关于rt-thread双网口指定网卡发送udp和tcp

发布于 2021-11-01 10:02:15 浏览：2539 订阅该版

想问下大家，当使用双网口的时候，其中网口e0指定为default网口,e1为第二网口,通过以下两种方法进行网卡绑定,发送udp广播(255.255.255.255):
1,
```c
interface.s_addr = inet_addr(E0_IP);
setsockopt(udp_socket, IPPROTO_IP, IP_MULTICAST_IF, &interface, sizeof(interface));
```
此方法无法指定网卡进行发送,E0_IP为我指定的IP地址,169.254.43.75,通过网线直连到doIP设备,发送的广播会通过另一个网卡发送出去,lwip打印如下
```
lwip_socket(PF_INET, SOCK_DGRAM, 0) = 1
lwip_setsockopt(1, SOL_SOCKET, optname=0x20, ..) -> on
Udp Socket = 1
The Interface:e0, IP No Change:169.254.43.75
Need Send is 169.254.43.75
inet_addr(169.254.43.75) = 1261174441
inet_addr(169.254.43.76) = 1277951657
interface.s_addr = 1261174441
borcast_ip = 255.255.255.255
lwip_sendto(1, data=2001cef4, short_size=8, flags=0x0 to=255.255.255.255 port=13400
udp_send
udp_send: not yet bound to a port, binding now
udp_bind(ipaddr = 0.0.0.0, port = 0)
udp_bind: bound to 0.0.0.0, port 49153)
udp_send: added header pbuf 2001fe68 before given pbuf 2000cc94
udp_send: sending datagram of length 16
udp_send: UDP packet length 16
udp_send: UDP checksum 0x2c33
udp_send: ip_output_if (,,,,0x11,)
ip4_output_if: e11
IP header:
+-------------------------------+
| 4 | 5 |  0x00 |        36     | (v, hl, tos, len)
+-------------------------------+
|       12      |000|       0   | (id, flags, offset)
+-------------------------------+
|  255  |   17  |    0xe672     | (ttl, proto, chksum)
+-------------------------------+
|  169  |  254  |   43  |   76  | (src)
+-------------------------------+
|  255  |  255  |  255  |  255  | (dest)
+-------------------------------+
```
2,
```c
bind(udp_socket, (struct sockaddr *)&server_addr, sizeof(struct sockaddr))
```
通过bind的方式进行发送,绑定成功,但是发送失败,返回120,打印如下
```
lwip_socket(PF_INET, SOCK_DGRAM, 0) = 1
lwip_setsockopt(1, SOL_SOCKET, optname=0x20, ..) -> on
Udp Socket = 1
The Interface:e0, IP No Change:169.254.43.75
Need Send is 169.254.43.75
lwip_bind(1, addr=169.254.43.75 port=0)
udp_bind(ipaddr = 169.254.43.75, port = 0)
udp_bind: bound to 169.254.43.75, port 49153)
lwip_bind(1) succeeded
borcast_ip = 255.255.255.255
lwip_sendto(1, data=2001cef4, short_size=8, flags=0x0 to=255.255.255.255 port=13400
udp_send
ret = -1, Err = 120, Unknown error
```
问下大佬们,怎么才能指定网卡并且正常发送出去呢?现在在rt-thread上,双网卡搞不定啊,求大佬们赐教!