Re: ANNOUNCE: new DHCP client for linux 2.6.x
Hi, Am Freitag 17 Februar 2006 20:39 schrieb Simon Barber: In 802.11 networks when connecting to a new AP on the same networks (same SSID security settings) you typically don't have to do DHCP again - but with some networks setups you do. In order to detect this, when connecting to a new AP always issue an ARP request for the default gateway - if you don't get a response, then kick off a dhcp request. I've just implemented the feature. As the client does not know the specific wireless settings, I've chosen this approach to verify the IP address: -downtime must be lower than 60 seconds -T1 (RENEWal time) has not passed yet -IP address of default gateway is ARP probed and must answer with the known MAC address of the default gateway. Maximum 3 (is configurable) tries with .5 sec delay. If any of this fails, the client tries to verify the IP address via DHCP for four seconds, then drops IP configuration and restarts if it is NAKed or not answered. Got to do more tests of course, but this sounds like a workable solution to me. Jamal: Your idea of influencing the statemachine from the called scripts hasn't been forgotten, but a communication channel from script to daemon must be well designed and there is still too much other stuff on my todo list. Stefan shameless readvertisement http://www.flamewarmaster.de/software/dhcpclient/ /shameless readvertisement - To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: ANNOUNCE: new DHCP client for linux 2.6.x
Stefan Rompf wrote : dhcpclient A DHCP client for linux 2.6, using modern kernel features, (c) 2006 Stefan Rompf. Motivation Using a notebook, I'm often traveling between different networks. After replugging, I always needed to issue a ifdown/ifup sequence because the DHCP client did not realize the temporary disconnection. This is an unneeded limitation because since 2.6, the kernel notifies userspace of these disconnection/reconnection events. Actually is was me who implemented this feature. Beginning with 2.6.17, the linux kernel will allow userspace to influence this signalling, so that for example a wpa supplicant can tell the dhcpclient that an association has finished and the client should try to get an IP address. Of course, you need software that support this feature. Unfortunately, most existing DHCP clients implemented their statemachine using siglongjmp() or one huge function, so there was no easy way extending them. So I wrote a new one. I congratulate you on your good work. I will share with you my personal gripe on most DHCP clients : they depend too much on those link signalling. I hope you appreciate the irony ;-) I'm personally setup with a WLAN in Ad-Hoc mode. I've got so many WLAN cards left over from previous projects that I don't really need an Access Point. One of the PC in Ad-Hoc mode act as a DHCP server (trivial to configure on most distro). In Ad-Hoc mode, you can't have any link notification. Think about it, an Ad-Hoc network with only a single node is valid, because you need to start somewhere. The PC with the DHCP server doesn't have any specific meaning at the link layer, and might actually go down sometimes (reboot to update kernel). After 'ifup', the DHCP client tries a few time to connect to the DHCP server, and if not in range, will give up and never retry. When I bring my laptop within range of my DHCP server, nothing happens. I have to manually restart the interface. If you are not familiar with WLAN Ad-Hoc mode, I'll give you a conceptual equivalent with Ethernet. Let suppose you have a Ethernet switch on your desk (or under your desk), and the uplink is *NOT* connected to the rest of the network. You plug your PC into the switch. You get a netlink event saying that you have a valid Ethernet link, but your DHCP will fail. At the point when you will connect the uplink to the switch, the PC will not notice it and DHCP will not get an address. In essence, in WLAN Ad-Hoc mode the link to the switch is always valid but the uplink may or may not be connected. Have fun... Jean - To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
RE: ANNOUNCE: new DHCP client for linux 2.6.x
A quick suggestion for a feature improvement... In 802.11 networks when connecting to a new AP on the same networks (same SSID security settings) you typically don't have to do DHCP again - but with some networks setups you do. In order to detect this, when connecting to a new AP always issue an ARP request for the default gateway - if you don't get a response, then kick off a dhcp request. Simon -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Stefan Rompf Sent: Friday, February 17, 2006 6:37 AM To: netdev@vger.kernel.org; linux-kernel@vger.kernel.org Subject: ANNOUNCE: new DHCP client for linux 2.6.x dhcpclient A DHCP client for linux 2.6, using modern kernel features, (c) 2006 Stefan Rompf. Motivation Using a notebook, I'm often traveling between different networks. After replugging, I always needed to issue a ifdown/ifup sequence because the DHCP client did not realize the temporary disconnection. This is an unneeded limitation because since 2.6, the kernel notifies userspace of these disconnection/reconnection events. Actually is was me who implemented this feature. Beginning with 2.6.17, the linux kernel will allow userspace to influence this