Ubuntu Manpage: gvpe.conf - configuration file for the GNU VPE daemon

NAME

       gvpe.conf - configuration file for the GNU VPE daemon

SYNOPSIS

          # global options for all nodes
          udp-port = 407
          mtu = 1492
          ifname = vpn0

          # first node is named branch1 and is at 1.2.3.4
          node = branch1
          hostname = 1.2.3.4

          # second node uses dns to resolve the address
          node = branch2
          hostname = www.example.net
          udp-port = 500       # this host uses a different udp-port

          # third node has no fixed ip address
          node = branch3
          connect = ondemand

DESCRIPTION

The gvpe config file consists of a series of lines that contain "variable = value" pairs.
Empty lines are ignored. Comments start with a "#" and extend to the end of the line. They
can be used on their own lines, or after any directives. Whitespace is allowed around the
"=" sign or after values, but not within the variable names or values themselves.

All settings are applied "in order", that is, later settings of the same variable
overwrite earlier ones.

The only exceptions to the above are the "on" and "include" directives:

on nodename ...
on !nodename ...
You can prefix any configuration directive with "on" and a nodename. GVPE will will
only "execute" it on the named node, or (if the nodename starts with "!") on all nodes
except the named one.

Example: set the MTU to 1450 everywhere, "loglevel" to "noise" on "branch1", and
"connect" to "ondemand" everywhere but on branch2.

mtu = 1450
on branch1 loglevel = noise
on !branch2 connect = ondemand

include relative-or-absolute-path
Reads the specified file (the path must not contain whitespace or "=" characters) and
evaluate all config directives in it as if they were spelled out in place of the
"include" directive.

The path is a printf format string, that is, you must escape any "%" by doubling it,
and you can have a single %s inside, which will be replaced by the current nodename.

Relative paths are interpreted relative to the GVPE config directory.

Example: include the file local.conf in the config directory on every node.

include local.conf

Example: include a file conf/nodename.conf

include conf/%s.conf

ANATOMY OF A CONFIG FILE

       Usually, a config file starts with a few global settings (like the UDP port to listen on),
       followed by node-specific sections that begin with a "node = nickname" line.

       Every node that is part of the network must have a section that starts with "node =
       nickname". The number and order of the nodes is important and must be the same on all
       nodes. It is not uncommon for node sections to be completely empty - if the default values
       are right.

       Node-specific settings can be used at any time. If used before the first node section they
       will set the default values for all following nodes.

CONFIG VARIABLES

GLOBAL SETTINGS
Global settings will affect the behaviour of the running gvpe daemon, that is, they are in
some sense node-specific (config files can set different values on different nodes using
"on"), but will affect the behaviour of the gvpe daemon and all connections it creates.

chroot = path or /
Tells GVPE to chroot(2) to the specified path after reading all necessary files,
binding to sockets and running the "if-up" script, but before running "node-up" or any
other scripts.

The special path / instructs GVPE to create (and remove) an empty temporary directory
to use as new root. This is most secure, but makes it impossible to use any scripts
other than the "if-up" one.

chuid = numerical-uid
chgid = numerical-gid
These two options tell GVPE to change to the given user and/or group id after reading
all necessary files, binding to sockets and running the "if-up" script.

Other scripts, such as "node-up", are run with the new user id or group id.

chuser = username
Alternative to "chuid" and "chgid": Sets both "chuid" and "chgid" to the user and
(primary) group ids of the specified user (for example, "nobody").

dns-forw-host = hostname/ip
The DNS server to forward DNS requests to for the DNS tunnel protocol (default:
127.0.0.1, changing it is highly recommended).

dns-forw-port = port-number
The port where the "dns-forw-host" is to be contacted (default: 53, which is fine in
most cases).

Normally, when the forwarding server changes the case of domain names then GVPE will
automatically set this to false.

dns-max-outstanding = integer-number-of-requests
The maximum number of outstanding DNS transport requests (default: 100). GVPE will
never issue more requests then the given limit without receiving replies. In heavily
overloaded situations it might help to set this to a low number (e.g. 3 or even 1) to
limit the number of parallel requests.

