NDB(8)NDB(8)

NAME

query, ipquery, mkhash, mkdb, mkhosts, cs, csquery, dns, dnstcp, dnsquery, dnsdebug, dnsgetip, inform – network database

SYNOPSIS

ndb/query [ -am ] [ -f dbfile ] attr value [ rattr ]
ndb/ipquery attr value rattr...
ndb/mkhash file attr
ndb/mkdb
ndb/mkhosts [ domain [ dbfile ] ]
ndb/cs [ -46n ] [ -f dbfile ] [ -x netmtpt ]
ndb/csquery [ -s ] [ /net/cs [ addr... ] ]
ndb/dns [ -norRs ] [ -a maxage ] [ -f dbfile ] [ -N target ] [ -x netmtpt ] [ -z program ]
ndb/dnstcp [ -arR ] [ -f dbfile ] [ -x netmtpt ] [ conn-dir ]
ndb/dnsquery [ -x ] [ /net/dns ]
ndb/dnsdebug [ -rx ] [ -f dbfile ] [ [ @server ] domain-name [ type ] ]
ndb/dnsgetip [ -ax ] domain-name
ndb/inform [ -x netmtpt ]

DESCRIPTION

The network database holds administrative information used by network programs such as dhcpd(8), ipconfig(8), con(1), etc.

Ndb/query searches the database dbfile (/lib/ndb/local by default) for an attribute of type attr and value value. If rattr is not specified, all entries matched by the search are printed. If rattr is specified, the value of the first pair with attribute rattr of all the matched entries normally is printed. Under -m and rattr, the values of all pairs with a rattr attribute within the first matching entry are printed. Under -a and rattr, all values of pairs with a rattr attribute within all entries are printed.

Ndb/ipquery uses ndbipinfo (see ndb(2)) to search for the values of the attributes rattr corresponding to the system with entries of attribute type attr and value value.

Ndb/inform sends an RFC2136 DNS inform packet to a nameserver to associate the host’s IP address with its DNS name. This is required if the domain’s nameserver is a Microsoft Windows Active Directory controller. The host’s domain name will be sent to the AD controller unless a tuple of the form inform=xxx is found in the host’s ndb entry.

Database maintenance

Ndb/mkhash creates a hash file for all entries with attribute attr in database file file. The hash files are used by ndb/query and by the ndb library routines.

Ndb/mkdb is used in concert with awk(1) scripts to convert uucp systems files and IP host files into database files. It is very specific to the situation at Murray Hill.

When the database files change underfoot, ndb/cs and ndb/dns track them properly. Nonetheless, to keep the database searches efficient it is necessary to run ndb/mkhash whenever the files are modified. It may be profitable to control this by a frequent cron(8) job.

Ndb/mkhosts generates a BSD style hosts, hosts.txt, and hosts.equiv files from an ndb data base file specified on the command line (default /lib/ndb/local). For local reasons the files are called hosts.1127, astro.txt, and hosts.equiv.

Connection service

Ndb/cs is a server used by dial(2) to translate network names. It is started at boot time. It finds out what networks are configured by looking for /net/*/clone when it starts. It can also be told about networks by writing to /net/cs a message of the form:

add net1 net2 ...  

Ndb/cs also sets the system name in /dev/sysname if it can figure it out. The options are:

Only look up IPv4 addresses (A records) when consulting DNS. The default is to also look up v6 addresses (AAAA records). Writing ipv4 to /net/cs will toggle IP v4 look-ups.  

Only look up IPv6 addresses in DNS. Writing ipv6 to /net/cs toggles v6 lookups.  

supplies the name of the data base file to use, default /lib/ndb/local.  

causes cs to do nothing but set the system name.  

specifies the mount point of the network.  

Ndb/csquery queries ndb/cs to see how it resolves addresses. Ndb/csquery prompts for addresses and prints what ndb/cs returns. Server defaults to /net/cs. If any addrs are specified, ndb/csquery prints their translations and immediately exits. The exit status will be nil only if all addresses were successfully translated. The -s flag sets exit status without printing any results.

Domain name service

Ndb/dns serves ndb/cs and remote systems by translating Internet domain names. Ndb/dns is started at boot time. By default dns serves only requests written to /net/dns. Programs must seek to offset 0 before reading or writing /net/dns or /net/cs. The options are:

sets the maximum time in seconds that an unreferenced domain name will remain cached. The default is one hour (3600).  

supplies the name of the data base file to use, default /lib/ndb/local.  

whenever a DNS zone that we serve changes, send UDP NOTIFY messages to any dns slaves for that zone (see the dnsslave attribute below).  

sets the goal for the number of domain names cached to target rather than the default of 8,000.  

used with -s, -o causes dns to assume that it straddles inside and outside networks and that the outside network is mounted on /net.alt. Queries for inside addresses will be sent via /net/udp (or /net/tcp in response to truncated replies) and those for outside addresses via /net.alt/udp (or /net.alt/tcp). This makes dns suitable for serving non-Plan-9 systems in an organization with firewalls, DNS proxies, etc., particularly if they don’t work very well. See ‘Straddling Server’ below for details.  

act as a resolver only: send ‘recursive’ queries, asking the other servers to complete lookups. If present, /env/DNSSERVER must be a space-separated list of such DNS servers’ IP addresses, otherwise optional ndb(6) dns attributes name DNS servers to forward queries to.  

ignore the ‘recursive’ bit on incoming requests. Do not complete lookups on behalf of remote systems.  

also answer domain requests sent to UDP port 53.  

specifies the mount point of the network.  

whenever we receive a UDP NOTIFY message, run program with the domain name of the area as its argument.  

