Hi An advantage of the fixed port which I want to insist on is "A user can choose an arbitrary port.". Neither remote-connection nor authentication matters particularly. It is a story before it. The reason why this user comes to need choice of a fixed port is as follows. If an user absolutely use the port number from 5900, either does not surely matter. But, for example, when the port number 5900-5920 is used by other uses, when there is a user hoping that I manage a port number by use to assign from 9000, A fxed port selection mode is necessary, because there is these situation. (The person who does not need a fixed port should choose an auto selection mode.) Any users will not hope to change other designs to use it for auto selection. Thanks, Shigeki Sakamoto. > On Tue, May 29, 2007 at 04:44:15PM +0900, S.Sakamoto wrote: > > Hi, Dan > > > > Thanks for your comment. > > > > > It will prove unreliable in practice, because even if you > > > fix a particular guest on port 5905, any other guest doing dynamic VNC port > > > assignment may choose this port before the hardcoded guest starts. > > This situation is surely thought. > > But, I think that problem is solved > > if it performs a repetition check of a port number in virt-inst. > > When it is this situation, at first, > > examine the port number that all other guests use when it starts a guest. > > Next, If the port number is fixed and repetition, > > output a message. [e.g."Repetition. Set a different port number."] > > (However, there is not a function setting a port for an existing guest now. > > If it is necessary at the same time, > > I make 'check of repetition' and 'function setting a port for an existing guest'.) > > > > > It is not going to be easy for virt-manager to do validation of this port number > > > either, since in the near future virt-manager may well be running remotely > > > from the host. > > If it adds a revision to libvirt side to get a port number from the information that acquired from xend, > > the acquisition of a port number will be easy. > > > > > this is a very small niche usecase > > I do not think so. and I think that there is a person to need surely. > > Because, I think that it can perform the prevention / maintenance > > by the pair of guest and port-number are managed. > > For example, The person who thinks about maintenance for the port which opened out > > had better be a fixed port number. > > If it does't know whether it has already opened or it will open out from now on, > > it will become difficult to deal with possibility of attack to an opening port. > > Therefore, > > the user who wants to open only a specific port for a firewall needs to fixed port number. > > And, even if it can get a dynamic port from remote connection in the future, > > he needs a fixed port number at the time of remote connection too, > > because he wants to connection with only a specific port. > > There's two possibilities to consider: > > a. The admin of the Dom0 permanently opens up a range of ports (eg 5900->5920) to allow > upto 20 vms to have their console accessed at any time. In this case, whether you > use fixed or dynamic ports per VM, you still need 20 ports open, to run 20 consoles. > > b. The admin of the Dom0 only opens specific ports for short periods of time. In this > case the admin will have to lookup what port corresponds to a VM, so it doesn't matter > whether we're using fixed or dynamic ports, the admin still has same amount of work > to lookup a port. > > So, I still don't see that using fixed ports in virt-manager has any benefit for the > administration POV. > > Neither of these two options are entirely satisfactory though - it would be desirable > to only open up a port when explicitly needed, and not require the admin to do any > work. One might even suggest that libvirt should have some form of API to let the > remote user request access to the cosnole - authenticated of course > > > virDomainAllowConsole(virDomainPtr, const char *ipaddr); > virDomainDisallowConsole(virDomainPtr, const char *ipaddr); > > Calling either of these functions would add neccessary iptables rule to allow > access to the console for that particular domain, from the specified ip address. > When the virConnectPtr object was closed, then any rules would also automatically > be removed. > > This would allow virt-manager to securely request access to the console without > needing permanent iptables rules. > > These's probably quite a bit more to think about wrt to iptables, consoles > and seecure authentication. In the very near future libvirt will have the > support for remote management merged and we'll be in a position to experiment > with these ideas for real. So I don't think we want to add support for fixed > port numbers in the virt-manager wizard until we've tried out some of these > ideas. > > Regards, > Dan. > -- > |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| > |=- Perl modules: http://search.cpan.org/~danberr/ -=| > |=- Projects: http://freshmeat.net/~danielpb/ -=| > |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=| >
