--- gvpe/doc/gvpe.conf.5	2011/03/08 17:33:30	1.29
+++ gvpe/doc/gvpe.conf.5	2012/12/04 10:29:43	1.30
@@ -0,0 +1,764 @@
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+.rm #[ #] #H #V #F C
+.\" ========================================================================
+.\"
+.IX Title "GVPE.CONF 5"
+.TH GVPE.CONF 5 "2012-07-06" "2.24" "GNU Virtual Private Ethernet"
+.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
+.\" way too many mistakes in technical documents.
+.if n .ad l
+.nh
+.SH "NAME"
+gvpe.conf \- configuration file for the GNU VPE daemon
+.SH "SYNOPSIS"
+.IX Header "SYNOPSIS"
+.Vb 4
+\&   # 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
+.Ve
+.SH "DESCRIPTION"
+.IX Header "DESCRIPTION"
+The gvpe config file consists of a series of lines that contain \f(CW\*(C`variable
+= value\*(C'\fR pairs. Empty lines are ignored. Comments start with a \f(CW\*(C`#\*(C'\fR 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 \f(CW\*(C`=\*(C'\fR sign or after
+values, but not within the variable names or values themselves.
+.PP
+All settings are applied \*(L"in order\*(R", that is, later settings of the same
+variable overwrite earlier ones.
+.PP
+The only exceptions to the above are the \*(L"on\*(R" and \*(L"include\*(R" directives:
+.IP "on nodename ..." 4
+.IX Item "on nodename ..."
+.PD 0
+.IP "on !nodename ..." 4
+.IX Item "on !nodename ..."
+.PD
+You can prefix any configuration directive with \f(CW\*(C`on\*(C'\fR and a nodename. \s-1GVPE\s0
+will will only \*(L"execute\*(R" it on the named node, or (if the nodename starts
+with \f(CW\*(C`!\*(C'\fR) on all nodes except the named one.
+.Sp
+Example: set the \s-1MTU\s0 to \f(CW1450\fR everywhere, \f(CW\*(C`loglevel\*(C'\fR to \f(CW\*(C`noise\*(C'\fR on
+\&\f(CW\*(C`branch1\*(C'\fR, and \f(CW\*(C`connect\*(C'\fR to \f(CW\*(C`ondemand\*(C'\fR everywhere but on branch2.
+.Sp
+.Vb 3
+\&   mtu = 1450
+\&   on branch1 loglevel = noise
+\&   on !branch2 connect = ondemand
+.Ve
+.IP "include relative-or-absolute-path" 4
+.IX Item "include relative-or-absolute-path"
+Reads the specified file (the path must not contain whitespace or \f(CW\*(C`=\*(C'\fR
+characters) and evaluate all config directives in it as if they were
+spelled out in place of the \f(CW\*(C`include\*(C'\fR directive.
+.Sp
+The path is a printf format string, that is, you must escape any \f(CW\*(C`%\*(C'\fR
+by doubling it, and you can have a single \f(CW%s\fR inside, which will be
+replaced by the current nodename.
+.Sp
+Relative paths are interpreted relative to the \s-1GVPE\s0 config directory.
+.Sp
+Example: include the file \fIlocal.conf\fR in the config directory on every
+node.
+.Sp
+.Vb 1
+\&   include local.conf
+.Ve
+.Sp
+Example: include a file \fIconf/\fRnodename\fI.conf\fR
+.Sp
+.Vb 1
+\&   include conf/%s.conf
+.Ve
+.SH "ANATOMY OF A CONFIG FILE"
+.IX Header "ANATOMY OF A CONFIG FILE"
+Usually, a config file starts with a few global settings (like the \s-1UDP\s0
+port to listen on), followed by node-specific sections that begin with a
+\&\f(CW\*(C`node = nickname\*(C'\fR line.
+.PP
+Every node that is part of the network must have a section that starts
+with \f(CW\*(C`node = nickname\*(C'\fR. 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.
