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Date: Mon, 11 Mar 2024 12:10:27 -0400
From: Xin Long <lucien.xin@...il.com>
To: network dev <netdev@...r.kernel.org>
Cc: davem@...emloft.net,
kuba@...nel.org,
Eric Dumazet <edumazet@...gle.com>,
Paolo Abeni <pabeni@...hat.com>,
Steve French <smfrench@...il.com>,
Namjae Jeon <linkinjeon@...nel.org>,
Chuck Lever III <chuck.lever@...cle.com>,
Jeff Layton <jlayton@...nel.org>,
Sabrina Dubroca <sd@...asysnail.net>,
Tyler Fanelli <tfanelli@...hat.com>,
Pengtao He <hepengtao@...omi.com>
Subject: [RFC PATCH net-next 5/5] Documentation: introduce quic.rst to provide description of QUIC protocol
This commit adds quic.rst to the documentation directory, providing
comprehensive information about the QUIC protocol. This new file
serves as a reference for users and developers seeking details on
QUIC implementation and usage.
Signed-off-by: Xin Long <lucien.xin@...il.com>
Signed-off-by: Tyler Fanelli <tfanelli@...hat.com>
Signed-off-by: Pengtao He <hepengtao@...omi.com>
---
Documentation/networking/quic.rst | 160 ++++++++++++++++++++++++++++++
1 file changed, 160 insertions(+)
create mode 100644 Documentation/networking/quic.rst
diff --git a/Documentation/networking/quic.rst b/Documentation/networking/quic.rst
new file mode 100644
index 000000000000..d885cbcb8ef1
--- /dev/null
+++ b/Documentation/networking/quic.rst
@@ -0,0 +1,160 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=================
+Linux Kernel QUIC
+=================
+
+Introduction
+============
+
+This is an implementation of the QUIC protocol as defined in RFC9000. QUIC
+is an UDP-Based Multiplexed and Secure Transport protocol, and it provides
+applications with flow-controlled streams for structured communication,
+low-latency connection establishment, and network path migration. QUIC
+includes security measures that ensure confidentiality, integrity, and
+availability in a range of deployment circumstances.
+
+This implementation of QUIC in the kernel space enables users to utilize
+the QUIC protocol through common socket APIs in user space. Additionally,
+kernel subsystems like SMB and NFS can seamlessly operate over the QUIC
+protocol after handshake using net/handshake APIs.
+
+This implementation offers fundamental support for the following RFCs:
+
+- RFC9000 - QUIC: A UDP-Based Multiplexed and Secure Transport
+- RFC9001 - Using TLS to Secure QUIC
+- RFC9002 - QUIC Loss Detection and Congestion Control
+- RFC9221 - An Unreliable Datagram Extension to QUIC
+- RFC9287 - Greasing the QUIC Bit
+- RFC9368 - Compatible Version Negotiation for QUIC
+- RFC9369 - QUIC Version 2
+- Handshake APIs for tlshd Use - NFS/SMB over QUIC
+
+Implementation
+==============
+
+The central idea is to implement QUIC within the kernel, incorporating an
+userspace handshake approach.
+
+Only the processing and creation of raw TLS Handshake Messages, facilitated
+by a tls library like gnutls, take place in userspace. These messages are
+exchanged through sendmsg/recvmsg() mechanisms, with cryptographic details
+carried in the control message (cmsg).
+
+The entirety of QUIC protocol, excluding TLS Handshake Messages processing
+and creation, resides in the kernel. Instead of utilizing a User Level
+Protocol (ULP) layer, it establishes a socket of IPPROTO_QUIC type (similar
+to IPPROTO_MPTCP) operating over UDP tunnels.
+
+Kernel consumers can initiate a handshake request from kernel to userspace
+via the existing net/handshake netlink. The userspace component, tlshd from
+ktls-utils, manages the QUIC handshake request processing.
+
+- Handshake Architecture:
+
+ +------+ +------+
+ | APP1 | | APP2 | ...
