LwIP协议栈移植说明
LWIP 的手动移植可以说非常麻烦，需要我们自己实现好多文件。最主要的是，需要实现的文件还没有个统一的说明，必须要东拼西凑！ LWIP 的移植由两部分组成，分别为 LWIP 协议栈和 contrib 应用实例 。目前，这两部分是由两个独立的版本库控制，并且由不同的人来负责的（好消息是从2.1.x之后，这俩要合并了）！我们在移植使用 LWIP 时，需要从官网分别下载这两部分的源代码！
其中，contrib 中是一些和平台移植相关的代码以及一些使用 LWIP 实现的应用，在移植时非常有用；LWIP 则是 TCP/IP 协议栈的核心源码！综上所述，LwIP 的移植主要分为以下这些部分：
- 运行环境的搭建： 有其需要注意的是，针对嵌入式的移植时，无论哪种模式，都需要首先需要处理硬件资源，例如在 STM32Fx 系列芯片移植时，需要提供文件：stm32f4x7_eth_bsp.c/h，已处理使用的硬件资源。
- 源代码文件的整理： 主要就是东拼西凑LWIP需要的文件（LWIP需要用户实现很多文件）
- LwIP 的基本配置： 根据自己的需要来配置功能
- 与 CPU 或编译器相关源文件： LWIP 需要用户的文件之一
- 与操作系统的接口源文件（仅在系统模式下使用）： LWIP 需要用户的文件之一
- 与底层网卡驱动的接口源文件： LWIP 需要用户的文件之一
- 初始化 LwIP：然后正常使用各功能即可。
第一步：LwIP的基本配置
LwIP 的配置主要通过文件 lwipopts.h 实现，移植时需要根据自己的需要，进行相关的配置，然后在自己的项目中添加该文件。一个在 STM32F4 芯片移植是的配置文件如下：
/**
******************************************************************************
* @file lwipopts.h
* @author MCD Application Team
* @version V1.1.0
* @date 31-July-2013
* @brief lwIP Options Configuration.
* This file is based on Utilities\lwip_v1.4.1\src\include\lwip\opt.h
* and contains the lwIP configuration for the STM32F4x7 demonstration.
******************************************************************************
* @attention
*
* © COPYRIGHT 2013 STMicroelectronics
*
* Licensed under MCD-ST Liberty SW License Agreement V2, (the "License");
* You may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.st.com/software_license_agreement_liberty_v2
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
******************************************************************************
*/
#ifndef __LWIPOPTS_H__
#define __LWIPOPTS_H__
/**
* SYS_LIGHTWEIGHT_PROT==1: if you want inter-task protection for certain
* critical regions during buffer allocation, deallocation and memory
* allocation and deallocation.
*/
#define SYS_LIGHTWEIGHT_PROT 0
#define ETHARP_TRUST_IP_MAC 0
#define IP_REASSEMBLY 0
#define IP_FRAG 0
#define ARP_QUEUEING 0
/**
* NO_SYS==1: Provides VERY minimal functionality. Otherwise,
* use lwIP facilities.
*/
#define NO_SYS 0
/* ---------- Memory options ---------- */
/* MEM_ALIGNMENT: should be set to the alignment of the CPU for which
lwIP is compiled. 4 byte alignment -> define MEM_ALIGNMENT to 4, 2
byte alignment -> define MEM_ALIGNMENT to 2. */
#define MEM_ALIGNMENT 4
/* MEM_SIZE: the size of the heap memory. If the application will send
a lot of data that needs to be copied, this should be set high. */
#define MEM_SIZE (5*1024)
/* MEMP_NUM_PBUF: the number of memp struct pbufs. If the application
sends a lot of data out of ROM (or other static memory), this
should be set high. */
#define MEMP_NUM_PBUF 100
/* MEMP_NUM_UDP_PCB: the number of UDP protocol control blocks. One
per active UDP "connection". */
#define MEMP_NUM_UDP_PCB 6
/* MEMP_NUM_TCP_PCB: the number of simulatenously active TCP
connections. */
#define MEMP_NUM_TCP_PCB 10
/* MEMP_NUM_TCP_PCB_LISTEN: the number of listening TCP
connections. */
#define MEMP_NUM_TCP_PCB_LISTEN 5
/* MEMP_NUM_TCP_SEG: the number of simultaneously queued TCP
segments. */
#define MEMP_NUM_TCP_SEG 20
/* MEMP_NUM_SYS_TIMEOUT: the number of simulateously active
timeouts. */
#define MEMP_NUM_SYS_TIMEOUT 10
/* ---------- Pbuf options ---------- */
/* PBUF_POOL_SIZE: the number of buffers in the pbuf pool. */
#define PBUF_POOL_SIZE 20
/* PBUF_POOL_BUFSIZE: the size of each pbuf in the pbuf pool. */
