CN103997500A - Achieving method of light-weight real-time TCP/IP protocol stack - Google Patents

Abstract

The invention provides an achieving method of a light-weight real-time TCP/IP protocol stack. A standard TCP/IP protocol stack is improved through protocol stack initialization, a socket interface module processing state, a transmission layer processing stage, a network layer processing stage, a media access control layer processing stage and a network card abstraction layer processing stage, system expandability is enhanced, system real-time performance is improved, and system overhead and communication delay are lowered.

Description

A Realization Method of Lightweight Real-time TCP/IP Protocol Stack

technical field

The invention belongs to the technical field of computer network and data communication, and specifically relates to a realization method of a lightweight real-time TCP/IP protocol stack.

Background technique

The implementation of the current standard TCP/IP protocol stack is complex and cannot meet the real-time requirements of specific applications. To ensure real-time communication solutions, most of the solutions are to modify and expand the data link layer, such as the following three solutions:

1. The Ethernet Powerlink proposed by B&R Austria introduced the SCNM (Time Slot Communication Network Management) algorithm to ensure the determinism of real-time Ethernet communication.

2. EtherCAT (Ethernet for Control Automation Technology) proposed by Beckhoff, Germany, adopts the precise clock synchronization mechanism defined in the IEEE1588 standard, and introduces the seat extension of the timestamp data type.

3. my country's first fieldbus national standard with independent intellectual property rights: "EPA Communication Standard" expands the data link layer specified in the ISO/IEC8802.3 protocol, and adds the Communication Scheduling Management Entity (CSME) ).

But these schemes are only to ensure the real-time communication, and the disadvantages of complex implementation of the protocol stack have not been solved, so it is of great significance to propose a lightweight real-time implementation method for the TCP/IP protocol stack.

Contents of the invention

The invention aims at realizing a light-weight real-time TCP/IP protocol stack, which is not only simple to implement, convenient to use, reduces system overhead and communication delay, but also can meet the requirements of specific applications for real-time performance.

Technical scheme of the present invention is:

The realization method of described a kind of lightweight real-time TCP/IP protocol stack, is characterized in that: comprise the following steps:

Step 1: Initialize the protocol stack;

Step 2: Complete the setting operation of socket interface priority, real-time indicators, blocking mode, maximum sending and receiving buffer pool size; complete the creation, binding, monitoring, closing and data sending and receiving interface implementation of socket interface; receive applications through socket interface Program requests, and format conversions for incompatible application requests;

Step 3: using the TCP protocol processing module or the UDP protocol processing module to process the network data packets;

Step 4: Packing and unpacking the network data packets by using the IP protocol processing module;

Step 5: In the medium access control module, adopt the medium access mechanism based on TDMA and the token ring mode to obtain the required network real-time performance;

Step 6: Perform unified data abstraction on the network card driver at the network card driver abstraction layer; when the network card device is enabled, register with the data abstraction of the network card driver, and complete the connection between the network card driver data abstraction and the network card driver; when the data to be sent When reaching the data abstraction layer of the network card driver, the specific network card device to be used is selected through the locally maintained routing table to complete the data transmission.

A further preferred solution, the implementation method of a lightweight real-time TCP/IP protocol stack is characterized in that: initializing the protocol stack includes: completing the opening of the network card service handle, the binding and opening of the network card device; Send buffer pool and global send buffer pool; set sending and receiving thread priority; add system service table items; set local IP address and MAC address, and map to user space through memory.

Further preferred scheme, described a kind of realization method of lightweight real-time TCP/IP protocol stack, is characterized in that: when creating socket interface, the type of socket interface is set, in kernel, allocates receiving buffer pool for each socket interface , and map it to the user space; when binding the socket interface, complete the binding operation of the socket interface, port number and destination host, send an ARP request to the destination host under the kernel to obtain the destination host MAC address, the protocol stack adopts static ARP mechanism to complete address resolution.

