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Full Discussion: Set host default gateway in C program.
Top Forums Programming Set host default gateway in C program. Post 302451331 by semash! on Monday 6th of September 2010 11:54:49 AM
Old 09-06-2010
Just to update, i found a easier solution to this problem.

Intead of using system() to run command-line programs, you can add a default gateway route by ioctl with SIOCADDRT and SIOCDELRT, it's very simple.
Code:
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <net/route.h>
#include <sys/types.h>
#include <sys/ioctl.h>

int main(char** args) {
  int sockfd;
  struct rtentry route;
  struct sockaddr_in *addr;
  int err = 0;

  // create the socket
 if((sockfd = socket(AF_INET, SOCK_DGRAM, 0)))<0){
perror("socket");
exit(1);
}

  memset(&route, 0, sizeof(route));
  addr = (struct sockaddr_in*) &route.rt_gateway;
  addr->sin_family = AF_INET;
  addr->sin_addr.s_addr = inet_addr("192.168.2.1");
  addr = (struct sockaddr_in*) &route.rt_dst;
  addr->sin_family = AF_INET;
  addr->sin_addr.s_addr = inet_addr("0.0.0.0");
  addr = (struct sockaddr_in*) &route.rt_genmask;
  addr->sin_family = AF_INET;
  addr->sin_addr.s_addr = inet_addr("0.0.0.0");
  route.rt_flags = RTF_UP | RTF_GATEWAY;
  route.rt_metric = 0;
  if ((err = ioctl(sockfd, SIOCADDRT, &route)) != 0) {
    perror("SIOCADDRT failed");
    exit(1);
  }
}

Hope this helps someone.
This User Gave Thanks to semash! For This Post:
Corona688
 

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LEARN ABOUT HPUX

ypset

ypset(1M)																 ypset(1M)

NAME

       ypset - bind to particular Network Information Service server

SYNOPSIS

       host] domain] server

   Remarks
       The  Network  Information  Service  (NIS) was formerly known as Yellow Pages (YP).  Although the name has changed, the functionality of the
       service remains the same.

DESCRIPTION

       tells to get Network Information Service (NIS) services for the specified domain from the process running on  server  (see  ypserv(1M)  and
       ypbind(1M)).  server is the NIS server that the NIS client binds to, and is specified as either a host name or an IP address.  If server is
       down or is not running this is not discovered until a local NIS client process tries to obtain a binding for the domain.  The  daemon  then
       tests  the  binding  set  by If the binding cannot be made to the requested server, attempts to rebind to another server in the same domain
       present in the ypservers file.

       NOTE: In order to run must be initiated with the or options.  For more information on how to initiate see ypbind(1M).

       The command is useful for binding a client node that is not on a broadcast network.  If a client node exists on a broadcast  network  which
       has no NIS server running, and if there is a network with one running that is available via a gateway, can establish a binding through that
       gateway.  It is also useful for debugging NIS client applications such as when a NIS map exists only at a single NIS server.

       In cases where several hosts on the local net are supplying NIS services, it is possible for to rebind to  another  host,  even	while  you
       attempt	to find out if the operation succeeded.  For example, typing followed by and receiving the reply may be confusing.  It could occur
       when host1 does not respond to because its process is not running or is overloaded, and host2, running gets the binding.

       The server is the NIS server to bind to, specified as either a host name or an IP address.

       Refer to ypfiles(4) and ypserv(1M) for an overview of the Network Information Service.

   Options
       recognizes the following options and command-line arguments:

	      Bind	     server for the Version 2 NIS protocol.

	      Set the binding on
			     host instead of locally.  host can be specified as a host name or an IP address.

	      Use	     domain instead of the default domain returned by (see domainname(1)).

DIAGNOSTICS

       The user is not root, or ypbind was run without the
	      flags.  See ypserv(1M) for explanations of the flags.

       The user is not root, or ypbind was run without one of the
	      flags.  See ypserv(1M) for explanations of the flags.

WARNINGS

       Starting with ONCplus version B.11.31.02, the NIS Version 1 protocol is no longer available.

AUTHOR

       was developed by Sun Microsystems, Inc.

SEE ALSO

       domainname(1), ypwhich(1), ypserv(1M), ypfiles(4).

																	 ypset(1M)
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