目前我的程序正在调用ifconfig来执行此操作。
看起来有点乱 - 可能ifconfig不在路径上,或者在某些非标准位置。然后我需要在发生故障时检查iproute2等效物。
有没有办法用C?
以编程方式设置它?非常感谢!
答案 0 :(得分:3)
您可以在ioctl调用中设置SIOCSIFMTU字段,如下所示:
struct ifreq ifr;
ifr.ifr_addr.sa_family = AF_INET;//address family
strncpy(ifr.ifr_name, "eth0", sizeof(ifr.ifr_name));//interface name where you want to set the MTU
ifr.ifr_mtu = 9100; //your MTU size here
if (ioctl(sockfd, SIOCSIFMTU, (caddr_t)&ifr) < 0)
//failed to set MTU. handle error.
上面的代码将使用ifreq结构中的ifr_mtu字段设置设备的MTU(如在ifr.name中)。
答案 1 :(得分:2)
您也可以使用netlink。完整示例:
#include <stdio.h>
#include <string.h>
#include <net/if.h>
#include <sys/socket.h>
#include <linux/rtnetlink.h>
#define IFACE_NAME "enp5s0"
int main(void) {
int ret, nl_sock;
unsigned int mtu = 8000;
struct rtattr *rta;
struct {
struct nlmsghdr nh;
struct ifinfomsg ifinfo;
char attrbuf[512];
} req;
nl_sock = socket(AF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE);
if(nl_sock < 0) {
perror("socket():");
return -1;
}
memset(&req, 0, sizeof req);
req.nh.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg));
req.nh.nlmsg_flags = NLM_F_REQUEST;
req.nh.nlmsg_type = RTM_NEWLINK; // RTM_SETLINK
req.ifinfo.ifi_family = AF_UNSPEC;
req.ifinfo.ifi_index = if_nametoindex(IFACE_NAME);
if(!req.ifinfo.ifi_index) {
perror("if_nametoindex():");
return -1;
}
printf("%s index: %d\n", IFACE_NAME, req.ifinfo.ifi_index);
req.ifinfo.ifi_change = 0xffffffff;
rta = (struct rtattr *)(((char *) &req) + NLMSG_ALIGN(req.nh.nlmsg_len));
rta->rta_type = IFLA_MTU;
rta->rta_len = RTA_LENGTH(sizeof(unsigned int));
req.nh.nlmsg_len = NLMSG_ALIGN(req.nh.nlmsg_len) + RTA_LENGTH(sizeof mtu);
memcpy(RTA_DATA(rta), &mtu, sizeof mtu);
ret = send(nl_sock, &req, req.nh.nlmsg_len, 0);
if(ret < 0) {
perror("send():");
return -1;
}
return 0;
}
另请阅读:rtnetlink(3),rtnetlink(7)