Re: [PATCH v2 1/3] btrfs-progs: add Kernel TLS to btrfs send/receive

[Wang Yugui <wangyugui@e16-tech.com>]

To: Sheng

some test result on 10Gbps.

Server:dell Precision T7610 Xeon(R) CPU E5-2660 v2
Client: dell PowerEdge T620 Xeon(R) CPU E5-2680 v2
OS: centos 8.3(gnutls-3.6.14-6.el8.x86_64)

test script:
server=10.0.0.76
ssh ${server} btrfs-5.9 subvolume delete /btrfs/movie2
ssh ${server} /usr/bin/time btrfs-5.9 receive --listen-addr :: --tcp-port 8080 /btrfs &
sleep 2
/usr/bin/time btrfs-5.9 send --conn-addr ${server} --tcp-port 8080 /archive/movie2 2>time.send
sleep 1
cat time.send

test result:
It works with about 200 MB/s. slow than expacted.
top result:
  PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
   7479 root      20   0   45568   5200   4540 R 100.0   0.0   8:16.05 btrfs-5.9 receive --listen-addr

#pstack 7479
#0  __crc32c_le (crc=2848417421, data=0x7ffe68ee038b "\277g\276+\022\nZ", length=<optimized out>) at crypto/crc32c.c:213
#1  0x00000000004637ed in crc32c_le (crc=crc@entry=0, data=data@entry=0x7ffe68edb004 "O\300", length=length@entry=49241) at crypto/crc32c.c:223
#2  0x000000000045b71a in read_cmd (sctx=0x7ffe68edb000) at common/send-stream.c:141
#3  read_and_process_cmd (sctx=0x7ffe68edb000) at common/send-stream.c:330

That is to say, for high speed network/disk config,  the current bottleneck
of btrfs send/receive is the CRC process in btrfs receive side.

Best Regards
Wang Yugui (wangyugui@e16-tech.com)
2021/01/02

> From: Sheng Mao <shngmao@gmail.com>
> 
> Currently, btrfs send outputs to a pipe or a file;
> btrfs receive inputs from a pipe or a file.
> The pipe can be a SSH or a stunnel connection.
> btrfs send/receive itself doesn't handle any connection.
> 
> Kernel introduces TLS in version 4.13 (referred as ktls).
> Ktls provides a transparent TLS 1.2/1.3 connection:
> from user space aspect, applications use a normal socket
> fd to read/write from/to. This model fits into btrfs send's
> design well: btrfs first writes to a pipe and then splices
> data from pipe to the final fd (which is a file or pipe).
> Ktls simply replaces the final fd with the ktls socket fd.
> According to ktls' author, ktls can boost performance for
> 2~7%. Ktls helps less on receiving side: btrfs receive
> processes data in user space. But btrfs receive still can
> use transparent TLS layer.
> 
> I have implemented ktls for btrfs send/receive. Here are
> the key features:
> 
> - Use GnuTLS for handshake. OpenSSL is not suitable for this
> task, we need to pass IV and key from handshake session to
> kernel setting.
> - Use PSK (pre-shared key) for handshake. User can use --key
> to use a key file or input password on prompt.
> - Key file is checked as PEM format first; if it fails, key
> file is treated as raw binary file.
> - Three TLS modes are supported: none (raw TCP), TLS 1.2 + GCM
> 128/256, TLS 1.3 + GCM 128.
> - DTLS, certificate, Secure Remote Password (SRP) are not
> supported yet.
> 
> Issue: #326
> Signed-off-by: Sheng Mao <shngmao@gmail.com>
> ---
>  common/ktls.c | 702 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  common/ktls.h |  57 ++++
>  2 files changed, 759 insertions(+)
>  create mode 100644 common/ktls.c
>  create mode 100644 common/ktls.h
> 
> diff --git a/common/ktls.c b/common/ktls.c
> new file mode 100644
> index 00000000..a4d670e3
> --- /dev/null
> +++ b/common/ktls.c
> @@ -0,0 +1,702 @@
> +/*
> + * Copyright (C) 2020 Sheng Mao.  All rights reserved.