+.PP
+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.
+.SH "CONFIG VARIABLES"
+.IX Header "CONFIG VARIABLES"
+.SS "\s-1GLOBAL\s0 \s-1SETTINGS\s0"
+.IX Subsection "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 \f(CW\*(C`on\*(C'\fR), but will affect the behaviour of
+the gvpe daemon and all connections it creates.
+.IP "dns-forw-host = hostname/ip" 4
+.IX Item "dns-forw-host = hostname/ip"
+The \s-1DNS\s0 server to forward \s-1DNS\s0 requests to for the \s-1DNS\s0 tunnel protocol
+(default: \f(CW127.0.0.1\fR, changing it is highly recommended).
+.IP "dns-forw-port = port-number" 4
+.IX Item "dns-forw-port = port-number"
+The port where the \f(CW\*(C`dns\-forw\-host\*(C'\fR is to be contacted (default: \f(CW53\fR,
+which is fine in most cases).
+.IP "dns-case-preserving = yes|true|on | no|false|off" 4
+.IX Item "dns-case-preserving = yes|true|on | no|false|off"
+Sets whether the \s-1DNS\s0 transport forwarding server preserves case (\s-1DNS\s0
+servers have to, but some access systems are even more broken than others)
+(default: true).
+.Sp
+Normally, when the forwarding server changes the case of domain names then
+\&\s-1GVPE\s0 will automatically set this to false.
+.IP "dns-max-outstanding = integer-number-of-requests" 4
+.IX Item "dns-max-outstanding = integer-number-of-requests"
+The maximum number of outstanding \s-1DNS\s0 transport requests
+(default: \f(CW100\fR). \s-1GVPE\s0 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. \f(CW3\fR or even \f(CW1\fR) to limit the
+number of parallel requests.
+.Sp
+The default should be working \s-1OK\s0 for most links.
+.IP "dns-overlap-factor = float" 4
+.IX Item "dns-overlap-factor = float"
+The \s-1DNS\s0 transport uses the minimum request latency (\fBmin_latency\fR) seen
+during a connection as it's timing base. This factor (default: \f(CW0.5\fR,
+must be > 0) is multiplied by \fBmin_latency\fR to get the maximum sending
+rate (= minimum send interval), i.e. a factor of \f(CW1\fR means that a new
+request might be generated every \fBmin_latency\fR seconds, which means on
+average there should only ever be one outstanding request.  A factor of
+\&\f(CW0.5\fR means that \s-1GVPE\s0 will send requests twice as often as the minimum
+latency measured.
+.Sp
+For congested or picky \s-1DNS\s0 forwarders you could use a value nearer to or
+exceeding \f(CW1\fR.
+.Sp
+The default should be working \s-1OK\s0 for most links.
+.IP "dns-send-interval = send-interval-in-seconds" 4
+.IX Item "dns-send-interval = send-interval-in-seconds"
+The minimum send interval (= maximum rate) that the \s-1DNS\s0 transport will
+use to send new \s-1DNS\s0 requests. \s-1GVPE\s0 will not exceed this rate even when
+the latency is very low. The default is \f(CW0.01\fR, which means \s-1GVPE\s0 will
+not send more than 100 \s-1DNS\s0 requests per connection per second. For
+high-bandwidth links you could go lower, e.g. to \f(CW0.001\fR or so. For
+congested or rate-limited links, you might want to go higher, say \f(CW0.1\fR,
+\&\f(CW0.2\fR or even higher.
+.Sp
+The default should be working \s-1OK\s0 for most links.
+.IP "dns-timeout-factor = float" 4
+.IX Item "dns-timeout-factor = float"
+Factor to multiply the \f(CW\*(C`min_latency\*(C'\fR (see \f(CW\*(C`dns\-overlap\-factor\*(C'\fR) by to
+get request timeouts. The default of \f(CW8\fR means that the \s-1DNS\s0 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.
