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>
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11        int nbd_set_handshake_flags (struct nbd_handle *h,
12                                     uint32_t flags);
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DESCRIPTION

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

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

49       On error "-1" is returned.
50
51       Refer to "ERROR HANDLING" in libnbd(3) for how to get further details
52       of the error.
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HANDLE STATE

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

59       This function first appeared in libnbd 1.2.
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61       If you need to test if this function is available at compile time check
62       if the following macro is defined:
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64        #define LIBNBD_HAVE_NBD_SET_HANDSHAKE_FLAGS 1
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SEE ALSO

67       nbd_create(3), nbd_get_handshake_flags(3),
68       nbd_set_request_structured_replies(3), libnbd(3).
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AUTHORS

71       Eric Blake
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73       Richard W.M. Jones
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76       Copyright (C) 2019-2020 Red Hat Inc.
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LICENSE

79       This library is free software; you can redistribute it and/or modify it
80       under the terms of the GNU Lesser General Public License as published
81       by the Free Software Foundation; either version 2 of the License, or
82       (at your option) any later version.
83
84       This library is distributed in the hope that it will be useful, but
85       WITHOUT ANY WARRANTY; without even the implied warranty of
86       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
87       Lesser General Public License for more details.
88
89       You should have received a copy of the GNU Lesser General Public
90       License along with this library; if not, write to the Free Software
91       Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
92       02110-1301 USA
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96libnbd-1.6.2                      2021-03-02        nbd_set_handshake_flags(3)
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