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public
> + * License v2 as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * General Public License for more details.
> + */
> +
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +
> +#include <arpa/inet.h>
> +#include <fcntl.h>
> +#include <netdb.h>
> +#include <netinet/in.h>
> +#include <netinet/ip.h>
> +#include <netinet/tcp.h>
> +#include <sys/mman.h>
> +#include <sys/socket.h>
> +#include <sys/stat.h>
> +#include <sys/types.h>
> +#include <unistd.h>
> +#include <termios.h>
> +#include <sys/stat.h>
> +
> +#include <linux/tls.h>
> +
> +#include <gnutls/gnutls.h>
> +
> +#include <common/utils.h>
> +
> +#include "ktls.h"
> +
> +enum { KTLS_MAX_PASSWORD_LENGTH = 256, KTLS_MAX_PRIORITY_STRING_LENTH = 256 };
> +
> +enum {
> +	KTLS_STAGE_NOT_HANDSHAKED,
> +	KTLS_STAGE_HAS_HANDSHAKED,
> +};
> +
> +enum ktls_tls_mode_t {
> +	KTLS_TLS_MODE_NONE = 0,
> +	KTLS_TLS_12_128_GCM,
> +	KTLS_TLS_13_128_GCM,
> +	KTLS_TLS_12_256_GCM
> +};
> +
> +struct ktls_session {
> +	gnutls_session_t session;
> +	gnutls_certificate_credentials_t crt_cred;
> +
> +	gnutls_psk_server_credentials_t psk_cred_server;
> +	gnutls_psk_client_credentials_t psk_cred_client;
> +
> +	uint8_t role;
> +	uint8_t stage;
> +	enum ktls_tls_mode_t tls_mode;
> +};
> +
> +static gnutls_datum_t ktls_psk_username = { 0 };
> +static gnutls_datum_t ktls_psk_key = { 0 };
> +
> +static void ktls_print_logs(int level, const char *msg)
> +{
> +	if (bconf.verbose >= level)
> +		printf("GnuTLS [%d]: %s", level, msg);
> +}
> +
> +int ktls_set_psk_session_from_password_prompt(struct ktls_session *session,
> +					      const char *username)
> +{
> +	struct termios orig_term_flags, passwd_term_flags;
> +	char passwd[KTLS_MAX_PASSWORD_LENGTH];
> +	int passwd_sz = 0;
> +	int stdin_fd = 0;
> +
> +	if (!session)
> +		return EXIT_FAILURE;
> +
> +	if (session->tls_mode == KTLS_TLS_MODE_NONE)
> +		return EXIT_SUCCESS;
> +
> +	passwd[0] = '\0';
> +
> +	stdin_fd = fileno(stdin);
> +
> +	if (!isatty(stdin_fd)) {
> +		error("tty needed for password input");
> +		return EXIT_FAILURE;
> +	}
> +
> +	tcgetattr(stdin_fd, &orig_term_flags);
> +	passwd_term_flags = orig_term_flags;
> +	passwd_term_flags.c_lflag &= ~ECHO;
> +	passwd_term_flags.c_lflag |= ECHONL;
> +
> +	if (tcsetattr(stdin_fd, TCSANOW, &passwd_term_flags)) {
> +		error("fail to hide password: %s", strerror(errno));
> +		return EXIT_FAILURE;
> +	}
> +
> +	printf("password: ");
> +	if (!fgets(passwd, sizeof(passwd), stdin)) {
> +		error("no password read");
> +		return EXIT_FAILURE;
> +	}
> +
> +	if (tcsetattr(fileno(stdin), TCSANOW, &orig_term_flags)) {
> +		error("fail to reset tty: %s", strerror(errno));
> +		return EXIT_FAILURE;
> +	}
> +
> +	passwd_sz = strlen(passwd);
> +	if (passwd_sz <= 0) {
> +		error("no password read");
> +		return EXIT_FAILURE;
> +	}
> +	if (passwd[passwd_sz - 1] == '\n') {
> +		passwd[passwd_sz - 1] = '\0';
> +		passwd_sz--;
> +	}
> +
> +	return ktls_set_psk_session(session, username,