The default should be working OK for most links.

dns-overlap-factor = float
The DNS transport uses the minimum request latency (min_latency) seen during a
connection as it's timing base. This factor (default: 0.5, must be > 0) is multiplied
by min_latency to get the maximum sending rate (= minimum send interval), i.e. a
factor of 1 means that a new request might be generated every min_latency seconds,
which means on average there should only ever be one outstanding request. A factor of
0.5 means that GVPE will send requests twice as often as the minimum latency measured.

For congested or picky DNS forwarders you could use a value nearer to or exceeding 1.

The default should be working OK for most links.

dns-send-interval = send-interval-in-seconds
The minimum send interval (= maximum rate) that the DNS transport will use to send new
DNS requests. GVPE will not exceed this rate even when the latency is very low. The
default is 0.01, which means GVPE will not send more than 100 DNS requests per
connection per second. For high-bandwidth links you could go lower, e.g. to 0.001 or
so. For congested or rate-limited links, you might want to go higher, say 0.1, 0.2 or
even higher.

The default should be working OK for most links.

dns-timeout-factor = float
Factor to multiply the "min_latency" (see "dns-overlap-factor") by to get request
timeouts. The default of 8 means that the DNS transport will resend the request when
no reply has been received for longer than eight times the minimum (= expected)
latency, assuming the request or reply has been lost.

For congested links a higher value might be necessary (e.g. 30). If the link is very
stable lower values (e.g. 2) might work nicely. Values near or below 1 makes no sense
whatsoever.

The default should be working OK for most links but will result in low throughput if
packet loss is high.

if-up = relative-or-absolute-path
Sets the path of a script that should be called immediately after the network
interface is initialized (but not necessarily up). The following environment variables
are passed to it (the values are just examples).

Variables that have the same value on all nodes:

CONFBASE=/etc/gvpe
The configuration base directory.

IFNAME=vpn0
The network interface to initialize.

IFTYPE=native # or tincd
IFSUBTYPE=linux # or freebsd, darwin etc..
The interface type ("native" or "tincd") and the subtype (usually the OS name in
lowercase) that this GVPE was configured for. Can be used to select the correct
syntax to use for network-related commands.

MTU=1436
The MTU to set the interface to. You can use lower values (if done consistently on
all nodes), but this is usually either inefficient or simply ineffective.

NODES=5
The number of nodes in this GVPE network.

Variables that are node-specific and with values pertaining to the node running this
GVPE:

IFUPDATA=string
The value of the configuration directive "if-up-data".

MAC=fe:fd:80:00:00:01
The MAC address the network interface has to use.

Might be used to initialize interfaces on platforms where GVPE does not do this
automatically. Please see the "gvpe.osdep(5)" man page for platform-specific
information.

NODENAME=branch1
The nickname of the node.

NODEID=1
The numerical node ID of the node running this instance of GVPE. The first node
mentioned in the config file gets ID 1, the second ID 2 and so on.

In addition, all node-specific variables (except "NODEID") will be available with a
postfix of "_nodeid", which contains the value for that node, e.g. the "MAC_1"
variable contains the MAC address of node #1, while the "NODENAME_22" variable
contains the name of node #22.

Here is a simple if-up script:

#!/bin/sh
ip link set $IFNAME up
[ $NODENAME = branch1 ] && ip addr add 10.0.0.1 dev $IFNAME
[ $NODENAME = branch2 ] && ip addr add 10.1.0.1 dev $IFNAME
ip route add 10.0.0.0/8 dev $IFNAME

More complicated examples (using routing to reduce ARP traffic) can be found in the
etc/ subdirectory of the distribution.

ifname = devname
Sets the tun interface name to the given name. The default is OS-specific and most
probably something like "tun0".

ifpersist = yes|true|on | no|false|off
Should the tun/tap device be made persistent, that is, should the device stay up even
when gvpe exits? Some versions of the tunnel device have problems sending packets when
gvpe is restarted in persistent mode, so if the connections can be established but you
cannot send packets from the local node, try to set this to "off" and do an ifconfig
down on the device.

ip-proto = numerical-ip-protocol
Sets the protocol number to be used for the rawip protocol. This is a global option
because all nodes must use the same protocol, and since there are no port numbers, you
cannot easily run more than one gvpe instance using the same protocol, nor can you
share the protocol with other programs.