Further preferred scheme, described a kind of implementation method of lightweight real-time TCP/IP protocol stack, is characterized in that: socket interface receives data and directly takes out data from buffer pool; Socket interface sends data, directly writes into protocol stack In the global send buffer pool allocated at initialization.

Further preferred scheme, described a kind of implementation method of lightweight real-time TCP/IP protocol stack, is characterized in that: when network adopts TCP transmission mode, socket interface transfers TCP protocol processing module to carry out packet processing, and described TCP protocol processing The module implements the state machine of the normal TCP process, splits large data packets, shields the function of IP fragmentation, and completes the flow and congestion control functions through the window size; when the network adopts UDP transmission mode, the socket interface calls the UDP protocol processing module to process data Packet processing, the UDP protocol processing module completes the UDP protocol encapsulation of the data packet, splits the large data packet, shields the IP fragmentation function, and omits the UDP checksum calculation function.

Further preferred scheme, described a kind of implementation method of lightweight real-time TCP/IP protocol stack, is characterized in that: IP protocol processing module realizes the encapsulation and unpacking of IP data packet, shields IP fragmentation, TOS field and fragmentation The slice offset field is used as a reserved field; wherein the IP protocol processing module includes an ARP protocol processing module and an ICMP protocol processing module, and the ARP protocol processing module maps the IP address to a MAC address; the ICMP protocol processing module is used for network control messages for sending and parsing.

Further preferred scheme, described a kind of implementation method of lightweight real-time TCP/IP protocol stack, is characterized in that: the medium access mechanism based on TDMA controls the data frame transmission time of each node; Adopt token ring mode to send data , any terminal station can calculate the maximum waiting time before transmitting.

Beneficial effect

Innovation point and advantage of the present invention are as follows:

1) In the medium access control module, two methods are used to solve the communication delay: the TDMA-based medium access mechanism controls the sending time of each node's data frame; The maximum waiting time can be calculated. Through these two methods, to get the required real-time network.

2) Set thread and data packet priority: In the initial stage of the protocol stack, set the priority of sending and receiving threads, so that the protocol stack can efficiently send and receive data, avoiding the preemption of other threads, affecting the rate of sending and receiving data; socket The interface module sets the priority of data packets to ensure that data with high priority can be sent first.

3) During the entire data sending and receiving process, the kernel space is mapped to the user space through the memory mapping technology, and the zero-copy technology is used to reduce the number of copies when the data packet passes through the TCP/IP protocol stack, so as to improve the real-time performance of Ethernet.

4) By tailoring and optimizing the standard TCP/IP protocol stack, the TCP/IP protocol stack is simple to implement, easy to use, and reduces system overhead and network delay. The TCP protocol processing module splits large data packets, shields the IP fragmentation function, and completes flow and congestion control through the window size; the IP protocol processing module shields IP fragmentation, and uses the TOS field and the fragmentation offset field as reserved field. The ARP protocol module maps the IP address to the MAC address, adopts the static ARP mechanism, and completes address resolution when the network is initialized.

5) Provide compatibility between different protocol stacks to provide a unified set of API interfaces to the application layer.

Description of drawings

Fig. 1 is the realization method flowchart of real-time TCP/IP protocol stack of the present invention;

Fig. 2 is a schematic diagram of the protocol organization structure of the present invention.

Detailed ways

Describe the present invention below in conjunction with specific embodiment:

The implementation method of the real-time TCP/IP protocol stack of the present invention improves the standard TCP/IP protocol stack, enhances the scalability of the system, improves the real-time performance of the system, and reduces system overhead and communication delay.

