Real-time Implementation of NAT and Firewall in VxWorks
This paper details the concept of Network Address Translators (NAT) and firewalls and how they can be integrated in VxWorks.
Wind River’s real-time operating system, VxWorks comes with a full-featured, BSD 4.4-compliant TCP/IP stack. It has complete routing support and is scalable, so developers can build products ranging from IP routing devices to full TCP/IP, SNMP-managed systems. Figure below shows the layered architecture of TCP/IP stack.
VxWorks allocates and initializes memory for the network stack at network initialization time. Out of this pre-allocated memory, the network stack uses the netBufLib routines to set up a memory pool. From this memory pool, the network stack gets the memory needed for data transfer.
The netBufLib routines deal with data in terms of mBlk structures, clBlk structures and clusters. The mBlk and clBlk structures provide information necessary to manage the data stored in clusters. The clusters, which come in different sizes, contain the data described by the mBlk and clBlk structures. By default, the VxWorks network stack creates six pools for clusters ranging in size from 64 bytes to 2048 bytes....