> +				    (const unsigned char *)passwd, passwd_sz);
> +}
> +
> +int ktls_set_psk_session_from_keyfile(struct ktls_session *session,
> +				      const char *username,
> +				      const char *key_file)
> +{
> +	int rc = GNUTLS_E_SUCCESS;
> +	struct stat file_stat;
> +	size_t sz = 0;
> +	FILE *fp = NULL;
> +	gnutls_datum_t input = { NULL, 0UL };
> +	gnutls_datum_t output = { NULL, 0UL };
> +
> +	if (!session)
> +		goto cleanup;
> +
> +	if (session->tls_mode == KTLS_TLS_MODE_NONE)
> +		return EXIT_SUCCESS;
> +
> +	if (stat(key_file, &file_stat)) {
> +		error("fail to open keyfile: %s", strerror(errno));
> +		goto cleanup;
> +	}
> +
> +	fp = fopen(key_file, "r");
> +	if (!fp) {
> +		error("fail to open keyfile: %s", strerror(errno));
> +		goto cleanup;
> +	}
> +
> +	input.size = file_stat.st_size;
> +
> +	input.data = gnutls_malloc(input.size);
> +
> +	sz = fread(input.data, 1, input.size, fp);
> +
> +	if (sz != input.size) {
> +		error("fail to read PEM");
> +		goto cleanup;
> +	}
> +
> +	rc = gnutls_pem_base64_decode2(NULL, &input, &output);
> +	if (rc != GNUTLS_E_SUCCESS) {
> +		error("Error! fail to decode PEM: %s", gnutls_strerror(rc));
> +		goto cleanup;
> +	}
> +
> +	return ktls_set_psk_session(session, username, output.data,
> +				    output.size);
> +
> +cleanup:
> +	return EXIT_FAILURE;
> +}
> +
> +struct ktls_session *ktls_create_session(bool is_sender)
> +{
> +	struct ktls_session *session = NULL;
> +
> +	session = (struct ktls_session *)malloc(sizeof(struct ktls_session));
> +	explicit_bzero(session, sizeof(*session));
> +
> +	gnutls_global_init();
> +
> +	session->role = is_sender ? GNUTLS_CLIENT : GNUTLS_SERVER;
> +	session->stage = KTLS_STAGE_NOT_HANDSHAKED;
> +
> +	gnutls_init(&session->session, session->role);
> +
> +	gnutls_global_set_log_level(bconf.verbose);
> +	gnutls_global_set_log_function(ktls_print_logs);
> +
> +	return session;
> +}
> +
> +void ktls_destroy_session(struct ktls_session *session)
> +{
> +	if (!session)
> +		return;
> +
> +	if (session->crt_cred)
> +		gnutls_certificate_free_credentials(session->crt_cred);
> +
> +	if (session->psk_cred_server)
> +		gnutls_psk_free_server_credentials(session->psk_cred_server);
> +
> +	if (session->psk_cred_client)
> +		gnutls_psk_free_client_credentials(session->psk_cred_client);
> +
> +	if (session->session) {
> +		if (session->stage == KTLS_STAGE_HAS_HANDSHAKED)
> +			gnutls_bye(session->session, GNUTLS_SHUT_RDWR);
> +		gnutls_deinit(session->session);
> +	}
> +
> +	gnutls_global_deinit();
> +
> +	explicit_bzero(session, sizeof(*session));
> +}
> +
> +static int ktls_connect_or_bind(int *sock, bool is_sender, int protocol,
> +				struct sockaddr *serv_addr, size_t serv_addr_sz)
> +{
> +	*sock = 0;
> +
> +	*sock = socket(protocol, SOCK_STREAM, 0);
> +	if (*sock == KTLS_INVALID_FD) {
> +		error("could not create socket: %s", strerror(errno));
> +		goto cleanup;
> +	}
> +
> +	if (is_sender) {
> +		if (connect(*sock, serv_addr, serv_addr_sz)) {
> +			error("fail to connect to server: %s", strerror(errno));
> +			goto cleanup;
