freebsd-dev/usr.sbin/ypbind/ypbind.8

204 lines
6.3 KiB
Groff
Raw Normal View History

1995-04-09 21:59:06 +00:00
.\" Copyright (c) 1991, 1993, 1995
.\" The Regents of the University of California. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\" must display the following acknowledgement:
.\" This product includes software developed by the University of
.\" California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
1999-08-28 01:35:59 +00:00
.\" $FreeBSD$
1995-04-09 21:59:06 +00:00
.\"
.Dd April 9, 1995
.Dt YPBIND 8
.Os
.Sh NAME
.Nm ypbind
.Nd "NIS domain binding daemon"
.Sh SYNOPSIS
1997-04-15 07:15:47 +00:00
.Nm
1995-04-09 21:59:06 +00:00
.Op Fl ypset
.Op Fl ypsetme
.Op Fl s
This commit adds support to ypbind(8) for binding to non-local servers. The standard SunOS ypbind(8) (and, until now, the FreeBSD ypbind) only selects servers based on whether or not they respond to clnt_broadcast(). Ypbind(8) broadcasts to the YPPROC_DOMAIN_NONACK procedure and waits for answers; whichever server answers first is the one ypbind uses for the local client binding. This mechanism fails when binding across subnets is desired. In order for a client on one subnet to bind to a server on another subnet, the gateway(s) between the client and server must be configured to forward broadcasts. If this is not possible, then a slave server must be installed on the remote subnet. If this is also not possible, you have to force the client to bind to the remote server with ypset(8). Unfortunately, this last option is less than ideal. If the remote server becomes unavailable, ypbind(8) will lose its binding and revert to its broadcast-based search behavior. Even if there are other servers available, or even if the original server comes back up, ypbind(8) will not be able to create a new binding since all the servers are on remote subnets where its broadcasts won't be heard. If the administrator isn't around to run ypset(8) again, the system is hosed. In some Linux NIS implementations, there exists a yp.conf file where you can explicitly specify a server address and avoid the use of ypbind altogether. This is not desireable since it removes the possibility of binding to an alternate server in the event that the one specified in yp.conf crashes. Some people have mentioned to me how they though the 'restricted mode' operation (using the -S flag) could be used as a solution for this problem since it allows one to specify a list of servers. In fact, this is not the case: the -S flag just tells ypbind(8) that when it listens for replies to its broadcasts, it should only honor them if the replying hosts appear in the specified restricted list. This behavior has now been changed. If you use the -m flag in conjunction with the -S flag, ypbind(8) will use a 'many-cast' instead of a broadcast for choosing a server. In many-cast mode, ypbind(8) will transmit directly to the YPPROC_DOMAIN_NONACK procedure of all the servers specified in the restricted mode list and then wait for a reply. As with the broadcast method, whichever server from the list answers first is used for the local binding. All other behavior is the same: ypbind(8) continues to ping its bound server every 60 seconds to insure it's still alive and will many-cast again if the server fails to respond. The code used to achieve this is in yp_ping.c; it includes a couple of modified RPC library routines. Note that it is not possible to use this mechanism without using the restricted list since we need to know the addresses of the available NIS servers ahead of time in order to transmit to them. Most-recently-requested by: Tom Samplonius
1997-05-25 19:49:33 +00:00
.Op Fl m
.Oo
.Fl S
.Sm off
.Ar domainname , server1 , server2 , ...
.Sm on
.Oc
1995-04-09 21:59:06 +00:00
.Sh DESCRIPTION
.Nm Ypbind
is the process that maintains NIS binding information.
At startup,
1995-04-09 21:59:06 +00:00
it searches for an NIS server responsible for serving the system's
default domain (as set by the
.Xr domainname 1
ypbind.c: Major overhaul. - Moved to a more client-driven model. We aggressively attempt to keep the default domain bound (as before) but we give up on non-default domains if we lose contact with a server and fail to get a response after one round of broadcasting. This helps drastically reduce the amount of network bandwitdh that ypbind consumes: if a client references the secondary domain at some later point, this will prod ypbind into establishing a new binding anyway, so continuously broadcasting without need is pointless. Note that we still actively seek out a binding for our default domain even if no client program has queried us yet. I'm not exactly sure if this matches SunOS's behavior or not, but I decided to do it this way since we can get into all sorts of trouble if our default domain comes unbound. Even so, we're still much quieter than we used to be. - Removed a bunch of no-longer pertinent comments and a couple of chunks of #ifdef 0'ed code that no longer fit in to the new layout. - Theo deRaadt must have become frustrated with the callback mechanism in clnt_broadcast(), because he shamelessly stole the clnt_broadcast() code right out of the RPC library and hacked it up to suit his needs. (Comments and all! :) I can understand why: clnt_broadcast() blocks while awaiting replies. Changing this behavior requires surgery. However, you can work around this: fork the broadcast into a child process and relay the results back to the parent via a pipe. (Careful obervation has shown that the SunOS ypbind forks children for broadcasting too, though I can only guess what sort of interprocess communication it uses. pipe() seems to do the job well enough.) This may seem like the long way around, but it's not really that hard to implement, and I'd prefer to use documented RPC library functions wherever possible. We're careful to limit the number of simultaneous broadcasters to avoid swamping the system (the current limit is 5). Each clnt_broadcast() call only sends out a small number of packets at increasing intervals. We're also careful not to spawn more than one bradcaster for a given domain. - Used clntudp_bufcreate() and