LWIP学习笔记（4）LWIP网络接口管理
网络接口简介
网卡是一块被设计用来允许计算机在计算机网络上进行通讯的计算机硬件。每一个网卡都有一个被称为MAC地址的独一无二的48位串行号，在osi模型的第一层。网卡的主要工作原理是整理计算机上发往网线的数据，并将数据分解为适当大小的数据包后向网络上发出去。
TCP/IP参考模型分为4层：应用层、传输层、网络层和网络接口层。网络接口层就对应着我们实际的网卡，LWIP支持多网口设计，lwip中使用netif来描述每个网络接口的特性，如接口的ip地址、接口状态等。那么如果有多个网卡的话lwip是如何来组织这些网卡呢？在lwip中用链表netif_list来管理众多的网卡，当上层有数据要发送的时候lwip会从链表中选择一个合适的网卡来将数据发出去。
netif.c/h实现网络接口管理，完成对网卡的抽象描述，网卡初始化，网卡发送数据，网卡接收数据等
netif.h定义了如下结构体
struct netif {
#if !LWIP_SINGLE_NETIF
//指向下一个netif结构
/** pointer to next in linked list */
struct netif *next;
#endif
#if LWIP_IPV4
/** IP address configuration in network byte order */
//ip地址
ip_addr_t ip_addr;
//子网掩码
ip_addr_t netmask;
//网关
ip_addr_t gw;
#endif /* LWIP_IPV4 */
#if LWIP_IPV6
/** Array of IPv6 addresses for this netif. */
ip_addr_t ip6_addr[LWIP_IPV6_NUM_ADDRESSES];
/** The state of each IPv6 address (Tentative, Preferred, etc).
* @see ip6_addr.h */
u8_t ip6_addr_state[LWIP_IPV6_NUM_ADDRESSES];
#if LWIP_IPV6_ADDRESS_LIFETIMES
/** Remaining valid and preferred lifetime of each IPv6 address, in seconds.
* For valid lifetimes, the special value of IP6_ADDR_LIFE_STATIC (0)
* indicates the address is static and has no lifetimes. */
u32_t ip6_addr_valid_life[LWIP_IPV6_NUM_ADDRESSES];
u32_t ip6_addr_pref_life[LWIP_IPV6_NUM_ADDRESSES];
#endif /* LWIP_IPV6_ADDRESS_LIFETIMES */
#endif /* LWIP_IPV6 */
/** This function is called by the network device driver
* to pass a packet up the TCP/IP stack. */
//从网卡接收到数据包给ip层函数指针
netif_input_fn input;
#if LWIP_IPV4
/** 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.
* For ethernet physical layer, this is usually etharp_output() */
//ip层发送数据包函数指针
netif_output_fn output;
#endif /* LWIP_IPV4 */
/** This function is called by ethernet_output() when it wants
* to send a packet on the interface. This function outputs
* the pbuf as-is on the link medium. */
//arp层调用发送数据包函数指针
netif_linkoutput_fn linkoutput;
#if LWIP_IPV6
/** This function is called by the IPv6 module when it wants
* to send a packet on the interface. This function typically
* first resolves the hardware address, then sends the packet.
