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qemu/block/ssh.c

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/*
* Secure Shell (ssh) backend for QEMU.
*
* Copyright (C) 2013 Red Hat Inc., Richard W.M. Jones <rjones@redhat.com>
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <libssh2.h>
#include <libssh2_sftp.h>
#include "block/block_int.h"
#include "qemu/sockets.h"
#include "qemu/uri.h"
#include "qapi/qmp/qint.h"
/* DEBUG_SSH=1 enables the DPRINTF (debugging printf) statements in
* this block driver code.
*
* TRACE_LIBSSH2=<bitmask> enables tracing in libssh2 itself. Note
* that this requires that libssh2 was specially compiled with the
* `./configure --enable-debug' option, so most likely you will have
* to compile it yourself. The meaning of <bitmask> is described
* here: http://www.libssh2.org/libssh2_trace.html
*/
#define DEBUG_SSH 0
#define TRACE_LIBSSH2 0 /* or try: LIBSSH2_TRACE_SFTP */
#define DPRINTF(fmt, ...) \
do { \
if (DEBUG_SSH) { \
fprintf(stderr, "ssh: %-15s " fmt "\n", \
__func__, ##__VA_ARGS__); \
} \
} while (0)
typedef struct BDRVSSHState {
/* Coroutine. */
CoMutex lock;
/* SSH connection. */
int sock; /* socket */
LIBSSH2_SESSION *session; /* ssh session */
LIBSSH2_SFTP *sftp; /* sftp session */
LIBSSH2_SFTP_HANDLE *sftp_handle; /* sftp remote file handle */
/* See ssh_seek() function below. */
int64_t offset;
bool offset_op_read;
/* File attributes at open. We try to keep the .filesize field
* updated if it changes (eg by writing at the end of the file).
*/
LIBSSH2_SFTP_ATTRIBUTES attrs;
/* Used to warn if 'flush' is not supported. */
char *hostport;
bool unsafe_flush_warning;
} BDRVSSHState;
static void ssh_state_init(BDRVSSHState *s)
{
memset(s, 0, sizeof *s);
s->sock = -1;
s->offset = -1;
qemu_co_mutex_init(&s->lock);
}
static void ssh_state_free(BDRVSSHState *s)
{
g_free(s->hostport);
if (s->sftp_handle) {
libssh2_sftp_close(s->sftp_handle);
}
if (s->sftp) {
libssh2_sftp_shutdown(s->sftp);
}
if (s->session) {
libssh2_session_disconnect(s->session,
"from qemu ssh client: "
"user closed the connection");
libssh2_session_free(s->session);
}
if (s->sock >= 0) {
close(s->sock);
}
}
static void GCC_FMT_ATTR(3, 4)
session_error_setg(Error **errp, BDRVSSHState *s, const char *fs, ...)
{
va_list args;
char *msg;
va_start(args, fs);
msg = g_strdup_vprintf(fs, args);
va_end(args);
if (s->session) {
char *ssh_err;
int ssh_err_code;
/* This is not an errno. See <libssh2.h>. */
ssh_err_code = libssh2_session_last_error(s->session,
&ssh_err, NULL, 0);
error_setg(errp, "%s: %s (libssh2 error code: %d)",
msg, ssh_err, ssh_err_code);
} else {
error_setg(errp, "%s", msg);
}
g_free(msg);
}
static void GCC_FMT_ATTR(3, 4)
sftp_error_setg(Error **errp, BDRVSSHState *s, const char *fs, ...)
{
va_list args;
char *msg;
va_start(args, fs);
msg = g_strdup_vprintf(fs, args);
va_end(args);
if (s->sftp) {
char *ssh_err;
int ssh_err_code;
unsigned long sftp_err_code;
/* This is not an errno. See <libssh2.h>. */
ssh_err_code = libssh2_session_last_error(s->session,
&ssh_err, NULL, 0);
/* See <libssh2_sftp.h>. */
sftp_err_code = libssh2_sftp_last_error((s)->sftp);
error_setg(errp,
"%s: %s (libssh2 error code: %d, sftp error code: %lu)",
msg, ssh_err, ssh_err_code, sftp_err_code);
} else {
error_setg(errp, "%s", msg);
}
g_free(msg);
}
static void GCC_FMT_ATTR(2, 3)
sftp_error_report(BDRVSSHState *s, const char *fs, ...)