+.Sp
+For congested links a higher value might be necessary (e.g. \f(CW30\fR). If
+the link is very stable lower values (e.g. \f(CW2\fR) might work
+nicely. Values near or below \f(CW1\fR makes no sense whatsoever.
+.Sp
+The default should be working \s-1OK\s0 for most links but will result in low
+throughput if packet loss is high.
+.IP "if-up = relative-or-absolute-path" 4
+.IX Item "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).
+.Sp
+Variables that have the same value on all nodes:
+.RS 4
+.IP "CONFBASE=/etc/gvpe" 4
+.IX Item "CONFBASE=/etc/gvpe"
+The configuration base directory.
+.IP "IFNAME=vpn0" 4
+.IX Item "IFNAME=vpn0"
+The network interface to initialize.
+.IP "IFTYPE=native # or tincd" 4
+.IX Item "IFTYPE=native # or tincd"
+.PD 0
+.IP "IFSUBTYPE=linux # or freebsd, darwin etc.." 4
+.IX Item "IFSUBTYPE=linux # or freebsd, darwin etc.."
+.PD
+The interface type (\f(CW\*(C`native\*(C'\fR or \f(CW\*(C`tincd\*(C'\fR) and the subtype (usually the
+\&\s-1OS\s0 name in lowercase) that this \s-1GVPE\s0 was configured for. Can be used to
+select the correct syntax to use for network-related commands.
+.IP "MTU=1436" 4
+.IX Item "MTU=1436"
+The \s-1MTU\s0 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.
+.IP "NODES=5" 4
+.IX Item "NODES=5"
+The number of nodes in this \s-1GVPE\s0 network.
+.RE
+.RS 4
+.Sp
+Variables that are node-specific and with values pertaining to the node
+running this \s-1GVPE:\s0
+.IP "IFUPDATA=string" 4
+.IX Item "IFUPDATA=string"
+The value of the configuration directive \f(CW\*(C`if\-up\-data\*(C'\fR.
+.IP "MAC=fe:fd:80:00:00:01" 4
+.IX Item "MAC=fe:fd:80:00:00:01"
+The \s-1MAC\s0 address the network interface has to use.
+.Sp
+Might be used to initialize interfaces on platforms where \s-1GVPE\s0 does not
+do this automatically.  Please see the \f(CW\*(C`gvpe.osdep(5)\*(C'\fR man page for
+platform-specific information.
+.IP "NODENAME=branch1" 4
+.IX Item "NODENAME=branch1"
+The nickname of the node.
+.IP "NODEID=1" 4
+.IX Item "NODEID=1"
+The numerical node \s-1ID\s0 of the node running this instance of \s-1GVPE\s0. The first
+node mentioned in the config file gets \s-1ID\s0 1, the second \s-1ID\s0 2 and so on.
+.RE
+.RS 4
+.Sp
+In addition, all node-specific variables (except \f(CW\*(C`NODEID\*(C'\fR) will be
+available with a postfix of \f(CW\*(C`_nodeid\*(C'\fR, which contains the value for that
+node, e.g. the \f(CW\*(C`MAC_1\*(C'\fR variable contains the \s-1MAC\s0 address of node #1, while
+the \f(CW\*(C`NODENAME_22\*(C'\fR variable contains the name of node #22.
+.Sp
+Here is a simple if-up script:
+.Sp
+.Vb 5
+\&   #!/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
+.Ve
+.Sp
+More complicated examples (using routing to reduce \s-1ARP\s0 traffic) can be
+found in the \fIetc/\fR subdirectory of the distribution.
+.RE
+.IP "ifname = devname" 4
+.IX Item "ifname = devname"
+Sets the tun interface name to the given name. The default is OS-specific
+and most probably something like \f(CW\*(C`tun0\*(C'\fR.
+.IP "ifpersist = yes|true|on | no|false|off" 4
+.IX Item "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 \f(CW\*(C`off\*(C'\fR and do an ifconfig down on the
+device.
