nbd_connect_uri(3)

1nbd_connect_uri(3)                  LIBNBD                  nbd_connect_uri(3)
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NAME

6       nbd_connect_uri - connect to NBD URI
7

SYNOPSIS

9        #include <libnbd.h>
10
11        int nbd_connect_uri (struct nbd_handle *h, const char *uri);
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DESCRIPTION

14       Connect (synchronously) to an NBD server and export by specifying the
15       NBD URI.  This call parses the URI and calls nbd_set_export_name(3) and
16       nbd_set_tls(3) and other calls as needed, followed by
17       nbd_connect_tcp(3) or nbd_connect_unix(3).
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19       This call returns when the connection has been made.
20
21   Example URIs supported
22       "nbd://example.com"
23           Connect over TCP, unencrypted, to "example.com" port 10809.
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25       "nbds://example.com"
26           Connect over TCP with TLS, to "example.com" port 10809.  If the
27           server does not support TLS then this will fail.
28
29       "nbd+unix:///foo?socket=/tmp/nbd.sock"
30           Connect over the Unix domain socket /tmp/nbd.sock to an NBD server
31           running locally.  The export name is set to "foo" (note without any
32           leading "/" character).
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34       "nbds+unix://alice@/?socket=/tmp/nbd.sock&tls-certificates=certs"
35           Connect over a Unix domain socket, enabling TLS and setting the
36           path to a directory containing certificates and keys.
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38       "nbd+vsock:///"
39           In this scenario libnbd is running in a virtual machine.  Connect
40           over "AF_VSOCK" to an NBD server running on the hypervisor.
41
42   Supported URI formats
43       The following schemes are supported in the current version of libnbd:
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45       "nbd:"
46           Connect over TCP without using TLS.
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48       "nbds:"
49           Connect over TCP.  TLS is required and the connection will fail if
50           the server does not support TLS.
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52       "nbd+unix:"
53       "nbds+unix:"
54           Connect over a Unix domain socket, without or with TLS
55           respectively.  The "socket" parameter is required.
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57       "nbd+vsock:"
58       "nbds+vsock:"
59           Connect over the "AF_VSOCK" transport, without or with TLS
60           respectively.
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62       The authority part of the URI ("[username@][servername][:port]") is
63       parsed depending on the transport.  For TCP it specifies the server to
64       connect to and optional port number.  For "+unix" it should not be
65       present.  For "+vsock" the server name is the numeric CID (eg. 2 to
66       connect to the host), and the optional port number may be present.  If
67       the "username" is present it is used for TLS authentication.
68
69       For all transports, an export name may be present, parsed in accordance
70       with the NBD URI specification.
71
72       Finally the query part of the URI can contain:
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74       socket=SOCKET
75           Specifies the Unix domain socket to connect on.  Must be present
76           for the "+unix" transport and must not be present for the other
77           transports.
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79       tls-certificates=DIR
80           Set the certificates directory.  See nbd_set_tls_certificates(3).
81           Note this is not allowed by default - see next section.
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83       tls-psk-file=PSKFILE
84           Set the PSK file.  See nbd_set_tls_psk_file(3).  Note this is not
85           allowed by default - see next section.
86
87   Disable URI features
88       For security reasons you might want to disable certain URI features.
89       Pre-filtering URIs is error-prone and should not be attempted.  Instead
90       use the libnbd APIs below to control what can appear in URIs.  Note you
91       must call these functions on the same handle before calling
92       nbd_connect_uri(3) or nbd_aio_connect_uri(3).
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94       TCP, Unix domain socket or "AF_VSOCK" transports
95           Default: all allowed
96
97           To select which transports are allowed call
98           nbd_set_uri_allow_transports(3).
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100       TLS Default: both non-TLS and TLS connections allowed
101
102           To force TLS off or on in URIs call nbd_set_uri_allow_tls(3).
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104       Connect to Unix domain socket in the local filesystem
105           Default: allowed
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107           To prevent this you must disable the "+unix" transport using
108           nbd_set_uri_allow_transports(3).
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110       Read from local files
111           Default: denied
112
113           To allow URIs to contain references to local files (eg. for
114           parameters like "tls-psk-file") call
115           nbd_set_uri_allow_local_file(3).
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117   Overriding the export name
118       It is possible to override the export name portion of a URI by using
119       nbd_set_opt_mode(3) to enable option mode, then using
120       nbd_set_export_name(3) and nbd_opt_go(3) as part of subsequent
121       negotiation.
122
123   Optional features
124       This call will fail if libnbd was not compiled with libxml2; you can
125       test whether this is the case with nbd_supports_uri(3).
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127       Support for URIs that require TLS will fail if libnbd was not compiled
128       with gnutls; you can test whether this is the case with
129       nbd_supports_tls(3).
130
131   Constructing a URI from an existing connection
132       See nbd_get_uri(3).
133

RETURN VALUE

135       If the call is successful the function returns 0.
136

ERRORS

138       On error "-1" is returned.
139
140       Refer to "ERROR HANDLING" in libnbd(3) for how to get further details
141       of the error.
142
143       The following parameters must not be NULL: "h", "uri".  For more
144       information see "Non-NULL parameters" in libnbd(3).
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HANDLE STATE

147       The handle must be newly created, otherwise this call will return an
148       error.
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VERSION

151       This function first appeared in libnbd 1.0.
152
153       If you need to test if this function is available at compile time check
154       if the following macro is defined:
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156        #define LIBNBD_HAVE_NBD_CONNECT_URI 1
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AUTHORS

169       Eric Blake
170
171       Richard W.M. Jones
172

COPYRIGHT

174       Copyright (C) 2019-2021 Red Hat Inc.
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LICENSE

177       This library is free software; you can redistribute it and/or modify it
178       under the terms of the GNU Lesser General Public License as published
179       by the Free Software Foundation; either version 2 of the License, or
180       (at your option) any later version.
181
182       This library is distributed in the hope that it will be useful, but
183       WITHOUT ANY WARRANTY; without even the implied warranty of
184       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
185       Lesser General Public License for more details.
186
187       You should have received a copy of the GNU Lesser General Public
188       License along with this library; if not, write to the Free Software
189       Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
190       02110-1301 USA
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194libnbd-1.14.2                     2023-01-03                nbd_connect_uri(3)