> +		}
> +		return EXIT_SUCCESS;
> +	}
> +
> +	if (setsockopt(*sock, SOL_SOCKET, SO_REUSEADDR, &(int){ 1 },
> +		       sizeof(int))) {
> +		error("fail to connect to server: %s", strerror(errno));
> +		goto cleanup;
> +	}
> +
> +	if (bind(*sock, serv_addr, serv_addr_sz) || listen(*sock, 1)) {
> +		error("fail to serve as server: %s", strerror(errno));
> +		goto cleanup;
> +	}
> +
> +	return EXIT_SUCCESS;
> +
> +cleanup:
> +	if (*sock >= 0)
> +		close(*sock);
> +	return EXIT_FAILURE;
> +}
> +
> +static int ktls_connect_domain(int *sock, bool is_sender, const char *host,
> +			       const uint16_t port)
> +{
> +	struct addrinfo hints = { 0 }, *res = NULL;
> +	int rc = 0;
> +	struct sockaddr_in addr4;
> +	struct sockaddr_in6 addr6;
> +
> +	memset(&hints, 0, sizeof(hints));
> +
> +	hints.ai_family = PF_UNSPEC;
> +	hints.ai_socktype = SOCK_STREAM;
> +	hints.ai_flags |= AI_CANONNAME;
> +
> +	if (getaddrinfo(host, NULL, &hints, &res)) {
> +		error("fail to get address info: %s", strerror(errno));
> +		return EXIT_FAILURE;
> +	}
> +
> +	while (res) {
> +		switch (res->ai_family) {
> +		case AF_INET:
> +			explicit_bzero(&addr4, sizeof(addr4));
> +			addr4.sin_addr =
> +				((struct sockaddr_in *)res->ai_addr)->sin_addr;
> +			addr4.sin_port = port;
> +			addr4.sin_family = res->ai_family;
> +			if (!ktls_connect_or_bind(
> +				    sock, is_sender, res->ai_family,
> +				    (struct sockaddr *)&addr4, sizeof(addr4))) {
> +				goto cleanup;
> +			}
> +			break;
> +		case AF_INET6:
> +			explicit_bzero(&addr6, sizeof(addr6));
> +			addr6.sin6_addr =
> +				((struct sockaddr_in6 *)res->ai_addr)->sin6_addr;
> +			addr6.sin6_port = port;
> +			addr6.sin6_family = res->ai_family;
> +			if (!ktls_connect_or_bind(
> +				    sock, is_sender, res->ai_family,
> +				    (struct sockaddr *)&addr6, sizeof(addr6))) {
> +				goto cleanup;
> +			}
> +			break;
> +		}
> +		res = res->ai_next;
> +	}
> +
> +	freeaddrinfo(res);
> +	return EXIT_FAILURE;
> +
> +cleanup:
> +	freeaddrinfo(res);
> +	return rc;
> +}
> +
> +static int ktls_connect_ip(int *sock, bool is_sender, const char *host,
> +			   const uint16_t port)
> +{
> +	struct sockaddr_in addr4;
> +	struct sockaddr_in6 addr6;
> +	struct sockaddr *serv_addr = NULL;
> +	size_t serv_addr_sz = 0;
> +	sa_family_t protol = AF_INET;
> +
> +	explicit_bzero(&addr4, sizeof(addr4));
> +	explicit_bzero(&addr6, sizeof(addr6));
> +
> +	if (inet_pton(AF_INET, host, &addr4.sin_addr) == 1) {
> +		serv_addr = (struct sockaddr *)&addr4;
> +		serv_addr_sz = sizeof(addr4);
> +		protol = addr4.sin_family = AF_INET;
> +		addr4.sin_port = port;
> +	}
> +
> +	if (!serv_addr && inet_pton(AF_INET6, host, &addr6.sin6_addr) == 1) {
> +		serv_addr = (struct sockaddr *)&addr6;
> +		serv_addr_sz = sizeof(addr6);
> +		protol = addr6.sin6_family = AF_INET6;
> +		addr6.sin6_port = port;
> +	}
> +
> +	if (!serv_addr)
> +		return KTLS_INVALID_FD;
> +
> +	return ktls_connect_or_bind(sock, is_sender, protol, serv_addr,
> +				    serv_addr_sz);
> +}
> +
