INET6_OPTION_SPACE(3) | NetBSD Library Functions Manual | INET6_OPTION_SPACE(3) |
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);
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]).
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.
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. (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.
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. (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.
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.
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.
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.
S. Deering and R. Hinden, Internet Protocol, Version 6 (IPv6) Specification, RFC 2460, December 1998.
December 10, 1999 | NetBSD 5.99 |