pathalias man page on 4.4BSD

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PATHALIAS(8)							  PATHALIAS(8)

NAME
       pathalias, makedb - mail routing tools

SYNOPSIS
       pathalias [ -ivcDfI ] [ -l host ] [ -d link ] [ files ...  ]

       makedb [ -a ] [ -o dbmfile ] [ files ...	 ]

DESCRIPTION
       Pathalias computes the shortest paths and corresponding routes from one
       host (computer system) to all other known, reachable hosts.   Pathalias
       reads host-to-host connectivity information on standard input or in the
       named files, and writes a list of host-route pairs on the standard out‐
       put.

       Here are the pathalias options:

       -i    Ignore case:  map all host names to lower case.  By default, case
	     is significant.

       -c    Print costs: print the path cost before each host-route pair.

       -v    Verbose: report some statistics on the standard error output.

       -D    Terminal domains: see domains section.

       -f    First hop cost: the printed cost is the cost to the  first	 relay
	     in	 a  path, instead of the cost of the path itself; implies (and
	     overrides) the -c option.

       -I    Internet connected: assume a DEDICATED link to  any  fully-quali‐
	     fied domain name encountered in the input stream.

       -l host
	     Set local host name to host.  By default, pathalias discovers the
	     local host name in a system-dependent way.

       -d arg
	     Declare a dead link, host, or network.  If arg  is	 of  the  form
	     ``host-1!host-2,''	 the  link from host-1 to host-2 is treated as
	     an extremely high cost (i.e., DEAD) link.	If  arg	 is  a	single
	     host  name,  that	host is treated as dead and is used as a relay
	     host of last resort on any path.  If arg is a network  name,  the
	     network requires a gateway.

       -t arg
	     Trace  input for link, host or network on the standard error out‐
	     put.  The form of arg is as above.

       -s file
	     Dump the edges that constitute the shortest path  tree  into  the
	     named file.

       Makedb  takes pathalias output and creates or appends to a dbm(3) data‐
       base.

       Here are the makedb options:

       -a    Append to an existing database; by default, makedb truncates  the
	     database.

       -o dbmfile
	     Identify the output file base name.

   Pathalias Input Format
       A  line	beginning with white space continues the preceding line.  Any‐
       thing following `#' on an input line is ignored.

       A list of host-to-host connections consists of a ``from'' host in  col‐
       umn  1,	followed by white space, followed by a comma-separated list of
       ``to' hosts, called links.  A link may be preceded  or  followed	 by  a
       network	character  to  use in the route.  Valid network characters are
       `!' (default), `@', `:', and `%'.  A link (and  network	character,  if
       present)	 may be followed by a ``cost'' enclosed in parentheses.	 Costs
       may be arbitrary arithmetic expressions involving numbers, parentheses,
       `+',  `-', `*', and `/'.	 Negative costs are prohibited.	 The following
       symbolic costs are recognized:

	      LOCAL	  25   (local-area network connection)
	      DEDICATED	  95   (high speed dedicated link)
	      DIRECT	 200   (toll-free call)
	      DEMAND	 300   (long-distance call)
	      HOURLY	 500   (hourly poll)
	      EVENING	1800   (time restricted call)
	      DAILY	5000   (daily poll, also called POLLED)
	      WEEKLY   30000   (irregular poll)

       In addition, DEAD is a very large number (effectively  infinite),  HIGH
       and   LOW  are  -5  and	+5  respectively,  for	baud-rate  or  quality
       bonuses/penalties, and FAST is -80, for adjusting costs of  links  that
       use high-speed (9.6 Kbaud or more) modems.  These symbolic costs repre‐
       sent an imperfect measure of bandwidth, monetary cost, and frequency of
       connections.   For  most	 mail traffic, it is important to minimize the
       number of hosts in a route, thus, e.g., HOURLY * 24 is much larger than
       DAILY.  If no cost is given, a default of 4000 is used.

       For  the	 most part, arithmetic expressions that mix symbolic constants
       other than HIGH, LOW, and FAST make no sense.  E.g., if a host calls  a
       local  neighbor	whenever  there	 is work, and additionally polls every
       evening, the cost is DIRECT, not DIRECT+EVENING.

       Some examples:

	      down	princeton!(DEDICATED), tilt,
			%thrash(LOCAL)
	      princeton topaz!(DEMAND+LOW)
	      topaz	@rutgers(LOCAL+1)

       If a link is encountered more than once, the least-cost occurrence dic‐
       tates  the  cost	 and network character.	 Links are treated as bidirec‐
       tional but asymmetric: for each link declared  in  the  input,  a  DEAD
       reverse link is assumed.

       If  the ``to'' host in a link is surrounded by angle brackets, the link
       is considered terminal, and further links beyond this one  are  heavily
       penalized.  E.g., with input

	      seismo	<research>(10), research(100), ihnp4(10)
	      research	allegra(10)
	      ihnp4	allegra(50)

       the path from seismo to research is direct, but the path from seismo to
       allegra uses ihnp4 as a relay, not research.

       The set of names by which a host is known to its	 neighbors  is	called
       its aliases.  Aliases are declared as follows:

	      name = alias, alias ...

       The  name  used in the route to or through aliased hosts is the name by
       which the host is known to its predecessor in the route.