> +int ktls_set_tls_mode(struct ktls_session *session, const char *mode)
> +{
> +	if (!session)
> +		return EXIT_FAILURE;
> +
> +	if (!strcmp("none", mode))
> +		session->tls_mode = KTLS_TLS_MODE_NONE;
> +	else if (!strcmp("tls_12_128_gcm", mode))
> +		session->tls_mode = KTLS_TLS_12_128_GCM;
> +	else if (!strcmp("tls_13_128_gcm", mode))
> +		session->tls_mode = KTLS_TLS_13_128_GCM;
> +	else if (!strcmp("tls_12_256_gcm", mode))
> +		session->tls_mode = KTLS_TLS_12_256_GCM;
> +	else {
> +		error("unknown tls mode: %s", mode);
> +		return EXIT_FAILURE;
> +	}
> +	return EXIT_SUCCESS;
> +}
> +
> +#define INIT_GCM_WITH_MODE(V, X)                                               \
> +	{                                                                      \
> +		struct tls12_crypto_info_aes_gcm_##X crypto_info;              \
> +\
> +		crypto_info.info.version = TLS_##V##_VERSION;                  \
> +		crypto_info.info.cipher_type = TLS_CIPHER_AES_GCM_##X;         \
> +		memcpy(crypto_info.iv, seq_number,                             \
> +		       TLS_CIPHER_AES_GCM_##X##_IV_SIZE);                      \
> +		memcpy(crypto_info.rec_seq, seq_number,                        \
> +		       TLS_CIPHER_AES_GCM_##X##_REC_SEQ_SIZE);                 \
> +		if (cipher_key.size != TLS_CIPHER_AES_GCM_##X##_KEY_SIZE) {    \
> +			error("mismatch in send key size: %d != %d\n",         \
> +			      cipher_key.size,                                 \
> +			      TLS_CIPHER_AES_GCM_##X##_KEY_SIZE);              \
> +			goto cleanup;                                          \
> +		}                                                              \
> +		memcpy(crypto_info.key, cipher_key.data,                       \
> +		       TLS_CIPHER_AES_GCM_##X##_KEY_SIZE);                     \
> +		memcpy(crypto_info.salt, iv.data,                              \
> +		       TLS_CIPHER_AES_GCM_##X##_SALT_SIZE);                    \
> +		if (setsockopt(sock, SOL_TLS, is_sender ? TLS_TX : TLS_RX,     \
> +			       &crypto_info, sizeof(crypto_info))) {           \
> +			error("fail to set kernel tls: %s", strerror(errno));  \
> +			goto cleanup;                                          \
> +		}                                                              \
> +	}
> +
> +int ktls_handshake_tls(struct ktls_session *session, int sock)
> +{
> +	int rc = 0;
> +	bool is_sender = false;
> +	int handshake_retry = 3;
> +	char tls_priority_list[KTLS_MAX_PRIORITY_STRING_LENTH];
> +	const char *tls_priority_templ =
> +		"NONE:+MAC-ALL:+COMP-NULL:+SIGN-ALL:+GROUP-ALL:+ECDHE-PSK:+DHE-PSK:%s:%s";
> +	const char *tls_priority_ver_mode = NULL;
> +
> +	gnutls_datum_t mac_key;
> +	gnutls_datum_t iv;
> +	gnutls_datum_t cipher_key;
> +	unsigned char seq_number[8];
> +
> +	if (!session || !session->session)
> +		return EXIT_FAILURE;
> +
> +	switch (session->tls_mode) {
> +	case KTLS_TLS_MODE_NONE:
> +		return EXIT_SUCCESS;
> +	case KTLS_TLS_12_128_GCM:
> +		tls_priority_ver_mode = "+VERS-TLS1.2:+AES-128-GCM";
> +		break;
> +	case KTLS_TLS_13_128_GCM:
