int
inet6_option_space(
int nbytes
)
int
inet6_option_init(
void *bp
, struct cmsghdr **cmsgp
, int type
)
int
inet6_option_append(
struct cmsghdr *cmsg
, const uint8_t *typep
, int multx
, int plusy
)
uint8_t *
inet6_option_alloc(
struct cmsghdr *cmsg
, int datalen
, int multx
, int plusy
)
int
inet6_option_next(
const struct cmsghdr *cmsg
, uint8_t **tptrp
)
int
inet6_option_find(
const struct cmsghdr *cmsg
, uint8_t **tptrp
, int type
)
netinet/in.h
>
header.
)
returns the number of bytes required to hold an option when it is stored as
ancillary data, including the
cmsghdr
structure at the beginning,
and any padding at the end
(to make its size a multiple of 8 bytes.)
The argument is the size of the structure defining the option,
which must include any pad bytes at the beginning
y
in the alignment term
``
xn
+
y
''
(the value,)
the type byte, the length byte, and the option data.
Note: If multiple options are stored in a single ancillary data
object, which is the recommended technique, this function
overestimates the amount of space required by the size of
N-1
cmsghdr
structures,
where
N
is the number of options to be stored in the object.
This is of little consequence, since it is assumed that most
Hop-by-Hop option headers and Destination option headers carry only
one option
(appendix B of [RFC 2460]).
)
is called once per ancillary data object that will
contain either Hop-by-Hop or Destination options.
It returns
0
on success or
-1
on an error.
bp
is a pointer to previously allocated space that will contain the
ancillary data object.
It must be large enough to contain all the
individual options to be added by later calls to
inet6_option_append()
and
inet6_option_alloc(
).
cmsgp
is a pointer to a pointer to a
cmsghdr
structure.
*cmsgp
is initialized by this function to point to the
cmsghdr
structure constructed by this function in the buffer pointed to by
bp
.
type
is either
IPV6_HOPOPTS
or
IPV6_DSTOPTS
.
This
type
is stored in the
cmsg_type
member of the
cmsghdr
structure pointed to by
*cmsgp
.
).
This function returns
0
if it succeeds or
-1
on an error.
cmsg
is a pointer to the
cmsghdr
structure that must have been
initialized by
inet6_option_init().
typep
is a pointer to the 8-bit option type.
It is assumed that this
field is immediately followed by the 8-bit option data length field,
which is then followed immediately by the option data.
The caller
initializes these three fields
(the type-length-value, or TLV)
before calling this function.
The option type must have a value from
2
to
255
,
inclusive.
and
1
are reserved for the
Pad1
and
PadN
options, respectively.
(0
)
The option data length must have a value between
0
and
255
,
inclusive, and is the length of the option data that follows.
multx
is the value
x
in the alignment term
``xn
+
y
''.
It must have a value of
1
,
2
,
4
,
or
8
.
plusy
is the value
y
in the alignment term
``xn
+
y
''.
It must have a value between
0
and
7
,
inclusive.
).
This function returns a pointer to the 8-bit
option type field that starts the option on success, or
NULL
on an error.
The difference between this function and
inet6_option_append()
is that the latter copies the contents of a previously built option into
the ancillary data object while the current function returns a
pointer to the space in the data object where the option's TLV must
then be built by the caller.
cmsg
is a pointer to the
cmsghdr
structure that must have been
initialized by
inet6_option_init().
datalen
is the value of the option data length byte for this option.
This value is required as an argument to allow the function to
determine if padding must be appended at the end of the option.
inet6_option_append()
function does not need a data length argument
since the option data length must already be stored by the caller.
(The)
multx
is the value
x
in the alignment term
``xn
+
y
''.
It must have a value of
1
,
2
,
4
,
or
8
.
plusy
is the value
y
in the alignment term
``xn
+
y
''.
It must have a value between
0
and
7
,
inclusive.
0
and
*tptrp
points to
the 8-bit option type field
data length, followed by the option data
(which is followed by the 8-bit option.)
If no more options remain
to be processed, the return value is
-1
and
*tptrp
is
NULL
.
If an error occurs, the return value is
-1
and
*tptrp
is not
NULL
.
cmsg
is a pointer to
cmsghdr
structure of which
cmsg_level
equals
IPPROTO_IPV6
and
cmsg_type
equals either
IPV6_HOPOPTS
or
IPV6_DSTOPTS
.
tptrp
is a pointer to a pointer to an 8-bit byte and
*tptrp
is used
by the function to remember its place in the ancillary data object
each time the function is called.
The first time this function is
called for a given ancillary data object,
*tptrp
must be set to
NULL
.
Each time this function returns success,
*tptrp
points to the 8-bit
option type field for the next option to be processed.
)
function, except this function lets the caller
specify the option type to be searched for, instead of always
returning the next option in the ancillary data object.
cmsg
is a
pointer to
cmsghdr
structure of which
cmsg_level
equals
IPPROTO_IPV6
and
cmsg_type
equals either
IPV6_HOPOPTS
or
IPV6_DSTOPTS
.
tptrp
is a pointer to a pointer to an 8-bit byte and
*tptrp
is used
by the function to remember its place in the ancillary data object
each time the function is called.
The first time this function is
called for a given ancillary data object,
*tptrp
must be set to
NULL
.
This function starts searching for an option of the specified type
beginning after the value of
*tptrp
.
If an option of the specified
type is located, this function returns
0
and
*tptrp
points to the 8-
bit option type field for the option of the specified type.
If an
option of the specified type is not located, the return value is
-1
and
*tptrp
is
NULL
.
If an error occurs, the return value is
-1
and
*tptrp
is not
NULL
.
)
and
inet6_option_append(
)
return
0
on success or
-1
on an error.
inet6_option_alloc()
returns
NULL
on an error.
On errors,
inet6_option_next()
and
inet6_option_find(
)
return
-1
setting
*tptrp
to non
NULL
value.