TCPIP协议栈lwip的移植

TCP/IP协议栈lwip的移植

新建几个头文件

Include/lwipopts.h

Include/arch/cc.h

Include/arch/perf.h

Include/arch/sys_arch.h

除头文件外还需要添加一个C文件：sys_arch.c。说明在doc/sys_arch.txt中。

修改netif/Ethernetif.c。

结构对齐的几个宏

对于一个结构下载下来的LWIP的通用定义如下：

PACK_STRUCT_BEGIN

struct icmp_echo_hdr {

PACK_STRUCT_FIELD(u8_t type);

PACK_STRUCT_FIELD(u8_t code);

PACK_STRUCT_FIELD(u16_t chksum);

PACK_STRUCT_FIELD(u16_t id);

PACK_STRUCT_FIELD(u16_t seqno);

} PACK_STRUCT_STRUCT;

PACK_STRUCT_EN

#define PACK_STRUCT_FIELD(x)

这个宏是为了字节序的转换，由于是用的小端，就不用转换了直接定义为

#define PACK_STRUCT_FIELD(x) x

#define PACK_STRUCT_STRUCT

#define PACK_STRUCT_BEGIN

#define PACK_STRUCT_END

以上三个宏都是为了做结构体对齐用：

对于gcc的编译器在结构体后跟个关键字就ok

struct ip_hdr {

} ;__attribute__ ((__packed__))

因此可以定义为

#define PACK_STRUCT_STRUCT __attribute__ ((__packed__))

#define PACK_STRUCT_BEGIN

#define PACK_STRUCT_END

对于vc的编译器就郁闷了,vc做结构体对齐是这样做的

#pragma pack(1) //结构体按照1字节对齐

struct ip_hdr {

} ;

#pragma pack() //结构体按照编译器默认值对齐

但是VC的编译器不允许将预处理做为宏，也就是不允许这种宏替代#define PACK_STRUCT_BEGIN #pragma pack(1)

所以想靠宏替换来完成字节对齐是不行了，于是就动了大工夫做了如下处理#ifdef WIN32

#define PACK_STRUCT_STRUCT

#define PACK_STRUCT_BEGIN

#define PACK_STRUCT_END

#else

#define PACK_STRUCT_STRUCT __attribute__ ((__packed__))

#define PACK_STRUCT_BEGIN

#define PACK_STRUCT_END

endif

PACK_STRUCT_BEGIN

#ifdef WIN32

#pragma pack(1)

#endif

struct icmp_echo_hdr {

PACK_STRUCT_FIELD(u8_t type);

PACK_STRUCT_FIELD(u8_t code);

PACK_STRUCT_FIELD(u16_t chksum);

PACK_STRUCT_FIELD(u16_t id);

PACK_STRUCT_FIELD(u16_t seqno);

} PACK_STRUCT_STRUCT;

#ifdef WIN32

#pragma pack()

#endif

PACK_STRUCT_END

这样一改在VC下和GCC都可以了，不过每个结构上都要修改一下，这个是黑郁闷黑郁闷啊

“轻量级”保护

"lightweight" synchronization mechanisms -

SYS_ARCH_DECL_PROTECT(x) - declare a protection state variable.

SYS_ARCH_PROTECT(x) - enterprotection mode.

SYS_ARCH_UNPROTECT(x) - leaveprotection mode.

这三个宏定义一个快速的“保护”和“解除保护”操作。例如进入保护可以是屏蔽中断或

使用一个信号量或mutex。注意：进入保护后还允许再次进入保护，旧的保护标志通

过lev返回，退出保护时再恢复。

如果没有定义这三个宏，Sys.h中有一段代码进行了判断。

#ifndef SYS_ARCH_PROTECT

如果没有定义SYS_ARCH_PROTECT，那么可以在lwipopts.h中定义宏SYS_LIGHTWEIGHT_PROT，并在sys_arch.c中定义函数sys_arch_protect()和sys_arch_unprotect(lev)