The default is 47 (GRE), which has a good chance of tunneling through firewalls (but
note that gvpe's rawip protocol is not GRE compatible). Other common choices are 50
(IPSEC, ESP), 51 (IPSEC, AH), 4 (IPIP tunnels) or 98 (ENCAP, rfc1241).

Many versions of Linux seem to have a bug that causes them to reorder packets for some
ip protocols (GRE, ESP) but not for others (AH), so choose wisely (that is, use 51,
AH).

http-proxy-host = hostname/ip
The "http-proxy-*" family of options are only available if gvpe was compiled with the
"--enable-http-proxy" option and enable tunneling of tcp connections through a http
proxy server.

"http-proxy-host" and "http-proxy-port" should specify the hostname and port number of
the proxy server. See "http-proxy-loginpw" if your proxy requires authentication.

Please note that gvpe will still try to resolve all hostnames in the configuration
file, so if you are behind a proxy without access to a DNS server better use numerical
IP addresses.

To make best use of this option disable all protocols except TCP in your config file
and make sure your routers (or all other nodes) are listening on a port that the proxy
allows (443, https, is a common choice).

If you have a router, connecting to it will suffice. Otherwise TCP must be enabled on
all nodes.

Example:

http-proxy-host = proxy.example.com
http-proxy-port = 3128 # 8080 is another common choice
http-proxy-auth = schmorp:grumbeere

http-proxy-port = proxy-tcp-port
The port where your proxy server listens.

http-proxy-auth = login:password
The optional login and password used to authenticate to the proxy server, separated by
a literal colon (":"). Only basic authentication is currently supported.

keepalive = seconds
Sets the keepalive probe interval in seconds (default: 60). After this many seconds of
inactivity the daemon will start to send keepalive probe every 3 seconds until it
receives a reply from the other end. If no reply is received within 15 seconds, the
peer is considered unreachable and the connection is closed.

mtu = bytes
Sets the maximum MTU that should be used on outgoing packets (basically the MTU of the
outgoing interface) The daemon will automatically calculate maximum overhead (e.g. UDP
header size, encryption blocksize...) and pass this information to the "if-up" script.

Recommended values are 1500 (ethernet), 1492 (pppoe), 1472 (pptp).

This value must be the minimum of the MTU values of all nodes.

nfmark = integer
This advanced option, when set to a nonzero value (default: 0), tries to set the
netfilter mark (or fwmark) value on all sockets gvpe uses to send packets.

This can be used to make gvpe use a different set of routing rules. For example, on
GNU/Linux, the "if-up" could set "nfmark" to 1000 and then put all routing rules into
table 99 and then use an ip rule to make gvpe traffic avoid that routing table, in
effect routing normal traffic via gvpe and gvpe traffic via the normal system routing
tables:

ip rule add not fwmark 1000 lookup 99

node = nickname
Not really a config setting but introduces a node section. The nickname is used to
select the right configuration section and must be passed as an argument to the gvpe
daemon.

node-up = relative-or-absolute-path
Sets a command (default: none) that should be called whenever a connection is
established (even on rekeying operations). Note that node-up/down scripts will be run
asynchronously, but execution is serialised, so there will only ever be one such
script running.

In addition to all the variables passed to "if-up" scripts, the following environment
variables will be set (values are just examples):

DESTNODE=branch2
The name of the remote node.

DESTID=2
The node id of the remote node.

DESTSI=rawip/88.99.77.55:0
The "socket info" of the target node, protocol dependent but usually in the format
protocol/ip:port.

DESTIP=188.13.66.8
The numerical IP address of the remote node (gvpe accepts connections from
everywhere, as long as the other node can authenticate itself).

DESTPORT=655 # deprecated
The protocol port used by the other side, if applicable.

STATE=up
Node-up scripts get called with STATE=up, node-change scripts get called with
STATE=change and node-down scripts get called with STATE=down.