{
va_list args;
va_start(args, fs);
error_vprintf(fs, args);
if ((s)->sftp) {
char *ssh_err;
int ssh_err_code;
unsigned long sftp_err_code;
/* This is not an errno. See <libssh2.h>. */
ssh_err_code = libssh2_session_last_error(s->session,
&ssh_err, NULL, 0);
/* See <libssh2_sftp.h>. */
sftp_err_code = libssh2_sftp_last_error((s)->sftp);
error_printf(": %s (libssh2 error code: %d, sftp error code: %lu)",
ssh_err, ssh_err_code, sftp_err_code);
}
va_end(args);
error_printf("\n");
}
static int parse_uri(const char *filename, QDict *options, Error **errp)
{
URI *uri = NULL;
QueryParams *qp = NULL;
int i;
uri = uri_parse(filename);
if (!uri) {
return -EINVAL;
}
if (strcmp(uri->scheme, "ssh") != 0) {
error_setg(errp, "URI scheme must be 'ssh'");
goto err;
}
if (!uri->server || strcmp(uri->server, "") == 0) {
error_setg(errp, "missing hostname in URI");
goto err;
}
if (!uri->path || strcmp(uri->path, "") == 0) {
error_setg(errp, "missing remote path in URI");
goto err;
}
qp = query_params_parse(uri->query);
if (!qp) {
error_setg(errp, "could not parse query parameters");
goto err;
}
if(uri->user && strcmp(uri->user, "") != 0) {
qdict_put(options, "user", qstring_from_str(uri->user));
}
qdict_put(options, "host", qstring_from_str(uri->server));
if (uri->port) {
qdict_put(options, "port", qint_from_int(uri->port));
}
qdict_put(options, "path", qstring_from_str(uri->path));
/* Pick out any query parameters that we understand, and ignore
* the rest.
*/
for (i = 0; i < qp->n; ++i) {
if (strcmp(qp->p[i].name, "host_key_check") == 0) {
qdict_put(options, "host_key_check",
qstring_from_str(qp->p[i].value));
}
}
query_params_free(qp);
uri_free(uri);
return 0;
err:
if (qp) {
query_params_free(qp);
}
if (uri) {
uri_free(uri);
}
return -EINVAL;
}
static void ssh_parse_filename(const char *filename, QDict *options,
Error **errp)
{
if (qdict_haskey(options, "user") ||
qdict_haskey(options, "host") ||
qdict_haskey(options, "port") ||
qdict_haskey(options, "path") ||
qdict_haskey(options, "host_key_check")) {
error_setg(errp, "user, host, port, path, host_key_check cannot be used at the same time as a file option");
return;
}
parse_uri(filename, options, errp);
}
static int check_host_key_knownhosts(BDRVSSHState *s,
const char *host, int port, Error **errp)
{
const char *home;
char *knh_file = NULL;
LIBSSH2_KNOWNHOSTS *knh = NULL;
struct libssh2_knownhost *found;
int ret, r;
const char *hostkey;
size_t len;
int type;
hostkey = libssh2_session_hostkey(s->session, &len, &type);
if (!hostkey) {
ret = -EINVAL;
session_error_setg(errp, s, "failed to read remote host key");
goto out;
}
knh = libssh2_knownhost_init(s->session);
if (!knh) {
ret = -EINVAL;
session_error_setg(errp, s,
"failed to initialize known hosts support");
goto out;
}
home = getenv("HOME");
if (home) {
knh_file = g_strdup_printf("%s/.ssh/known_hosts", home);
} else {
knh_file = g_strdup_printf("/root/.ssh/known_hosts");
}
/* Read all known hosts from OpenSSH-style known_hosts file. */
libssh2_knownhost_readfile(knh, knh_file, LIBSSH2_KNOWNHOST_FILE_OPENSSH);
r = libssh2_knownhost_checkp(knh, host, port, hostkey, len,
