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 following directives:

node nodename
Introduces a node section. The nodename is used to select the right configuration section and is the
same string as is passed as an argument to the gvpe daemon.

Multiple node statements with the same node name are supported and will be merged together.

global
This statement switches back to the global section, which is mainly useful if you want to include a
second config file, e..g for local customisations. To do that, simply include this at the very end of
your config file:

global
include local.conf

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-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). The first %s is
replaced by the nodename - any other use of % must be written as %%.

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 be able to share the same config directory between nodes.

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 this way though.

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.

serial = string
The configuration serial number. This can be any string up to 16 bytes length. Only when the serial
matches on both sides of a connection will the connection succeed. This is not a security mechanism
and eay to spoof, this mechanism exists to alert users that their config is outdated.

It's recommended to specify this is a date string such as 2013-05-05 or 20121205084417.

The exact algorithm is as this: if a connection request is received form a node with an identical
serial, then it succeeds normally.

If the remote serial is lower than the local serial, it is ignored.

If the remote serial is higher than the local serial, a warning message is logged.

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.

low-power = yes|true|on | no|false|off
If true, designates a node as a low-power node. Low-power nodes use larger timeouts and try to reduce
cpu time. Other nodes talking to a low-power node will also use larger timeouts, and will use less
aggressive optimisations, in the hope of reducing load. Security is not compromised.

The typical low-power node would be a mobile phone, where wakeups and encryption can significantly
increase power drain.

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 (default path of the) private key of the current host.

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

AUTHOR

       Marc Lehmann <gvpe@schmorp.de>

3.0                                                2016-11-12                                       GVPE.CONF(5)

NAME

SYNOPSIS

DESCRIPTION

ANATOMY OF A CONFIG FILE

CONFIG VARIABLES

CONFIG DIRECTORY LAYOUT

SEE ALSO

AUTHOR