Add documentation for kernel QUIC code.
Signed-off-by: Adel Abouchaev adel.abushaev@gmail.com
---
Added quic.rst reference to the index.rst file; identation in quic.rst file. Reported-by: kernel test robot lkp@intel.com
Added SPDX license GPL 2.0. --- Documentation/networking/index.rst | 1 + Documentation/networking/quic.rst | 186 +++++++++++++++++++++++++++++ 2 files changed, 187 insertions(+) create mode 100644 Documentation/networking/quic.rst
diff --git a/Documentation/networking/index.rst b/Documentation/networking/index.rst index 03b215bddde8..656fa1dac26b 100644 --- a/Documentation/networking/index.rst +++ b/Documentation/networking/index.rst @@ -90,6 +90,7 @@ Contents: plip ppp_generic proc_net_tcp + quic radiotap-headers rds regulatory diff --git a/Documentation/networking/quic.rst b/Documentation/networking/quic.rst new file mode 100644 index 000000000000..127802d27a42 --- /dev/null +++ b/Documentation/networking/quic.rst @@ -0,0 +1,186 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=========== +KERNEL QUIC +=========== + +Overview +======== + +QUIC is a secure general-purpose transport protocol that creates a stateful +interaction between a client and a server. QUIC provides end-to-end integrity +and confidentiality. Refer to RFC 9000 for more information on QUIC. + +The kernel Tx side offload covers the encryption of the application streams +in the kernel rather than in the application. These packets are 1RTT packets +in QUIC connection. Encryption of every other packets is still done by the +QUIC library in user space. + + + +User Interface +============== + +Creating a QUIC connection +-------------------------- + +QUIC connection originates and terminates in the application, using one of many +available QUIC libraries. The code instantiates QUIC client and QUIC server in +some form and configures them to use certain addresses and ports for the +source and destination. The client and server negotiate the set of keys to +protect the communication during different phases of the connection, maintain +the connection and perform congestion control. + +Requesting to add QUIC Tx kernel encryption to the connection +------------------------------------------------------------- + +Each flow that should be encrypted by the kernel needs to be registered with +the kernel using socket API. A setsockopt() call on the socket creates an +association between the QUIC connection ID of the flow with the encryption +parameters for the crypto operations: + +.. code-block:: c + + struct quic_connection_info conn_info; + char conn_id[5] = {0x01, 0x02, 0x03, 0x04, 0x05}; + const size_t conn_id_len = sizeof(conn_id); + char conn_key[16] = {0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, + 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f}; + char conn_iv[12] = {0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, + 0x08, 0x09, 0x0a, 0x0b}; + char conn_hdr_key[16] = {0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, + 0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f + }; + + conn_info.cipher_type = TLS_CIPHER_AES_GCM_128; + + memset(&conn_info.key, 0, sizeof(struct quic_connection_info_key)); + conn_info.key.conn_id_length = 5; + memcpy(&conn_info.key.conn_id[QUIC_MAX_CONNECTION_ID_SIZE + - conn_id_len], + &conn_id, conn_id_len); + + memcpy(&conn_info.payload_key, conn_key, sizeof(conn_key)); + memcpy(&conn_info.payload_iv, conn_iv, sizeof(conn_iv)); + memcpy(&conn_info.header_key, conn_hdr_key, sizeof(conn_hdr_key)); + + setsockopt(fd, SOL_UDP, UDP_QUIC_ADD_TX_CONNECTION, &conn_info, + sizeof(conn_info)); + + +Requesting to remove QUIC Tx kernel crypto offload control messages +------------------------------------------------------------------- + +All flows are removed when the socket is closed. To request an explicit remove +of the offload for the connection during the lifetime of the socket the process +is similar to adding the flow. Only the connection ID and its length are +necessary to supply to remove the connection from the offload: + +.. code-block:: c + + memset(&conn_info.key, 0, sizeof(struct quic_connection_info_key)); + conn_info.key.conn_id_length = 5; + memcpy(&conn_info.key.conn_id[QUIC_MAX_CONNECTION_ID_SIZE + - conn_id_len], + &conn_id, conn_id_len); + setsockopt(fd, SOL_UDP, UDP_QUIC_DEL_TX_CONNECTION, &conn_info, + sizeof(conn_info)); + +Sending QUIC application data +----------------------------- + +For QUIC Tx encryption offload, the application should use sendmsg() socket +call and provide ancillary data with information on connection ID length and +offload flags for the kernel to perform the encryption and GSO support if +requested. + +.. code-block:: c + + size_t cmsg_tx_len = sizeof(struct quic_tx_ancillary_data); + uint8_t cmsg_buf[CMSG_SPACE(cmsg_tx_len)]; + struct quic_tx_ancillary_data * anc_data; + size_t quic_data_len = 4500; + struct cmsghdr * cmsg_hdr; + char quic_data[9000]; + struct iovec iov[2]; + int send_len = 9000; + struct msghdr msg; + int err; + + iov[0].iov_base = quic_data; + iov[0].iov_len = quic_data_len; + iov[1].iov_base = quic_data + 4500; + iov[1].iov_len = quic_data_len; + + if (client.addr.sin_family == AF_INET) { + msg.msg_name = &client.addr; + msg.msg_namelen = sizeof(client.addr); + } else { + msg.msg_name = &client.addr6; + msg.msg_namelen = sizeof(client.addr6); + } + + msg.msg_iov = iov; + msg.msg_iovlen = 2; + msg.msg_control = cmsg_buf; + msg.msg_controllen = sizeof(cmsg_buf); + cmsg_hdr = CMSG_FIRSTHDR(&msg); + cmsg_hdr->cmsg_level = IPPROTO_UDP; + cmsg_hdr->cmsg_type = UDP_QUIC_ENCRYPT; + cmsg_hdr->cmsg_len = CMSG_LEN(cmsg_tx_len); + anc_data = CMSG_DATA(cmsg_hdr); + anc_data->flags = 0; + anc_data->next_pkt_num = 0x0d65c9; + anc_data->conn_id_length = conn_id_len; + err = sendmsg(self->sfd, &msg, 0); + +QUIC Tx offload in kernel will read the data from userspace, encrypt and +copy it to the ciphertext within the same operation. + + +Sending QUIC application data with GSO +-------------------------------------- +When GSO is in use, the kernel will use the GSO fragment size as the target +for ciphertext. The packets from the user space should align on the boundary +of GSO fragment size minus the size of the tag for the chosen cipher. For the +GSO fragment 1200, the plain packets should follow each other at every 1184 +bytes, given the tag size of 16. After the encryption, the rest of the UDP +and IP stacks will follow the defined value of GSO fragment which will include +the trailing tag bytes. + +To set up GSO fragmentation: + +.. code-block:: c + + setsockopt(self->sfd, SOL_UDP, UDP_SEGMENT, &frag_size, + sizeof(frag_size)); + +If the GSO fragment size is provided in ancillary data within the sendmsg() +call, the value in ancillary data will take precedence over the segment size +provided in setsockopt to split the payload into packets. This is consistent +with the UDP stack behavior. + +Integrating to userspace QUIC libraries +--------------------------------------- + +Userspace QUIC libraries integration would depend on the implementation of the +QUIC protocol. For MVFST library, the control plane is integrated into the +handshake callbacks to properly configure the flows into the socket; and the +data plane is integrated into the methods that perform encryption and send +the packets to the batch scheduler for transmissions to the socket. + +MVFST library can be found at https://github.com/facebookincubator/mvfst. + +Statistics +========== + +QUIC Tx offload to the kernel has counters +(``/proc/net/quic_stat``): + +- ``QuicCurrTxSw`` - + number of currently active kernel offloaded QUIC connections +- ``QuicTxSw`` - + accumulative total number of offloaded QUIC connections +- ``QuicTxSwError`` - + accumulative total number of errors during QUIC Tx offload to kernel +