LIBSSH2_KNOWNHOST_TYPE_PLAIN|
LIBSSH2_KNOWNHOST_KEYENC_RAW,
&found);
switch (r) {
case LIBSSH2_KNOWNHOST_CHECK_MATCH:
/* OK */
DPRINTF("host key OK: %s", found->key);
break;
case LIBSSH2_KNOWNHOST_CHECK_MISMATCH:
ret = -EINVAL;
session_error_setg(errp, s,
"host key does not match the one in known_hosts"
" (found key %s)", found->key);
goto out;
case LIBSSH2_KNOWNHOST_CHECK_NOTFOUND:
ret = -EINVAL;
session_error_setg(errp, s, "no host key was found in known_hosts");
goto out;
case LIBSSH2_KNOWNHOST_CHECK_FAILURE:
ret = -EINVAL;
session_error_setg(errp, s,
"failure matching the host key with known_hosts");
goto out;
default:
ret = -EINVAL;
session_error_setg(errp, s, "unknown error matching the host key"
" with known_hosts (%d)", r);
goto out;
}
/* known_hosts checking successful. */
ret = 0;
out:
if (knh != NULL) {
libssh2_knownhost_free(knh);
}
g_free(knh_file);
return ret;
}
static unsigned hex2decimal(char ch)
{
if (ch >= '0' && ch <= '9') {
return (ch - '0');
} else if (ch >= 'a' && ch <= 'f') {
return 10 + (ch - 'a');
} else if (ch >= 'A' && ch <= 'F') {
return 10 + (ch - 'A');
}
return -1;
}
/* Compare the binary fingerprint (hash of host key) with the
* host_key_check parameter.
*/
static int compare_fingerprint(const unsigned char *fingerprint, size_t len,
const char *host_key_check)
{
unsigned c;
while (len > 0) {
while (*host_key_check == ':')
host_key_check++;
if (!qemu_isxdigit(host_key_check[0]) ||
!qemu_isxdigit(host_key_check[1]))
return 1;
c = hex2decimal(host_key_check[0]) * 16 +
hex2decimal(host_key_check[1]);
if (c - *fingerprint != 0)
return c - *fingerprint;
fingerprint++;
len--;
host_key_check += 2;
}
return *host_key_check - '\0';
}
static int
check_host_key_hash(BDRVSSHState *s, const char *hash,
int hash_type, size_t fingerprint_len, Error **errp)
{
const char *fingerprint;
fingerprint = libssh2_hostkey_hash(s->session, hash_type);
if (!fingerprint) {
session_error_setg(errp, s, "failed to read remote host key");
return -EINVAL;
}
if(compare_fingerprint((unsigned char *) fingerprint, fingerprint_len,
hash) != 0) {
error_setg(errp, "remote host key does not match host_key_check '%s'",
hash);
return -EPERM;
}
return 0;
}
static int check_host_key(BDRVSSHState *s, const char *host, int port,
const char *host_key_check, Error **errp)
{
/* host_key_check=no */
if (strcmp(host_key_check, "no") == 0) {
return 0;
}
/* host_key_check=md5:xx:yy:zz:... */
if (strncmp(host_key_check, "md5:", 4) == 0) {
return check_host_key_hash(s, &host_key_check[4],
LIBSSH2_HOSTKEY_HASH_MD5, 16, errp);
}
/* host_key_check=sha1:xx:yy:zz:... */
if (strncmp(host_key_check, "sha1:", 5) == 0) {
return check_host_key_hash(s, &host_key_check[5],
LIBSSH2_HOSTKEY_HASH_SHA1, 20, errp);
}
/* host_key_check=yes */
if (strcmp(host_key_check, "yes") == 0) {
return check_host_key_knownhosts(s, host, port, errp);
}
error_setg(errp, "unknown host_key_check setting (%s)", host_key_check);
return -EINVAL;
}
static int authenticate(BDRVSSHState *s, const char *user, Error **errp)
{
int r, ret;
const char *userauthlist;
LIBSSH2_AGENT *agent = NULL;
