1nbd_set_handshake_flags(3)          LIBNBD          nbd_set_handshake_flags(3)
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NAME

6       nbd_set_handshake_flags - control use of handshake flags
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SYNOPSIS

9        #include <libnbd.h>
10
11        int nbd_set_handshake_flags (
12              struct nbd_handle *h, uint32_t flags
13            );
14

DESCRIPTION

16       By default, libnbd tries to negotiate all possible handshake flags that
17       are also supported by the server, since omitting a handshake flag can
18       prevent the use of other functionality such as TLS encryption or
19       structured replies.  However, for integration testing, it can be useful
20       to reduce the set of flags supported by the client to test that a
21       particular server can handle various clients that were compliant to
22       older versions of the NBD specification.
23
24       The "flags" argument is a bitmask, including zero or more of the
25       following handshake flags:
26
27       "LIBNBD_HANDSHAKE_FLAG_FIXED_NEWSTYLE" = 1
28           The server gracefully handles unknown option requests from the
29           client, rather than disconnecting.  Without this flag, a client
30           cannot safely request to use extensions such as TLS encryption or
31           structured replies, as the request may cause an older server to
32           drop the connection.
33
34       "LIBNBD_HANDSHAKE_FLAG_NO_ZEROES" = 2
35           If the client is forced to use "NBD_OPT_EXPORT_NAME" instead of the
36           preferred "NBD_OPT_GO", this flag allows the server to send fewer
37           all-zero padding bytes over the connection.
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39       For convenience, the constant "LIBNBD_HANDSHAKE_FLAG_MASK" is available
40       to describe all flags supported by this build of libnbd.  Future NBD
41       extensions may add further flags, which in turn may be enabled by
42       default in newer libnbd.  As such, when attempting to disable only one
43       specific bit, it is wiser to first call nbd_get_handshake_flags(3) and
44       modify that value, rather than blindly setting a constant value.
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RETURN VALUE

47       If the call is successful the function returns 0.
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ERRORS

50       On error -1 is returned.
51
52       Refer to "ERROR HANDLING" in libnbd(3) for how to get further details
53       of the error.
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55       The following parameters must not be NULL: "h".  For more information
56       see "Non-NULL parameters" in libnbd(3).
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HANDLE STATE

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

63       This function first appeared in libnbd 1.2.
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65       If you need to test if this function is available at compile time check
66       if the following macro is defined:
67
68        #define LIBNBD_HAVE_NBD_SET_HANDSHAKE_FLAGS 1
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SEE ALSO

71       nbd_create(3), nbd_get_handshake_flags(3),
72       nbd_set_request_structured_replies(3), libnbd(3).
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AUTHORS

75       Eric Blake
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77       Richard W.M. Jones
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80       Copyright Red Hat
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LICENSE

83       This library is free software; you can redistribute it and/or modify it
84       under the terms of the GNU Lesser General Public License as published
85       by the Free Software Foundation; either version 2 of the License, or
86       (at your option) any later version.
87
88       This library is distributed in the hope that it will be useful, but
89       WITHOUT ANY WARRANTY; without even the implied warranty of
90       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
91       Lesser General Public License for more details.
92
93       You should have received a copy of the GNU Lesser General Public
94       License along with this library; if not, write to the Free Software
95       Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
96       02110-1301 USA
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100libnbd-1.16.5                     2023-09-26        nbd_set_handshake_flags(3)
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