m_pullup Kernel Service

Purpose

Adjusts an mbuf chain so that a given number of bytes is in contiguous memory in the data area of the head mbuf structure.

Syntax

#include <sys/types.h>
#include <sys/errno.h>
#include <sys/mbuf.h>

struct mbuf *m_pullup ( m, size) struct mbuf *m; int size;

Parameters

Item	Description
m	Specifies the mbuf chain to be adjusted.
size	Specifies the number of bytes to be contiguous.

Description

The m_pullup kernel service guarantees that the mbuf structure at the head of a chain has in contiguous memory within its data area at least the number of data bytes specified by the size parameter.

Execution Environment

The m_pullup kernel service can be called from either the process or interrupt environment.

Return Values

Upon successful completion, the head structure in the altered mbuf chain is returned.

A value of null is returned and the original chain is deallocated under the following circumstances:

The size of the chain is less than indicated by the size parameter.
The number indicated by the size parameter is greater than the data portion of the head-size mbuf structure.