+.IP "ip-proto = numerical-ip-protocol" 4
+.IX Item "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.
+.Sp
+The default is 47 (\s-1GRE\s0), which has a good chance of tunneling
+through firewalls (but note that gvpe's rawip protocol is not \s-1GRE\s0
+compatible). Other common choices are 50 (\s-1IPSEC\s0, \s-1ESP\s0), 51 (\s-1IPSEC\s0, \s-1AH\s0), 4
+(\s-1IPIP\s0 tunnels) or 98 (\s-1ENCAP\s0, rfc1241).
+.Sp
+Many versions of Linux seem to have a bug that causes them to reorder
+packets for some ip protocols (\s-1GRE\s0, \s-1ESP\s0) but not for others (\s-1AH\s0), so
+choose wisely (that is, use 51, \s-1AH\s0).
+.IP "http-proxy-host = hostname/ip" 4
+.IX Item "http-proxy-host = hostname/ip"
+The \f(CW\*(C`http\-proxy\-*\*(C'\fR family of options are only available if gvpe was
+compiled with the \f(CW\*(C`\-\-enable\-http\-proxy\*(C'\fR option and enable tunneling of
+tcp connections through a http proxy server.
+.Sp
+\&\f(CW\*(C`http\-proxy\-host\*(C'\fR and \f(CW\*(C`http\-proxy\-port\*(C'\fR should specify the hostname and
+port number of the proxy server. See \f(CW\*(C`http\-proxy\-loginpw\*(C'\fR if your proxy
+requires authentication.
+.Sp
+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 \s-1DNS\s0
+server better use numerical \s-1IP\s0 addresses.
+.Sp
+To make best use of this option disable all protocols except \s-1TCP\s0 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).
+.Sp
+If you have a router, connecting to it will suffice. Otherwise \s-1TCP\s0 must be
+enabled on all nodes.
+.Sp
+Example:
+.Sp
+.Vb 3
+\&   http\-proxy\-host = proxy.example.com
+\&   http\-proxy\-port = 3128       # 8080 is another common choice
+\&   http\-proxy\-auth = schmorp:grumbeere
+.Ve
+.IP "http-proxy-port = proxy-tcp-port" 4
+.IX Item "http-proxy-port = proxy-tcp-port"
+The port where your proxy server listens.
+.IP "http-proxy-auth = login:password" 4
+.IX Item "http-proxy-auth = login:password"
+The optional login and password used to authenticate to the proxy server,
+separated by a literal colon (\f(CW\*(C`:\*(C'\fR). Only basic authentication is
+currently supported.
+.IP "keepalive = seconds" 4
+.IX Item "keepalive = seconds"
+Sets the keepalive probe interval in seconds (default: \f(CW60\fR). 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.
+.IP "loglevel = noise|trace|debug|info|notice|warn|error|critical" 4
+.IX Item "loglevel = noise|trace|debug|info|notice|warn|error|critical"
+Set the logging level. Connection established messages are logged at level
+\&\f(CW\*(C`info\*(C'\fR, notable errors are logged with \f(CW\*(C`error\*(C'\fR. Default is \f(CW\*(C`info\*(C'\fR.
+.IP "mtu = bytes" 4
+.IX Item "mtu = bytes"
+Sets the maximum \s-1MTU\s0 that should be used on outgoing packets (basically
+the \s-1MTU\s0 of the outgoing interface) The daemon will automatically calculate
+maximum overhead (e.g. \s-1UDP\s0 header size, encryption blocksize...) and pass
+this information to the \f(CW\*(C`if\-up\*(C'\fR script.
+.Sp
+Recommended values are 1500 (ethernet), 1492 (pppoe), 1472 (pptp).
+.Sp
+This value must be the minimum of the \s-1MTU\s0 values of all nodes.
+.IP "node = nickname" 4
+.IX Item "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.
+.IP "node-up = relative-or-absolute-path" 4
+.IX Item "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.