> +		tls_priority_ver_mode = "+VERS-TLS1.3:+AES-128-GCM";
> +		break;
> +	case KTLS_TLS_12_256_GCM:
> +		tls_priority_ver_mode = "+VERS-TLS1.2:+AES-256-GCM";
> +		break;
> +	default:
> +		error("unknown tls mode");
> +		goto cleanup;
> +	}
> +
> +	is_sender = session->role == GNUTLS_CLIENT;
> +
> +	if (is_sender && session->psk_cred_client) {
> +		rc = gnutls_credentials_set(session->session, GNUTLS_CRD_PSK,
> +					    session->psk_cred_client);
> +		if (rc != GNUTLS_E_SUCCESS) {
> +			error("fail to set PSK for client: %s",
> +			      gnutls_strerror(rc));
> +			goto cleanup;
> +		}
> +	}
> +
> +	if (!is_sender && session->psk_cred_server) {
> +		rc = gnutls_credentials_set(session->session, GNUTLS_CRD_PSK,
> +					    session->psk_cred_server);
> +		if (rc != GNUTLS_E_SUCCESS) {
> +			error("fail to set PSK for server: %s",
> +			      gnutls_strerror(rc));
> +			goto cleanup;
> +		}
> +	}
> +
> +	if (session->crt_cred) {
> +		rc = gnutls_credentials_set(session->session,
> +					    GNUTLS_CRD_CERTIFICATE,
> +					    session->crt_cred);
> +
> +		if (rc == GNUTLS_E_SUCCESS) {
> +			error("fail to set certificate: %s",
> +			      gnutls_strerror(rc));
> +			goto cleanup;
> +		}
> +	}
> +
> +	snprintf(tls_priority_list, KTLS_MAX_PRIORITY_STRING_LENTH,
> +		 tls_priority_templ,
> +		 is_sender ? "+CTYPE-CLI-ALL" : "+CTYPE-SRV-ALL",
> +		 tls_priority_ver_mode);
> +
> +	rc = gnutls_priority_set_direct(session->session, tls_priority_list,
> +					NULL);
> +	if (rc != GNUTLS_E_SUCCESS) {
> +		error("fail to set priority: %s", gnutls_strerror(rc));
> +		goto cleanup;
> +	}
> +
> +	gnutls_transport_set_int(session->session, sock);
> +
> +	gnutls_handshake_set_timeout(session->session,
> +				     GNUTLS_DEFAULT_HANDSHAKE_TIMEOUT);
> +
> +	do {
> +		if (handshake_retry < 0) {
> +			error("exhaust retries on handshake");
> +			break;
> +		}
> +		rc = gnutls_handshake(session->session);
> +		handshake_retry--;
> +	} while (rc < 0 && !gnutls_error_is_fatal(rc));
> +
> +	if (gnutls_error_is_fatal(rc)) {
> +		error("fail on handshake: %s", gnutls_strerror(rc));
> +		goto cleanup;
> +	}
> +	if (bconf.verbose > 0) {
> +		char *desc = gnutls_session_get_desc(session->session);
> +
> +		printf("TLS session info: %s\n", desc);
> +		gnutls_free(desc);
> +	}
> +
> +	session->stage = KTLS_STAGE_HAS_HANDSHAKED;
> +
> +	rc = gnutls_record_get_state(session->session, is_sender ? 0 : 1,
> +				     &mac_key, &iv, &cipher_key, seq_number);
> +	if (rc != GNUTLS_E_SUCCESS) {
> +		error("fail on retrieve TLS record: %s", gnutls_strerror(rc));
> +		goto cleanup;
> +	}
> +
> +	if (setsockopt(sock, SOL_TCP, TCP_ULP, "tls", sizeof("tls"))) {
> +		error("fail to set kernel TLS on socket: %s", strerror(errno));
> +		goto cleanup;
> +	}
> +
> +	switch (session->tls_mode) {
> +	case KTLS_TLS_12_128_GCM:
> +		INIT_GCM_WITH_MODE(1_2, 128);
> +		break;
> +	case KTLS_TLS_13_128_GCM:
> +		INIT_GCM_WITH_MODE(1_3, 128);
> +		break;
> +	case KTLS_TLS_12_256_GCM:
> +		INIT_GCM_WITH_MODE(1_2, 256);
> +		break;