When the -r option is specified, the servers used come from the dns attribute in the database. For example, to specify a set of dns servers that will resolve requests for systems on the network mh-net:

 

ipnet=mh-net ip=135.104.0.0 ipmask=255.255.0.0
	dns=ns1.cs.bell-labs.com
	dns=ns2.cs.bell-labs.com
dom=ns1.cs.bell-labs.com ip=135.104.1.11
dom=ns2.cs.bell-labs.com ip=135.104.1.12

The server for a domain is indicated by a database entry containing both a dom and a ns attribute.

 

dom=
	ns=A.ROOT-SERVERS.NET
	ns=B.ROOT-SERVERS.NET
	ns=C.ROOT-SERVERS.NET
dom=A.ROOT-SERVERS.NET ip=198.41.0.4
dom=B.ROOT-SERVERS.NET ip=128.9.0.107
dom=C.ROOT-SERVERS.NET ip=192.33.4.12

The last three lines provide a mapping for the server names to their ip addresses. This is only a hint and will be superseded from whatever is learned from servers owning the domain.

Authoritative Name Servers

You can also serve a subtree of the domain name space from the local database. You indicate subtrees that you would like to serve by adding an soa= attribute to the root entry. For example, the Bell Labs CS research domain is:

 

dom=cs.bell-labs.com soa=
	refresh=3600 ttl=3600
	ns=plan9.bell-labs.com
	ns=ns1.cs.bell-labs.com
	ns=ns2.cs.bell-labs.com
	mb=presotto@plan9.bell-labs.com
	mx=mail.research.bell-labs.com pref=20
	mx=plan9.bell-labs.com pref=10
	dnsslave=nslocum.cs.bell-labs.com
	dnsslave=vex.cs.bell-labs.com

Here, the mb entry is the mail address of the person responsible for the domain (default postmaster). The mx entries list mail exchangers for the domain name and refresh and ttl define the area refresh interval and the minimum TTL for records in this domain. The dnsslave entries specify slave DNS servers that should be notified when the domain changes. The notification also requires the -n flag.

Reverse Domains

You can also serve reverse lookups (returning the name that goes with an IP address) by adding an soa= attribute to the entry defining the root of the reverse space.

For example, to provide reverse lookup for all addresses in starting with 135.104 or fd00::, ndb must contain a record like:

 

dom=104.135.in-addr.arpa soa=
	dom=d.f.ip6.arpa soa=	# special case, rfc 4193
	refresh=3600 ttl=3600
	ns=plan9.bell-labs.com
	ns=ns1.cs.bell-labs.com
	ns=ns2.cs.bell-labs.com

Notice the form of the reverse address. For IPv4, it’s the bytes of the address range you are serving reversed and expressed in decimal, and with .in-addr.arpa appended. For IPv6, it’s the nibbles (4-bit fields) of the address range you are serving reversed and expressed in hexadecimal, and with .ip6.arpa appended. These are the standard forms for a domain name in a PTR record.

If such an soa entry exists in the database, reverse addresses will automatically be generated from any IP addresses in the database that are under this root. For example

 

dom=ns1.cs.bell-labs.com ip=135.104.1.11

will automatically create both forward and reverse entries for ns1.cs.bell-labs.com. Unlike other DNS servers, there’s no way to generate inconsistent forward and reverse entries.

Classless reverse delegation

Following RFC 2317, it is possible to serve reverse DNS data for IPv4 subnets smaller than /24. Declare the non-/24 subnet, the reverse domain and the individual systems.

For example, this is how to serve RFC-2317 ptr records for the subnet 65.14.39.128/123.

 

ipnet=our-t1 ip=65.14.39.128 ipmask=/123
dom=128.39.14.65.in-addr.arpa soa=
	refresh=3600 ttl=3600
	ns=ns1.our-domain.com
	ns=ns2.our-domain.com
ip=65.14.39.129 dom=router.our-domain.com

Delegating Name Service Authority

Delegation of a further subtree to another set of name servers is indicated by an soa=delegated attribute.

 

dom=bignose.cs.research.bell-labs.com
	soa=delegated
	ns=anna.cs.research.bell-labs.com
	ns=dj.cs.research.bell-labs.com

Nameservers within the delegated domain (as in this example) must have their IP addresses listed elsewhere in ndb files.

