Kernel Module Implementation of IPv4/IPv6 Translation Mechanisms for IPv4-oriented Applications

摘要

Only IPv6 addresses are currently being assigned to hosts because IPv4 addresses will be exhausted in the near future. However, almost all network applications still lack support for IPv6 communication. Therefore, users will suffer from the unavailability of IPv6 oriented applications. Bump-In-the-Stack (BIS) mechanisms can allow hosts to communicate with other hosts through IPv6 networks using existing IPv4-oriented applications. These mechanisms will be required to achieve a smooth transition from IPv4 to IPv6 networks in the near future. However, detailed implementation schemes are dependent upon the operating system. Additionally, since conventional network address translation mechanisms usually perform in a user space, throughput performance degrades as a result of the memory copy between kernel space and user space. Recently, Session Initiation Protocol (SIP) has been used to achieve multimedia communication. However, BIS does not support address translation mechanisms for embedded IP addresses in packet payload, such as in SIP messages. This paper presents a specially developed Linux kernel module for IPv4/IPv6 address translation supporting SIP messages. The kernel module can hook all packets in a Linux network socket using Linux netfilter mechanisms. The advantages are high throughput, as the memory copy is limited to a socket buffer in a Linux network stack, and flexible installation to an original Linux kernel. Thus, the kernel module allows users to achieve IPv4/IPv6 address translation by installing it in a generic Linux kernel, without modifying the kernel source.