struct libssh2_agent_publickey *identity;
struct libssh2_agent_publickey *prev_identity = NULL;
userauthlist = libssh2_userauth_list(s->session, user, strlen(user));
if (strstr(userauthlist, "publickey") == NULL) {
ret = -EPERM;
error_setg(errp,
"remote server does not support \"publickey\" authentication");
goto out;
}
/* Connect to ssh-agent and try each identity in turn. */
agent = libssh2_agent_init(s->session);
if (!agent) {
ret = -EINVAL;
session_error_setg(errp, s, "failed to initialize ssh-agent support");
goto out;
}
if (libssh2_agent_connect(agent)) {
ret = -ECONNREFUSED;
session_error_setg(errp, s, "failed to connect to ssh-agent");
goto out;
}
if (libssh2_agent_list_identities(agent)) {
ret = -EINVAL;
session_error_setg(errp, s,
"failed requesting identities from ssh-agent");
goto out;
}
for(;;) {
r = libssh2_agent_get_identity(agent, &identity, prev_identity);
if (r == 1) { /* end of list */
break;
}
if (r < 0) {
ret = -EINVAL;
session_error_setg(errp, s,
"failed to obtain identity from ssh-agent");
goto out;
}
r = libssh2_agent_userauth(agent, user, identity);
if (r == 0) {
/* Authenticated! */
ret = 0;
goto out;
}
/* Failed to authenticate with this identity, try the next one. */
prev_identity = identity;
}
ret = -EPERM;
error_setg(errp, "failed to authenticate using publickey authentication "
"and the identities held by your ssh-agent");
out:
if (agent != NULL) {
/* Note: libssh2 implementation implicitly calls
* libssh2_agent_disconnect if necessary.
*/
libssh2_agent_free(agent);
}
return ret;
}
static int connect_to_ssh(BDRVSSHState *s, QDict *options,
int ssh_flags, int creat_mode, Error **errp)
{
int r, ret;
const char *host, *user, *path, *host_key_check;
int port;
if (!qdict_haskey(options, "host")) {
ret = -EINVAL;
error_setg(errp, "No hostname was specified");
goto err;
}
host = qdict_get_str(options, "host");
if (qdict_haskey(options, "port")) {
port = qdict_get_int(options, "port");
} else {
port = 22;
}
if (!qdict_haskey(options, "path")) {
ret = -EINVAL;
error_setg(errp, "No path was specified");
goto err;
}
path = qdict_get_str(options, "path");
if (qdict_haskey(options, "user")) {
user = qdict_get_str(options, "user");
} else {
user = g_get_user_name();
if (!user) {
error_setg_errno(errp, errno, "Can't get user name");
ret = -errno;
goto err;
}
}
if (qdict_haskey(options, "host_key_check")) {
host_key_check = qdict_get_str(options, "host_key_check");
} else {
host_key_check = "yes";
}
/* Construct the host:port name for inet_connect. */
g_free(s->hostport);
s->hostport = g_strdup_printf("%s:%d", host, port);
/* Open the socket and connect. */
s->sock = inet_connect(s->hostport, errp);
if (s->sock < 0) {
ret = -errno;
goto err;
}
/* Create SSH session. */
s->session = libssh2_session_init();
if (!s->session) {
ret = -EINVAL;
session_error_setg(errp, s, "failed to initialize libssh2 session");
goto err;
}
#if TRACE_LIBSSH2 != 0
libssh2_trace(s->session, TRACE_LIBSSH2);
#endif
r = libssh2_session_handshake(s->session, s->sock);
if (r != 0) {
ret = -EINVAL;
session_error_setg(errp, s, "failed to establish SSH session");
