ping 过程如何选择网卡
路由（routing）就是通过互联的网络把信息从源地址传输到目的地址的活动，发送端必然需要找到一个网卡将数据报发送出去，ping 的过程中需要通过 ip4_route 发现合适的网卡；
LwIP 中发现网卡的默认规则是，遍历挂接的网卡设备， 比对远程主机的ip和网卡的ip是否在同一网段，如果是，则返回同一网段的网卡；
如果 定义了钩子函数LWIP_HOOK_IP4_ROUTE_SRC，如果上面无法找到对应网卡时，则会 通过该钩子函数查找网卡；
如果1，2均未找到网卡，返回默认网卡；
实现过程
rt-threadcomponents
et
etdevsrc
etdev.c增加查找网卡动作；
int netdev_cmd_ping(char* target_name, rt_uint32_t times, rt_size_t size, char *netdev_name)
{
#define NETDEV_PING_DATA_SIZE 32
/** ping receive timeout - in milliseconds */
#define NETDEV_PING_RECV_TIMEO (2 * RT_TICK_PER_SECOND)
/** ping delay - in milliseconds */
#define NETDEV_PING_DELAY (1 * RT_TICK_PER_SECOND)
/* check netdev ping options */
#define NETDEV_PING_IS_COMMONICABLE(netdev)
((netdev) && (netdev)->ops && (netdev)->ops->ping &&
netdev_is_up(netdev) && netdev_is_link_up(netdev))
struct netdev *netdev = RT_NULL;
struct netdev_ping_resp ping_resp;
int index, ret = 0;
if (size == 0)
{
size = NETDEV_PING_DATA_SIZE;
}
if (netdev_name != RT_NULL)
{
netdev = netdev_get_by_name(netdev_name);
if (netdev == RT_NULL)
{
rt_kprintf("ping: not found network interface device, using default.
");
netdev = netdev_default;
}
}
if (!NETDEV_PING_IS_COMMONICABLE(netdev))
{
/* using first internet up status network interface device */
netdev = netdev_get_first_by_flags(NETDEV_FLAG_LINK_UP);
if (netdev == RT_NULL)
{
rt_kprintf("ping: not found available network interface device.
");
return -RT_ERROR;
}
else if (netdev->ops == RT_NULL || netdev->ops->ping == RT_NULL)
{
rt_kprintf("ping: network interface device(%s) not support ping feature.
", netdev->name);
return -RT_ERROR;
}
else if (!netdev_is_up(netdev) || !netdev_is_link_up(netdev))
{
rt_kprintf("ping: network interface device(%s) status error.
", netdev->name);
return -RT_ERROR;
}
}
rt_kprintf("network interface: %s
", netdev->name);
for (index = 0; index < times; index++)
{
int delay_tick = 0;
rt_tick_t start_tick = 0;
rt_memset(&ping_resp, 0x00, sizeof(struct netdev_ping_resp));
start_tick = rt_tick_get();
ret = netdev->ops->ping(netdev, (const char *)target_name, size, NETDEV_PING_RECV_TIMEO, &ping_resp);
if (ret == -RT_ETIMEOUT)
{
rt_kprintf("ping: from %s icmp_seq=%d timeout
",
(ip_addr_isany(&(ping_resp.ip_addr))) ? target_name : inet_ntoa(ping_resp.ip_addr), index);
}
else if (ret == -RT_ERROR)
{
rt_kprintf("ping: unknown %s %s
",
(ip_addr_isany(&(ping_resp.ip_addr))) ? "host" : "address",
(ip_addr_isany(&(ping_resp.ip_addr))) ? target_name : inet_ntoa(ping_resp.ip_addr));
}
else
{
if (ping_resp.ttl == 0)
{
rt_kprintf("%d bytes from %s icmp_seq=%d time=%d ms
",
ping_resp.data_len, inet_ntoa(ping_resp.ip_addr), index, ping_resp.ticks);
}
else
{
rt_kprintf("%d bytes from %s icmp_seq=%d ttl=%d time=%d ms
",
ping_resp.data_len, inet_ntoa(ping_resp.ip_addr), index, ping_resp.ttl, ping_resp.ticks);
}
}
/* if the response time is more than NETDEV_PING_DELAY, no need to delay */
delay_tick = ((rt_tick_get() - start_tick) > NETDEV_PING_DELAY) || (index == times) ? 0 : NETDEV_PING_DELAY;
rt_thread_delay(delay_tick);
}
return RT_EOK;
}
rt-threadcomponents
et
etdevsrc
etdev.c修改ping命令，增加网卡参数；
int netdev_ping(int argc, char **argv)
{
if (argc == 1)
{
rt_kprintf("Please input: ping
");
}
else if (argc == 3)
{
netdev_cmd_ping(argv[1], 4, 0, argv[2]);