#if SYS_LIGHTWEIGHT_PROT

#define SYS_ARCH_DECL_PROTECT(lev) sys_prot_t lev

/** SYS_ARCH_PROTECT

* Perform a "fast" protect. This could be implemented by

* disabling interrupts for an embedded system or by using a semaphore or

* mutex. The implementation should allow calling SYS_ARCH_PROTECT when * already protected. The old protection level is returned in the variable

* "lev". This macro will default to calling the sys_arch_protect() function

* which should be implemented in sys_arch.c. If a particular port needs a

* different implementation, then this macro may be defined in sys_arch.h

*/

#define SYS_ARCH_PROTECT(lev) lev = sys_arch_protect()

/** SYS_ARCH_UNPROTECT

* Perform a "fast" set of the protection level to "lev". This could be

* implemented by setting the interrupt level to "lev" within the MACRO or by

* using a semaphore or mutex. This macro will default to calling the

* sys_arch_unprotect() function which should be implemented in

* sys_arch.c. If a particular port needs a different implementation, then

* this macro may be defined in sys_arch.h

*/

#define SYS_ARCH_UNPROTECT(lev) sys_arch_unprotect(lev)

sys_prot_t sys_arch_protect(void);

void sys_arch_unprotect(sys_prot_t pval);

#else

#define SYS_ARCH_DECL_PROTECT(lev)

#define SYS_ARCH_PROTECT(lev)

#define SYS_ARCH_UNPROTECT(lev)

#endif /* SYS_LIGHTWEIGHT_PROT */

#endif /* SYS_ARCH_PROTECT */

LWIP_COMPAT_MUTEX

定义此宏表示用信号量来代替mutex。

Init.c

不定义NO_SYS和“#define NO_SYS0”的效果是一样的。

下面这些宏对代码有影响：LWIP_SOCKET

LWIP_ARP

LWIP_RAW

LWIP_UDP

LWIP_TCP

LWIP_SNMP

LWIP_AUTOIP

LWIP_IGMP

LWIP_DNS

LWIP_TIMERS

void

lwip_init(void)

{

/* Sanity check user-configurable values */ lwip_sanity_check();

/* Modules initialization */

stats_init();

#if !NO_SYS

sys_init();

#endif /* !NO_SYS */

mem_init();

memp_init();

pbuf_init();

netif_init();

#if LWIP_SOCKET

lwip_socket_init();

#endif /* LWIP_SOCKET */

ip_init();

#if LWIP_ARP

etharp_init();

#endif /* LWIP_ARP */

#if LWIP_RAW

raw_init();

#endif /* LWIP_RAW */

#if LWIP_UDP

udp_init();

#endif /* LWIP_UDP */

#if LWIP_TCP

tcp_init();

#endif /* LWIP_TCP */

#if LWIP_SNMP

snmp_init();

#endif /* LWIP_SNMP */

#if LWIP_AUTOIP

autoip_init();

#endif /* LWIP_AUTOIP */

#if LWIP_IGMP

igmp_init();

#endif /* LWIP_IGMP */

#if LWIP_DNS

dns_init();

#endif /* LWIP_DNS */

#if LWIP_TIMERS

sys_timeouts_init();

#endif /* LWIP_TIMERS */

}

netif_add函数

它添加一个网络接口到lwip，一个网卡应该是一个网络接口。本地回环也是一个网络接口，它已经在tcpip_init中的lwip_init调用netif_init被添加。

/**

* Add a network interface to the list of lwIP netifs.

*

* @param netif a pre-allocated netif structure

* @param ipaddr IP address for the new netif

* @param netmask network mask for the new netif

* @param gw default gateway IP address for the new netif

* @param state opaque data passed to the new netif

* @param init callback function that initializes the interface

* @param input callback function that is called to pass

* ingress packets up in the protocol layer stack.

*

* @return netif, or NULL if failed.

*/

struct netif *

netif_add(struct netif *netif, ip_addr_t *ipaddr, ip_addr_t *netmask,

ip_addr_t *gw, void *state, netif_init_fn init, netif_input_fn input)

Struct net_if

在初始化用netif_add添加到lwip中。

/** Generic data structure used for all lwIP network interfaces.

