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.
The only exception to the above is the "on" directive that can prefix
any name = value setting and will only "execute" it on the named
node, or (if the nodename starts with "!") on all nodes except the
named one.
For 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
All settings are applied "in order", that is, later settings of the
same variable overwrite earlier ones.
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.
- 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).
- 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.
- loglevel =
noise|trace|debug|info|notice|warn|error|critical
- Set the logging level. Connection established messages are
logged at level info, notable errors are logged with error. Default is
info.
- 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.
- 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: 3600).
Connections are reestablished every rekey seconds, making them use a new
encryption key.
- 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 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-dns = yes|true|on | no|false|off
- See gvpe.protocol(7) for a description of the DNS
transport protocol. Avoid this protocol if you can.
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-icmp = yes|true|on | no|false|off
- See gvpe.protocol(7) for a description of the ICMP
transport protocol.
Enable the ICMP transport using ICMP packets of type icmp-type on this
node.
- enable-rawip = yes|true|on | no|false|off
- See gvpe.protocol(7) for a description of the RAW IP
transport protocol.
Enable the RAW IPv4 transport using the ip-proto protocol (default:
no).
- enable-tcp = yes|true|on | no|false|off
- See gvpe.protocol(7) for a description of the TCP
transport protocol.
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-udp = yes|true|on | no|false|off
- See gvpe.protocol(7) for a description of the UDP
transport protocol.
Enable the UDPv4 transport using the udp-port port (default: no, unless no
other protocol is enabled for a node, in which case this protocol is
enabled automatically).
NOTE: Please specify enable-udp = yes if you want to use it even though it
might get switched on automatically, as some future version might default
to another default protocol.
- 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.
SEE ALSO¶
gvpe(5),
gvpe(8),
gvpectrl(8).
AUTHOR¶
Marc Lehmann <gvpe@schmorp.de>