#define PBUF_POOL_BUFSIZE 500
/* ---------- TCP options ---------- */
#define LWIP_TCP 1
#define TCP_TTL 255
/* Controls if TCP should queue segments that arrive out of
order. Define to 0 if your device is low on memory. */
#define TCP_QUEUE_OOSEQ 0
/* TCP Maximum segment size. */
#define TCP_MSS (1500 - 40) /* TCP_MSS = (Ethernet MTU - IP header size - TCP header size) */
/* TCP sender buffer space (bytes). */
#define TCP_SND_BUF (5*TCP_MSS)
/* TCP_SND_QUEUELEN: TCP sender buffer space (pbufs). This must be at least
as much as (2 * TCP_SND_BUF/TCP_MSS) for things to work. */
#define TCP_SND_QUEUELEN (4* TCP_SND_BUF/TCP_MSS)
/* TCP receive window. */
#define TCP_WND (2*TCP_MSS)
/* ---------- ICMP options ---------- */
#define LWIP_ICMP 1
/* ---------- DHCP options ---------- */
/* Define LWIP_DHCP to 1 if you want DHCP configuration of
interfaces. DHCP is not implemented in lwIP 0.5.1, however, so
turning this on does currently not work. */
#define LWIP_DHCP 1
/* ---------- UDP options ---------- */
#define LWIP_UDP 1
#define UDP_TTL 255
/* ---------- Statistics options ---------- */
#define LWIP_STATS 0
#define LWIP_PROVIDE_ERRNO 1
/* ---------- link callback options ---------- */
/* LWIP_NETIF_LINK_CALLBACK==1: Support a callback function from an interface
* whenever the link changes (i.e., link down)
*/
#define LWIP_NETIF_LINK_CALLBACK 1
/*
--------------------------------------
---------- Checksum options ----------
--------------------------------------
*/
/*
The STM32F4x7 allows computing and verifying the IP, UDP, TCP and ICMP checksums by hardware:
- To use this feature let the following define uncommented.
- To disable it and process by CPU comment the the checksum.
*/
/*
注意：校验和可以选择 由硬件来处理。如果硬件支持该功能，则加载其配置文件（其中需要定义 CHECKSUM_BY_HARDWARE ）
*/
#include "stm32f4x7_eth_conf.h"
#ifdef CHECKSUM_BY_HARDWARE /* 如果芯片的配置中开启了硬件处理校验和，则对LwIP进行配置 */
/* CHECKSUM_GEN_IP==0: Generate checksums by hardware for outgoing IP packets.*/
#define CHECKSUM_GEN_IP 0
/* CHECKSUM_GEN_UDP==0: Generate checksums by hardware for outgoing UDP packets.*/
#define CHECKSUM_GEN_UDP 0
/* CHECKSUM_GEN_TCP==0: Generate checksums by hardware for outgoing TCP packets.*/
#define CHECKSUM_GEN_TCP 0
/* CHECKSUM_CHECK_IP==0: Check checksums by hardware for incoming IP packets.*/
#define CHECKSUM_CHECK_IP 0
/* CHECKSUM_CHECK_UDP==0: Check checksums by hardware for incoming UDP packets.*/
#define CHECKSUM_CHECK_UDP 0
/* CHECKSUM_CHECK_TCP==0: Check checksums by hardware for incoming TCP packets.*/
#define CHECKSUM_CHECK_TCP 0
/* CHECKSUM_CHECK_ICMP==0: Check checksums by hardware for incoming ICMP packets.*/
#define CHECKSUM_GEN_ICMP 0
#else
/* CHECKSUM_GEN_IP==1: Generate checksums in software for outgoing IP packets.*/
#define CHECKSUM_GEN_IP 1
/* CHECKSUM_GEN_UDP==1: Generate checksums in software for outgoing UDP packets.*/
#define CHECKSUM_GEN_UDP 1
/* CHECKSUM_GEN_TCP==1: Generate checksums in software for outgoing TCP packets.*/
#define CHECKSUM_GEN_TCP 1
/* CHECKSUM_CHECK_IP==1: Check checksums in software for incoming IP packets.*/
#define CHECKSUM_CHECK_IP 1
/* CHECKSUM_CHECK_UDP==1: Check checksums in software for incoming UDP packets.*/
#define CHECKSUM_CHECK_UDP 1
/* CHECKSUM_CHECK_TCP==1: Check checksums in software for incoming TCP packets.*/
#define CHECKSUM_CHECK_TCP 1