* The following fields should be filled in by the initialization

* function for the device driver: hwaddr_len, hwaddr[], mtu, flags */

struct netif {

/** pointer to next in linked list */

struct netif *next;

/** IP address configuration in network byte order */

ip_addr_t ip_addr;

ip_addr_t netmask;

ip_addr_t gw;

/** This function is called by the network device driver

* to pass a packet up the TCP/IP stack. */

netif_input_fn input; // 网卡数据接收函数，自定义设置

/** This function is called by the IP module when it wants

* to send a packet on the interface. This function typically

* first resolves the hardware address, then sends the packet. */

netif_output_fn output; //发送无连接的数据包，如广播包，多播包，最终还

是调用下面的linkoutput函数。固定设置为etharp_output。

/** This function is called by the ARP module when it wants

* to send a packet on the interface. This function outputs

* the pbuf as-is on the link medium. */

netif_linkoutput_fn linkoutput; //发送有连接的数据包，已经包含MAC，类型等数据。

#if LWIP_NETIF_STATUS_CALLBACK

/** This function is called when the netif state is set to up or down

*/

netif_status_callback_fn status_callback;

#endif /* LWIP_NETIF_STATUS_CALLBACK */

#if LWIP_NETIF_LINK_CALLBACK

/** This function is called when the netif link is set to up or down

*/

netif_status_callback_fn link_callback;

#endif /* LWIP_NETIF_LINK_CALLBACK */

/** This field can be set by the device driver and could point

* to state information for the device. */

void *state; //一般设置为网卡的私有数据，如netif->state = ethernetif;

#if LWIP_DHCP

/** the DHCP client state information for this netif */

struct dhcp *dhcp;

#endif /* LWIP_DHCP */

#if LWIP_AUTOIP

/** the AutoIP client state information for this netif */

struct autoip *autoip;

#endif

#if LWIP_NETIF_HOSTNAME

/* the hostname for this netif, NULL is a valid value */

char* hostname;

#endif /* LWIP_NETIF_HOSTNAME */

/** maximum transfer unit (in bytes) */

u16_t mtu;

/** number of bytes used in hwaddr */

u8_t hwaddr_len;

/** link level hardware address of this interface */

u8_t hwaddr[NETIF_MAX_HWADDR_LEN];

/** flags (see NETIF_FLAG_ above) */

u8_t flags;

/** descriptive abbreviation */

char name[2];

/** number of this interface */

u8_t num;

#if LWIP_SNMP

/** link type (from "snmp_ifType" enum from snmp.h) */

u8_t link_type;

/** (estimate) link speed */

u32_t link_speed;

/** timestamp at last change made (up/down) */

u32_t ts;

/** counters */

u32_t ifinoctets;

u32_t ifinucastpkts;

u32_t ifinnucastpkts;

u32_t ifindiscards;

u32_t ifoutoctets;

u32_t ifoutucastpkts;

u32_t ifoutnucastpkts;

u32_t ifoutdiscards;

#endif /* LWIP_SNMP */

#if LWIP_IGMP

/** This function could be called to add or delete a entry in the multicast filter table of the ethernet MAC.*/

netif_igmp_mac_filter_fn igmp_mac_filter;

#endif /* LWIP_IGMP */

#if LWIP_NETIF_HWADDRHINT

u8_t *addr_hint;

#endif /* LWIP_NETIF_HWADDRHINT */

#if ENABLE_LOOPBACK

/* List of packets to be queued for ourselves. */

struct pbuf *loop_first;

struct pbuf *loop_last;

#if LWIP_LOOPBACK_MAX_PBUFS

u16_t loop_cnt_current;

#endif /* LWIP_LOOPBACK_MAX_PBUFS */

#endif /* ENABLE_LOOPBACK */

};

struct pbuf

一个网络包可能由多个pbuf组成，字段tot_len指定这个网络包的大小，字段len 是当前pbuf包含数据的大小。

判断一个网络包的最后一个包不能以next字段等于空来判断，它可能不为空，下一个pbuf为下一个网络包的内容。应该计算tot_len来判断一个包的结束。

struct pbuf {

/** next pbuf in singly linked pbuf chain */

struct pbuf *next; //下一个pbuf

/** pointer to the actual data in the buffer */

void *payload; // 当前结构数据内容

/**

* total length of this buffer and all next buffers in chain

* belonging to the same packet.

