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cs, csquery - connection server


ndb/cs [ -f database ] [ -v ] [ -x net ]

ndb/csquery [ -x net ] [ -s server ] [ address ... ]


Cs spawns a process that serves a single file /net/cs, in the current name space, answering requests by client processes to translate symbolic network and service names into instructions for connecting to the given service. It is normally accessed indirectly by calls to sys-dial(2).

The network data is taken from the network database files, described in ndb(6). By default, it is /lib/ndb/local but the -f option can specify a different one.

Each write to /net/cs makes a query, expressed in one of two forms. The first form is a network address of the same form as the addr parameter to dial: network!netaddr!service where service and network are optional for some networks. The write returns an error if the address cannot be translated. Otherwise, the file offset should be reset to 0 using sys-seek(2) and each subsequent read will return either end-of-file (if there are no further translations), or a single line containing a translation of the form:

/net/proto/clone address!port

The first field is the name of the clone file for a network protocol or interface. To make a connection or announce a service, open that file, and write the text in the second field preceded by connect or announce as required. (All this activity is normally encapsulated in a call to sys-dial(2)). Cs produces a translation for each network and for each network address on which a symbolic netaddr is found. When announcing a service, netaddr can be * to represent any local interface, and the resulting recipes read from /net/cs will not include an address! part.

Cs interprets a netaddr of the form $server specially: it looks for an attribute server in the database in the entry for the current host, then in the entry for each network that contains it (if specified), and finally in a site-wide entry labelled with the attribute infernosite. If found, the value of the attribute replaces the netaddr before further translation.

In the second form of query, the text written contains space-separated attribute/value pairs following an initial !:

! attr1=val1 [ attr2=val2 ... ]

Cs looks for an ndb(6) entry that contains attribute/value pairs matching those in the query. Any value but val1 may be `*', to signify that the entry must contain the given attribute but with any value. As before, the write returns an error if no entry matches. Otherwise, each subsequent read returns the whole of the next matching entry, in ndb(6) form.

The file /net/cs persists until it is removed or unmounted from /net, or the cs process is killed (see kill(1)). The -v option causes cs to print each translation request and results (if any) on standard error. The -x option gives an alternative mount point for cs, when there is more than one network stack (see ip(3)). It causes it cs to serve net/cs instead of /net/cs.

Cs is normally started once, after dns(8) if used, but before most other applications including the various listeners described in svc(8). If another instance of cs(8) is started on the same mount point, the file it serves replaces the earlier one if permissions allow. (On Plan 9, Plan 9's native connection service will be used by default if Inferno's cs is not started.)

Csquery queries the given server (default: /net/cs) for a translation of each address and prints the results, one per line. If no address is given, csquery prompts for address(es) to translate which it reads from the standard input, printing the results of each translation on the standard output. The -x option gives an alternative mount point for cs, when there is more than one network stack (see ip(3)).

Cs uses ndb(6) to map protocol and service names to Internet port numbers. When running hosted, if entries are not in ndb(6), cs applies the built-in srv(2), if available, to have the host system try the translation. Consequently, entries in ndb(6) take precedence over the host's system-wide configuration. (This is helpful for adding symbolic names for Inferno services without requiring administrative privileges on the host system.)


Check the translation of the symbolic name $signer:

> net!$signer!inflogin


service directory
connection service
domain name service
map from symbolic service names to servers




sys-dial(2), ndb(6), dns(8)

CS(8 ) Rev:  Sun Feb 22 17:41:22 GMT 2009