goto err;
}
/* Check the remote host's key against known_hosts. */
ret = check_host_key(s, host, port, host_key_check, errp);
if (ret < 0) {
goto err;
}
/* Authenticate. */
ret = authenticate(s, user, errp);
if (ret < 0) {
goto err;
}
/* Start SFTP. */
s->sftp = libssh2_sftp_init(s->session);
if (!s->sftp) {
session_error_setg(errp, s, "failed to initialize sftp handle");
ret = -EINVAL;
goto err;
}
/* Open the remote file. */
DPRINTF("opening file %s flags=0x%x creat_mode=0%o",
path, ssh_flags, creat_mode);
s->sftp_handle = libssh2_sftp_open(s->sftp, path, ssh_flags, creat_mode);
if (!s->sftp_handle) {
session_error_setg(errp, s, "failed to open remote file '%s'", path);
ret = -EINVAL;
goto err;
}
r = libssh2_sftp_fstat(s->sftp_handle, &s->attrs);
if (r < 0) {
sftp_error_setg(errp, s, "failed to read file attributes");
return -EINVAL;
}
/* Delete the options we've used; any not deleted will cause the
* block layer to give an error about unused options.
*/
qdict_del(options, "host");
qdict_del(options, "port");
qdict_del(options, "user");
qdict_del(options, "path");
qdict_del(options, "host_key_check");
return 0;
err:
if (s->sftp_handle) {
libssh2_sftp_close(s->sftp_handle);
}
s->sftp_handle = NULL;
if (s->sftp) {
libssh2_sftp_shutdown(s->sftp);
}
s->sftp = NULL;
if (s->session) {
libssh2_session_disconnect(s->session,
"from qemu ssh client: "
"error opening connection");
libssh2_session_free(s->session);
}
s->session = NULL;
return ret;
}
static int ssh_file_open(BlockDriverState *bs, QDict *options, int bdrv_flags,
Error **errp)
{
BDRVSSHState *s = bs->opaque;
int ret;
int ssh_flags;
ssh_state_init(s);
ssh_flags = LIBSSH2_FXF_READ;
if (bdrv_flags & BDRV_O_RDWR) {
ssh_flags |= LIBSSH2_FXF_WRITE;
}
/* Start up SSH. */
ret = connect_to_ssh(s, options, ssh_flags, 0, errp);
if (ret < 0) {
goto err;
}
/* Go non-blocking. */
libssh2_session_set_blocking(s->session, 0);
return 0;
err:
if (s->sock >= 0) {
close(s->sock);
}
s->sock = -1;
return ret;
}
static QemuOptsList ssh_create_opts = {
.name = "ssh-create-opts",
.head = QTAILQ_HEAD_INITIALIZER(ssh_create_opts.head),
.desc = {
{
.name = BLOCK_OPT_SIZE,
.type = QEMU_OPT_SIZE,
.help = "Virtual disk size"
},
{ /* end of list */ }
}
};
static int ssh_create(const char *filename, QemuOpts *opts, Error **errp)
{
int r, ret;
int64_t total_size = 0;
QDict *uri_options = NULL;
BDRVSSHState s;
ssize_t r2;
char c[1] = { '\0' };
ssh_state_init(&s);
/* Get desired file size. */
total_size = ROUND_UP(qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0),
BDRV_SECTOR_SIZE);
DPRINTF("total_size=%" PRIi64, total_size);
uri_options = qdict_new();
r = parse_uri(filename, uri_options, errp);
if (r < 0) {
ret = r;
goto out;
}
r = connect_to_ssh(&s, uri_options,
LIBSSH2_FXF_READ|LIBSSH2_FXF_WRITE|
LIBSSH2_FXF_CREAT|LIBSSH2_FXF_TRUNC,
0644, errp);
if (r < 0) {
ret = r;
goto out;
}
if (total_size > 0) {
libssh2_sftp_seek64(s.sftp_handle, total_size-1);
r2 = libssh2_sftp_write(s.sftp_handle, c, 1);
if (r2 < 0) {
sftp_error_setg(errp, &s, "truncate failed");
ret = -EINVAL;
goto out;
}