* For ethernet physical layer, this is usually ethip6_output() */
netif_output_ip6_fn output_ip6;
#endif /* LWIP_IPV6 */
#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 */
#if LWIP_NETIF_REMOVE_CALLBACK
/** This function is called when the netif has been removed */
netif_status_callback_fn remove_callback;
#endif /* LWIP_NETIF_REMOVE_CALLBACK */
/** This field can be set by the device driver and could point
* to state information for the device. */
记录一些设备信息
void *state;
#ifdef netif_get_client_data
void* client_data[LWIP_NETIF_CLIENT_DATA_INDEX_MAX + LWIP_NUM_NETIF_CLIENT_DATA];
#endif
#if LWIP_NETIF_HOSTNAME
/* the hostname for this netif, NULL is a valid value */
const char* hostname;
#endif /* LWIP_NETIF_HOSTNAME */
#if LWIP_CHECKSUM_CTRL_PER_NETIF
u16_t chksum_flags;
#endif /* LWIP_CHECKSUM_CTRL_PER_NETIF*/
/** maximum transfer unit (in bytes) */
//网络接口传送的最大数据包，发送和接收最大的数据包
u16_t mtu;
#if LWIP_IPV6 && LWIP_ND6_ALLOW_RA_UPDATES
/** maximum transfer unit (in bytes), updated by RA */
u16_t mtu6;
#endif /* LWIP_IPV6 && LWIP_ND6_ALLOW_RA_UPDATES */
/** link level hardware address of this interface */
// MAC地址的长度
u8_t hwaddr[NETIF_MAX_HWADDR_LEN];
/** number of bytes used in hwaddr */
//MAC地址的字节
u8_t hwaddr_len;
/** flags (@see @ref netif_flags) */
//该接口状态、属性
u8_t flags;
/** descriptive abbreviation */
// 该接口名字
char name[2];
/** number of this interface. Used for @ref if_api and @ref netifapi_netif,
* as well as for IPv6 zones */
// 该接口编号
u8_t num;
#if LWIP_IPV6_AUTOCONFIG
/** is this netif enabled for IPv6 autoconfiguration */
u8_t ip6_autoconfig_enabled;
#endif /* LWIP_IPV6_AUTOCONFIG */
#if LWIP_IPV6_SEND_ROUTER_SOLICIT
/** Number of Router Solicitation messages that remain to be sent. */
u8_t rs_count;
#endif /* LWIP_IPV6_SEND_ROUTER_SOLICIT */
#if MIB2_STATS
/** link type (from "snmp_ifType" enum from snmp_mib2.h) */
u8_t link_type;
/** (estimate) link speed */
u32_t link_speed;
/** timestamp at last change made (up/down) */
u32_t ts;
/** counters */
struct stats_mib2_netif_ctrs mib2_counters;
#endif /* MIB2_STATS */
#if LWIP_IPV4 && LWIP_IGMP
/** This function could be called to add or delete an entry in the multicast
filter table of the ethernet MAC.*/
netif_igmp_mac_filter_fn igmp_mac_filter;
#endif /* LWIP_IPV4 && LWIP_IGMP */
#if LWIP_IPV6 && LWIP_IPV6_MLD
/** This function could be called to add or delete an entry in the IPv6 multicast
filter table of the ethernet MAC. */
netif_mld_mac_filter_fn mld_mac_filter;
#endif /* LWIP_IPV6 && LWIP_IPV6_MLD */
#if LWIP_NETIF_USE_HINTS
struct netif_hint *hints;
#endif /* LWIP_NETIF_USE_HINTS */
#if ENABLE_LOOPBACK
/* List of packets to be queued for ourselves. */
struct pbuf *loop_first; //指向发给自己数据包第一个pbuf
struct pbuf *loop_last; //指向发给自己数据包最后一个pbuf
#if LWIP_LOOPBACK_MAX_PBUFS
u16_t loop_cnt_current;
#endif /* LWIP_LOOPBACK_MAX_PBUFS */
#endif /* ENABLE_LOOPBACK */
};
netif_add
// 把netif结构添加到netif list的链表中,lwip才可以管理该网口
struct netif *
netif_add(struct netif *netif,
#if LWIP_IPV4
const ip4_addr_t *ipaddr, const ip4_addr_t *netmask, const ip4_addr_t *gw,