       Fully connected networks, such as the ARPANET or a local-area  network,
       are declared as follows:

	      net = {host, host, ...}

       The  host-list  may be preceded or followed by a routing character (`!'
       default), and may be followed by a cost (default	 4000).	  The  network
       name is optional; if not given, pathalias makes one up.

	      etherhosts = {rahway, milan, joliet}!(LOCAL)
	      ringhosts = @{gimli, alida, almo}(DEDICATED)
	      = {etherhosts, ringhosts}(0)

       The  routing  character	used in a route to a network member is the one
       encountered when ``entering'' the network.  See also  the  sections  on
       gateways and domains .

       Connection data may be given while hiding host names by declaring

	      private {host, host, ...}

       Pathalias  will	not generate routes for private hosts, but may produce
       routes through them.  The scope of a private declaration	 extends  from
       the declaration to the end of the input file in which it appears, or to
       a private declaration with an empty host list, whichever	 comes	first.
       The  latter  scope rule offers a way to retain the semantics of private
       declarations when reading from the standard input.

       Dead hosts, links, or networks may be presented in the input stream  by
       declaring

	      dead {arg, ...}

       where arg has the same form as the argument to the -d option.

       To force a specific cost for a link, delete all prior declarations with

	      delete {host-1!host-2}

       and  declare  the link as desired.  To delete a host and all its links,
       use

	      delete {host}

       Error diagnostics refer to the file in which the error was  found.   To
       alter the file name, use

	      file {filename}

       Fine-tuning  is	possible  by adjusting the weights of all links from a
       given host, as in

	      adjust {host-1, host-2(LOW), host-3(-1)}

       If no cost is given a default of 4000 is used.

       Input from compressed  (and  uncompressed)  files  can  be  piped  into
       pathalias with the following script.

	      for i in $*; do
			case $i in
			*.Z) echo "file {`expr $i : '\(.*\).Z'`}"
			     zcat $i ;;
			*)   echo "file {$i}"
			     cat $i ;;
			esac
			echo "private {}"
	      done | pathalias

   Output Format
       A  list	of  host-route	pairs is written to the standard output, where
       route is a string appropriate for use with printf(3), e.g.,

	      rutgers	princeton!topaz!%s@rutgers

       The ``%s'' in the route string should be replaced by the user  name  at
       the destination host.  (This task is normally performed by a mailer.)

       Except  for  domains,  the  name	 of a network is never used in routes.
       Thus, in the earlier example,  the  path	 from  down  to	 up  would  be
       ``up!%s,'' not ``princeton-ethernet!up!%s.''

   Gateways
       A network is represented by a pseudo-host and a set of network members.
       Links from the members to the network have  the	weight	given  in  the
       input,  while  the  cost from the network to the members is zero.  If a
       network is declared dead, the member-to-network links are marked	 dead,
       which effectively prohibits access to the network from its members.

       However,	 if the input also shows an explicit link from any host to the
       network, then that host can be used as a gateway.  (In particular,  the
       gateway need not be a network member.)

       E.g., if CSNET is declared dead and the input contains

	      CSNET = {...}
	      csnet-relay	  CSNET

       then routes to CSNET hosts will use csnet-relay as a gateway.

   Domains
       A  network  whose name begins with `.' is called a domain.  Domains are
       presumed to require gateways, i.e., they are DEAD.  The route given  by
       a  path through a domain is similar to that for a network, but here the
       domain name is tacked onto the end of the next  host.   Subdomains  are
       permitted.

       E.g.,

	      harvard	.EDU	  # harvard is gateway to .EDU domain
	      .EDU	= {.BERKELEY, .UMICH}
	      .BERKELEY = {ernie}

       yields

	      ernie	...!harvard!ernie.BERKELEY.EDU!%s

       Output  is given for the nearest gateway to a domain, e.g., the example
       above gives

	      .EDU	...!harvard!%s

       Output is given for a subdomain if it has a different  route  than  its
       parent domain, or if all its ancestor domains are private.

       If  the -D option is given on the command line, pathalias treats a link
       from a domain to a host member of that domain as terminal.  This	 prop‐
       erty extends to host members of subdomains, etc, and discourages routes
       that use any domain member as a relay.

   Databases
       Makedb builds a dbm(3) database from the standard  input	 or  from  the
       named  files.   Input is expected to be sequence of ASCII records, each
       consisting of a key field and a data field separated by a  single  tab.
       If the tab is missing, the data field is assumed to be empty.

FILES ET AL.
       /usr/local/lib/palias.{dir,pag}	   default dbm output
       newsgroup comp.mail.maps		   likely location of some input files
       getopt(3),  available  from comp.sources.unix archives (if not in the C
       library).

BUGS
       The -i option should be the default.

       The order of arguments is significant.  In particular, -i and -t should
       appear early.

       Pathalias can generate hybrid (i.e. ambiguous) routes, which are abhor‐
       rent and most certainly should not be given as examples in  the	manual
       entry.  Experienced mappers largely shun `@' when preparing input; this
       is historical, but  also	 reflects  UUCP's  facile  syntax  for	source
       routes.

       Multiple	 `@'s  in  routes  are	loathsome, so pathalias resorts to the
       ``magic %'' rule when necessary.	 This  convention  is  not  documented
       anywhere, including here.

       The  -D	option elides insignificant routes to domain members.  This is
       benign, perhaps even beneficial, but confusing, since the  behavior  is
       undocumented and somewhat unpredictable.

SEE ALSO
       P.  Honeyman  and S.M. Bellovin, ``PATHALIAS or The Care and Feeding of
       Relative Addresses,'' in Proc. Summer USENIX Conf., Atlanta, 1986.

Public Domain			    3/2/93			  PATHALIAS(8)
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