'When Linus Torvalds announced Linux kernel 6.6's first release candidate, it included a newly-stable version of KSMBD, which is Samsung's in-kernel server for the SMB protocol (for sharing files/folders/printers over a network).

An announcement in 2021 had said that "For many cases the current userspace server choices were suboptimal either due to memory footprint, performance or difficulty integrating well with advanced Linux features."

LWN noted at the time that Linux has been using "the user-space Samba solution since shortly after the beginning."

In a sense, ksmbd is not meant to compete with Samba; indeed, it has been developed in cooperation with the Samba project. It is, however, meant to be a more performant and focused solution than Samba is; at this point, Samba includes a great deal of functionality beyond simple file serving. Ksmbd claims significant performance improvements on a wide range of benchmarks...One other reason — which tends to be spoken rather more quietly — is that a new implementation can be licensed under GPLv2, while Samba is GPLv3.

The Register notes that when Samba switched to GPL 3, "one result was that Apple dropped Samba from Mac OS X and replaced it with its own, in-house server called SMBX." And they also remember that a month after its debut in 2021, "Linux sysadmins got to enjoy KSMBD's first security exploit."

What's changed now is that it has faced considerable security testing and as a result it is no longer marked as experimental. It's been developed with the assistance of the Samba team, which itself documents how to use it. It's compatible with existing Samba configuration files. As the team says, "It is not meant to replace the existing Samba fileserver 'smbd', but rather be an extension and will integrate with Samba in the future...."

KSMBD is also important in that placing such core server functionality right inside the kernel represents a significant potential attack surface for crackers... The new bcachefs file system will not be going into kernel 6.6, and its developer is not happy.

"It's taken some time to get KSMBD to a state that was considered stable," points out Linux magazine. That time has come, and KSMBD is planned for Linux kernel 6.6.:

But why is KSMBD important? First off, it promises considerable performance gains and better support for modern features such as Remote Direct Memory Access (RDMA)... KSMBD also adds enhanced security, considerably better performance for both single and multi-thread read/write, better stability, and higher compatibility. In the end, hopefully, this KSMBD will also mean easier share setups in Linux without having to jump through the same hoops one must with the traditional Samba setup.'

-- source: https://linux.slashdot.org/story/23/09/16/0412208

Cheers, Peter