Created
August 3, 2018 08:36
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Simple c++ code that detects interface changes
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| /* | |
| * Detects interface plug or removal with given name, starts forks wpa_supplicant accordingly | |
| * g++ wpa_forker.cpp -std=c++11 -lpthread | |
| * | |
| */ | |
| #include <iostream> | |
| #include <cstdlib> | |
| #include <cstdio> | |
| #include <csignal> | |
| #include <cstring> | |
| #include <thread> | |
| #include <pthread.h> | |
| #include <vector> | |
| #include <unistd.h> | |
| #include <sys/types.h> | |
| #include <sys/socket.h> | |
| #include <linux/netlink.h> | |
| #include <linux/rtnetlink.h> | |
| #include <net/if.h> | |
| #include <netinet/in.h> | |
| #include <sys/ioctl.h> | |
| #include <ifaddrs.h> | |
| #include <wait.h> | |
| #define WPA_PATH "/sbin/wpa_supplicant" | |
| #define WPA_CONFIG_PATH "/etc/wpa_supplicant/wpa_supplicant.conf" | |
| #define BUF_SIZE 4096 | |
| struct wpa_process { | |
| char iface_name[IFNAMSIZ]; | |
| char iface_hwaddr[IFHWADDRLEN]; | |
| pid_t pid = -1; | |
| void syscallHwaddr(){ | |
| struct ifreq ifr; | |
| strncpy(ifr.ifr_name, iface_name, IFNAMSIZ); | |
| int sock = socket(AF_INET, SOCK_DGRAM, 0); | |
| if(ioctl(sock, SIOCGIFHWADDR, &ifr) == 0){ | |
| strncpy(iface_hwaddr, ifr.ifr_hwaddr.sa_data, IFHWADDRLEN); | |
| } | |
| close(sock); | |
| } | |
| void run(bool verbose = true){ | |
| std::thread th([&](bool verbose, wpa_process* process) { | |
| if (process->pid > 0) { | |
| return; | |
| } | |
| if ((process->pid = fork()) == 0) { | |
| char *args[] = { | |
| (char *) WPA_PATH, // dummpy param to avoid argv[0] | |
| (char *) "-i", | |
| process->iface_name, | |
| (char *) "-c", | |
| (char *) WPA_CONFIG_PATH, | |
| (char *) (verbose ? "-d" : ""), | |
| (char *) nullptr | |
| }; | |
| execv((char *) WPA_PATH, args); | |
| } else if (process->pid > 0) { | |
| int status; | |
| wait(&status); | |
| } else { | |
| perror("fork failed"); | |
| } | |
| },verbose, this); | |
| th.detach(); | |
| } | |
| void stop(){ | |
| std::cout << "should stop" << std::endl; | |
| kill(pid, SIGINT); | |
| pid = -1; | |
| } | |
| }; | |
| struct ifaddrs* get_interfaces(){ | |
| struct ifaddrs* addrs; | |
| getifaddrs(&addrs); | |
| return addrs; | |
| } | |
| struct wpa_process process; | |
| int open_netlink(){ | |
| int sock; | |
| struct sockaddr_nl addr; | |
| memset((void*)&addr, 0, sizeof(addr)); | |
| if((sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE))< 0 ){ | |
| perror("Can't connect to socket"); | |
| return sock; | |
| } | |
| addr.nl_family = AF_NETLINK; | |
| addr.nl_pid = (u_int32_t) getpid(); | |
| addr.nl_groups = RTMGRP_LINK; | |
| if( bind(sock, (struct sockaddr*) &addr, sizeof(addr)) < 0){ | |
| return -1; | |
| } | |
| return sock; | |
| } | |
| int read_event(int sockint){ | |
| ssize_t status ; | |
| int ret =0 ; | |
| char buf[BUF_SIZE]; | |
| struct iovec iov = { | |
| .iov_base = buf, | |
| .iov_len = sizeof(buf) | |