+.Sp
+In addition to all the variables passed to \f(CW\*(C`if\-up\*(C'\fR scripts, the following
+environment variables will be set (values are just examples):
+.RS 4
+.IP "DESTNODE=branch2" 4
+.IX Item "DESTNODE=branch2"
+The name of the remote node.
+.IP "DESTID=2" 4
+.IX Item "DESTID=2"
+The node id of the remote node.
+.IP "DESTSI=rawip/88.99.77.55:0" 4
+.IX Item "DESTSI=rawip/88.99.77.55:0"
+The \*(L"socket info\*(R" of the target node, protocol dependent but usually in
+the format protocol/ip:port.
+.IP "DESTIP=188.13.66.8" 4
+.IX Item "DESTIP=188.13.66.8"
+The numerical \s-1IP\s0 address of the remote node (gvpe accepts connections from
+everywhere, as long as the other node can authenticate itself).
+.IP "DESTPORT=655 # deprecated" 4
+.IX Item "DESTPORT=655 # deprecated"
+The protocol port used by the other side, if applicable.
+.IP "STATE=up" 4
+.IX Item "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.
+.RE
+.RS 4
+.Sp
+Here is a nontrivial example that uses nsupdate to update the name => ip
+mapping in some \s-1DNS\s0 zone:
+.Sp
+.Vb 6
+\&   #!/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.
+.Ve
+.RE
+.IP "node-change = relative-or-absolute-path" 4
+.IX Item "node-change = relative-or-absolute-path"
+Same as \f(CW\*(C`node\-change\*(C'\fR, but gets called whenever something about a
+connection changes (such as the source \s-1IP\s0 address).
+.IP "node-down = relative-or-absolute-path" 4
+.IX Item "node-down = relative-or-absolute-path"
+Same as \f(CW\*(C`node\-up\*(C'\fR, but gets called whenever a connection is lost.
+.IP "pid-file = path" 4
+.IX Item "pid-file = path"
+The path to the pid file to check and create
+(default: \f(CW\*(C`LOCALSTATEDIR/run/gvpe.pid\*(C'\fR).
+.IP "private-key = relative-path-to-key" 4
+.IX Item "private-key = relative-path-to-key"
+Sets the path (relative to the config directory) to the private key
+(default: \f(CW\*(C`hostkey\*(C'\fR). This is a printf format string so every \f(CW\*(C`%\*(C'\fR must
+be doubled. A single \f(CW%s\fR is replaced by the hostname, so you could
+use paths like \f(CW\*(C`hostkeys/%s\*(C'\fR to fetch the files at the location where
+\&\f(CW\*(C`gvpectrl\*(C'\fR puts them.
+.Sp
+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.
+.IP "rekey = seconds" 4
+.IX Item "rekey = seconds"
+Sets the rekeying interval in seconds (default: \f(CW3600\fR). Connections are
+reestablished every \f(CW\*(C`rekey\*(C'\fR seconds, making them use a new encryption
+key.
+.IP "nfmark = integer" 4
+.IX Item "nfmark = integer"
+This advanced option, when set to a nonzero value (default: \f(CW0\fR), tries
+to set the netfilter mark (or fwmark) value on all sockets gvpe uses to
+send packets.
+.Sp
+This can be used to make gvpe use a different set of routing rules. For
+example, on GNU/Linux, the \f(CW\*(C`if\-up\*(C'\fR could set \f(CW\*(C`nfmark\*(C'\fR to 1000 and then
+put all routing rules into table \f(CW99\fR 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:
+.Sp
+.Vb 1
+\&   ip rule add not fwmark 1000 lookup 99
+.Ve
+.SS "\s-1NODE\s0 \s-1SPECIFIC\s0 \s-1SETTINGS\s0"
+.IX Subsection "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.
+.IP "allow-direct = nodename" 4
+.IX Item "allow-direct = nodename"
+Allow direct connections to this node. See \f(CW\*(C`deny\-direct\*(C'\fR for more info.
