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Full Discussion: Set host default gateway in C program.
Top Forums Programming Set host default gateway in C program. Post 302446007 by Corona688 on Tuesday 17th of August 2010 11:16:28 AM
Old 08-17-2010
Usually, even in C, you'd just use the commandline tools. This will make for a much more portable program. Otherwise, the ioctl's will vary wildly across systems. I'm not sure it even uses ioctl to do so in linux at all, for that matter -- it might be netlink these days, which is a lot more impenetrable.

Suppose you have IP 192.168.1.2, mask 255.255.255.0, DNS server 192.168.1.1, gateway 192.168.1.1. You can change the IP and netmask of an interface with the ifconfig tool, like so:

Code:
/sbin/ifconfig eth0 ip 192.168.1.2 netmask 255.255.255.0

You can alter DNS parameters by managing the list of hosts in /etc/resolv.conf .
Code:
echo nameserver 192.168.1.1 > /etc/resolv.conf

And gateways are done through the route command.
Code:
/sbin/route add default gateway 192.168.1.1 eth0

If you really insist on doing it with ioctl, try runing strace ifconfig eth0 ip 192.168.1.2 netmask 255.255.255.0 to see what raw ioctl it uses; that's how I found things like the serial port ioctls...
Last edited by Corona688; 08-17-2010 at 12:23 PM.. Reason: fixed mutation
 

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LEARN ABOUT DEBIAN

pbuilder-uml.conf

pbuilder-uml.conf(5)						     pbuilder						      pbuilder-uml.conf(5)

NAME

       pbuilder-uml.conf - configuration file for user-mode-linux port of pbuilder

DESCRIPTION

       /etc/pbuilder/pbuilder-uml.conf contains default values used in pbuilder-user-mode-linux program invocation.

FORMAT

       MY_ETH0=tuntap,,,192.168.0.2
	      Configures ethernet setting used for booting linux.  See how rootstrap boots your system, and copy that.

	      Specify --eth0=slirp,12345,/usr/bin/slirp-fullbolt to use the slirp connection.

       UML_IP=192.168.0.3
	      IP address to use for guest OS.

	      This can be set to dhcp for obtaining IP address through DHCP.

       UML_NETMASK=255.255.255.0
	      Guest OS netmask

       UML_NETWORK=192.168.0.0
	      Guest OS network

       UML_BROADCAST=255.255.255.255
	      Guest OS broadcast

       UML_GATEWAY=192.168.0.1
	      Guest OS gateway

       PBUILDER_UML_IMAGE=${HOME}/uml-image
	      Guest OS file system image.

       UML_MOUNT_TMPFS=no
	      Whether to mount tmpfs inside the guest image.  This is probably mostly useless.

       BUILDPLACE=${HOME}/tmp/
	      The  location  which build will take place.  pbuilder-user-mode-linux will place temporary COW files to there.  The user running UML
	      needs to be able to access that directory.

       UML_MEM=128
	      The amount of memory allowed for UML.  Give more value to here.

       UML_HOSTNAME=uml-host
	      The hostname for the UML.

	      The hostname should be available in /etc/hosts so that hostname -f will be able to return the FQDN.

       UML_BUILDRESULT=/directory/of/build/result
	      The directory where build result of pbuilder-user-mode-linux is stored.

       ROOTSTRAP_IMAGESIZE=size-in-megabytes
	      The size, in MB, of the disk iamge to create. Defaults to 1000.

NOTES

       It is advised to set APTCACHEHARDLINK to no in ~/.pbuilderrc.  see pbuilderrc(5) for details.

AUTHOR

       Initial coding, and main maintenance is done by Junichi Uekawa <dancer@debian.org>.

       The homepage is available at http://pbuilder.alioth.debian.org

FILES

       /etc/pbuilder/pbuilder-uml.conf, ${HOME}/.pbuilderrc

SEE ALSO

       /usr/share/doc/pbuilder/pbuilder-doc.html, pbuilder-user-mode-linux(1), pbuilder(8), pbuilderrc(5), pdebuild(1)

Debian								    2003 Jan 8						      pbuilder-uml.conf(5)
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