow support for additional 110 DCE/RPC management calls (and future support 111 for Witness protocol e.g.) 112ksmbd/nfsd interoperability Planned for future. The features that ksmbd 113 support are Leases, Notify, ACLs and Share modes. 114SMB3.1.1 Compression Planned for future. 115SMB3.1.1 over QUIC Planned for future. 116Signing/Encryption over RDMA Planned for future. 117SMB3.1.1 GMAC signing support Planned for future. 118============================== ================================================= 119 120 121How to run 122========== 123 1241. Download ksmbd-tools(https://github.com/cifsd-team/ksmbd-tools/releases) and 125 compile them. 126 127 - Refer README(https://github.com/cifsd-team/ksmbd-tools/blob/master/README.md) 128 to know how to use ksmbd.mountd/adduser/addshare/control utils 129 130 $ ./autogen.sh 131 $ ./configure --with-rundir=/run 132 $ make && sudo make install 133 1342. Create /usr/local/etc/ksmbd/ksmbd.conf file, add SMB share in ksmbd.conf file. 135 136 - Refer ksmbd.conf.example in ksmbd-utils, See ksmbd.conf manpage 137 for details to configure shares. 138 139 $ man ksmbd.conf 140 1413. Create user/password for SMB share. 142 143 - See ksmbd.adduser manpage. 144 145 $ man ksmbd.adduser 146 $ sudo ksmbd.adduser -a <Enter USERNAME for SMB share access> 147 1484. Insert ksmbd.ko module after build your kernel. No need to load module 149 if ksmbd is built into the kernel. 150 151 - Set ksmbd in menuconfig(e.g. $ make menuconfig) 152 [*] Network File Systems ---> 153 <M> SMB3 server support (EXPERIMENTAL) 154 155 $ sudo modprobe ksmbd.ko 156 1575. Start ksmbd user space daemon 158 159 $ sudo ksmbd.mountd 160 1616. Access share from Windows or Linux using SMB3 client (cifs.ko or smbclient of samba) 162 163Shutdown KSMBD 164============== 165 1661. kill user and kernel space daemon 167 # sudo ksmbd.control -s 168 169How to turn debug print on 170========================== 171 172Each layer 173/sys/class/ksmbd-control/debug 174 1751. Enable all component prints 176 # sudo ksmbd.control -d "all" 177 1782. Enable one of components (smb, auth, vfs, oplock, ipc, conn, rdma) 179 # sudo ksmbd.control -d "smb" 180 1813. Show what prints are enabled. 182 # cat /sys/class/ksmbd-control/debug 183 [smb] auth vfs oplock ipc conn [rdma] 184 1854. Disable prints: 186 If you try the selected component once more, It is disabled without brackets. 187