#endif /* LWIP_IPV4 */
void *state, netif_init_fn init, netif_input_fn input)
{
#if LWIP_IPV6
s8_t i;
#endif
LWIP_ASSERT_CORE_LOCKED();
#if LWIP_SINGLE_NETIF
if (netif_default != NULL) {
LWIP_ASSERT("single netif already set", 0);
return NULL;
}
#endif
LWIP_ERROR("netif_add: invalid netif", netif != NULL, return NULL);
LWIP_ERROR("netif_add: No init function given", init != NULL, return NULL);
#if LWIP_IPV4
if (ipaddr == NULL) {
ipaddr = ip_2_ip4(IP4_ADDR_ANY);
}
if (netmask == NULL) {
netmask = ip_2_ip4(IP4_ADDR_ANY);
}
if (gw == NULL) {
gw = ip_2_ip4(IP4_ADDR_ANY);
}
/* reset new interface configuration state */
//地址清零
ip_addr_set_zero_ip4(&netif->ip_addr);
ip_addr_set_zero_ip4(&netif->netmask);
ip_addr_set_zero_ip4(&netif->gw);
netif->output = netif_null_output_ip4;
#endif /* LWIP_IPV4 */
#if LWIP_IPV6
for (i = 0; i < LWIP_IPV6_NUM_ADDRESSES; i++) {
ip_addr_set_zero_ip6(&netif->ip6_addr[i]);
netif->ip6_addr_state[i] = IP6_ADDR_INVALID;
#if LWIP_IPV6_ADDRESS_LIFETIMES
netif->ip6_addr_valid_life[i] = IP6_ADDR_LIFE_STATIC;
netif->ip6_addr_pref_life[i] = IP6_ADDR_LIFE_STATIC;
#endif /* LWIP_IPV6_ADDRESS_LIFETIMES */
}
netif->output_ip6 = netif_null_output_ip6;
#endif /* LWIP_IPV6 */
NETIF_SET_CHECKSUM_CTRL(netif, NETIF_CHECKSUM_ENABLE_ALL);
netif->mtu = 0;
netif->flags = 0;
#ifdef netif_get_client_data
memset(netif->client_data, 0, sizeof(netif->client_data));
#endif /* LWIP_NUM_NETIF_CLIENT_DATA */
#if LWIP_IPV6
#if LWIP_IPV6_AUTOCONFIG
/* IPv6 address autoconfiguration not enabled by default */
netif->ip6_autoconfig_enabled = 0;
#endif /* LWIP_IPV6_AUTOCONFIG */
nd6_restart_netif(netif);
#endif /* LWIP_IPV6 */
#if LWIP_NETIF_STATUS_CALLBACK
netif->status_callback = NULL;
#endif /* LWIP_NETIF_STATUS_CALLBACK */
#if LWIP_NETIF_LINK_CALLBACK
netif->link_callback = NULL;
#endif /* LWIP_NETIF_LINK_CALLBACK */
#if LWIP_IGMP
netif->igmp_mac_filter = NULL;
#endif /* LWIP_IGMP */
#if LWIP_IPV6 && LWIP_IPV6_MLD
netif->mld_mac_filter = NULL;
#endif /* LWIP_IPV6 && LWIP_IPV6_MLD */
#if ENABLE_LOOPBACK
netif->loop_first = NULL;
netif->loop_last = NULL;
#endif /* ENABLE_LOOPBACK */
/* remember netif specific state information data */
netif->state = state;
netif->num = netif_num;
netif->input = input;
NETIF_RESET_HINTS(netif);
#if ENABLE_LOOPBACK && LWIP_LOOPBACK_MAX_PBUFS
netif->loop_cnt_current = 0;
#endif /* ENABLE_LOOPBACK && LWIP_LOOPBACK_MAX_PBUFS */
#if LWIP_IPV4
netif_set_addr(netif, ipaddr, netmask, gw);
#endif /* LWIP_IPV4 */
/* call user specified initialization function for netif */
if (init(netif) != ERR_OK) {
return NULL;
}
#if LWIP_IPV6 && LWIP_ND6_ALLOW_RA_UPDATES
/* Initialize the MTU for IPv6 to the one set by the netif driver.
This can be updated later by RA. */
netif->mtu6 = netif->mtu;
#endif /* LWIP_IPV6 && LWIP_ND6_ALLOW_RA_UPDATES */
#if !LWIP_SINGLE_NETIF
/* Assign a unique netif number in the range [0..254], so that (num+1) can
serve as an interface index that fits in a u8_t.
We assume that the new netif has not yet been added to the list here.
This algorithm is O(n^2), but that should be OK for lwIP.
