Comtrol eCos - Manual (Page 539)

Chapter 38. TCP/IP Library Reference
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.
inet6_option_append
This function appends a Hop-by-Hop option or a Destination option into an
ancillary data object that has been initialized by inet6_option_init().
This function returns 0 if it succeeds or -1 on an error.
cmsg is a pointer to the cmsghdr structure that must have been initial-
ized 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 ini-
tializes these three fields (the type-length-value, or TLV) before call-
ing this function.
The option type must have a value from 2 to 255, inclusive. (0 and 1 are
reserved for the Pad1 and PadN options, respectively.)
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.
inet6_option_alloc
This function appends a Hop-by-Hop option or a Destination option into an
ancillary data object that has been initialized by inet6_option_init().
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 initial-
ized 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. (The
inet6_option_append() function does not need a data length argument since
the option data length must already be stored by the caller.)
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.
435