LwIP协议栈(2):网络接口
2015-07-16 20:43
316 查看
在LwIP中,物理网络硬件接口结构保存在一个全局链表中,它们通过结构体中的 next 指针连接。
struct netif { /// pointer to next in linked list */ struct netif *next; /// IP address configuration in network byte order */ ip_addr_t ip_addr; //IP地址 ip_addr_t netmask; //子网掩码 ip_addr_t gw; //网关地址 netif_input_fn input; //设备驱动调用该函数传递一个包给TCP/IP协议栈 //IP模块调用该函数传递一个包给网卡,output 函数的第三个参数 ipaddr 是应该接收实际的链路层帧的主机的 IP 地址。 //它不必与 IP 信息包的目的地址相同。特别地,当要发送 IP 信息包到一个并不在本地网络里的主机上时,链路层帧会被发送到网络里的一个路由器上。 //在这种情况下给output函数的IP地址将是这个路由器的地址。 netif_output_fn output; netif_linkoutput_fn linkoutput; //ARP模块调用该函数传递一个包给网卡 void *state; //由设备驱动设置,指向设备状态信息 #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 */ u16_t mtu; //一次传送的最大字节数,以太网一般为1500 u8_t hwaddr_len; //物理地址长度,一般是以太网MAC地址长度,6字节 u8_t hwaddr[NETIF_MAX_HWADDR_LEN]; //物理地址,一般是以太网MAC地址 /// flags (see NETIF_FLAG_ above) */ u8_t flags; //使能标志符,比如设置NETIF_FLAG_LINK_UP,接收到数据包才会向上传 /// descriptive abbreviation */ char name[2]; //设备驱动类型 /// number of this interface */ u8_t num; // List of packets to be queued for ourselves. */ struct pbuf *loop_first; //环回,指向发给自己数据包的第一个pbuf struct pbuf *loop_last; //环回,指向发给自己数据包的最后一个pbuf };
/* * 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) { static u8_t netifnum = 0; // reset new interface configuration state */ ip_addr_set_zero(&netif->ip_addr); ip_addr_set_zero(&netif->netmask); ip_addr_set_zero(&netif->gw); netif->flags = 0; // remember netif specific state information data */ netif->state = state; netif->num = netifnum++; netif->input = input; netif_set_addr(netif, ipaddr, netmask, gw); // call user specified initialization function for netif */ if (init(netif) != ERR_OK) { //用户自定义初始化函数 return NULL; } // add this netif to the list */ netif->next = netif_list; netif_list = netif; snmp_inc_iflist(); return netif; } //用户自定义初始化函数 err_t ethernetif_init(struct netif *netif) { netif->name[0] = IFNAME0; //比如蓝牙设备(bluetooth)的网络接口可以是bt,随便啦 netif->name[1] = IFNAME1; netif->output = etharp_output; //IP模块发送数据包函数 netif->linkoutput = low_level_output; // //ARP模块发送数据包函数 low_level_init(netif); //底层硬件初始化函数 return ERR_OK; } static void low_level_init(struct netif *netif) { netif->hwaddr_len = ETHARP_HWADDR_LEN; //设置MAC地址长度 netif->hwaddr[0] = 'F'; //设置网卡MAC地址 netif->hwaddr[1] = 'O'; netif->hwaddr[2] = 'R'; netif->hwaddr[3] = 'E'; netif->hwaddr[4] = 'S'; netif->hwaddr[5] = 'T'; netif->mtu = 1500; //最大允许传输单元 //允许该网卡的广播和ARP功能,并且该网卡允许有硬件链路连接 netif->flags = NETIF_FLAG_BROADCAST | \ NETIF_FLAG_ETHARP | NETIF_FLAG_LINK_UP; E1280_init(netif->hwaddr); //具体网卡初始化函数 } /* * Send an IP packet to be received on the same netif (loopif-like). * The pbuf is simply copied and handed back to netif->input. * In multithreaded mode, this is done directly since netif->input must put * the packet on a queue. * In callback mode, the packet is put on an internal queue and is fed to * netif->input by netif_poll(). * * @param netif the lwip network interface structure * @param p the (IP) packet to 'send' * @param ipaddr the ip address to send the packet to (not used) * @return ERR_OK if the packet has been sent * ERR_MEM if the pbuf used to copy the packet couldn't be allocated */ err_t netif_loop_output(struct netif *netif, struct pbuf *p, ip_addr_t *ipaddr) { struct pbuf *r; err_t err; struct pbuf *last; SYS_ARCH_DECL_PROTECT(lev); LWIP_UNUSED_ARG(ipaddr); // Allocate a new pbuf */ r = pbuf_alloc(PBUF_LINK, p->tot_len, PBUF_RAM); if (r == NULL) { return ERR_MEM; } // Copy the whole pbuf queue p into the single pbuf r */ if ((err = pbuf_copy(r, p)) != ERR_OK) { //拷贝要发送的数据到r中 pbuf_free(r); return err; } // Put the packet on a linked list which gets emptied through calling netif_poll(). */ //可以调用netif_poll函数将当前loop链表上所有数据提交给IP层 // let last point to the last pbuf in chain r */ for (last = r; last->next != NULL; last = last->next); SYS_ARCH_PROTECT(lev); if(netif->loop_first != NULL) { //原来的loop中还有数据 netif->loop_last->next = r; //接到原来数据的后面 netif->loop_last = last; } else { netif->loop_first = r; netif->loop_last = last; } SYS_ARCH_UNPROTECT(lev); return ERR_OK; } /* * 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; } } /* * 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); //拷贝接收到的数据到一个新的pbuf // 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: // full packet send to tcpip_thread to process */ if (netif->input(p, netif)!=ERR_OK) //调用上层(IP/ARP)函数进行处理 { pbuf_free(p); p = NULL; } break; default: pbuf_free(p); p = NULL; break; } }
相关文章推荐
- perl http 请求一些奇怪的问题
- 网络框架 - 安卓之Apache MINA
- 无线网络知识
- 网络命令
- linux_c 网络开发日记(1)
- 如何入侵目标的网络DIY指南
- HTML5第三弹:亦酷亦萌的网络拓扑图
- 网络检错MBProssHUD库的使用
- 【Linux 内核网络协议栈源码剖析】recvfrom 函数剖析
- Https和Http
- tracert详解
- 最大网络流算法
- Charles — mac下网络封包分析工具
- ice和java socket网络传输的对比
- Android多媒体学习七:访问网络上的Audio对应的M3U文件,实现网络音频流的播放
- Go语言使用http下载文件
- 网络技术
- 【网络流】 TOJ 3864. SanXI
- HttpClient上传文件到微信素材乱码问题解决
- C语言解析17monipdb.dat(http://www.ipip.net/)免费数据库