*/
{
struct netif *netif2;
int num_netifs;
do {
if (netif->num == 255) {
netif->num = 0;
}
num_netifs = 0;
for (netif2 = netif_list; netif2 != NULL; netif2 = netif2->next) {
LWIP_ASSERT("netif already added", netif2 != netif);
num_netifs++;
LWIP_ASSERT("too many netifs, max. supported number is 255", num_netifs <= 255);
if (netif2->num == netif->num) {
netif->num++;
break;
}
}
} while (netif2 != NULL);
}
if (netif->num == 254) {
netif_num = 0;
} else {
netif_num = (u8_t)(netif->num + 1);
}
/* add this netif to the list */
netif->next = netif_list;
netif_list = netif;
#endif /* "LWIP_SINGLE_NETIF */
mib2_netif_added(netif);
#if LWIP_IGMP
/* start IGMP processing */
if (netif->flags & NETIF_FLAG_IGMP) {
igmp_start(netif);
}
#endif /* LWIP_IGMP */
LWIP_DEBUGF(NETIF_DEBUG, ("netif: added interface %c%c IP",
netif->name[0], netif->name[1]));
#if LWIP_IPV4
LWIP_DEBUGF(NETIF_DEBUG, (" addr "));
ip4_addr_debug_print(NETIF_DEBUG, ipaddr);
LWIP_DEBUGF(NETIF_DEBUG, (" netmask "));
ip4_addr_debug_print(NETIF_DEBUG, netmask);
LWIP_DEBUGF(NETIF_DEBUG, (" gw "));
ip4_addr_debug_print(NETIF_DEBUG, gw);
#endif /* LWIP_IPV4 */
LWIP_DEBUGF(NETIF_DEBUG, ("\n"));
netif_invoke_ext_callback(netif, LWIP_NSC_NETIF_ADDED, NULL);
return netif;
}
网络接口相关函数
- netif_add
// 把netif结构添加到netif list的链表中,lwip才可以管理该网口
//添加网口
struct netif *
netif_add(struct netif *netif,
#if LWIP_IPV4
const ip4_addr_t *ipaddr, const ip4_addr_t *netmask, const ip4_addr_t *gw,
#endif /* LWIP_IPV4 */
void *state, netif_init_fn init, netif_input_fn input)
{
#if LWIP_IPV6
s8_t i;
#endif
LWIP_ASSERT_CORE_LOCKED();
#if LWIP_SINGLE_NETIF
if (netif_default != NULL) {
LWIP_ASSERT("single netif already set", 0);
return NULL;
}
#endif
LWIP_ERROR("netif_add: invalid netif", netif != NULL, return NULL);
LWIP_ERROR("netif_add: No init function given", init != NULL, return NULL);
#if LWIP_IPV4
if (ipaddr == NULL) {
ipaddr = ip_2_ip4(IP4_ADDR_ANY);
}
if (netmask == NULL) {
netmask = ip_2_ip4(IP4_ADDR_ANY);
}
if (gw == NULL) {
gw = ip_2_ip4(IP4_ADDR_ANY);
}
/* reset new interface configuration state */
//地址清零
ip_addr_set_zero_ip4(&netif->ip_addr);
ip_addr_set_zero_ip4(&netif->netmask);
ip_addr_set_zero_ip4(&netif->gw);
netif->output = netif_null_output_ip4;
#endif /* LWIP_IPV4 */
#if LWIP_IPV6
for (i = 0; i < LWIP_IPV6_NUM_ADDRESSES; i++) {
ip_addr_set_zero_ip6(&netif->ip6_addr[i]);
netif->ip6_addr_state[i] = IP6_ADDR_INVALID;
#if LWIP_IPV6_ADDRESS_LIFETIMES
netif->ip6_addr_valid_life[i] = IP6_ADDR_LIFE_STATIC;
netif->ip6_addr_pref_life[i] = IP6_ADDR_LIFE_STATIC;
#endif /* LWIP_IPV6_ADDRESS_LIFETIMES */
}
netif->output_ip6 = netif_null_output_ip6;
#endif /* LWIP_IPV6 */
NETIF_SET_CHECKSUM_CTRL(netif, NETIF_CHECKSUM_ENABLE_ALL);
netif->mtu = 0;
netif->flags = 0;
#ifdef netif_get_client_data
memset(netif->client_data, 0, sizeof(netif->client_data));
#endif /* LWIP_NUM_NETIF_CLIENT_DATA */
#if LWIP_IPV6
#if LWIP_IPV6_AUTOCONFIG
/* IPv6 address autoconfiguration not enabled by default */
netif->ip6_autoconfig_enabled = 0;
#endif /* LWIP_IPV6_AUTOCONFIG */
nd6_restart_netif(netif);
#endif /* LWIP_IPV6 */
#if LWIP_NETIF_STATUS_CALLBACK
netif->status_callback = NULL;
#endif /* LWIP_NETIF_STATUS_CALLBACK */
#if LWIP_NETIF_LINK_CALLBACK
netif->link_callback = NULL;
#endif /* LWIP_NETIF_LINK_CALLBACK */
#if LWIP_IGMP
netif->igmp_mac_filter = NULL;
#endif /* LWIP_IGMP */
#if LWIP_IPV6 && LWIP_IPV6_MLD
netif->mld_mac_filter = NULL;
#endif /* LWIP_IPV6 && LWIP_IPV6_MLD */
#if ENABLE_LOOPBACK
netif->loop_first = NULL;
netif->loop_last = NULL;
#endif /* ENABLE_LOOPBACK */
/* remember netif specific state information data */
netif->state = state;
netif->num = netif_num;
netif->input = input;
NETIF_RESET_HINTS(netif);
#if ENABLE_LOOPBACK && LWIP_LOOPBACK_MAX_PBUFS
netif->loop_cnt_current = 0;
#endif /* ENABLE_LOOPBACK && LWIP_LOOPBACK_MAX_PBUFS */
#if LWIP_IPV4
netif_set_addr(netif, ipaddr, netmask, gw);
#endif /* LWIP_IPV4 */
/* call user specified initialization function for netif */
if (init(netif) != ERR_OK) {
return NULL;
}
#if LWIP_IPV6 && LWIP_ND6_ALLOW_RA_UPDATES
/* Initialize the MTU for IPv6 to the one set by the netif driver.