Wildcards, MX and CNAME records

Wild-carded domain names can also be used. For example, to specify a mail forwarder for all Bell Labs research systems:

 

dom=*.research.bell-labs.com
	mx=research.bell-labs.com

‘Cname’ aliases may be established by adding a cname attribute giving the real domain name; the name attached to the dom attribute is the alias. ‘Cname’ aliases are severely restricted; the aliases may have no other attributes than dom and are daily further restricted in their use by new RFCs.

 

cname=anna.cs.bell-labs.com dom=www.cs.bell-labs.com

makes www.... a synonym for the canonical name anna.....

Straddling Server

Many companies have an inside network protected from outside access with firewalls. They usually provide internal ‘root’ DNS servers (of varying reliability and correctness) that serve internal domains and pass on DNS queries for outside domains to the outside, relaying the results back and caching them for future use. Some companies don’t even let DNS queries nor replies through their firewalls at all, in either direction.

In such a situation, running dns -so on a machine that imports access to the outside network via /net.alt from a machine that straddles the firewalls, or that straddles the firewalls itself, will let internal machines query such a machine and receive answers from outside nameservers for outside addresses and inside nameservers for inside addresses, giving the appearance of a unified domain name space, while bypassing the corporate DNS proxies or firewalls. This is different from running dns -s and dns -sRx /net.alt -f /lib/ndb/external on the same machine, which keeps the inside and outside namespaces entirely separate.

Under -o, several sys names are significant: inside-dom, inside-ns, and outside-ns. Inside-dom should contain a series of dom pairs naming domains internal to the organization. Inside-ns should contain a series of ip pairs naming the internal DNS ‘root’ servers. Outside-ns should contain a series of ip pairs naming the external DNS servers to consult.

Zone Transfers and TCP

Dnstcp is invoked, usually from /rc/bin/service/tcp53, to answer DNS queries with long answers via TCP, notably to transfer a zone within the database dbfile (default /lib/ndb/local) to its invoker on the network at netmtpt (default /net). Standard input will be read for DNS requests and the DNS answers will appear on standard output. Recursion is disabled by -R; acting as a pure resolver is enabled by -r. Unless the -a flag is provided, clients requesting DNS zone transfer must be listed with a dnsslave attribute for the relevant domain. If conn-dir is provided, it is assumed to be a directory within netmtpt/tcp and is used to find the caller’s address.

DNS Queries and Debugging

Ndb/dnsquery can be used to query ndb/dns to see how it resolves requests. Ndb/dnsquery prompts for commands of the form

domain-name request-type  

where request-type can be ip, ipv6, mx, ns, cname, ptr.... In the case of the inverse query type, ptr, dnsquery will reverse the ip address and tack on the .in-addr.arpa if necessary. The -x option switches ndb/dnsquery to query the dns server on /net.alt instead of /net

Ndb/dnsdebug is like ndb/dnsquery but bypasses the local server. It communicates via UDP (and sometimes TCP) with the domain name servers in the same way that the local resolver would and displays all packets received. The query can be specified on the command line or can be prompted for. The queries look like those of ndb/dnsquery with one addition. Ndb/dnsdebug can be directed to query a particular name server by the command @name-server. From that point on, all queries go to that name server rather than being resolved by dnsdebug. The @ command returns query resolution to dnsdebug. Finally, any command preceded by a @name-server sets the name server only for that command.

Normally dnsdebug uses the /net interface and the database file /lib/ndb/local. The -f option supplies the name of the data base file to use. The -r option is the same as for ndb/dns. The -x option directs dnsdebug to use the /net.alt interface and /lib/ndb/external database file.

Ndb/dnsgetip resolves and prints A and AAAA records without consulting ndb/dns . By default, ndb/dnsgetip queries A records first and then AAAA records. As with ndb/dns, /env/DNSSERVER or ndb(6) dns attributes are used as the DNS server. The -a flag will return all records. The -x option switches ndb/dnsgetip to query the dns server through /net.alt instead of /net.

EXAMPLES

Look up helix in ndb.

 

% ndb/query sys helix
sys=helix dom=helix.research.bell-labs.com bootf=/mips/9powerboot
	ip=135.104.117.31 ether=080069020427

Look up plan9.bell-labs.com and its IP address in the DNS.

 

% ndb/dnsquery
> plan9.bell-labs.com ip
plan9.bell-labs.com ip	204.178.31.2
> 204.178.31.2 ptr
2.31.178.204.in-addr.arpa ptr	plan9.bell-labs.com
2.31.178.204.in-addr.arpa ptr	ampl.com
>

Print the names of all systems that boot via PXE.

 

% ndb/query -a bootf /386/9bootpxe sys

FILES

resolver’s DNS servers’ IP addresses.  

first database file searched  

hash files for /lib/ndb/local  

service file for ndb/cs  

where /srv/cs gets mounted  

service file for ndb/dns  

where /srv/dns gets mounted  

SOURCE

/sys/src/cmd/ndb

SEE

ndb(2), ndb(6)

BUGS

Ndb databases are case-sensitive; ethernet addresses must be in lower-case hexadecimal.