In this embodiment, at first the real-time TCP/IP protocol stack of the present invention includes IP protocol, TCP protocol, UDP protocol, ICMP protocol and ARP protocol; secondly, in order to enhance real-time performance, a media access control module is added; finally, in order to enhance Scalability and compatibility of application programs, the socket interface module and network card driver abstraction layer have been added; the media access control module is to meet the real-time requirements of network communication; the socket interface module is to meet the general network socket programming interface, compatible with large Most network applications; the network card driver abstraction layer is a unified management layer for the network card driver, and the data processed in the real-time TCP/IP protocol stack will be sent to the specific network card device through the network card driver abstraction layer. The specific steps are as follows:

Step 1: Initialize the protocol stack: complete the opening of the network card service handle, the binding and opening of the network card device; allocate the global retransmission buffer pool and the global transmission buffer pool, so that no memory allocation is required during data transmission; set the transmission, Receive thread priority, so that the protocol stack can efficiently send and receive data, thereby avoiding the preemption of other threads; add system service table items to complete the addition of system service functions; set the local IP address and MAC address, and through memory mapping to the user space; when the user sends data, the data can be directly written into the buffer pool, thereby omitting the data copy process from the user to the kernel.

Step 2: socket interface module processing stage: complete the setting operation of socket interface priority, real-time indicators, blocking mode, maximum sending and receiving buffer pool size; and perform format conversion on incompatible application requests to ensure high priority data Prioritize transmission to improve the real-time performance of Ethernet; complete socket creation, binding, monitoring, closing, and data sending and receiving interface implementation.

When creating a socket, set the type of the socket, allocate a receiving buffer pool for each socket in the kernel, and map it to the user space; when binding the socket, complete the binding operation of the socket, port number and destination host, in The kernel sends an ARP request to the destination host to obtain the MAC address of the destination host. The static ARP mechanism is used in the protocol stack to complete address resolution, so that there is no need to send the ARP request again during the data transmission process.

Sending and receiving data, through memory mapping and zero-copy technology, makes it more efficient. Among them, receiving data is directly taken out of the buffer pool, reducing the data copy process from the kernel to the user; sending data is directly written to the protocol In the global send buffer pool allocated when the stack is initialized, the data copy operation from the user to the kernel is reduced. In the specific implementation process, the application program completes network programming by calling the socket interface, and the socket interface module completes specific operations according to the socket interface function called by the application program. In this embodiment, the socket interface module only handles the requests of the TCP/IP protocol family, and does not support the requests of other protocol families, and only supports the socket transmission type with SOCK_DGREAM and SOCK_STREAM as parameters.

Step 3: transport layer processing stage: adopt TCP protocol processing module or UDP protocol processing module to process network packet; after network adopts TCP transmission mode, socket will call TCP protocol processing module to carry out data packet processing, described TCP protocol processing The module will implement the state machine of the normal TCP process, split large data packets, shield the IP fragmentation function, and complete the flow and congestion control functions through the window size; when the network adopts UDP transmission mode, the socket will call the UDP protocol The processing module performs data packet processing, and the UDP protocol processing module can complete the UDP protocol encapsulation of the data packet, split the large data packet, shield the IP fragmentation function, and omit functions such as the calculation of the UDP checksum.

Step 4: Network layer processing stage: use the IP protocol processing module to pack and unpack network data packets; the IP protocol processing module realizes the packaging and unpacking of IP data packets, shields IP fragments, and separates TOS fields and fragments shift field as a reserved field. The IP protocol processing module includes an ARP protocol processing module and an ICMP protocol processing module. The ARP protocol processing module maps an IP address to a MAC address; the ICMP protocol processing module sends and analyzes network control messages.

Step 5: Media access control layer processing stage: use two methods to solve communication delay: use TDMA-based media access mechanism to control the sending time of data frames of each node; use token ring to send data, any terminal station transmits The maximum waiting time can be calculated before. Through these two methods, to get the required real-time network.

Step 6: Network card abstraction layer processing stage: Perform unified data abstraction on the network card driver at the network card driver abstraction layer. Since there are many network cards used in network devices and the network card drivers are very different, the unification of the network card driver is standardized through the data abstraction of the driver management.

This step mainly maintains the currently available network card device. When the network card device is enabled, it registers with the data abstraction of the network card driver, and completes the connection between the network card driver data abstraction and the network card driver; when the data to be sent reaches the network card driver data abstraction layer, The specific network card device to be used is selected through the locally maintained routing table to complete the data transmission.