This can be updated later by RA. */
netif->mtu6 = netif->mtu;
#endif /* LWIP_IPV6 && LWIP_ND6_ALLOW_RA_UPDATES */
#if !LWIP_SINGLE_NETIF
/* Assign a unique netif number in the range [0..254], so that (num+1) can
serve as an interface index that fits in a u8_t.
We assume that the new netif has not yet been added to the list here.
This algorithm is O(n^2), but that should be OK for lwIP.
*/
{
struct netif *netif2;
int num_netifs;
do {
if (netif->num == 255) {
netif->num = 0;
}
num_netifs = 0;
for (netif2 = netif_list; netif2 != NULL; netif2 = netif2->next) {
LWIP_ASSERT("netif already added", netif2 != netif);
num_netifs++;
LWIP_ASSERT("too many netifs, max. supported number is 255", num_netifs <= 255);
if (netif2->num == netif->num) {
netif->num++;
break;
}
}
} while (netif2 != NULL);
}
if (netif->num == 254) {
netif_num = 0;
} else {
netif_num = (u8_t)(netif->num + 1);
}
/* add this netif to the list */
netif->next = netif_list;
netif_list = netif;
#endif /* "LWIP_SINGLE_NETIF */
mib2_netif_added(netif);
#if LWIP_IGMP
/* start IGMP processing */
if (netif->flags & NETIF_FLAG_IGMP) {
igmp_start(netif);
}
#endif /* LWIP_IGMP */
LWIP_DEBUGF(NETIF_DEBUG, ("netif: added interface %c%c IP",
netif->name[0], netif->name[1]));
#if LWIP_IPV4
LWIP_DEBUGF(NETIF_DEBUG, (" addr "));
ip4_addr_debug_print(NETIF_DEBUG, ipaddr);
LWIP_DEBUGF(NETIF_DEBUG, (" netmask "));
ip4_addr_debug_print(NETIF_DEBUG, netmask);
LWIP_DEBUGF(NETIF_DEBUG, (" gw "));
ip4_addr_debug_print(NETIF_DEBUG, gw);
#endif /* LWIP_IPV4 */
LWIP_DEBUGF(NETIF_DEBUG, ("\n"));
netif_invoke_ext_callback(netif, LWIP_NSC_NETIF_ADDED, NULL);
return netif;
}
- netif_set_default(struct netif *netif)
void
netif_set_default(struct netif *netif)
{
LWIP_ASSERT_CORE_LOCKED();
if (netif == NULL) {
/* remove default route */
mib2_remove_route_ip4(1, netif);
} else {
/* install default route */
mib2_add_route_ip4(1, netif);
}
// netif_default：默认网口
netif_default = netif;
LWIP_DEBUGF(NETIF_DEBUG, ("netif: setting default interface %c%c\n",
netif ? netif->name[0] : '\'', netif ? netif->name[1] : '\''));
}
- netif_set_up(struct netif *netif)
//打开netif网口
void
netif_set_up(struct netif *netif)
{
LWIP_ASSERT_CORE_LOCKED();
LWIP_ERROR("netif_set_up: invalid netif", netif != NULL, return);
if (!(netif->flags & NETIF_FLAG_UP)) {
//NETIF_FLAG_UP：
netif_set_flags(netif, NETIF_FLAG_UP);
MIB2_COPY_SYSUPTIME_TO(&netif->ts);
NETIF_STATUS_CALLBACK(netif);
#if LWIP_NETIF_EXT_STATUS_CALLBACK
{
netif_ext_callback_args_t args;
args.status_changed.state = 1;
netif_invoke_ext_callback(netif, LWIP_NSC_STATUS_CHANGED, &args);
}
#endif
netif_issue_reports(netif, NETIF_REPORT_TYPE_IPV4 | NETIF_REPORT_TYPE_IPV6);
#if LWIP_IPV6
nd6_restart_netif(netif);
#endif /* LWIP_IPV6 */
}
}