s.attrs.filesize = total_size;
}
ret = 0;
out:
ssh_state_free(&s);
if (uri_options != NULL) {
QDECREF(uri_options);
}
return ret;
}
static void ssh_close(BlockDriverState *bs)
{
BDRVSSHState *s = bs->opaque;
ssh_state_free(s);
}
static int ssh_has_zero_init(BlockDriverState *bs)
{
BDRVSSHState *s = bs->opaque;
/* Assume false, unless we can positively prove it's true. */
int has_zero_init = 0;
if (s->attrs.flags & LIBSSH2_SFTP_ATTR_PERMISSIONS) {
if (s->attrs.permissions & LIBSSH2_SFTP_S_IFREG) {
has_zero_init = 1;
}
}
return has_zero_init;
}
static void restart_coroutine(void *opaque)
{
Coroutine *co = opaque;
DPRINTF("co=%p", co);
qemu_coroutine_enter(co, NULL);
}
static coroutine_fn void set_fd_handler(BDRVSSHState *s, BlockDriverState *bs)
{
int r;
IOHandler *rd_handler = NULL, *wr_handler = NULL;
Coroutine *co = qemu_coroutine_self();
r = libssh2_session_block_directions(s->session);
if (r & LIBSSH2_SESSION_BLOCK_INBOUND) {
rd_handler = restart_coroutine;
}
if (r & LIBSSH2_SESSION_BLOCK_OUTBOUND) {
wr_handler = restart_coroutine;
}
DPRINTF("s->sock=%d rd_handler=%p wr_handler=%p", s->sock,
rd_handler, wr_handler);
aio_set_fd_handler(bdrv_get_aio_context(bs), s->sock,
rd_handler, wr_handler, co);
}
static coroutine_fn void clear_fd_handler(BDRVSSHState *s,
BlockDriverState *bs)
{
DPRINTF("s->sock=%d", s->sock);
aio_set_fd_handler(bdrv_get_aio_context(bs), s->sock, NULL, NULL, NULL);
}
/* A non-blocking call returned EAGAIN, so yield, ensuring the
* handlers are set up so that we'll be rescheduled when there is an
* interesting event on the socket.
*/
static coroutine_fn void co_yield(BDRVSSHState *s, BlockDriverState *bs)
{
set_fd_handler(s, bs);
qemu_coroutine_yield();
clear_fd_handler(s, bs);
}
/* SFTP has a function `libssh2_sftp_seek64' which seeks to a position
* in the remote file. Notice that it just updates a field in the
* sftp_handle structure, so there is no network traffic and it cannot
* fail.
*
* However, `libssh2_sftp_seek64' does have a catastrophic effect on
* performance since it causes the handle to throw away all in-flight
* reads and buffered readahead data. Therefore this function tries
* to be intelligent about when to call the underlying libssh2 function.
*/
#define SSH_SEEK_WRITE 0
#define SSH_SEEK_READ 1
#define SSH_SEEK_FORCE 2
static void ssh_seek(BDRVSSHState *s, int64_t offset, int flags)
{
bool op_read = (flags & SSH_SEEK_READ) != 0;
bool force = (flags & SSH_SEEK_FORCE) != 0;
if (force || op_read != s->offset_op_read || offset != s->offset) {
DPRINTF("seeking to offset=%" PRIi64, offset);
libssh2_sftp_seek64(s->sftp_handle, offset);
s->offset = offset;
s->offset_op_read = op_read;
}
}
static coroutine_fn int ssh_read(BDRVSSHState *s, BlockDriverState *bs,
int64_t offset, size_t size,
QEMUIOVector *qiov)
{
ssize_t r;
size_t got;
char *buf, *end_of_vec;
struct iovec *i;
DPRINTF("offset=%" PRIi64 " size=%zu", offset, size);
ssh_seek(s, offset, SSH_SEEK_READ);
/* This keeps track of the current iovec element ('i'), where we
* will write to next ('buf'), and the end of the current iovec
* ('end_of_vec').