| }; | |
| struct sockaddr_nl snl; | |
| struct msghdr msg = { /** @see man recvmsg */ | |
| .msg_name = (void*)&snl, | |
| .msg_namelen = sizeof(snl), | |
| .msg_iov = &iov, | |
| .msg_iovlen = 1, | |
| .msg_control = nullptr, | |
| .msg_controllen = 0, | |
| .msg_flags = 0 | |
| }; | |
| status = recvmsg(sockint , &msg, 0); | |
| if(status < 0 ){ | |
| if( errno == EWOULDBLOCK || errno == EAGAIN){ | |
| return ret; | |
| } | |
| printf("read_netlink: Error recvmsg: %lu\n", status); | |
| perror("read_netlink: Error: "); | |
| return (int)status; | |
| } | |
| if(status == 0) { | |
| printf("read_netlink: EOF\n"); | |
| } | |
| int i = 0; | |
| for( | |
| auto h = (struct nlmsghdr *) buf; | |
| NLMSG_OK(h, (unsigned int)status); | |
| h = NLMSG_NEXT(h, status), i++ ) | |
| { | |
| if(h->nlmsg_type == NLMSG_DONE){ | |
| return ret; | |
| } else if ( h->nlmsg_type == NLMSG_ERROR) { | |
| printf("read_netlink: Message is an error\n"); | |
| return -1; | |
| } | |
| // Now we can call handler | |
| auto ifi = (struct ifinfomsg*) NLMSG_DATA(h); | |
| struct ifreq ifr; | |
| ifr.ifr_ifindex = ifi->ifi_index; | |
| int ifreqsock = socket(AF_INET, SOCK_DGRAM, IPPROTO_IP); | |
| ioctl(ifreqsock, SIOCGIFNAME, &ifr); | |
| close(ifreqsock); | |
| switch(h->nlmsg_type){ | |
| case RTM_NEWADDR: | |
| break; | |
| case RTM_DELADDR: | |
| break; | |
| case RTM_NEWROUTE: | |
| break; | |
| case RTM_DELROUTE: | |
| break; | |
| case RTM_NEWLINK: | |
| if(ifi->ifi_change == 0xFFFFFFFF){ | |
| std::cout << "=========================================================> " << i << std::endl; | |
| std::cout << "INTERFACE ADDED: " << std::string(ifr.ifr_name) << std::endl; | |
| if(strcmp(ifr.ifr_name, process.iface_name) == 0){ | |
| process.run(false); | |
| } | |
| } | |
| break; | |
| case RTM_DELLINK: | |
| if(ifi->ifi_change == 0xFFFFFFFF){ | |
| std::cout << "=========================================================> " << i << std::endl; | |
| std::cout << "INTERFACE REMOVED: " << std::string(ifr.ifr_name)<< std::endl; | |
| if(strcmp(ifr.ifr_name, process.iface_name) == 0){ | |
| process.stop(); | |
| } | |
| } | |
| break; | |
| default: | |
| break; | |
| } | |
| } | |
| return 0; | |
| } | |
| int main(int argc, char* argv[]) { | |
| if(argc < 2){ | |
| printf("Wrong number of arguments\n"); | |
| return EXIT_FAILURE; | |
| } | |
| strcpy(process.iface_name, argv[1]); | |
| process.syscallHwaddr(); | |
| struct ifaddrs* addrs; | |
| getifaddrs(&addrs); | |
| for(;addrs; addrs = addrs->ifa_next){ | |
| if(addrs->ifa_addr && addrs->ifa_addr->sa_family == AF_PACKET){ | |
| if(strcmp(addrs->ifa_name, process.iface_name) == 0){ | |
| process.run(false); | |
| } | |
| } | |
| } | |
| int nls = open_netlink(); | |
| printf("Started watching: \n"); | |
| if( nls < 0 ){ | |
| perror("Open Error"); | |
| } | |
| do{ | |
| if( read_event(nls) < 0 ){ | |
| break; | |
| } | |
| } while( true ); | |
| return EXIT_SUCCESS; | |
| } |
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