inet6_opt_finish()--Finish Adding Options to IPv6 Extension Header

Syntax

  #include <netinet/in.h>

  int inet6_opt_finish(void *extension_buffer,
                       socklen_t extension_length,
                       int offset)

  Service Program Name: QSOSRV1IP6

  Default Public Authority: *USE

  Threadsafe: Yes

The inet6_opt_finish() function returns the length of the IPv6 extension header, including padding, to make the extension header 8-byte aligned. If extension_buffer is not NULL, it will add the padding option, Pad1 or PadN of required length, for alignment.

Parameters

extension_buffer: (Input/Output) Pointer to the buffer that contains the extension header.
extension_length: (Input) Total number of bytes in the buffer pointed to by extension_buffer.
offset: (Input) Length of the existing extension header.
The value returned from inet6_opt_init() or a previous call to inet6_opt_append() can be used here.

Authorities

No authorization is required.

Return Value

inet6_opt_finish() returns an integer. Possible values are:

-1 (unsuccessful)
n (successful, where n is the updated total number of bytes in the extension header, including padding, to make the extension header 8-byte aligned

Error Conditions

When inet6_opt_finish() fails, errno can be set to one of the following:

[EFAULT]

Bad address.

The system detected an address that was not valid while attempting to access the buffer pointed to by the extension_buffer parameter.

[EINVAL]

Parameter not valid.

This error code indicates one of the following:

The extension_length field contains a value that is not positive.
The offset field contains a value that is not positive.
The necessary padding will not fit in the extension header.

Usage Notes

inet6_opt_finish() is normally called twice when building an options header.

The first call is used to calculate the final total length of the extension header, as shown in this example:

     int currentlen, extlen;
     void *extbuf;
     void *databufp;
     currentlen = inet6_opt_init(NULL, 0);
     currentlen = inet6_opt_append(NULL, 0, currentlen, OPT_X, 12, 8, NULL);
     currentlen = inet6_opt_finish(NULL, 0, currentlen);

After the total length is calculated and the extension header is built, the required padding is added as follows:

     extlen = currentlen;
     extbuf = malloc(extlen);
     currentlen = inet6_opt_init(extbuf, extlen);
     currentlen = inet6_opt_append(extbuf, extlen, currentlen, OPT_X, 12, 8, &databufp);
     currentlen = inet6_opt_finish(extbuf, extlen, currentlen);

Related Information

inet6_opt_append()--Append New Option to IPv6 Extension Header
inet6_opt_find()--Extract Option of Specified Type from IPv6 Extension Header
inet6_opt_get_val()--Retrieve Data Item from an IPv6 Option
inet6_opt_init()--Get Length of IPv6 Extension Header
inet6_opt_next()--Extract the Next Option from the IPv6 Extension Header
inet6_opt_set_val()--Insert Data Items into IPv6 Option

API introduced: V6R1

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