路线集 :SIOCADDRT失败:不适合设备的ioctl
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20-12-2019 - |
题
这个典型的"路由添加默认gw IP"程序给我错误 :
SIOCADDRT失败:不适合设备的ioctl
我做了ifconfig来验证接口名称。有没有办法列出我的设备的所有适当的ioctl?
int main(char** args) {
int sockfd;
struct rtentry route;
struct sockaddr_in *addr;
int err = 0;
// create the socket
if(sockfd = socket(AF_INET, SOCK_DGRAM, 0)<0){
perror("socket");
exit(1);
}
memset(&route, 0, sizeof(route));
addr = (struct sockaddr_in*) &route.rt_gateway;
addr->sin_family = AF_INET;
addr->sin_addr.s_addr = inet_addr("192.168.10.1");
addr = (struct sockaddr_in*) &route.rt_dst;
addr->sin_family = AF_INET;
addr->sin_addr.s_addr = INADDR_ANY;
addr = (struct sockaddr_in*) &route.rt_genmask;
addr->sin_family = AF_INET;
addr->sin_addr.s_addr = INADDR_ANY;
route.rt_dev = "eth0";
route.rt_flags = RTF_UP | RTF_GATEWAY;
route.rt_metric = 0;
if ((err = ioctl(sockfd, SIOCADDRT, &route)) != 0) {
perror("SIOCADDRT failed");
exit(1);
}
}
将代码更改为:
addr = (struct sockaddr_in*) &route.rt_gateway;
addr->sin_family = AF_INET;
addr->sin_addr.s_addr = inet_addr("192.168.10.1");
addr = (struct sockaddr_in*) &route.rt_dst;
addr->sin_family = AF_INET;
addr->sin_addr.s_addr = inet_addr("192.168.10.3");
addr = (struct sockaddr_in*) &route.rt_genmask;
addr->sin_family = AF_INET;
addr->sin_addr.s_addr = inet_addr("255.255.255.0");
gdb输出 :
37 if ((err = ioctl(sockfd, SIOCADDRT, &route)) != 0) {
(gdb) p route
$1 = {rt_pad1 = 0, rt_dst = {sa_family = 2, sa_data = "\000\000\300\250\n\003\000\000\000\000\000\000\000"},
rt_gateway = {sa_family = 2, sa_data = "\000\000\300\250\n\001\000\000\000\000\000\000\000"},
rt_genmask = {sa_family = 2, sa_data = "\000\000\377\377\377\000\000\000\000\000\000\000\000"},
rt_flags = 3, rt_pad2 = 0, rt_pad3 = 0, rt_tos = 0 '\000', rt_class = 0 '\000', rt_pad4 = {0, 0, 0},
rt_metric = 0, rt_dev = 0x4008af "em1", rt_mtu = 0, rt_window = 0, rt_irtt = 0}
(gdb) n
38 perror("SIOCADDRT failed");
(gdb)
SIOCADDRT failed: Invalid argument
解决方案
我想错误就在这里:
// create the socket
if(sockfd = socket(AF_INET, SOCK_DGRAM, 0)<0)
表达式 socket(AF_INET, SOCK_DGRAM, 0)<0
在分配之前被评估。这是因为赋值运算符的优先级低于函数调用和比较。你可以在这篇维基百科文章中阅读更多关于它的信息:
所以你真正拥有的是:
// create the socket
if(sockfd = (socket(AF_INET, SOCK_DGRAM, 0)<0))
评估结果为:
// create the socket
if(sockfd = 0)
所以你试图执行一个 ioctl()
在无效的文件描述符上。
将赋值包装成括号或将表达式移出条件,如下所示:
// create the socket
int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
if(sockfd < 0)
顺便说一句,GCC或Clang应该检测到它,如果你通过 -Wall
选择。
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