As an AI language model, I can provide you with the general steps to monitor kernel ARP using Netlink in C programming language.
- Include the necessary headers:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/socket.h>
#include <linux/netlink.h>
#include <linux/if_arp.h>
#include <arpa/inet.h>
- Create a netlink socket:
int fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
if(fd == -1){
perror("socket");
return -1;
}
- Bind the socket to the kernel:
struct sockaddr_nl sa;
memset(&sa, 0, sizeof(sa));
sa.nl_family = AF_NETLINK;
sa.nl_pid = getpid();
sa.nl_groups = RTMGRP_LINK | RTMGRP_IPV4_IFADDR;
if(bind(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1){
perror("bind");
return -1;
}
- Define the buffer and receive messages:
#define BUFSIZE 8192
char buf[BUFSIZE];
while(1){
int len = recv(fd, buf, BUFSIZE, 0);
if(len == -1){
perror("recv");
break;
}
struct nlmsghdr *nh = (struct nlmsghdr *)buf;
while(NLMSG_OK(nh, len)){
if(nh->nlmsg_type == NLMSG_DONE){
break;
}
if(nh->nlmsg_type == NLMSG_ERROR){
fprintf(stderr, "Netlink error: %s\n", strerror(errno));
break;
}
if(nh->nlmsg_type == RTM_NEWLINK){
struct ifinfomsg *ifi = (struct ifinfomsg *)NLMSG_DATA(nh);
if(ifi->ifi_family == AF_LINK){
struct rtattr *rta = IFLA_RTA(ifi);
int rtl = IFLA_PAYLOAD(nh);
for(; RTA_OK(rta, rtl); rta = RTA_NEXT(rta, rtl)){
if(rta->rta_type == IFLA_IFNAME){
printf("Interface %d : %s\n", ifi->ifi_index, (char *)RTA_DATA(rta));
break;
}
}
}
}
if(nh->nlmsg_type == RTM_NEWADDR){
struct ifaddrmsg *ifa = (struct ifaddrmsg *)NLMSG_DATA(nh);
if(ifa->ifa_family == AF_INET){
struct rtattr *rta = IFA_RTA(ifa);
int rtl = IFA_PAYLOAD(nh);
for(; RTA_OK(rta, rtl); rta = RTA_NEXT(rta, rtl)){
if(rta->rta_type == IFA_LOCAL){
char addr[INET_ADDRSTRLEN];
inet_ntop(AF_INET, RTA_DATA(rta), addr, INET_ADDRSTRLEN);
printf("ARP received on interface %d from %s\n", ifa->ifa_index, addr);
break;
}
}
}
}
nh = NLMSG_NEXT(nh, len);
}
}
This code will print out the interface and IP addresses of received ARP messages. Note that it assumes IPv4 and Ethernet interfaces. You can modify it to support other protocols and interfaces.
Please note that this is just a skeleton code. You need to add error handling and other necessary features to make it work flawlessly.