}
else
{
netdev_cmd_ping(argv[1], 4, 0, RT_NULL);
}
return 0;
}
FINSH_FUNCTION_EXPORT_ALIAS(netdev_ping, __cmd_ping, ping network host);
rt-threadcomponents
etlwip-2.0.2srclwipopts.h 使能钩子函数
#define LWIP_HOOK_IP4_ROUTE_SRC(dest, src) lwip_ip4_route_src(dest, src
rt-threadcomponents
etlwip-2.0.2srcarchsys_arch.c 增加 Lwip 钩子函数；
```c
struct netif
lwip_ip4_route_src(const ip4_addr_t dest, const ip4_addr_t src)
{
struct netif netif;
rt_kprintf(“addr 0x%x 0x%x
”, dest->addr, src->addr);
/ iterate through netifs /
for (netif = netif_list; netif != NULL; netif = netif->next) {
/ is the netif up, does it have a link and a valid address? /
if (netif_is_up(netif) && netif_is_link_up(netif) && !ip4_addr_isany_val(netif_ip4_addr(netif))) {
/ gateway matches on a non broadcast interface? (i.e. peer in a point to point interface) */
if (src != NULL)
{
rt_kprintf(“iter netif %s
”, netif->name);
if (ip4_addr_cmp(src, netif_ip4_addr(netif)))
{
rt_kprintf(“found ip4 route src %s
”, netif->name);
return netif;
}
}
}
}
netif = netif_default;
rt_kprintf(“use ip4 route src %s
”, netif->name);
return netif;
}
5. `rt-threadcomponents
etlwip-2.0.2src
etifethernetif.c`中增加绑定本地 ip；
```c
int lwip_netdev_ping(struct netdev *netif, const char *host, size_t data_len,
uint32_t timeout, struct netdev_ping_resp *ping_resp)
{
int s, ttl, recv_len, result = 0;
int elapsed_time;
rt_tick_t recv_start_tick;
#if LWIP_VERSION_MAJOR >= 2U
struct timeval recv_timeout = { timeout / RT_TICK_PER_SECOND, timeout % RT_TICK_PER_SECOND };
#else
int recv_timeout = timeout * 1000UL / RT_TICK_PER_SECOND;
#endif
ip_addr_t target_addr;
struct addrinfo hint, *res = RT_NULL;
struct sockaddr_in *h = RT_NULL;
struct in_addr ina;
struct sockaddr_in local;
RT_ASSERT(netif);
RT_ASSERT(host);
RT_ASSERT(ping_resp);
rt_kprintf("lwip ping
");
rt_kprintf("==========
");
rt_memset(&hint, 0x00, sizeof(hint));
/* convert URL to IP */
if (lwip_getaddrinfo(host, RT_NULL, &hint, &res) != 0)
{
return -RT_ERROR;
}
rt_memcpy(&h, &res->ai_addr, sizeof(struct sockaddr_in *));
rt_memcpy(&ina, &h->sin_addr, sizeof(ina));
lwip_freeaddrinfo(res);
if (inet_aton(inet_ntoa(ina), &target_addr) == 0)
{
return -RT_ERROR;
}
rt_memcpy(&(ping_resp->ip_addr), &target_addr, sizeof(ip_addr_t));
/* new a socket */
if ((s = lwip_socket(AF_INET, SOCK_RAW, IP_PROTO_ICMP)) < 0)
{
return -RT_ERROR;
}
local.sin_len = sizeof(local);
local.sin_family = AF_INET;
local.sin_port = 0;
// local.sin_addr.s_addr = htons(IP_ADDR_ANY);
// local.sin_addr.s_addr = htonl(netif->ip_addr.addr);
local.sin_addr.s_addr = (netif->ip_addr.addr);
lwip_bind(s, (struct sockaddr *)&local, sizeof(struct sockaddr_in));
rt_kprintf("bind to %x
", local.sin_addr.s_addr);
lwip_setsockopt(s, SOL_SOCKET, SO_RCVTIMEO, &recv_timeout, sizeof(recv_timeout));
if (lwip_ping_send(s, &target_addr, data_len) == ERR_OK)
{
recv_start_tick = rt_tick_get();
if ((recv_len = lwip_ping_recv(s, &ttl)) >= 0)
{
elapsed_time = (rt_tick_get() - recv_start_tick) * 1000UL / RT_TICK_PER_SECOND;
ping_resp->data_len = recv_len;
ping_resp->ttl = ttl;
ping_resp->ticks = elapsed_time;
}
else
{
result = -RT_ETIMEOUT;
goto __exit;
}
}
else
{
result = -RT_ETIMEOUT;
goto __exit;
}
__exit:
lwip_close(s);
return result;
原作者：yukelab
