IPv4-capable XDMCP server in Debian squeeze?
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From: Per Lundberg on 28 May 2010 18:10 Hi there! Isn't there any XDMCP-capable server available in squeeze that can speak ipv4 any more? I read about the "net.ipv6.bindv6only" issue (in a bug report). However, that setting is most assuredly set to 0 when I check with sysctl -a. I also forcibly disabled IPv6 support altogether (since I don't need it), also by using a sysctl interface, but it still doesn't help me. Both when trying with xdm and gdm, they *only* bind to the udp6 socket. Quite broken if you ask me, _especially when ipv6 support is disabled in the kernel_! I haven't tried with KDM so far (and I'd rather not, since I have no interest in running KDE). Any hints? The reason I want IPv4 XDMCP is that I will connect to the server from a Windows XP machine, using Xming. I wasn't aware that this has suddenly become an awful lot of work, since the introduction of the wonderful new toy called IPv6... :-) (Please, Cc any replies to my email address since I don't subscribe to the mailing list. Thanks) -- Best regards, Per Lundberg -- To UNSUBSCRIBE, email to debian-user-REQUEST(a)lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmaster(a)lists.debian.org Archive: http://lists.debian.org/AANLkTinNLqhlR4Lzl9BhCeRS7Bxd13Y0flr_eyJF-hr-(a)mail.gmail.com
From: Carl Johnson on 29 May 2010 14:00 Per Lundberg <perlun(a)gmail.com> writes: > Hi there! > > Isn't there any XDMCP-capable server available in squeeze that can > speak ipv4 any more? > > I read about the "net.ipv6.bindv6only" issue (in a bug report). > However, that setting is most assuredly set to 0 when I check with > sysctl -a. > I also forcibly disabled IPv6 support altogether (since I don't need > it), also by using a sysctl interface, but it still doesn't help me. It can't be binding to an interface that doesn't exist, so it sounds as though you haven't disabled it properly. You can type '/sbin/ifconfig' and look for inet6 entries. You shouldn't have any if IPv6 is disabled. You can check for anything listening on IPv6 with 'netstat -l6'. Have you looked at the Debian wiki page at 'http://wiki.debian.org/DebianIPv6'? If you have followed those directions for disabling, did you reboot afterwards? > Both when trying with xdm and gdm, they *only* bind to the udp6 > socket. Quite broken if you ask me, _especially when ipv6 support is > disabled in the kernel_! I just looked at mine (kdm) and it only seems to be listening to IPv6, but I am pretty sure it will also connect to IPv4. I just checked google and there are some similar problems listed and some suggestions on how to solve them. One suggests using module aliases to prevent loading the IPv6 module (http://www.linux.com/community/blogs/disable-ipv6-on-debian-lenny-quick-howto.html). > I haven't tried with KDM so far (and I'd rather not, since I have no > interest in running KDE). I wouldn't expect it to be different. > Any hints? The reason I want IPv4 XDMCP is that I will connect to the > server from a Windows XP machine, using Xming. I wasn't aware that > this has suddenly become an awful lot of work, since the introduction > of the wonderful new toy called IPv6... :-) > > (Please, Cc any replies to my email address since I don't subscribe to > the mailing list. Thanks) Done. -- Carl Johnson carlj(a)peak.org -- To UNSUBSCRIBE, email to debian-user-REQUEST(a)lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmaster(a)lists.debian.org Archive: http://lists.debian.org/877hmmr3nl.fsf(a)cjlinux.localnet