*/
i = &qiov->iov[0];
buf = i->iov_base;
end_of_vec = i->iov_base + i->iov_len;
/* libssh2 has a hard-coded limit of 2000 bytes per request,
* although it will also do readahead behind our backs. Therefore
* we may have to do repeated reads here until we have read 'size'
* bytes.
*/
for (got = 0; got < size; ) {
again:
DPRINTF("sftp_read buf=%p size=%zu", buf, end_of_vec - buf);
r = libssh2_sftp_read(s->sftp_handle, buf, end_of_vec - buf);
DPRINTF("sftp_read returned %zd", r);
if (r == LIBSSH2_ERROR_EAGAIN || r == LIBSSH2_ERROR_TIMEOUT) {
co_yield(s, bs);
goto again;
}
if (r < 0) {
sftp_error_report(s, "read failed");
s->offset = -1;
return -EIO;
}
if (r == 0) {
/* EOF: Short read so pad the buffer with zeroes and return it. */
qemu_iovec_memset(qiov, got, 0, size - got);
return 0;
}
got += r;
buf += r;
s->offset += r;
if (buf >= end_of_vec && got < size) {
i++;
buf = i->iov_base;
end_of_vec = i->iov_base + i->iov_len;
}
}
return 0;
}
static coroutine_fn int ssh_co_readv(BlockDriverState *bs,
int64_t sector_num,
int nb_sectors, QEMUIOVector *qiov)
{
BDRVSSHState *s = bs->opaque;
int ret;
qemu_co_mutex_lock(&s->lock);
ret = ssh_read(s, bs, sector_num * BDRV_SECTOR_SIZE,
nb_sectors * BDRV_SECTOR_SIZE, qiov);
qemu_co_mutex_unlock(&s->lock);
return ret;
}
static int ssh_write(BDRVSSHState *s, BlockDriverState *bs,
int64_t offset, size_t size,
QEMUIOVector *qiov)
{
ssize_t r;
size_t written;
char *buf, *end_of_vec;
struct iovec *i;
DPRINTF("offset=%" PRIi64 " size=%zu", offset, size);
ssh_seek(s, offset, SSH_SEEK_WRITE);
/* This keeps track of the current iovec element ('i'), where we
* will read from next ('buf'), and the end of the current iovec
* ('end_of_vec').
*/
i = &qiov->iov[0];
buf = i->iov_base;
end_of_vec = i->iov_base + i->iov_len;
for (written = 0; written < size; ) {
again:
DPRINTF("sftp_write buf=%p size=%zu", buf, end_of_vec - buf);
r = libssh2_sftp_write(s->sftp_handle, buf, end_of_vec - buf);
DPRINTF("sftp_write returned %zd", r);
if (r == LIBSSH2_ERROR_EAGAIN || r == LIBSSH2_ERROR_TIMEOUT) {
co_yield(s, bs);
goto again;
}
if (r < 0) {
sftp_error_report(s, "write failed");
s->offset = -1;
return -EIO;
}
/* The libssh2 API is very unclear about this. A comment in
* the code says "nothing was acked, and no EAGAIN was
* received!" which apparently means that no data got sent
* out, and the underlying channel didn't return any EAGAIN
* indication. I think this is a bug in either libssh2 or
* OpenSSH (server-side). In any case, forcing a seek (to
* discard libssh2 internal buffers), and then trying again
* works for me.
