man socket(7)里對該選項的描述：

SO_BINDTODEVICEBind this socket to a particular device like “eth0”, as speci‐fied in the passed interface name. If the name is an emptystring or the option length is zero, the socket device bindingis removed. The passed option is a variable-length null-ter‐minated interface name string with the maximum size of IFNAM‐SIZ. If a socket is bound to an interface, only packetsreceived from that particular interface are processed by thesocket. Note that this works only for some socket types, par‐ticularly AF_INET sockets. It is not supported for packetsockets (use normal bind(2) there).Before Linux 3.8, this socket option could be set, but couldnot retrieved with getsockopt(2). Since Linux 3.8, it isreadable. The optlen argument should contain the buffer sizeavailable to receive the device name and is recommended to beIFNAMSIZ bytes. The real device name length is reported backin the optlen argument.將套接字綁定到指定接口，例如eth0等。如果綁定了接口，這個套接字只能處理由該接口收到的數(shù)據(jù)。 注意，并不是所有套接字類型都有這個選項。AF_INET套接字支持，但是packet 套接字不支持(不過，可以使用bind函數(shù)綁定地址)

如果有多個接口，例如eth0, eth1, ethx......，就可以在創(chuàng)建套接字的時候綁定相應(yīng)的接口發(fā)送數(shù)據(jù)，例如我的電腦里有兩個接口 ：

在創(chuàng)建套接字的時候就可以綁定相應(yīng)的接口發(fā)送數(shù)據(jù)，demo：

/** Desrciption : 套接字選項SO_BINDTODEVICE使用，需要root權(quán)限執(zhí)行* Author : mason* Date : 201809*/#include <stdlib.h> #include <stdio.h> #include <unistd.h> #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #include <net/if.h> #include <errno.h>int main() {int sock;struct sockaddr_in addr, raddr;char buffer[] = "hello world";/* 指定接口 */struct ifreq nif;char *inface = "eth0";strcpy(nif.ifr_name, inface);/* 創(chuàng)建套接字 */sock = socket(AF_INET, SOCK_DGRAM, 0);if (-1 == sock){printf("create socket fail \r\n");return;}else{printf("create socket success \r\n");}if (inet_aton("192.168.80.129", &addr.sin_addr) != 1){printf("addr convert fail \r\n");close(sock);return;}addr.sin_family = AF_INET;addr.sin_port = htons(8000);if (inet_aton("192.168.80.1", &raddr.sin_addr) != 1){printf("addr convert fail \r\n");close(sock);return;}raddr.sin_family = AF_INET;raddr.sin_port = htons(8000);#if 0 //綁定地址if (bind(sock, (struct sockadd *)&addr, sizeof(addr)) != 0){printf("bind fail \r\n");close(sock);return ;}else{printf("bind success \r\n");}#endif/* 綁定接口 */if (setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, (char *)&nif, sizeof(nif)) < 0){close(sock);printf("bind interface fail, errno: %d \r\n", errno);return ; }else{printf("bind interface success \r\n");}/* 發(fā)送 */sendto(sock, buffer, sizeof(buffer), 0, ((struct sockadd *)&raddr),sizeof(raddr));close(sock);return; }

分別綁定eth0, eth1發(fā)送數(shù)據(jù)，抓包如下圖，可以看到有不同的源地址發(fā)送。

程序執(zhí)行的時候需要使用sudo權(quán)限，不然會提示綁定接口失敗。

感覺類似的功能完全可以由bind接口實現(xiàn)，即綁定指定IP地址。

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