> +	default:
> +		error("unknown tls mode");
> +		goto cleanup;
> +	}
> +
> +	if (bconf.verbose > 0)
> +		fprintf(stderr, "ktls init done\n");
> +
> +	return EXIT_SUCCESS;
> +
> +cleanup:
> +	return EXIT_FAILURE;
> +}
> +
> +static int ktls_cp_datum(gnutls_datum_t *to, const gnutls_datum_t *from)
> +{
> +	if (!to || !from)
> +		return EXIT_FAILURE;
> +
> +	to->size = from->size;
> +	to->data = (unsigned char *)gnutls_malloc(to->size);
> +	memmove(to->data, from->data, to->size);
> +
> +	return EXIT_SUCCESS;
> +}
> +
> +static int ktls_cmp_datum(const gnutls_datum_t *lhs, const gnutls_datum_t *rhs)
> +{
> +	if (!lhs && !rhs)
> +		return EXIT_SUCCESS;
> +
> +	if (!lhs || !rhs)
> +		return EXIT_FAILURE;
> +
> +	if (lhs->size != rhs->size)
> +		return EXIT_FAILURE;
> +
> +	return memcmp(lhs->data, rhs->data, lhs->size);
> +}
> +
> +static int ktls_set_datum(gnutls_datum_t *to, const unsigned char *from,
> +			  int from_size)
> +{
> +	if (!to || !from || !from_size)
> +		return EXIT_FAILURE;
> +
> +	if (from_size < 0)
> +		from_size = strlen((const char *)from);
> +
> +	to->size = from_size;
> +	to->data = (unsigned char *)gnutls_malloc(to->size);
> +	memmove(to->data, from, from_size);
> +
> +	return EXIT_SUCCESS;
> +}
> +
> +static int tls_psk_client_callback(gnutls_session_t session,
> +				   gnutls_datum_t *username,
> +				   gnutls_datum_t *key)
> +{
> +	if (ktls_cp_datum(username, &ktls_psk_username) ||
> +	    ktls_cp_datum(key, &ktls_psk_key))
> +		return EXIT_FAILURE;
> +
> +	return EXIT_SUCCESS;
> +}
> +
> +static int tls_psk_server_callback(gnutls_session_t session,
> +				   const gnutls_datum_t *username,
> +				   gnutls_datum_t *key)
> +{
> +	if (ktls_cmp_datum(username, &ktls_psk_username) ||
> +	    ktls_cp_datum(key, &ktls_psk_key))
> +		return EXIT_FAILURE;
> +
> +	return EXIT_SUCCESS;
> +}
> +
> +int ktls_set_psk_session(struct ktls_session *session, const char *username,
> +			 const unsigned char *passwd, const size_t sz_passwd)
> +{
> +	bool is_sender = false;
> +	int rc = 0;
> +
> +	if (!session || !session->session)
> +		goto cleanup;
> +
> +	is_sender = session->role == GNUTLS_CLIENT;
> +
> +	if (!is_sender && !session->psk_cred_server) {
> +		rc = gnutls_psk_allocate_server_credentials(
> +			&session->psk_cred_server);
> +		if (rc != GNUTLS_E_SUCCESS) {
> +			error("fail on set psk for server: %s",
> +			      gnutls_strerror(rc));
> +			goto cleanup;
> +		}
> +		gnutls_psk_set_server_credentials_function2(
> +			session->psk_cred_server, tls_psk_server_callback);
> +	}
> +
> +	if (is_sender && !session->psk_cred_client) {
> +		rc = gnutls_psk_allocate_client_credentials(
> +			&session->psk_cred_client);
> +		if (rc != GNUTLS_E_SUCCESS) {
> +			error("fail on set psk for client: %s",
> +			      gnutls_strerror(rc));
> +			goto cleanup;
> +		}
> +		gnutls_psk_set_client_credentials_function2(
> +			session->psk_cred_client, tls_psk_client_callback);
> +	}
> +
> +	if (!ktls_psk_key.size)
> +		gnutls_free(ktls_psk_key.data);
> +
> +	if (!ktls_psk_username.size)
