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List all network interfaces with netlink
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#include <stdio.h> | |
#include <unistd.h> | |
#include <memory.h> | |
#include <sys/types.h> | |
#include <sys/socket.h> | |
#include <linux/types.h> | |
#include <linux/netlink.h> | |
#include <linux/rtnetlink.h> | |
#define BUF_SIZE 8192 | |
int fd; | |
int b; | |
int msg_len; | |
int attr_len; | |
char buf[BUF_SIZE]; | |
struct sockaddr_nl kernel; | |
struct sockaddr_nl local; | |
struct msghdr msg; | |
struct iovec iov; | |
struct nlmsghdr *nlmsg_ptr; | |
struct ifinfomsg *ifi_ptr; | |
struct rtattr *attr_ptr; | |
struct nl_req_s | |
{ | |
struct nlmsghdr hdr; | |
struct rtgenmsg gen; | |
}; | |
typedef struct nl_req_s nl_req_t; | |
nl_req_t req; | |
int main() | |
{ | |
memset(&kernel, 0, sizeof(kernel)); | |
memset(&local, 0, sizeof(local)); | |
memset(&msg, 0, sizeof(msg)); | |
memset(&req, 0, sizeof(req)); | |
kernel.nl_family = AF_NETLINK; | |
local.nl_family = AF_NETLINK; | |
local.nl_pid = getpid(); | |
local.nl_groups = 0; | |
req.hdr.nlmsg_len = NLMSG_LENGTH(sizeof(struct rtgenmsg)); | |
req.hdr.nlmsg_type = RTM_GETLINK; | |
req.hdr.nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP; | |
req.hdr.nlmsg_pid = getpid(); | |
req.hdr.nlmsg_seq = 1; | |
req.gen.rtgen_family = AF_PACKET; | |
iov.iov_base = &req; | |
iov.iov_len = req.hdr.nlmsg_len; | |
msg.msg_iov = &iov; | |
msg.msg_iovlen = 1; | |
msg.msg_name = &kernel; | |
msg.msg_namelen = sizeof(kernel); | |
fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE); | |
if (fd < 0) return -1; | |
b = bind(fd, (struct sockaddr *)&local, sizeof(local)); | |
if (b < 0) return -2; | |
sendmsg(fd, (struct msghdr *)&msg, 0); | |
memset(&iov, 0, sizeof(iov)); | |
iov.iov_base = buf; | |
iov.iov_len = BUF_SIZE; | |
msg_len = recvmsg(fd, &msg, 0); | |
nlmsg_ptr = (struct nlmsghdr *)buf; | |
while(NLMSG_OK(nlmsg_ptr, msg_len)) | |
{ | |
if(nlmsg_ptr->nlmsg_type != RTM_NEWLINK) continue; | |
ifi_ptr = NLMSG_DATA(nlmsg_ptr); | |
attr_ptr = IFLA_RTA(ifi_ptr); | |
attr_len = nlmsg_ptr->nlmsg_len - NLMSG_LENGTH(sizeof(*ifi_ptr)); | |
while(RTA_OK(attr_ptr, attr_len)) | |
{ | |
if(attr_ptr->rta_type == IFLA_IFNAME) printf("%s\n", (char *)RTA_DATA(attr_ptr)); | |
attr_ptr = RTA_NEXT(attr_ptr, attr_len); | |
} | |
nlmsg_ptr = NLMSG_NEXT(nlmsg_ptr, msg_len); | |
} | |
} |
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Not bad. Very clear code. But there is an error. You are receiving only 1 netlink message. So not all the interfaces are present.
you need another cycle over recvmsg()
Something like this.