+.IP "compress = yes|true|on | no|false|off" 4
+.IX Item "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: \f(CW\*(C`yes\*(C'\fR). 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.
+.IP "connect = ondemand | never | always | disabled" 4
+.IX Item "connect = ondemand | never | always | disabled"
+Sets the connect mode (default: \f(CW\*(C`always\*(C'\fR). It can be \f(CW\*(C`always\*(C'\fR (always
+try to establish and keep a connection to the given node), \f(CW\*(C`never\*(C'\fR
+(never initiate a connection to the given host, but accept connections),
+\&\f(CW\*(C`ondemand\*(C'\fR (try to establish a connection when there are outstanding
+packets in the queue and take it down after the keepalive interval) or
+\&\f(CW\*(C`disabled\*(C'\fR (node is bad, don't talk to it).
+.Sp
+Routers will automatically be forced to \f(CW\*(C`always\*(C'\fR unless they are
+\&\f(CW\*(C`disabled\*(C'\fR, to ensure all nodes can talk to each other.
+.IP "deny-direct = nodename | *" 4
+.IX Item "deny-direct = nodename | *"
+Deny direct connections to the specified node (or all nodes when \f(CW\*(C`*\*(C'\fR
+is given). Only one node can be specified, but you can use multiple
+\&\f(CW\*(C`allow\-direct\*(C'\fR and \f(CW\*(C`deny\-direct\*(C'\fR statements. This only makes sense in
+networks with routers, as routers are required for indirect connections.
+.Sp
+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 \f(CW\*(C`deny\-direct = *\*(C'\fR and \f(CW\*(C`allow\-direct = othernodename\*(C'\fR (the other
+node \fImust\fR be a router for this to work).
+.Sp
+The algorithm to check whether a connection may be direct is as follows:
+.Sp
+1. Other node mentioned in an \f(CW\*(C`allow\-direct\*(C'\fR? If yes, allow the connection.
+.Sp
+2. Other node mentioned in a \f(CW\*(C`deny\-direct\*(C'\fR? If yes, deny direct connections.
+.Sp
+3. Allow the connection.
+.Sp
+That is, \f(CW\*(C`allow\-direct\*(C'\fR takes precedence over \f(CW\*(C`deny\-direct\*(C'\fR.
+.Sp
+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.
+.IP "dns-domain = domain-suffix" 4
+.IX Item "dns-domain = domain-suffix"
+The \s-1DNS\s0 domain suffix that points to the \s-1DNS\s0 tunnel server for this node.
+.Sp
+The domain must point to a \s-1NS\s0 record that points to the \fIdns-hostname\fR,
+i.e.
+.Sp
+.Vb 2
+\&   dns\-domainname = tunnel.example.net
+\&   dns\-hostname   = tunnel\-server.example.net
+.Ve
+.Sp
+Corresponds to the following \s-1DNS\s0 entries in the \f(CW\*(C`example.net\*(C'\fR domain:
+.Sp
+.Vb 2
+\&   tunnel.example.net.         NS tunnel\-server.example.net.
+\&   tunnel\-server.example.net.  A  13.13.13.13
+.Ve
+.IP "dns-hostname = hostname/ip" 4
+.IX Item "dns-hostname = hostname/ip"
+The address to bind the \s-1DNS\s0 tunnel socket to, similar to the \f(CW\*(C`hostname\*(C'\fR,
+but for the \s-1DNS\s0 tunnel protocol only. Default: \f(CW0.0.0.0\fR, but that might
+change.
+.IP "dns-port = port-number" 4
+.IX Item "dns-port = port-number"
+The port to bind the \s-1DNS\s0 tunnel socket to. Must be \f(CW53\fR on \s-1DNS\s0 tunnel servers.
+.IP "enable-dns = yes|true|on | no|false|off" 4
+.IX Item "enable-dns = yes|true|on | no|false|off"
+See \fIgvpe.protocol\fR\|(7) for a description of the \s-1DNS\s0 transport
+protocol. Avoid this protocol if you can.