+ +------+ +------+
+ +-------------------------------------------------+
+ | libquic (ktls-utils) |<--------------+
+ | {quic_handshake_server/client/param()} | |
+ +-------------------------------------------------+ +---------------------+
+ {send/recvmsg()} {set/getsockopt()} | tlshd (ktls-utils) |
+ [CMSG handshake_info] [SOCKOPT_CRYPTO_SECRET] +---------------------+
+ [SOCKOPT_TRANSPORT_PARAM_EXT]
+ | ^ | ^ | ^
+ Userspace | | | | | |
+ ------------|-|----------------------------|-|------------------------|-|--------------
+ Kernel | | | | | |
+ v | v | v |
+ +--------------------------------------------------+ +-------------+
+ | socket (IPPRTOTO_QUIC) | protocol |<----+ | handshake |
+ +--------------------------------------------------+ | | netlink APIs|
+ | inqueue | outqueue | cong | path | connection_id | | +-------------+
+ +--------------------------------------------------+ | | |
+ | packet | frame | crypto | pnmap | | +-----+ +-----+
+ +--------------------------------------------------+ | | | | |
+ | input | output | |---| SMB | | NFS | ...
+ +--------------------------------------------------+ | | | | |
+ | UDP tunnels | | +-----+ +--+--+
+ +--------------------------------------------------+ +--------------|
+
+- Post Handshake Architecture:
+
+ +------+ +------+
+ | APP1 | | APP2 | ...
+ +------+ +------+
+ {send/recvmsg()} {set/getsockopt()}
+ [CMSG stream_info] [SOCKOPT_KEY_UPDATE]
+ [SOCKOPT_CONNECTION_MIGRATION]
+ [SOCKOPT_STREAM_OPEN/RESET/STOP_SENDING]
+ [...]
+ | ^ | ^
+ Userspace | | | |
+ ------------|-|----------------------------|-|----------------
+ Kernel | | | |
+ v | v |
+ +--------------------------------------------------+
+ | socket (IPPRTOTO_QUIC) | protocol |<----+ {kernel_send/recvmsg()}
+ +--------------------------------------------------+ | {kernel_set/getsockopt()}
+ | inqueue | outqueue | cong | path | connection_id | |
+ +--------------------------------------------------+ |
+ | packet | frame | crypto | pnmap | | +-----+ +-----+
+ +--------------------------------------------------+ | | | | |
+ | input | output | |---| SMB | | NFS | ...
+ +--------------------------------------------------+ | | | | |
+ | UDP tunnels | | +-----+ +--+--+
+ +--------------------------------------------------+ +--------------|
+
+Usage
+=====
+
+This implementation supports a mapping of QUIC into sockets APIs. Similar
+to TCP and SCTP, a typical Server and Client use the following system call
+sequence to communicate:
+
+ Client Server
+ ------------------------------------------------------------------
+ sockfd = socket(IPPROTO_QUIC) listenfd = socket(IPPROTO_QUIC)
+ bind(sockfd) bind(listenfd)
+ listen(listenfd)
+ connect(sockfd)
+ quic_client_handshake(sockfd)
+ sockfd = accecpt(listenfd)
+ quic_server_handshake(sockfd, cert)
+
+ sendmsg(sockfd) recvmsg(sockfd)
+ close(sockfd) close(sockfd)
+ close(listenfd)
+
+Please note that quic_client_handshake() and quic_server_handshake() functions
+are currently sourced from libquic in the github lxin/quic repository, and might
+be integrated into ktls-utils in the future. These functions are responsible for
+receiving and processing the raw TLS handshake messages until the completion of
+the handshake process.
+
+For utilization by kernel consumers, it is essential to have the tlshd service
+(from ktls-utils) installed and running in userspace. This service receives
+and manages kernel handshake requests for kernel sockets. In kernel, the APIs
+closely resemble those used in userspace:
+
+ Client Server
+ ------------------------------------------------------------------------
+ __sock_create(IPPROTO_QUIC, &sock) __sock_create(IPPROTO_QUIC, &sock)
+ kernel_bind(sock) kernel_bind(sock)
+ kernel_listen(sock)
+ kernel_connect(sock)
+ tls_client_hello_x509(args:{sock})
+ kernel_accept(sock, &newsock)
+ tls_server_hello_x509(args:{newsock})
+
+ kernel_sendmsg(sock) kernel_recvmsg(newsock)
+ sock_release(sock) sock_release(newsock)
+ sock_release(sock)
+
+Please be aware that tls_client_hello_x509() and tls_server_hello_x509() are
+APIs from net/handshake/. They are employed to dispatch the handshake request
+to the userspace tlshd service and subsequently block until the handshake
+process is completed.
+
+The QUIC module is currently labeled as "EXPERIMENTAL".
--
2.43.0
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