> +		gnutls_free(ktls_psk_username.data);
> +
> +	if (ktls_set_datum(&ktls_psk_username, (const unsigned char *)username,
> +			   -1) ||
> +	    ktls_set_datum(&ktls_psk_key, passwd, sz_passwd))
> +		goto cleanup;
> +
> +	return EXIT_SUCCESS;
> +
> +cleanup:
> +	return EXIT_FAILURE;
> +}
> +
> +int ktls_create_sock_oneshot(struct ktls_session *session, const char *host,
> +			     const char *port)
> +{
> +	int sock = 0;
> +	int nport = 0;
> +	bool is_sender;
> +
> +	if (!session || !session->session)
> +		return EXIT_FAILURE;
> +
> +	is_sender = session->role == GNUTLS_CLIENT;
> +
> +	nport = atoi(port);
> +
> +	if (nport >= 0 && nport <= 65535)
> +		nport = htons((uint16_t)nport);
> +
> +	if (ktls_connect_ip(&sock, is_sender, host, (uint16_t)nport))
> +		if (ktls_connect_domain(&sock, is_sender, host, nport))
> +			goto cleanup;
> +
> +	if (!is_sender) {
> +		int accepted_sock = KTLS_INVALID_FD;
> +
> +		accepted_sock = accept(sock, (struct sockaddr *)NULL, NULL);
> +		close(sock);
> +		sock = accepted_sock;
> +	}
> +
> +	if (ktls_handshake_tls(session, sock))
> +		goto cleanup;
> +
> +	return sock;
> +
> +cleanup:
> +	close(sock);
> +	return KTLS_INVALID_FD;
> +}
> diff --git a/common/ktls.h b/common/ktls.h
> new file mode 100644
> index 00000000..d744e18e
> --- /dev/null
> +++ b/common/ktls.h
> @@ -0,0 +1,57 @@
> +/*
> + * Copyright (C) 2020 Sheng Mao.  All rights reserved.
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public
> + * License v2 as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * General Public License for more details.
> + */
> +
> +#ifndef __BTRFS_KTLS_H__
> +#define __BTRFS_KTLS_H__
> +
> +#include <stdbool.h>
> +#include <stddef.h>
> +
> +#ifdef __cplusplus
> +extern "C" {
> +#endif
> +
> +struct ktls_session;
> +
> +enum { KTLS_INVALID_FD = -1 };
> +
> +struct ktls_session *ktls_create_session(bool is_sender);
> +void ktls_destroy_session(struct ktls_session *session);
> +
> +// ktls_set_psk_session sets PSK (pre-shared key). username is NULL-terminated
> +// string; passwd is sized string. Memory of both strings are managed by
> +// caller. currently, this API only allows to set PSK before calling
> +// ktls_handshake_*()
> +int ktls_set_psk_session(struct ktls_session *session, const char *username,
> +			 const unsigned char *passwd, const size_t sz_passwd);
> +
> +int ktls_set_psk_session_from_password_prompt(struct ktls_session *session,
> +					      const char *username);
> +
> +int ktls_set_psk_session_from_keyfile(struct ktls_session *session,
> +				      const char *username,
> +				      const char *key_file);
> +
> +int ktls_set_tls_mode(struct ktls_session *session, const char *mode);
> +
> +int ktls_handshake_tls(struct ktls_session *session, int sock);
> +
> +// ktls_create_sock_oneshot returns a sock fd on success.
> +int ktls_create_sock_oneshot(struct ktls_session *session, const char *host,
> +			     const char *port);
> +
> +#ifdef __cplusplus
> +}
> +#endif
> +
> +#endif // __BTRFS_KTLS_H__
> -- 
> 2.29.2