From: Per Lundberg on 29 May 2010 15:50 On Sat, May 29, 2010 at 8:58 PM, Carl Johnson <carlj(a)peak.org> wrote: Hi Carl, and thanks for your reply! (I'll include my full original email, since I extended the audience to the debian-devel list as well) > Per Lundberg <perlun(a)gmail.com> writes: > >> Isn't there any XDMCP-capable server available in squeeze that can >> speak ipv4 any more? >> >> I read about the "net.ipv6.bindv6only" issue (in a bug report). >> However, that setting is most assuredly set to 0 when I check with >> sysctl -a. >> I also forcibly disabled IPv6 support altogether (since I don't need >> it), also by using a sysctl interface, but it still doesn't help me. > It can't be binding to an interface that doesn't exist, so it sounds > as though you haven't disabled it properly. You can type > '/sbin/ifconfig' and look for inet6 entries. You shouldn't have any > if IPv6 is disabled. You can check for anything listening on IPv6 > with 'netstat -l6'. Have you looked at the Debian wiki page at > 'http://wiki.debian.org/DebianIPv6'? If you have followed those > directions for disabling, did you reboot afterwards? Yes, the sysctl thing from the Wiki page is exactly the same method I'm using. I just rebooted, and this is the output from netstat -l6 afterwards: per(a)terah:~$ netstat -l6 Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State tcp6 0 0 [::]:ssh [::]:* LISTEN tcp6 0 0 [::]:microsoft-ds [::]:* LISTEN tcp6 0 0 [::]:netbios-ssn [::]:* LISTEN tcp6 0 0 [::]:57650 [::]:* LISTEN udp6 0 0 [::]:xdmcp [::]:* The sysctl is definitely in effect, though: per(a)terah:/etc/sysctl.d$ /sbin/sysctl -a | grep ipv6 | grep disable net.ipv6.conf.all.disable_ipv6 = 1 net.ipv6.conf.default.disable_ipv6 = 1 net.ipv6.conf.lo.disable_ipv6 = 1 net.ipv6.conf.eth1.disable_ipv6 = 1 net.ipv6.conf.eth2.disable_ipv6 = 1 net.ipv6.conf.eth0.disable_ipv6 = 1 ....and ifconfig doesn't show any ipv6 addresses. > I just looked at mine (kdm) and it only seems to be listening to IPv6, > but I am pretty sure it will also connect to IPv4. I just checked > google and there are some similar problems listed and some suggestions > on how to solve them. One suggests using module aliases to prevent > loading the IPv6 module > (http://www.linux.com/community/blogs/disable-ipv6-on-debian-lenny-quick-howto.html). Yeah, I read the idea about module aliases as well, but it seems pointless since IPv6 isn't a module on my system (using the 2.6.32-3-amd64 kernel from squeeze). It's interesting however that you say that you expect it to work with IPv4 even though it has only bound the ipv6 socket. I guess you could be right (depending on how the actual ipv4-to-ipv6 stuff works...). In my case however, I can't get a working XMDCP login screen so I'm suspecting this is the problem. (Please, Cc any replies to my email address since I don't subscribe to the mailing lists. Thanks) -- Best regards, Per Lundberg -- To UNSUBSCRIBE, email to debian-user-REQUEST(a)lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmaster(a)lists.debian.org Archive: http://lists.debian.org/AANLkTikBzDJjFe0joDa0hQXd4qFCFVIBW_yhCfciWwLI(a)mail.gmail.com
From: Julien Cristau on 29 May 2010 16:00 On Sat, May 29, 2010 at 22:32:07 +0300, Per Lundberg wrote: > >> Isn't there any XDMCP-capable server available in squeeze that can > >> speak ipv4 any more? I'm fairly sure xdmcp over ipv4 works just fine with both xdm and gdm in squeeze, because I tested them (and made them work with the bindv6only=1 setting) a month or two ago. Cheers, Julien
From: Julien Cristau on 29 May 2010 16:30
On Sat, May 29, 2010 at 23:16:06 +0300, Per Lundberg wrote: > On Sat, May 29, 2010 at 10:54 PM, Julien Cristau <jcristau(a)debian.org> wrote: > > Hi Julien, > > > I'm fairly sure xdmcp over ipv4 works just fine with both xdm and gdm in > > squeeze, because I tested them (and made them work with the bindv6only=1 > > setting) a month or two ago. > > OK, that's interesting... Just for the sake of it, I even tried > enabling the bindv6only (net.ipv6.bindv6only=1) setting, to see if it > would make any difference. Negative; it still only binds to the udp6 > socket. > > per(a)terah:/etc/sysctl.d$ sudo netstat -l -n -p | grep 177 > udp6 0 0 :::177 :::* > 1632/xdm > That's fine, bind() on in6addr_any lets you receive ipv4 packets when IPV6_V6ONLY is turned off (which xdm does even if the system default is backwards). > Do you have any active XDM setup where you could try this yourself? As > I hinted in my previous email, I'm not 100% sure of this, but doesn't > the above udp6 line mean that it will *only* work from an ipv6-capable > client...? Sorry, I can't test right now, but no, as I said above an udp6 socket can talk to ipv4 hosts. Cheers, Julien |