Wyodrębnij bieżącą trasę z komunikatu netlink, kod dołączony

Question

Próbuję monitorować zmiany trasy za pomocą gniazda netlink, ale jak mam pobrać zaktualizowany adres trasy?

Kod:

#include <sys/socket.h> 
#include <stdlib.h> 
#include <stdio.h> 
#include <string.h> 
#include <linux/netlink.h> 
#include <linux/rtnetlink.h> 
#define ERR_RET(x) do { perror(x); return EXIT_FAILURE; } while (0); 

void loop (int sock) 
{ 
    struct sockaddr_nl nladdr; 
    struct msghdr msg; 
    struct iovec iov[2]; 
    struct nlmsghdr nlh; 
    char buffer[65536]; 

    iov[0].iov_base = (void *)&nlh; 
    iov[0].iov_len = sizeof(nlh); 
    iov[1].iov_base = (void *)buffer; 
    iov[1].iov_len = sizeof(buffer); 

    msg.msg_name = (void *)&(nladdr); 
    msg.msg_namelen = sizeof(nladdr); 
    msg.msg_iov = iov; 
    msg.msg_iovlen = sizeof(iov)/sizeof(struct iovec); 

    if (recvmsg (sock, &msg, 0)) 
    { 
     if (nlh.nlmsg_type == RTM_NEWROUTE) 
     { 
      printf ("New route message\n"); 
     } 
     else if (nlh.nlmsg_type == RTM_DELROUTE) 
     { 
      printf ("Del route message\n"); 
     } 
    } 
} 

int main(int argc, char *argv[]) 
{ 
    int sock = -1; 
    struct sockaddr_nl addr; 
    bzero (&addr, sizeof(addr)); 

    if ((sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE)) < 0) 
     ERR_RET("socket"); 

    addr.nl_family = AF_NETLINK; 
    addr.nl_groups = RTMGRP_IPV4_ROUTE; 

    if (bind(sock,(struct sockaddr *)&addr,sizeof(addr))<0) 
     ERR_RET("bind"); 

    while (1) 
     loop (sock); 
    return 0; 
} 

Answer 1

edytowany kod i dodać dwa konstrukcjom(), aby uzyskać potrzebne informacje przy frezowaniu zmianę tabeli (kod jest skomentował).

/* The purpose of this program is to monitor routing 
* table changes 
*/ 

#include <sys/socket.h> 
#include <stdlib.h> 
#include <stdio.h> 
#include <string.h> 
#include <linux/netlink.h> 
#include <linux/rtnetlink.h> 
#include <arpa/inet.h> 
#include <unistd.h> 

#define ERR_RET(x) do { perror(x); return EXIT_FAILURE; } while (0); 
#define BUFFER_SIZE 4095 

int loop (int sock, struct sockaddr_nl *addr) 
{ 
    int  received_bytes = 0; 
    struct nlmsghdr *nlh; 
    char destination_address[32]; 
    char gateway_address[32]; 
    struct rtmsg *route_entry; /* This struct represent a route entry \ 
            in the routing table */ 
    struct rtattr *route_attribute; /* This struct contain route \ 
              attributes (route type) */ 
    int  route_attribute_len = 0; 
    char buffer[BUFFER_SIZE]; 

    bzero(destination_address, sizeof(destination_address)); 
    bzero(gateway_address, sizeof(gateway_address)); 
    bzero(buffer, sizeof(buffer)); 

    /* Receiving netlink socket data */ 
    while (1) 
    { 
     received_bytes = recv(sock, buffer, sizeof(buffer), 0); 
     if (received_bytes < 0) 
      ERR_RET("recv"); 
     /* cast the received buffer */ 
     nlh = (struct nlmsghdr *) buffer; 
     /* If we received all data ---> break */ 
     if (nlh->nlmsg_type == NLMSG_DONE) 
      break; 
     /* We are just intrested in Routing information */ 
     if (addr->nl_groups == RTMGRP_IPV4_ROUTE) 
      break; 
    } 

    /* Reading netlink socket data */ 
    /* Loop through all entries */ 
    /* For more informations on some functions : 
    * http://www.kernel.org/doc/man-pages/online/pages/man3/netlink.3.html 
    * http://www.kernel.org/doc/man-pages/online/pages/man7/rtnetlink.7.html 
    */ 

    for (; NLMSG_OK(nlh, received_bytes); \ 
        nlh = NLMSG_NEXT(nlh, received_bytes)) 
    { 
     /* Get the route data */ 
     route_entry = (struct rtmsg *) NLMSG_DATA(nlh); 

     /* We are just intrested in main routing table */ 
     if (route_entry->rtm_table != RT_TABLE_MAIN) 
      continue; 

     /* Get attributes of route_entry */ 
     route_attribute = (struct rtattr *) RTM_RTA(route_entry); 

     /* Get the route atttibutes len */ 
     route_attribute_len = RTM_PAYLOAD(nlh); 
     /* Loop through all attributes */ 
     for (; RTA_OK(route_attribute, route_attribute_len); \ 
      route_attribute = RTA_NEXT(route_attribute, route_attribute_len)) 
     { 
      /* Get the destination address */ 
      if (route_attribute->rta_type == RTA_DST) 
      { 
       inet_ntop(AF_INET, RTA_DATA(route_attribute), \ 
         destination_address, sizeof(destination_address)); 
      } 
      /* Get the gateway (Next hop) */ 
      if (route_attribute->rta_type == RTA_GATEWAY) 
      { 
       inet_ntop(AF_INET, RTA_DATA(route_attribute), \ 
         gateway_address, sizeof(gateway_address)); 
      } 
     } 

     /* Now we can dump the routing attributes */ 
     if (nlh->nlmsg_type == RTM_DELROUTE) 
      fprintf(stdout, "Deleting route to destination --> %s and gateway %s\n", \ 
       destination_address, gateway_address); 
     if (nlh->nlmsg_type == RTM_NEWROUTE) 
      printf("Adding route to destination --> %s and gateway %s\n", \ 
          destination_address, gateway_address); 
    } 

    return 0; 
} 

int main(int argc, char **argv) 
{ 
    int sock = -1; 
    struct sockaddr_nl addr; 

    /* Zeroing addr */ 
    bzero (&addr, sizeof(addr)); 

    if ((sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE)) < 0) 
     ERR_RET("socket"); 

    addr.nl_family = AF_NETLINK; 
    addr.nl_groups = RTMGRP_IPV4_ROUTE; 

    if (bind(sock,(struct sockaddr *)&addr,sizeof(addr)) < 0) 
     ERR_RET("bind"); 

    while (1) 
     loop (sock, &addr); 

    /* Close socket */ 
    close(sock); 

    return 0; 
} 

można przetestować jak to na przykład (jako root, aby dodać trasy do tablicy routingu):

root@UnixServer# route add -host 10.113.0.0 gw bsdBox 
root@UnixServer# route del -host 10.113.0.0 gw bsdBox 

W moim komputerze mam to wyjście:

toc@UnixServer:~$./route_monitor 
Adding route to destination --> 10.113.0.0 and gateway 192.168.1.1 
Deleting route to destination --> 10.113.0.0 and gateway 192.168.1.1 
^C