signalling, so that for example a wpa supplicant can tell the dhcpclient that an association has finished and the client should try to get an IP address. Of course, you need software that support this feature. Unfortunately, most existing DHCP clients implemented their statemachine using siglongjmp() or one huge function, so there was no easy way extending them. So I wrote a new one. Features * RFC2131 compatible DHCP client, tested with ISC dhcpd directly and via a Cisco IOS relay agent, Cisco IOS DHCP server and dnsmasq. * uses netlink for interface configuration * does act on link state messages * calls a script on every state change to allow updating resolv.conf etc * small, compiles with [1]uclibc Status Currently, this is alpha software. It shouldn't be used in production environment, but I'm looking forward for people who like to test it in different environments and for (reasonable ;-) feature suggestions! Support The webpage is at [2]http://www.flamewarmaster.de/software/dhcpclient/ There is a mailing list available on [3]http://www.flamewarmaster.de/mailman/listinfo/dhcpclient/ References 1. http://www.uclibc.org/ 2. http://www.flamewarmaster.de/software/dhcpclient/ 3. http://www.flamewarmaster.de/mailman/listinfo/dhcpclient/ - To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html - To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: ANNOUNCE: new DHCP client for linux 2.6.x
Am Freitag 17 Februar 2006 19:39 schrieb Jean Tourrilhes: I congratulate you on your good work. Thanks! I will share with you my personal gripe on most DHCP clients : they depend too much on those link signalling. I hope you appreciate the irony ;-) Someone needs a feature, another one hates it ;-) After 'ifup', the DHCP client tries a few time to connect to the DHCP server, and if not in range, will give up and never retry. When I bring my laptop within range of my DHCP server, nothing happens. I have to manually restart the interface. ... but still, my client may be interesting for you because it doesn't give up. If it cannot get an IP address, the backoff between DHCP discovers goes up to the RFC 2131 mandated 64 seconds, but it will keep trying. Stefan - To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: ANNOUNCE: new DHCP client for linux 2.6.x
Am Freitag 17 Februar 2006 20:39 schrieb Simon Barber: In 802.11 networks when connecting to a new AP on the same networks (same SSID security settings) you typically don't have to do DHCP again - but with some networks setups you do. In order to detect this, when connecting to a new AP always issue an ARP request for the default gateway - if you don't get a response, then kick off a dhcp request. good idea, I'll revisit this after if have ARP probing implemented. Right now, my client goes to INIT_REBOOT and tries to verify the address for four seconds without giving up IP configuration. This puts more load onto the DHCP server, but should lead to the same result. Stefan - To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: ANNOUNCE: new DHCP client for linux 2.6.x
On Fri, 2006-17-02 at 21:49 +0100, Stefan Rompf wrote: Am Freitag 17 Februar 2006 20:39 schrieb Simon Barber: In 802.11 networks when connecting to a new AP on the same networks (same SSID security settings) you typically don't have to do DHCP again - but with some networks setups you do. In order to detect this, when connecting to a new AP always issue an ARP request for the default gateway - if you don't get a response, then kick off a dhcp request. good idea, I'll revisit this after if have ARP probing implemented. Right now, my client goes to INIT_REBOOT and tries to verify the address for four seconds without giving up IP configuration. This puts more load onto the DHCP server, but should lead to the same result. A nice feature is to have scripts invoked at different DHCP states/hooks. This way you let people who want to do ARP probing do it from a user space script before transitioning for example to INIT_REBOOT. cheers, jamal - To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: ANNOUNCE: new DHCP client for linux 2.6.x
On Fri, Feb 17, 2006 at 09:44:39PM +0100, Stefan Rompf wrote: Am Freitag 17 Februar 2006 19:39 schrieb Jean Tourrilhes: I congratulate you on your good work. Thanks! I will share with you my personal gripe on most DHCP clients : they depend too much on those link signalling. I hope you appreciate the irony ;-) Someone needs a feature, another one hates it ;-) After 'ifup', the DHCP client tries a few time to connect to the DHCP server, and if not in range, will give up and never retry. When I bring my laptop within range of my DHCP server, nothing happens. I have to manually restart the interface. ... but still, my client may be interesting for you because it doesn't give up. If it cannot get an IP address, the backoff between DHCP discovers goes up to the RFC 2131 mandated 64 seconds, but it will keep trying. Yep, that seems to be the proper behaviour. The only other thing missing is setting the DHCP lease time to some reasonable value in the server so that when I go out of range it goes back to searching, but that's clearly not a client issue... So, it seems that your new client would address the need of Ad-Hoc mode users. Pretty cool. Stefan Thanks ! Jean - To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