+.Sp
+Enable the \s-1DNS\s0 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 \f(CW\*(C`\-\-enable\-dns\*(C'\fR option.
+.IP "enable-icmp = yes|true|on | no|false|off" 4
+.IX Item "enable-icmp = yes|true|on | no|false|off"
+See \fIgvpe.protocol\fR\|(7) for a description of the \s-1ICMP\s0 transport protocol.
+.Sp
+Enable the \s-1ICMP\s0 transport using \s-1ICMP\s0 packets of type \f(CW\*(C`icmp\-type\*(C'\fR on this
+node.
+.IP "enable-rawip = yes|true|on | no|false|off" 4
+.IX Item "enable-rawip = yes|true|on | no|false|off"
+See \fIgvpe.protocol\fR\|(7) for a description of the \s-1RAW\s0 \s-1IP\s0 transport protocol.
+.Sp
+Enable the \s-1RAW\s0 IPv4 transport using the \f(CW\*(C`ip\-proto\*(C'\fR protocol
+(default: \f(CW\*(C`no\*(C'\fR).
+.IP "enable-tcp = yes|true|on | no|false|off" 4
+.IX Item "enable-tcp = yes|true|on | no|false|off"
+See \fIgvpe.protocol\fR\|(7) for a description of the \s-1TCP\s0 transport protocol.
+.Sp
+Enable the TCPv4 transport using the \f(CW\*(C`tcp\-port\*(C'\fR port
+(default: \f(CW\*(C`no\*(C'\fR). Support for this transport protocol is only available
+when gvpe was compiled using the \f(CW\*(C`\-\-enable\-tcp\*(C'\fR option.
+.IP "enable-udp = yes|true|on | no|false|off" 4
+.IX Item "enable-udp = yes|true|on | no|false|off"
+See \fIgvpe.protocol\fR\|(7) for a description of the \s-1UDP\s0 transport protocol.
+.Sp
+Enable the UDPv4 transport using the \f(CW\*(C`udp\-port\*(C'\fR port (default: \f(CW\*(C`no\*(C'\fR).
+.IP "hostname = hostname | ip    [can not be defaulted]" 4
+.IX Item "hostname = hostname | ip    [can not be defaulted]"
+Forces the address of this node to be set to the given \s-1DNS\s0 hostname or \s-1IP\s0
+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.
+.Sp
+Note that \s-1DNS\s0 resolving is done synchronously, pausing the daemon. If that
+is an issue you need to specify \s-1IP\s0 addresses.
+.IP "icmp-type = integer" 4
+.IX Item "icmp-type = integer"
+Sets the type value to be used for outgoing (and incoming) packets sent
+via the \s-1ICMP\s0 transport.
+.Sp
+The default is \f(CW0\fR (which is \f(CW\*(C`echo\-reply\*(C'\fR, also known as
+\&\*(L"ping-reply\*(R"). Other useful values include \f(CW8\fR (\f(CW\*(C`echo\-request\*(C'\fR, a.k.a.
+\&\*(L"ping\*(R") and \f(CW11\fR (\f(CW\*(C`time\-exceeded\*(C'\fR), but any 8\-bit value can be used.
+.IP "if-up-data = value" 4
+.IX Item "if-up-data = value"
+The value specified using this directive will be passed to the \f(CW\*(C`if\-up\*(C'\fR
+script in the environment variable \f(CW\*(C`IFUPDATA\*(C'\fR.
+.IP "inherit-tos = yes|true|on | no|false|off" 4
+.IX Item "inherit-tos = yes|true|on | no|false|off"
+Whether to inherit the \s-1TOS\s0 settings of packets sent to the tunnel when
+sending packets to this node (default: \f(CW\*(C`yes\*(C'\fR). If set to \f(CW\*(C`yes\*(C'\fR then
+outgoing tunnel packets will have the same \s-1TOS\s0 setting as the packets sent
+to the tunnel device, which is usually what you want.
