Default Gateway

[gregory.menke at gsfc.nasa.gov]

Mike Bertosh writes:
 > Hi all,
 > 
 > I am trying to create a function that I can call to change the default gateway address. I 
 > am using the rtrequest() function to remove the default gateway from the routing table 
 > and then add the new address.Is there a function that will already do this for me? 
 > Here is the code I have been trying to get to work.
 > 


The code snippet below sets a gateway for 128.183/16, accessed by
either of two ethernet interfaces.  The ethernet addresses themselves
are 192.168.100.102 and 200.102.  So its not a default gateway, though
I imagine the calls could be generalized for that.  It looks similar
to what you're doing.  Why do you need the rtfree()?


Gregm


#define DOWNLINK_ADDRESS        "128.183.0.0"
#define DOWNLINK_NETMASK        "255.255.0.0"

#define DOWNLINK1_GATEWAY       "192.168.100.1"
#define DOWNLINK2_GATEWAY       "192.168.200.1"




void setup_downlink_routes()
{
   struct sockaddr_in address;
   struct sockaddr_in netmask;
   struct sockaddr_in gateway;

   memset(&address,0,sizeof(address));
   address.sin_len = sizeof(address);
   address.sin_family = AF_INET;
   address.sin_addr.s_addr = inet_addr( DOWNLINK_ADDRESS );

   memset(&netmask,0,sizeof(netmask));
   netmask.sin_len = sizeof(netmask);
   netmask.sin_family = AF_INET;
   netmask.sin_addr.s_addr = inet_addr( DOWNLINK_NETMASK );

   memset(&gateway,0,sizeof(gateway));
   gateway.sin_len = sizeof(gateway);
   gateway.sin_family = AF_INET;
   gateway.sin_addr.s_addr = inet_addr( DOWNLINK1_GATEWAY );
   if (rtems_bsdnet_rtrequest( RTM_ADD,
                               (struct sockaddr *)&address,
                               (struct sockaddr *)&gateway,
                               (struct sockaddr *)&netmask,
                               (RTF_UP | RTF_GATEWAY | RTF_STATIC), NULL) < 0)
   {
      printf("Can't create gateway for route %s/%s: %s\n",
             DOWNLINK_ADDRESS,
             DOWNLINK_NETMASK,
             strerror(errno) );
   }
}


int select_downlink_route(int selroute)
{
   char *offgateway, *ongateway;

   struct sockaddr_in address;
   struct sockaddr_in netmask;
   struct sockaddr_in gateway;

   if( selroute == 0 )
   {
      offgateway = DOWNLINK2_GATEWAY;
      ongateway  = DOWNLINK1_GATEWAY;
   }
   else if( selroute == 1 )
   {
      offgateway = DOWNLINK1_GATEWAY;
      ongateway  = DOWNLINK2_GATEWAY;
   }
   else
      return -1;

   memset(&address,0,sizeof(address));
   address.sin_len = sizeof(address);
   address.sin_family = AF_INET;
   address.sin_addr.s_addr = inet_addr( DOWNLINK_ADDRESS );

   memset(&netmask,0,sizeof(netmask));
   netmask.sin_len = sizeof(netmask);
   netmask.sin_family = AF_INET;
   netmask.sin_addr.s_addr = inet_addr( DOWNLINK_NETMASK );

   memset(&gateway,0,sizeof(gateway));
   gateway.sin_len = sizeof(gateway);
   gateway.sin_family = AF_INET;
   gateway.sin_addr.s_addr = inet_addr( offgateway );

   rtems_bsdnet_rtrequest( RTM_DELETE,
                           (struct sockaddr *)&address,
                           (struct sockaddr *)&gateway,
                           (struct sockaddr *)&netmask,
                           (RTF_GATEWAY | RTF_STATIC), NULL);

   gateway.sin_addr.s_addr = inet_addr( ongateway );

   rtems_bsdnet_rtrequest( RTM_ADD,
                           (struct sockaddr *)&address,
                           (struct sockaddr *)&gateway,
                           (struct sockaddr *)&netmask,
                           (RTF_UP | RTF_GATEWAY | RTF_STATIC), NULL);
   return 0;
}









Mike Bertosh writes:
 > Hi all,
 > 
 > I am trying to create a function that I can call to change the default gateway address. I 
 > am using the rtrequest() function to remove the default gateway from the routing table 
 > and then add the new address.Is there a function that will already do this for me? 
 > Here is the code I have been trying to get to work.
 >