NAME

dtcps —

Dynamic Tunnel Configuration Protocol daemon

SYNOPSIS

dtcps [-cdDoU] [-b udp-port] [-g address] [-i interfaces] [-I udp-interface] [-p port] [prefix]

DESCRIPTION

dtcps implements Dynamic Tunnel Configuration Protocol (DTCP for short) proposed by Trumpet. This listens to IPv4 TCP port 20200 (or port specified by port), for DTCP client connections.

dtcps will use APOP password database file (pop.auth) as password database.

Clients requesting tunnel typed “tunnelonly” will get simple IPv6-over-IPv4 tunnel. No global address will be assigned to the configured tunnel link. It is up to administrators to assign global IPv6 address to the client host, or to the client network. Static assignment by hand or use of router advertisement packet should do the trick. Use of router renumbering protocol may be a candidate.

Clients requesting tunnel typed “network” aka “tunnelroute” will get IPv6-over-IPv4 tunnel with appropriate static route for the connected user installed. This can be used for prefix delegation. The routes for each user is specified in /usr/local/etc/routetable. No global address will be assigned to the configured tunnel link.

If prefix argument is specified, dtcps will accept tunnel request for “host” tunnel type. The tunnel type needs a pair of temporary global IPv6 address for the configured tunnel link, like 3ffe:ffff:ffff:ffff::5 and 3ffe:ffff:ffff:ffff::6. The address pair will be assigned from specified prefix. Prefixlen for the temporary global address will be 128, and it will be computed by using interface number of tunnel interface.

dtcps assumes all gif interfaces are available to use. If -i interfaces argument is specified, dtcps will use only specified interfaces. interfaces accepts regular expression.

If interfaces is not regular expression but an exact interface name, dtcps acts as interface cloning mode which dtcps creates and deletes interfaces appropriately. In this mode, interfaces means a lower interface to be created.

With interface cloning mode, if -o is specified, dtcps creates the interfaces appropriately, but prevents destroying and reuses created interfaces.

If -U is specified, dtcps accepts request for an IPv6 over an UDP/IPv4 tunnel as well. The lower value of an UDP port is specified by -b, and its default is “4028”. dtcps assumes all netgraph interfaces are available to use. If -I interface argument is specified, dtcps creates and deletes interfaces appropriately. interface means a lower interface to be created. An IPv6 over an UDP/IPv4 tunnel requires Netgraph. (Experimental)

You may want to use specific interface for certain user. You can specify the interface to 3rd field of /usr/local/etc/routetable. It can be used not only for tunnel typed “network” but also “tunnelonly” and “host”. If you don't want to assign prefix for your user, you can specify ‘-’ for 2nd field.

-D prevents dtcps from daemonizing on invocation.

-c disables interface cloning mode.

-d puts dtcps into debug mode.

In normal situation, you cannot serv DTCP from behind your NAT box. However, you may serv DTCP in such situation with the help of NAT box. In such case, you need to respond actual global address to a client. -g address is specified, dtcps responds the address as the actuall IPv4 global address of your NAT box.

RETURN VALUES

dtcps will exit with positive value on errors.

FILES

/usr/local/etc/routetable: This file is used for “network” tunnel type, and maps between the user and the assigned IPv6 prefix for the user. The format is a space separated list of the user name, the assigned IPv6 prefix and the interface. The IPv6 prefix is a pair of IPv6 address and prefixlen like addr/prefixlen. Multiple IPv6 prefixes can be specified by using comma as separator. The interface is optional, and if interface is specified, the interface is used for the user.
/usr/local/etc/qpopper/pop.auth: The APOP password database.
/var/run/dtcps.pid: Contains the process ID of the dtcps listening for connections. The content of this file is not sensitive; it can be world-readable.

HISTORY

The dtcps command first appeared in WIDE/KAME IPv6 protocol stack kit.

“network” tunnel type and other useful facilities were added by Hajimu UMEMOTO ⟨ume@mahoroba.org⟩.

BUGS

DTCP needs to keep TCP connection between server and client. Therefore, maximum number of client served by single dtcps will be bounded by the maximum number of filehandle allowed to a process (100 or so).

dtcps invokes several external commands, like ifconfig(8) and gifconfig(8). Command search path must be configured properly before invoking dtcps.

dtcps requires qpopauth shipped with qpopper to maintain APOP password database. There is dtcpauth for this purpose. Though the ability of dtcpauth is still limitted, you can use it for the replacement for qpopauth.

dtcps was written in Ruby. :-)