edge

Section: SUPERUSER COMMANDS (8)
Updated: 17 Mar 2010
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NAME

edge - n2n edge node daemon

SYNOPSIS

edge [-d <tun device>] -a <tun IP address> -c <community> {-k <encrypt key>|-K <keyfile>} [-s <netmask>] -l <supernode host:port> [-p <local port>] [-u <UID>] [-g <GID>] [-f] [-m <MAC address>] [-r] [-v]

DESCRIPTION

N2N is a peer-to-peer VPN system. Edge is the edge node daemon for n2n which creates a TAP interface to expose the n2n virtual LAN. On startup n2n creates the TAP interface and configures it then registers with the supernode so it can begin to find other nodes in the community.

OPTIONS

-d <name>: sets the TAP device name as seen in ifconfig. Only available on Linux.
-a {<addr>|static:<addr>|dhcp:0.0.0.0}: sets the n2n virtual LAN IP address being claimed. This is a private IP address. All IP addresses in an n2n community typical belong to the same /24 network (ie. only the last octet of the IP addresses varies). If DHCP is used to assign interface addresses then specify the address as -a dhcp:0.0.0.0
-b: cause edge to perform hostname resolution for the supernode address each time the supernode is periodically contacted. This can cause reliability problems because all packet processing stops while the supernode address is resolved which might take 15 seconds.
-c <community>: sets the n2n community name. All edges within the same community appear on the same LAN (layer 2 network segment). Community name is 16 bytes in length. A name smaller than this is padded with 0x00 bytes and a name longer than this is truncated to take the first 16 bytes.
-h: write usage then exit.
-k <keystring>: sets the twofish encryption key from ASCII text (see also N2N_KEY in ENVIRONMENT). All edges communicating must use the same key and community name. If neither -k nor -K is used to specify a key source then edge uses cleartext mode (no encryption). The -k and -K options are mutually exclusive.
-K <keyfile>: Reads a key-schedule file <keyfile> and populates the internal transform operations with the data found there. This mechanism allows keys to roll at pre-determined times for a group of hosts. Accurate time synchronisation is not required as older keys can be decoded for some time after expiry. If neither -k nor -K is used to specify a key source then edge uses cleartext mode (no encryption). The -k and -K options are mutually exclusive.
-l <addr>:<port>: sets the n2n supernode IP address and port to register to. Up to 2 supernodes can be specified by two invocations of -l <addr>:<port>. eg. edge -l 12.34.56.78:7654 -l 98.76.54.32:7654
-p <num>: binds edge to the given UDP port. Useful for keeping the same external socket across restarts of edge. This allows peer edges which know the edge socket to continue p2p operation without going back to the supernode.
-t <num>: binds the edge management system to the given UDP port. Default 5644. Use this if you need to run multiple instance of edge; or something is bound to that port.
-u <uid>: causes the edge process to drop to the given user ID when privileges are no longer required (UNIX).
-g <gid>: causes the edge process to drop to the given group ID when privileges are no longer required (UNIX).
-f: disables daemon mode (UNIX) and causes edge to run in the foreground.
-m <MAC>: start the TAP interface with the given MAC address. This is highly recommended as it means the same address will be used if edge stops and restarts. If this is not done, the ARP caches of all peers will be wrong and packets will not flow to this edge until the next ARP refresh.
-M <MTU>: set the MTU of the edge interface in bytes. MTU is the largest packet fragment size allowed to be moved throught the interface. The default is 1400.
-s <netmask>: set the netmask of edge interface in IPv4 dotted decimal notation. The default is 255.255.255.0 (ie. /24).
-r: enable IP packet forwarding/routing through the n2n virtual LAN. Without this option, IP packets arriving over n2n are dropped if not for the -a <addr> (or DHCP assigned) IP address of the edge interface.
-E: accept packets destined for multicast ethernet MAC addresses. These addresses are used in multicast ethernet and IPv6 neighbour discovery. If this option is not present these multicast packets are discarded as most users do not need or understand them.
-v: more verbose logging (may be specified several times for more verbosity).

ENVIRONMENT

N2N_KEY: set the encryption key so it is not visible on the command line

EXAMPLES

edge -d n2n0 -c mynetwork -k encryptme -u 99 -g 99 -m DE:AD:BE:EF:01:23 -a 192.168.254.7 -p 50001 -l 123.121.120.119:7654: Start edge with TAP device n2n0 on community "mynetwork" with community supernode at 123.121.120.119 UDP port 7654 and bind the locally used UDP port to 50001. Use "encryptme" as the single permanent shared encryption key. Assign MAC address DE:AD:BE:EF:01:23 to the n2n interface and drop to user=99 and group=99 after the TAP device is successfull configured.

Add the -f option to stop edge running as a daemon.

Somewhere else setup another edge with similar parameters, eg.

edge -d n2n0 -c mynetwork -k encryptme -u 99 -g 99 -m DE:AD:BE:EF:01:21 -a 192.168.254.5 -p 50001 -l 123.121.120.119:7654

Now you can ping from 192.168.254.5 to 192.168.254.7.

The MAC address (-m <MAC>) and virtual IP address (-a <addr>) must be different on all edges in the same community.

KEY SCHEDULE FILES

(See n2n_v2(7) for more details).

The -K <keyfile> option reads a key schedule file.

edge -d n2n0 -c mynetwork -K /path/to/file -u 99 -g 99 -m DE:AD:BE:EF:01:21 -a 192.168.254.5 -p 50001 -l 123.121.120.119:7654

The key schedule file consists of line, one per key in the schedule. The purpose of key schedules is to encourage regular changing of the encryption keys used by a community. The file structure also allows for full binary keys to be specified as compared to the ASCII keys allowed by the single key injection. Each key line consists of the following:

<from> <until> <transform> <data>

<from> and <until> are ASCII decimal values of the UNIX times during which the key is valid. <transform> is the index of the transform that <data> applies to. <data> is some text which is parsed by the transform module to derive the key for that line.

Supported <transform> values are:

2 = TwoFish

<data> has the form <SA>_<hex_key>. eg.

1252327945 1252328305 2 602_3d7c7769b34b2a4812f8c0e9d87ce9

This specifies security association number 602 and a 16-octet key of numeric value 0x3d7c7769b34b2a4812f8c0e9d87ce9. <SA> is a 32-bit unsigned integer which is used to identify the encryption key to the receiver. The SA number is sent unencrypted so the receiver may find the correct key from the key schedule. <hex_key> is up to 16 octets although shorter keys are allowed.

3 = AES-CBC

<data> has the form <SA>_<hex_key>. Same rules as TwoFish.

CLEARTEXT MODE

If neither -k nor -K is specified then edge uses cleartext mode. In cleartext mode there is no transform of the packet data it is simply encrypted. This is useful for debugging n2n as packet contents can be seen clearly.

To prevent accidental exposure of data, edge only enters cleartext mode when no keying parameters are specified. In the case where keying parameters are specified but no valid keys can be determined, edge exits with an error at startup. If all keys become invalid while running, edge continues to encode using the last key that was valid.

MANAGEMENT INTERFACE

Edge provides a very simple management system on UDP port 5644. Send a newline to receive a status output. Send 'reload' to cause re-read of the keyfile. Send 'stop' to cause edge to exit cleanly.

EXIT STATUS

edge is a daemon and any exit is an error.

AUTHORS

Richard Andrews: andrews (at) ntop.org - n2n-1 maintainer and main author of n2n-2
Luca Deri: deri (at) ntop.org - original author of n2n
Don Bindner: (--) - significant contributions to n2n-1

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