NAME

ndb − Network database

DESCRIPTION

The network database consists of files describing machines known to the local installation and machines known publicly.  The files comprise multi-line tuples made up of attribute/value pairs of the form attr=value or sometimes just attr. Each line starting without white space starts a new tuple. Lines starting with ­# are comments. 

The file ­/lib/ndb/local is the root of the database.  Other files are included in the database if a tuple with an attribute-value pair of attribute ­database and no value exists in /lib/ndb/local .  Within the ­database tuple, each pair with attribute ­file identifies a file to be included in the database.  The files are searched in the order they appear.  For example:

database=
file=/lib/ndb/common
file=/lib/ndb/local
file=/lib/ndb/global

declares the database to be composed of the three files /lib/ndb/common, /lib/ndb/local, and /lib/ndb/global.  By default, ­/lib/ndb/local is searched before the others.  However, ­/lib/ndb/local may be included in the ­database to redefine its ordering. 

Within tuples, pairs on the same line bind tighter than pairs on different lines. 

Programs search the database directly using the routines in ndb(2) or indirectly using ­ndb/cs and ­ndb/dns (see ndb(8)). Both ­ndb/cs and the routine ­ndbipinfo impose structure on the otherwise flat database by using knowledge specific to the network.  The internet is made up of networks which can be subnetted multiple times.  A network must have an ­ipnet attribute and is uniquely identified by the values of its ­ip and ­ipmask attributes.  If the ­ipmask is missing, the relevant Class A, B or C one is used. 

A search for an attribute associated with a network or host starts at the lowest level, the entry for the host or network itself, and works its way up, bit by bit, looking at entries for nets/subnets that include the network or host.  The search ends when the attribute is found.  For example, consider at the following entries:

ipnet=murray-hill ip=135.104.0.0 ipmask=255.255.0.0
dns=135.104.10.1
ntp=ntp.cs.bell-labs.com
ipnet=plan9 ip=135.104.9.0 ipmask=255.255.255.0
ntp=oncore.cs.bell-labs.com
smtp=smtp1.cs.bell-labs.com
ip=135.104.9.6 sys=anna dom=anna.cs.bell-labs.com
smtp=smtp2.cs.bell-labs.com

Here ­anna is on the subnet ­plan9 which is in turn on the class B net murray-hill.  Assume that we’re searching for anna’s ­NTP and ­SMTP servers.  The search starts by looking for an entry with sys=anna.  We find the anna entry.  Since it has an ­smtp=smtp2.cs.bell-labs.com pair, we’re done looking for that attribute.  To fulfill the NTP request, we continue by looking for networks that include anna’s IP address.  We lop off the right most one bit from anna’s address and look for an ­ipnet= entry with ip=135.104.9.4.  Not finding one, we drop another bit and look for an ­ipnet= entry with ip=135.104.9.0.  There is such an entry and it has the pair, ntp=oncore.cs.bell-labs.com, ending our search. 

­Ndb/cs can be made to perform such network aware searches by using metanames in the dialstring.  A metaname is a ­$ followed by an attribute name.  ­Ndb/cs looks up the attribute relative to the system it is running on.  Thus, with the above example, if a program called

dial("tcp!$smtp!smtp", 0, 0, 0);

the dial would connect to the SMTP port of smtp2.cs.bell-labs.com. 

A number of attributes are meaningful to programs and thus reserved.  They are:

­sys system name

­dom Internet domain name

­ip Internet address

­ether Ethernet address (must be lower-case hexadecimal)

­bootf file to download for initial bootstrap

­ipnet Internet network name

­ipmask Internet network mask

­ipgw Internet gateway

­auth authentication server to be used

­authdom authentication domain.  Plan 9 supports multiple authentication domains.  To specify an authentication server for a particular domain, add a tuple containing both ­auth and ­authdom attributes and values. 

­fs file server to be used

­tcp a TCP service name

­udp a UDP service name

­il an IL service name

­port a TCP, UDP, or IL port number

­restricted
a TCP service that can be called only by ports numbered less that 1024

­proto a protocol supported by a host.  The pair ­proto=il is needed by ­cs (see ndb(8)) in tuples for hosts that support the IL protocol

­dnsdomain a domain name that ­ndb/dns adds onto any unrooted names when doing a search There may be multiple ­dnsdomain pairs. 

­dns a DNS server to use (for DNS and DHCP)

­ntp an NTP server to use (for DHCP)

­smtp an SMTP server to use (for DHCP)

­time a time server to use (for DHCP)

­wins a Windows name server (for DHCP)

­mx mail exchanger (for DNS and DHCP)

­soa start of area (for DNS)

The file ­/lib/ndb/auth is used during authentication to decide who has the power to ‘speak for’ other users; see authsrv(6).

EXAMPLES

A tuple for the CPU server, spindle. 

sys = spindle
dom=spindle.research.bell-labs.com
bootf=/mips/9powerboot
ip=135.104.117.32 ether=080069020677
proto=il

Entries for the network ­mh-astro-net and its subnets. 

ipnet=mh-astro-net ip=135.104.0.0 ipmask=255.255.255.0
fs=bootes.research.bell-labs.com
ipgw=r70.research.bell-labs.com
auth=p9auth.research.bell-labs.com
ipnet=unix-room ip=135.104.117.0
ipgw=135.104.117.1
ipnet=third-floor ip=135.104.51.0
ipgw=135.104.51.1

Mappings between TCP service names and port numbers. 

tcp=sysmonport=401
tcp=rexecport=512restricted
tcp=9fsport=564

FILES

­/lib/ndb/local
first database file searched

SEE ALSO

dial(2), ndb(2), ndb(8), dhcpd(8), ipconfig(8), con(1)

Plan 9  —  February 15, 2005