+.IP "max-retry = positive-number" 4
+.IX Item "max-retry = positive-number"
+The maximum interval in seconds (default: \f(CW3600\fR, 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. \f(CW120\fR) on
+connections to routers that usually are stable but sometimes are down, to
+assure quick reconnections even after longer downtimes.
+.IP "max-ttl = seconds" 4
+.IX Item "max-ttl = seconds"
+Expire packets that couldn't be sent after this many seconds
+(default: \f(CW60\fR). 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.
+.IP "max-queue = positive\-number>=1" 4
+.IX Item "max-queue = positive-number>=1"
+The maximum number of packets that will be queued (default: \f(CW512\fR)
+for this node. If more packets are sent then earlier packets will be
+expired. See \f(CW\*(C`max\-ttl\*(C'\fR, above.
+.IP "router-priority = 0 | 1 | positive\-number>=2" 4
+.IX Item "router-priority = 0 | 1 | positive-number>=2"
+Sets the router priority of the given node (default: \f(CW0\fR, disabled).
+.Sp
+If some node tries to connect to another node but it doesn't have a
+hostname, it asks a router node for it's \s-1IP\s0 address. The router node
+chosen is the one with the highest priority larger than \f(CW1\fR that is
+currently reachable. This is called a \fImediated\fR connection, as the
+connection itself will still be direct, but it uses another node to
+mediate between the two nodes.
+.Sp
+The value \f(CW0\fR disables routing, that means if the node receives a packet
+not for itself it will not forward it but instead drop it.
+.Sp
+The special value \f(CW1\fR 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).
+.Sp
+The idea behind this is that some hosts can, if required, bump the
+\&\f(CW\*(C`router\-priority\*(C'\fR setting to higher than \f(CW1\fR in their local config to
+route through specific hosts. If \f(CW\*(C`router\-priority\*(C'\fR is \f(CW0\fR, then routing
+will be refused, so \f(CW1\fR serves as a \*(L"enable, but do not use by default\*(R"
+switch.
+.Sp
+Nodes with \f(CW\*(C`router\-priority\*(C'\fR set to \f(CW2\fR or higher will always be forced
+to \f(CW\*(C`connect\*(C'\fR = \f(CW\*(C`always\*(C'\fR (unless they are \f(CW\*(C`disabled\*(C'\fR).
+.IP "tcp-port = port-number" 4
+.IX Item "tcp-port = port-number"
+Similar to \f(CW\*(C`udp\-port\*(C'\fR (default: \f(CW655\fR), but sets the \s-1TCP\s0 port number.
+.IP "udp-port = port-number" 4
+.IX Item "udp-port = port-number"
+Sets the port number used by the \s-1UDP\s0 protocol (default: \f(CW655\fR, not
+officially assigned by \s-1IANA\s0!).
+.SH "CONFIG DIRECTORY LAYOUT"
+.IX Header "CONFIG DIRECTORY LAYOUT"
+The default (or recommended) directory layout for the config directory is:
+.IP "gvpe.conf" 4
+.IX Item "gvpe.conf"
+The config file.
+.IP "if-up" 4
+.IX Item "if-up"
+The if-up script
+.IP "node-up, node-down" 4
+.IX Item "node-up, node-down"
+If used the node up or node-down scripts.
+.IP "hostkey" 4
+.IX Item "hostkey"
+The private key (taken from \f(CW\*(C`hostkeys/nodename\*(C'\fR) of the current host.
+.IP "pubkey/nodename" 4
+.IX Item "pubkey/nodename"
+The public keys of the other nodes, one file per node.
+.SH "SEE ALSO"
+.IX Header "SEE ALSO"
+\&\fIgvpe\fR\|(5), \fIgvpe\fR\|(8), \fIgvpectrl\fR\|(8).
+.SH "AUTHOR"
+.IX Header "AUTHOR"
+Marc Lehmann <gvpe@schmorp.de>