/* CHECKSUM_CHECK_ICMP==1: Check checksums by hardware for incoming ICMP packets.*/
#define CHECKSUM_GEN_ICMP 1
#endif
/*
----------------------------------------------
---------- Sequential layer options ----------
----------------------------------------------
*/
/**
* LWIP_NETCONN==1: Enable Netconn API (require to use api_lib.c)
*/
#define LWIP_NETCONN 1
/*
------------------------------------
---------- Socket options ----------
------------------------------------
*/
/**
* LWIP_SOCKET==1: Enable Socket API (require to use sockets.c)
*/
#define LWIP_SOCKET 0
/*
-----------------------------------
---------- DEBUG options ----------
-----------------------------------
*/
#define LWIP_DEBUG 0
/*
---------------------------------
---------- OS options ----------
---------------------------------
*/
#define TCPIP_THREAD_NAME "TCP/IP"
#define TCPIP_THREAD_STACKSIZE 1000
#define TCPIP_MBOX_SIZE 5
#define DEFAULT_UDP_RECVMBOX_SIZE 2000
#define DEFAULT_TCP_RECVMBOX_SIZE 2000
#define DEFAULT_ACCEPTMBOX_SIZE 2000
#define DEFAULT_THREAD_STACKSIZE 500
#define TCPIP_THREAD_PRIO (configMAX_PRIORITIES - 2)
#define LWIP_COMPAT_MUTEX 1
#define LWIP_COMPAT_MUTEX_ALLOWED 1
#endif /* __LWIPOPTS_H__ */
/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/
第五步：初始化LwIP
在处理完以上需要移植的个文件后，接下来就可以在自己的项目中建立初始化函数来对LwIP进行初始化了，以下为使用系统时的一个初始化例子。
void LwIP_Init(void)
{
ip_addr_t ipaddr;
ip_addr_t netmask;
ip_addr_t gw;
#ifdef USE_DHCP
uint8_t iptab[4] = {0};
uint8_t iptxt[20];
#endif
/* 创建tcp_ip线程，初始化LwIP的各部分 */
tcpip_init(NULL, NULL);
/* 设置IP地址等信息 */
#ifdef USE_DHCP
ipaddr.addr = 0;
netmask.addr = 0;
gw.addr = 0;
#else
IP4_ADDR(&ipaddr, IP_ADDR0, IP_ADDR1, IP_ADDR2, IP_ADDR3);
IP4_ADDR(&netmask, NETMASK_ADDR0, NETMASK_ADDR1, NETMASK_ADDR2, NETMASK_ADDR3);
IP4_ADDR(&gw, GW_ADDR0, GW_ADDR1, GW_ADDR2, GW_ADDR3);
#endif
/* 以下就是添加网络接口了 */
/* - netif_add(struct netif *netif, struct ip_addr *ipaddr,
struct ip_addr *netmask, struct ip_addr *gw,
void *state, err_t (* init)(struct netif *netif),
err_t (* input)(struct pbuf *p, struct netif *netif))
Adds your network interface to the netif_list. Allocate a struct
netif and pass a pointer to this structure as the first argument.
Give pointers to cleared ip_addr structures when using DHCP,
or fill them with sane numbers otherwise. The state pointer may be NULL.
The init function pointer must point to a initialization function for
your ethernet netif interface. The following code illustrates it's use.*/
netif_add(&xnetif, &ipaddr, &netmask, &gw, NULL, ðernetif_init, &tcpip_input);
/* Registers the default network interface.*/
netif_set_default(&xnetif);
if (EthStatus == (ETH_INIT_FLAG | ETH_LINK_FLAG))
{
/* Set Ethernet link flag */
xnetif.flags |= NETIF_FLAG_LINK_UP;
/* When the netif is fully configured this function must be called.*/
netif_set_up(&xnetif);
#ifdef USE_DHCP
DHCP_state = DHCP_START;
#endif /* USE_DHCP */
}
else
{
/* When the netif link is down this function must be called.*/
netif_set_down(&xnetif);
#ifdef USE_DHCP
DHCP_state = DHCP_LINK_DOWN;
#endif /* USE_DHCP */
}
/* Set the link callback function, this function is called on change of link status*/
netif_set_link_callback(&xnetif, ETH_link_callback);
}
首先看以下tcpip_init函数，该函数负责建立tcp_ip线程，并且初始化LwIP的各部分功能，具体看以下图片。
设置IP地址这块没啥可说的，接下来就是添加网络接口，具体参见 LwIP 之 ethernetif.c。