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OpenVPN is a userspace software existing since around 2005 that allows users to create secure tunnels. So far OpenVPN has implemented all operations in userspace, which implies several back and forth between kernel and user land in order to process packets (encapsulate/decapsulate, encrypt/decrypt, rerouting..). With `ovpn` we intend to move the fast path (data channel) entirely in kernel space and thus improve user measured throughput over the tunnel. `ovpn` is implemented as a simple virtual network device driver, that can be manipulated by means of the standard RTNL APIs. A device of kind `ovpn` allows only IPv4/6 traffic and can be of type: * P2P (peer-to-peer): any packet sent over the interface will be encapsulated and transmitted to the other side (typical OpenVPN client or peer-to-peer behaviour); * P2MP (point-to-multipoint): packets sent over the interface are transmitted to peers based on existing routes (typical OpenVPN server behaviour). After the interface has been created, OpenVPN in userspace can configure it using a new Netlink API. Specifically it is possible to manage peers and their keys. The OpenVPN control channel is multiplexed over the same transport socket by means of OP codes. Anything that is not DATA_V2 (OpenVPN OP code for data traffic) is sent to userspace and handled there. This way the `ovpn` codebase is kept as compact as possible while focusing on handling data traffic only (fast path). Any OpenVPN control feature (like cipher negotiation, TLS handshake, rekeying, etc.) is still fully handled by the userspace process. When userspace establishes a new connection with a peer, it first performs the handshake and then passes the socket to the `ovpn` kernel module, which takes ownership. From this moment on `ovpn` will handle data traffic for the new peer. When control packets are received on the link, they are forwarded to userspace through the same transport socket they were received on, as userspace is still listening to them. Some events (like peer deletion) are sent to a Netlink multicast group. Although it wasn't easy to convince the community, `ovpn` implements only a limited number of the data-channel features supported by the userspace program. Each feature that made it to `ovpn` was attentively vetted to avoid carrying too much legacy along with us (and to give a clear cut to old and probalby-not-so-useful features). Notably, only encryption using AEAD ciphers (specifically ChaCha20Poly1305 and AES-GCM) was implemented. Supporting any other cipher out there was not deemed useful. Both UDP and TCP sockets are supported. As explained above, in case of P2MP mode, OpenVPN will use the main system routing table to decide which packet goes to which peer. This implies that no routing table was re-implemented in the `ovpn` kernel module. This kernel module can be enabled by selecting the CONFIG_OVPN entry in the networking drivers section. NOTE: this first patch introduces the very basic framework only. Features are then added patch by patch, however, although each patch will compile and possibly not break at runtime, only after having applied the full set it is expected to see the ovpn module fully working. Cc: steffen.klassert@secunet.com Cc: antony.antony@secunet.com Signed-off-by: Antonio Quartulli <antonio@openvpn.net> Link: https://patch.msgid.link/20250415-b4-ovpn-v26-1-577f6097b964@openvpn.net Reviewed-by: Sabrina Dubroca <sd@queasysnail.net> Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name> Signed-off-by: Paolo Abeni <pabeni@redhat.com> |
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| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.