*

* For non-queue packet chains this is the invariant:

* p->tot_len == p->len + (p->next? p->next->tot_len: 0)

*/

u16_t tot_len;

/** length of this buffer */

u16_t len;

/** pbuf_type as u8_t instead of enum to save space */

u8_t /*pbuf_type*/ type;

/** misc flags */

u8_t flags;

/**

* the reference count always equals the number of pointers

* that refer to this pbuf. This can be pointers from an application,

* the stack itself, or pbuf->next pointers from a chain.

*/

u16_t ref;

};

Ethernetif.c

它是你要移植的网卡驱动程序与lwip连接的文件。源代码提供了一个模板。

struct ethernetif结构

它是网卡私有数据结构

struct ethernetif {

struct eth_addr *ethaddr;

/* Add whatever per-interface state that is needed here. */在这里添加自定义的数据

};

ethernetif_input

网卡有数据时应该调用这个函数。过程大致如下：网卡读任务中断处理

(1)信号量pend(等待数据到来中断)

(2)pend成功，调用ethernetif_input

(3)回到步骤1. 如果有中断表明数据包到达，给“网卡读任务”发送信号量。

ethernetif_input做的工作有：

（1）调用low_level_input读取数据包

（2）判断数据包的以太网类型并调用netif->input。netif->input是在协议栈初始化添加的。如netif_add(mLocalNetif, &ipaddr, &netmask, &gw, NULL,ethernetif_init, tcpip_input)，那么它是tcpip_input，tcpip_input做的工作发送消息给tcpip主线线程，它把数据包交给上层处理。

/**

* This function should be called when a packet is ready to be read

* from the interface. It uses the function low_level_input() that

* should handle the actual reception of bytes from the network

* interface. Then the type of the received packet is determined and

* the appropriate input function is called.

*

* @param netif the lwip network interface structure for this ethernetif

*/

static void

ethernetif_input(struct netif *netif)

{

struct ethernetif *ethernetif;

struct eth_hdr *ethhdr;

struct pbuf *p;

ethernetif = netif->state;

/* move received packet into a new pbuf */

p = low_level_input(netif);

/* no packet could be read, silently ignore this */

if (p == NULL) return;

/* points to packet payload, which starts with an Ethernet header */

ethhdr = p->payload;

switch (htons(ethhdr->type)) {

/* IP or ARP packet? */

case ETHTYPE_IP:

case ETHTYPE_ARP:

#if PPPOE_SUPPORT

/* PPPoE packet? */

case ETHTYPE_PPPOEDISC:

case ETHTYPE_PPPOE:

#endif /* PPPOE_SUPPORT */

/* full packet send to tcpip_thread to process */

if (netif->input(p, netif)!=ERR_OK)

{ LWIP_DEBUGF(NETIF_DEBUG, ("ethernetif_input: IP input error\n"));

pbuf_free(p);

p = NULL;

}

break;

default:

pbuf_free(p);

p = NULL;

break;

}

ethernetif_init

在初始化协议栈时，netif_add(mLocalNetif,&ipaddr, &netmask, &gw, NULL, ethernetif_init, tcpip_input)。

ethernetif_init做的工作：

（1）初始化struct ethernetif

（2）初始化struct net_if

（3）调用硬件初始化low_level_init(netif);

/**

* Should be called at the beginning of the program to set up the

* network interface. It calls the function low_level_init() to do the

* actual setup of the hardware.

*

* This function should be passed as a parameter to netif_add().