Here is a nontrivial example that uses nsupdate to update the name => ip mapping in
some DNS zone:

#!/bin/sh
{
echo update delete $DESTNODE.lowttl.example.net. a
echo update add $DESTNODE.lowttl.example.net. 1 in a $DESTIP
echo
} | nsupdate -d -k $CONFBASE:key.example.net.

node-change = relative-or-absolute-path
Same as "node-change", but gets called whenever something about a connection changes
(such as the source IP address).

node-down = relative-or-absolute-path
Same as "node-up", but gets called whenever a connection is lost.

pid-file = path
The path to the pid file to check and create (default: "LOCALSTATEDIR/run/gvpe.pid").

private-key = relative-path-to-key
Sets the path (relative to the config directory) to the private key (default:
"hostkey"). This is a printf format string so every "%" must be doubled. A single %s
is replaced by the hostname, so you could use paths like "hostkeys/%s" to fetch the
files at the location where "gvpectrl" puts them.

Since only the private key file of the current node is used and the private key file
should be kept secret per-node to avoid spoofing, it is not recommended to use this
feature.

rekey = seconds
Sets the rekeying interval in seconds (default: 3607). Connections are reestablished
every "rekey" seconds, making them use a new encryption key.

seed-device = path
The random device used to initially and regularly seed the random number generator
(default: /dev/urandom). Randomness is of paramount importance to the security of the
algorithms used in gvpe.

On program start and every seed-interval, gvpe will read 64 octets.

Setting this path to the empty string will disable this functionality completely (the
underlying crypto library will likely look for entropy sources on it's own though, so
not all is lost).

seed-interval = seconds
The number of seconds between reseeds of the random number generator (default: 3613).
A value of 0 disables this regular reseeding.

NODE SPECIFIC SETTINGS
The following settings are node-specific, that is, every node can have different settings,
even within the same gvpe instance. Settings that are set before the first node section
set the defaults, settings that are set within a node section only apply to the given
node.

allow-direct = nodename
Allow direct connections to this node. See "deny-direct" for more info.

compress = yes|true|on | no|false|off
For the current node, this specified whether it will accept compressed packets, and
for all other nodes, this specifies whether to try to compress data packets sent to
this node (default: "yes"). Compression is really cheap even on slow computers, has no
size overhead at all and will only be used when the other side supports compression,
so enabling this is often a good idea.

connect = ondemand | never | always | disabled
Sets the connect mode (default: "always"). It can be "always" (always try to establish
and keep a connection to the given node), "never" (never initiate a connection to the
given host, but accept connections), "ondemand" (try to establish a connection when
there are outstanding packets in the queue and take it down after the keepalive
interval) or "disabled" (node is bad, don't talk to it).

Routers will automatically be forced to "always" unless they are "disabled", to ensure
all nodes can talk to each other.

deny-direct = nodename | *
Deny direct connections to the specified node (or all nodes when "*" is given). Only
one node can be specified, but you can use multiple "allow-direct" and "deny-direct"
statements. This only makes sense in networks with routers, as routers are required
for indirect connections.

Sometimes, a node cannot reach some other nodes for reasons of network connectivity.
For example, a node behind a firewall that only allows connections to/from a single
other node in the network. In this case one should specify "deny-direct = *" and
"allow-direct = othernodename" (the other node must be a router for this to work).

The algorithm to check whether a connection may be direct is as follows:

1. Other node mentioned in an "allow-direct"? If yes, allow the connection.

2. Other node mentioned in a "deny-direct"? If yes, deny direct connections.

3. Allow the connection.

That is, "allow-direct" takes precedence over "deny-direct".

The check is done in both directions, i.e. both nodes must allow a direct connection
before one is attempted, so you only need to specify connect limitations on one node.

dns-domain = domain-suffix
The DNS domain suffix that points to the DNS tunnel server for this node.

The domain must point to a NS record that points to the dns-hostname, i.e.

dns-domainname = tunnel.example.net
dns-hostname = tunnel-server.example.net

Corresponds to the following DNS entries in the "example.net" domain:

tunnel.example.net. NS tunnel-server.example.net.
tunnel-server.example.net. A 13.13.13.13

dns-hostname = hostname/ip
The address to bind the DNS tunnel socket to, similar to the "hostname", but for the
DNS tunnel protocol only. Default: 0.0.0.0, but that might change.

dns-port = port-number
The port to bind the DNS tunnel socket to. Must be 53 on DNS tunnel servers.

Enable the DNS tunneling protocol on this node, either as server or as client. Support
for this transport protocol is only available when gvpe was compiled using the
"--enable-dns" option.