*/
if (r == 0) {
ssh_seek(s, offset + written, SSH_SEEK_WRITE|SSH_SEEK_FORCE);
co_yield(s, bs);
goto again;
}
written += r;
buf += r;
s->offset += r;
if (buf >= end_of_vec && written < size) {
i++;
buf = i->iov_base;
end_of_vec = i->iov_base + i->iov_len;
}
if (offset + written > s->attrs.filesize)
s->attrs.filesize = offset + written;
}
return 0;
}
static coroutine_fn int ssh_co_writev(BlockDriverState *bs,
int64_t sector_num,
int nb_sectors, QEMUIOVector *qiov)
{
BDRVSSHState *s = bs->opaque;
int ret;
qemu_co_mutex_lock(&s->lock);
ret = ssh_write(s, bs, sector_num * BDRV_SECTOR_SIZE,
nb_sectors * BDRV_SECTOR_SIZE, qiov);
qemu_co_mutex_unlock(&s->lock);
return ret;
}
static void unsafe_flush_warning(BDRVSSHState *s, const char *what)
{
if (!s->unsafe_flush_warning) {
error_report("warning: ssh server %s does not support fsync",
s->hostport);
if (what) {
error_report("to support fsync, you need %s", what);
}
s->unsafe_flush_warning = true;
}
}
#ifdef HAS_LIBSSH2_SFTP_FSYNC
static coroutine_fn int ssh_flush(BDRVSSHState *s, BlockDriverState *bs)
{
int r;
DPRINTF("fsync");
again:
r = libssh2_sftp_fsync(s->sftp_handle);
if (r == LIBSSH2_ERROR_EAGAIN || r == LIBSSH2_ERROR_TIMEOUT) {
co_yield(s, bs);
goto again;
}
if (r == LIBSSH2_ERROR_SFTP_PROTOCOL &&
libssh2_sftp_last_error(s->sftp) == LIBSSH2_FX_OP_UNSUPPORTED) {
unsafe_flush_warning(s, "OpenSSH >= 6.3");
return 0;
}
if (r < 0) {
sftp_error_report(s, "fsync failed");
return -EIO;
}
return 0;
}
static coroutine_fn int ssh_co_flush(BlockDriverState *bs)
{
BDRVSSHState *s = bs->opaque;
int ret;
qemu_co_mutex_lock(&s->lock);
ret = ssh_flush(s, bs);
qemu_co_mutex_unlock(&s->lock);
return ret;
}
#else /* !HAS_LIBSSH2_SFTP_FSYNC */
static coroutine_fn int ssh_co_flush(BlockDriverState *bs)
{
BDRVSSHState *s = bs->opaque;
unsafe_flush_warning(s, "libssh2 >= 1.4.4");
return 0;
}
#endif /* !HAS_LIBSSH2_SFTP_FSYNC */
static int64_t ssh_getlength(BlockDriverState *bs)
{
BDRVSSHState *s = bs->opaque;
int64_t length;
/* Note we cannot make a libssh2 call here. */
length = (int64_t) s->attrs.filesize;
DPRINTF("length=%" PRIi64, length);
return length;
}
static BlockDriver bdrv_ssh = {
.format_name = "ssh",
.protocol_name = "ssh",
.instance_size = sizeof(BDRVSSHState),
.bdrv_parse_filename = ssh_parse_filename,
.bdrv_file_open = ssh_file_open,
.bdrv_create = ssh_create,
.bdrv_close = ssh_close,
.bdrv_has_zero_init = ssh_has_zero_init,
.bdrv_co_readv = ssh_co_readv,
.bdrv_co_writev = ssh_co_writev,
.bdrv_getlength = ssh_getlength,
.bdrv_co_flush_to_disk = ssh_co_flush,
.create_opts = &ssh_create_opts,
};
static void bdrv_ssh_init(void)
{
int r;
r = libssh2_init(0);
if (r != 0) {
fprintf(stderr, "libssh2 initialization failed, %d\n", r);
exit(EXIT_FAILURE);
}
bdrv_register(&bdrv_ssh);
}
block_init(bdrv_ssh_init);
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