6:46 a.m.
This adds new parameters, create=(true|false), create-size=SIZE and
create-mode=MODE to create and truncate the remote file.
---
plugins/ssh/nbdkit-ssh-plugin.pod | 37 +++++++++++++++++--
plugins/ssh/ssh.c | 60 +++++++++++++++++++++++++++++--
2 files changed, 93 insertions(+), 4 deletions(-)
diff --git a/plugins/ssh/nbdkit-ssh-plugin.pod b/plugins/ssh/nbdkit-ssh-plugin.pod
index 3f401c15..648fa94d 100644
--- a/plugins/ssh/nbdkit-ssh-plugin.pod
+++ b/plugins/ssh/nbdkit-ssh-plugin.pod
@@ -5,8 +5,10 @@ nbdkit-ssh-plugin - access disk images over the SSH protocol
=head1 SYNOPSIS
nbdkit ssh host=HOST [path=]PATH
- [compression=true] [config=CONFIG_FILE] [identity=FILENAME]
- [known-hosts=FILENAME] [password=PASSWORD|-|+FILENAME]
+ [compression=true] [config=CONFIG_FILE]
+ [create=true] [create-mode=MODE] [create-size=SIZE]
+ [identity=FILENAME] [known-hosts=FILENAME]
+ [password=PASSWORD|-|+FILENAME]
[port=PORT] [timeout=SECS] [user=USER]
[verify-remote-host=false]
@@ -62,6 +64,37 @@ The C<config> parameter is optional. If it is I<not>
specified at all
then F<~/.ssh/config> and F</etc/ssh/ssh_config> are both read.
Missing or unreadable files are ignored.
+=item B<create=true>
+
+(nbdkit E<ge> 1.32)
+
+If set, the remote file will be created if it does not exist already.
+Note the remote file is created on first NBD connection to nbdkit.
+
+If using this option, you must use C<create-size>. C<create-mode> can
+be used to control the permissions of the new file.
+
+=item B<create-mode=>MODE
+
+(nbdkit E<ge> 1.32)
+
+If using C<create=true> specify the default permissions of the new
+remote file. You can use octal modes like C<create-mode=0777>. The
+default is C<0600>, ie. only readable and writable by the remote user.
+
+The SFTP server may apply a L<umask(2)> which is specific to the
+remote system and cannot be queried from the client, so the final
+permissions may be more restrictive than requested. For OpenSSH I
+found that files are always created with mode & 0700 whatever mode is
+specified here, but other servers might be different.
+
+=item B<create-size=>SIZE
+
+(nbdkit E<ge> 1.32)
+
+If using C<create=true>, specify the virtual size of the new disk.
+C<SIZE> can use modifiers like C<100M> etc.
+
=item B<host=>HOST
Specify the name or IP address of the remote host.
diff --git a/plugins/ssh/ssh.c b/plugins/ssh/ssh.c
index 3b2b21c8..66998813 100644
--- a/plugins/ssh/ssh.c
+++ b/plugins/ssh/ssh.c
@@ -63,6 +63,9 @@ static const char *known_hosts = NULL;
static const_string_vector identities = empty_vector;
static uint32_t timeout = 0;
static bool compression = false;
+static bool create = false;
+static int64_t create_size = -1;
+static unsigned create_mode = S_IRUSR | S_IWUSR /* 0600 */;
/* config can be:
* NULL => parse options from default file
@@ -167,6 +170,27 @@ ssh_config (const char *key, const char *value)
return -1;
compression = r;
}
+ else if (strcmp (key, "create") == 0) {
+ r = nbdkit_parse_bool (value);
+ if (r == -1)
+ return -1;
+ create = r;
+ }
+ else if (strcmp (key, "create-size") == 0) {
+ create_size = nbdkit_parse_size (value);
+ if (create_size == -1)
+ return -1;
+ }
+ else if (strcmp (key, "create-mode") == 0) {
+ r = nbdkit_parse_unsigned (key, value, &create_mode);
+ if (r == -1)
+ return -1;
+ /* OpenSSH checks this too. */
+ if (create_mode > 0777) {
+ nbdkit_error ("create-mode must be <= 0777");
+ return -1;
+ }
+ }
else {
nbdkit_error ("unknown parameter '%s'", key);
@@ -186,6 +210,13 @@ ssh_config_complete (void)
return -1;
}
+ /* If create=true, create-size must be supplied. */
+ if (create && create_size == -1) {
+ nbdkit_error ("if using create=true, you must specify the size "
+ "of the new remote file using create-size=SIZE");
+ return -1;
+ }
+
return 0;
}
@@ -200,7 +231,10 @@ ssh_config_complete (void)
"identity=<FILENAME> Prepend private key (identity) file.\n" \
"timeout=SECS Set SSH connection timeout.\n" \
"verify-remote-host=false Ignore known_hosts.\n" \
- "compression=true Enable compression."
+ "compression=true Enable compression.\n" \
+ "create=true Create the remote file.\n" \
+ "create-mode=MODE Set the permissions of the remote file.\n" \
+ "create-size=SIZE Set the size of the remote file."
/* The per-connection handle. */
struct ssh_handle {
@@ -480,7 +514,8 @@ ssh_open (int readonly)
goto err;
}
access_type = readonly ? O_RDONLY : O_RDWR;
- h->file = sftp_open (h->sftp, path, access_type, S_IRWXU);
+ if (create) access_type |= O_CREAT;
+ h->file = sftp_open (h->sftp, path, access_type, create_mode);
if (!h->file) {
nbdkit_error ("cannot open file for %s: %s",
readonly ? "reading" : "writing",
@@ -488,6 +523,27 @@ ssh_open (int readonly)
goto err;
}
+ if (create) {
+ /* There's no sftp_truncate call. However OpenSSH lets you call
+ * SSH_FXP_SETSTAT + SSH_FILEXFER_ATTR_SIZE which invokes
+ * truncate(2) on the server. Libssh doesn't provide a binding
+ * for SSH_FXP_FSETSTAT so we have to pass the session + path.
+ */
+ struct sftp_attributes_struct attrs = {
+ .flags = SSH_FILEXFER_ATTR_SIZE,
+ .size = create_size,
+ };
+
+ r = sftp_setstat (h->sftp, path, &attrs);
+ if (r != SSH_OK) {
+ nbdkit_error ("truncate failed: %s", ssh_get_error (h->session));
+ goto err;
+ }
+ }
+
+ /* On the next open, don't create or truncate the file. */
+ create = false;
+
nbdkit_debug ("opened libssh handle");
return h;
--
2.35.1