Enable the ICMP transport using ICMP packets of type "icmp-type" on this node.

Enable the RAW IPv4 transport using the "ip-proto" protocol (default: "no").

Enable the TCPv4 transport using the "tcp-port" port (default: "no"). Support for this
transport protocol is only available when gvpe was compiled using the "--enable-tcp"
option.

Enable the UDPv4 transport using the "udp-port" port (default: "no").

hostname = hostname | ip [can not be defaulted]
Forces the address of this node to be set to the given DNS hostname or IP address. It
will be resolved before each connect request, so dyndns should work fine. If this
setting is not specified and a router is available, then the router will be queried
for the address of this node. Otherwise, the connection attempt will fail.

Note that DNS resolving is done synchronously, pausing the daemon. If that is an issue
you need to specify IP addresses.

icmp-type = integer
Sets the type value to be used for outgoing (and incoming) packets sent via the ICMP
transport.

The default is 0 (which is "echo-reply", also known as "ping-reply"). Other useful
values include 8 ("echo-request", a.k.a. "ping") and 11 ("time-exceeded"), but any
8-bit value can be used.

if-up-data = value
The value specified using this directive will be passed to the "if-up" script in the
environment variable "IFUPDATA".

inherit-tos = yes|true|on | no|false|off
Whether to inherit the TOS settings of packets sent to the tunnel when sending packets
to this node (default: "yes"). If set to "yes" then outgoing tunnel packets will have
the same TOS setting as the packets sent to the tunnel device, which is usually what
you want.

max-retry = positive-number
The maximum interval in seconds (default: 3600, one hour) between retries to establish
a connection to this node. When a connection cannot be established, gvpe uses
exponential back-off capped at this value. It's sometimes useful to set this to a much
lower value (e.g. 120) on connections to routers that usually are stable but sometimes
are down, to assure quick reconnections even after longer downtimes.

max-ttl = seconds
Expire packets that couldn't be sent after this many seconds (default: 60). Gvpe will
normally queue packets for a node without an active connection, in the hope of
establishing a connection soon. This value specifies the maximum lifetime a packet
will stay in the queue, if a packet gets older, it will be thrown away.

max-queue = positive-number>=1
The maximum number of packets that will be queued (default: 512) for this node. If
more packets are sent then earlier packets will be expired. See "max-ttl", above.

router-priority = 0 | 1 | positive-number>=2
Sets the router priority of the given node (default: 0, disabled).

If some node tries to connect to another node but it doesn't have a hostname, it asks
a router node for it's IP address. The router node chosen is the one with the highest
priority larger than 1 that is currently reachable. This is called a mediated
connection, as the connection itself will still be direct, but it uses another node to
mediate between the two nodes.

The value 0 disables routing, that means if the node receives a packet not for itself
it will not forward it but instead drop it.

The special value 1 allows other hosts to route through the router host, but they will
never route through it by default (i.e. the config file of another node needs to
specify a router priority higher than one to choose such a node for routing).

The idea behind this is that some hosts can, if required, bump the "router-priority"
setting to higher than 1 in their local config to route through specific hosts. If
"router-priority" is 0, then routing will be refused, so 1 serves as a "enable, but do
not use by default" switch.

Nodes with "router-priority" set to 2 or higher will always be forced to "connect" =
"always" (unless they are "disabled").

tcp-port = port-number
Similar to "udp-port" (default: 655), but sets the TCP port number.

udp-port = port-number
Sets the port number used by the UDP protocol (default: 655, not officially assigned
by IANA!).

CONFIG DIRECTORY LAYOUT

       The default (or recommended) directory layout for the config directory is:

       gvpe.conf
           The config file.

       if-up
           The if-up script

       node-up, node-down
           If used the node up or node-down scripts.

       hostkey
           The private key (taken from "hostkeys/nodename") of the current host.

       pubkey/nodename
           The public keys of the other nodes, one file per node.

AUTHOR

       Marc Lehmann <gvpe@schmorp.de>

NAME

SYNOPSIS

DESCRIPTION

ANATOMY OF A CONFIG FILE

CONFIG VARIABLES

CONFIG DIRECTORY LAYOUT

SEE ALSO

AUTHOR