The implementation method of the real-time TCP/IP protocol stack of the present invention improves the standard TCP/IP protocol stack, enhances the scalability of the system, improves the real-time performance of the system, and reduces system overhead and communication delay.

Finally, it should be noted that: the above embodiments are only used to illustrate and not limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that: you can still modify the present invention Or an equivalent replacement, and any modification or partial replacement that does not depart from the spirit and scope of the present invention shall fall within the scope of the claims of the present invention.

Claims (7)

1. a kind of implementation method of lightweight real-time TCP/IP protocol stack, is characterized in that: comprise the following steps: Step 1: Initialize the protocol stack; Step 2: Complete the setting operation of socket interface priority, real-time indicators, blocking mode, maximum sending and receiving buffer pool size; complete the creation, binding, monitoring, closing and data sending and receiving interface implementation of socket interface; receive applications through socket interface Program requests, and format conversions for incompatible application requests; Step 3: using the TCP protocol processing module or the UDP protocol processing module to process the network data packets; Step 4: Packing and unpacking the network data packets by using the IP protocol processing module; Step 5: In the medium access control module, adopt the medium access mechanism based on TDMA and the token ring mode to obtain the required network real-time performance; Step 6: Perform unified data abstraction on the network card driver at the network card driver abstraction layer; when the network card device is enabled, register with the data abstraction of the network card driver, and complete the connection between the network card driver data abstraction and the network card driver; when the data to be sent When reaching the data abstraction layer of the network card driver, the specific network card device to be used is selected through the locally maintained routing table to complete the data transmission. 2. according to the realization method of a kind of lightweight real-time TCP/IP protocol stack described in claim 1, it is characterized in that: initialization protocol stack comprises: finish the opening of network card service handle, the binding of network card equipment, open operation; Retransmit buffer pool and global send buffer pool; set sending and receiving thread priority; add system service table items; set local IP address and MAC address, and map to user space through memory. 3. according to the realization method of a kind of lightweight real-time TCP/IP protocol stack described in claim 1 or 2, it is characterized in that: when creating socket interface, the type of socket interface is set, in kernel, for each socket interface distribution receiving Buffer pool, and map it to user space; when binding the socket interface, complete the binding operation of the socket interface, port number and destination host, send an ARP request to the destination host under the kernel to obtain the destination host MAC address, protocol stack The static ARP mechanism is adopted to complete address resolution. 4. according to the realization method of a kind of lightweight real-time TCP/IP protocol stack described in claim 3, it is characterized in that: socket interface receives data and directly takes out data from the buffer pool; socket interface sends data, directly writes into protocol In the global send buffer pool allocated when the stack is initialized. 5. according to the realization method of a kind of lightweight real-time TCP/IP protocol stack described in claim 4, it is characterized in that: when network adopts TCP transmission mode, socket interface transfers TCP protocol processing module to carry out packet processing, and described TCP protocol The processing module implements the state machine of the normal TCP process, splits large data packets, shields the function of IP fragmentation, and completes the flow and congestion control functions through the window size; when the network adopts UDP transmission mode, the socket interface calls the UDP protocol processing module to perform Data packet processing, the UDP protocol processing module completes the UDP protocol encapsulation of the data packet, splits the large data packet, shields the IP fragmentation function, and omits the UDP checksum calculation function. 6. according to the realization method of a kind of lightweight real-time TCP/IP protocol stack described in claim 5, it is characterized in that: IP protocol processing module realizes the packet and the unpacking of IP packet, shields IP fragmentation, TOS field and Fragment offset field is as reserved field; Wherein IP protocol processing module comprises ARP protocol processing module and ICMP protocol processing module, described ARP protocol processing module maps IP address to MAC address; Described ICMP protocol processing module is to network control report The text is sent and parsed. 7. according to the realization method of a kind of lightweight real-time TCP/IP protocol stack described in claim 6, it is characterized in that: the medium access mechanism based on TDMA controls the data frame sending moment of each node; Adopt token ring mode to send data, any terminal station can calculate the maximum waiting time before transmission.