* @param netif the lwip network interface structure for this ethernetif

* @return ERR_OK if the loopif is initialized

* ERR_MEM if private data couldn't be allocated

* any other err_t on error

*/

err_t

ethernetif_init(struct netif *netif)

{

struct ethernetif *ethernetif;

LWIP_ASSERT("netif != NULL", (netif != NULL));

ethernetif = mem_malloc(sizeof(struct ethernetif));

if (ethernetif == NULL) {

LWIP_DEBUGF(NETIF_DEBUG, ("ethernetif_init: out of memory\n"));

return ERR_MEM;

}

#if LWIP_NETIF_HOSTNAME

/* Initialize interface hostname */

netif->hostname = "lwip";

#endif /* LWIP_NETIF_HOSTNAME */

/*

* Initialize the snmp variables and counters inside the struct netif.

* The last argument should be replaced with your link speed, in units

* of bits per second.

*/

NETIF_INIT_SNMP(netif, snmp_ifType_ethernet_csmacd,

LINK_SPEED_OF_YOUR_NETIF_IN_BPS);

netif->state = ethernetif;

netif->name[0] = IFNAME0;

netif->name[1] = IFNAME1;

/* We directly use etharp_output() here to save a function call.

* You can instead declare your own function an call etharp_output()

* from it if you have to do some checks before sending (e.g. if link

* is available...) */

netif->output = etharp_output;

netif->linkoutput = low_level_output;

ethernetif->ethaddr = (struct eth_addr *)&(netif->hwaddr[0]);

/* initialize the hardware */

low_level_init(netif);

return ERR_OK;

}

low_level_init

它是网卡硬件初始化的代码。它被ethernetif_init调用。

/**

* In this function, the hardware should be initialized.

* Called from ethernetif_init().

*

* @param netif the already initialized lwip network interface structure * for this ethernetif

*/

static void

low_level_init(struct netif *netif)

{

struct ethernetif *ethernetif = netif->state;

/* set MAC hardware address length */

netif->hwaddr_len = ETHARP_HWADDR_LEN;

/* set MAC hardware address */

netif->hwaddr[0] = 0x00;

netif->hwaddr[1] = 0x50;

netif->hwaddr[2] = 0x50;

netif->hwaddr[3] = 0x50;

netif->hwaddr[4] = 0x50;

netif->hwaddr[5] = 0x01;

/* maximum transfer unit */

netif->mtu = 1500;

/* device capabilities */

/* don't set NETIF_FLAG_ETHARP if this device is not an ethernet one */ netif->flags = NETIF_FLAG_BROADCAST | NETIF_FLAG_ETHARP | NETIF_FLAG_LINK_UP;

/* Do whatever else is needed to initialize interface. */

}

low_level_output

它是实现网卡发送数据的函数。

它发送链表structpbuf中的所有数据。

在代码：

netif->linkoutput = low_level_output;

中，low_level_output被赋于netif->linkoutput。

/**

* This function should do the actual transmission of the packet. The packet is * contained in the pbuf that is passed to the function. This pbuf

* might be chained.

*

* @param netif the lwip network interface structure for this ethernetif

* @param p the MAC packet to send (e.g. IP packet including MAC addresses and type)

* @return ERR_OK if the packet could be sent

* an err_t value if the packet couldn't be sent

*

* @note Returning ERR_MEM here if a DMA queue of your MAC is full can lead to

* strange results. You might consider waiting for space in the DMA queue * to become availale since the stack doesn't retry to send a packet

* dropped because of memory failure (except for the TCP timers).

*/

static err_t

low_level_output(struct netif *netif, struct pbuf *p)

{

struct ethernetif *ethernetif = netif->state;

struct pbuf *q;

initiate transfer();

#if ETH_PAD_SIZE

pbuf_header(p, -ETH_PAD_SIZE); /* drop the padding word */

#endif

for(q = p; q != NULL; q = q->next) {

/* Send the data from the pbuf to the interface, one pbuf at a

time. The size of the data in each pbuf is kept in the ->len

variable. */

send data from(q->payload, q->len);

}

signal that packet should be sent();

#if ETH_PAD_SIZE

pbuf_header(p, ETH_PAD_SIZE); /* reclaim the padding word */

#endif

LINK_STATS_INC(link.xmit);