clnt_call() to implement a ping() function for directly querying a particular server so that we can check if it's still alive. This lets me completely remove the old bradcasting code and use actual RPC library calls instead, at the cost of more than a few handfulls of torn-out hair. (Make no mistake folks: I *HATE* RPC.) Currently, the ping interval is one minute. - Fixed another potential 'nfds too big for select()' bug: use _rpc_dtablesize() instead of getdtablesize(). - Quieted gcc -Wall a bit. - Probably a bunch of other stuff that I've forgotten. ypbind.8: - Updated man page to reflect modifications. ypwhich.c: - Small mind-o fix from last time: decode error results from ypbind correctly (*groan*) yplib.c: - same as above - Change behavior of _yp_dobind() a little: if we get back a 'Domain not bound' error for a given domain, retry a few times before giving up and passing the error back to the caller. We have to sleep for a few seconds between tries since the 'Domain not bound' error comes back immediately (by repeatedly looping, we end up pounding on ypbind). We retry at most 20 times at 5 second intervals. This gives us a full minute to get a response. This seems to deviate a bit from SunOS behavior -- it appears to wait forever -- but I don't like the idea of perpetually hanging inside a library call. Note that this should fix the problems some people have with bindings not being established fast enough at boot time; sometimes amd is started in /etc/rc after ypbind has run but before it gets a binding set up. The automounter gets annoyed at this and tends to exit. By pausing ther YP calls until a binding is ready, we avoid this situation. - Another _yp_dobind() change: if we determine that our binding files are unlocked or nonexistent, jump directly to code that pokes ypbind into restablishing the binding. Again, if it fails, we'll time out eventually and return.
1995-04-26 19:03:16 +00:00
command) using network broadcasts.
Once it receives a reply,
1995-04-09 21:59:06 +00:00
it will store the address of the server and other
information in a special file located in
.Pa /var/yp/binding .
The NIS routines in the standard C library can then use this file
when processing NIS requests.
There may be several such files
1995-04-09 21:59:06 +00:00
since it is possible for an NIS client to be bound to more than
one domain.
.Pp
After a binding has been established,
1997-04-15 07:15:47 +00:00
.Nm
1995-04-09 21:59:06 +00:00
will send DOMAIN_NONACK requests to the NIS server at one minute
intervals.
If it fails to receive a reply to one of these requests,
1997-04-15 07:15:47 +00:00
.Nm
ypbind.c: Major overhaul. - Moved to a more client-driven model. We aggressively attempt to keep the default domain bound (as before) but we give up on non-default domains if we lose contact with a server and fail to get a response after one round of broadcasting. This helps drastically reduce the amount of network bandwitdh that ypbind consumes: if a client references the secondary domain at some later point, this will prod ypbind into establishing a new binding anyway, so continuously broadcasting without need is pointless. Note that we still actively seek out a binding for our default domain even if no client program has queried us yet. I'm not exactly sure if this matches SunOS's behavior or not, but I decided to do it this way since we can get into all sorts of trouble if our default domain comes unbound. Even so, we're still much quieter than we used to be. - Removed a bunch of no-longer pertinent comments and a couple of chunks of #ifdef 0'ed code that no longer fit in to the new layout. - Theo deRaadt must have become frustrated with the callback mechanism in clnt_broadcast(), because he shamelessly stole the clnt_broadcast() code right out of the RPC library and hacked it up to suit his needs. (Comments and all! :) I can understand why: clnt_broadcast() blocks while awaiting replies. Changing this behavior requires surgery. However, you can work around this: fork the broadcast into a child process and relay the results back to the parent via a pipe. (Careful obervation has shown that the SunOS ypbind forks children for broadcasting too, though I can only guess what sort of interprocess communication it uses. pipe() seems to do the job well enough.) This may seem like the long way around, but it's not really that hard to implement, and I'd prefer to use documented RPC library functions wherever possible. We're careful to limit the number of simultaneous broadcasters to avoid swamping the system (the current limit is 5). Each clnt_broadcast() call only sends out a small number of packets at increasing intervals. We're also careful not to spawn more than one bradcaster for a given domain. - Used clntudp_bufcreate() and clnt_call() to implement a ping() function for directly querying a particular server so that we can check if it's still alive. This lets me completely remove the old bradcasting code and use actual RPC library calls instead, at the cost of more than a few handfulls of torn-out hair. (Make no mistake folks: I *HATE* RPC.) Currently, the ping interval is one minute. - Fixed another potential 'nfds too big for select()' bug: use _rpc_dtablesize() instead of getdtablesize(). - Quieted gcc -Wall a bit. - Probably a bunch of other stuff that I've forgotten. ypbind.8: - Updated man page to reflect modifications. ypwhich.c: - Small mind-o fix from last time: decode error results from ypbind correctly (*groan*) yplib.c: - same as above - Change behavior of _yp_dobind() a little: if we get back a 'Domain not bound' error for a given domain, retry a few times before giving up and passing the error back to the caller. We have to sleep for a few seconds between tries since the 'Domain not bound' error comes back immediately (by repeatedly looping, we end up pounding on ypbind). We retry at most 20 times at 5 second intervals. This gives us a full minute to get a response. This seems to deviate a bit from SunOS behavior -- it appears to wait forever -- but I don't like the idea of perpetually hanging inside a library call. Note that this should fix the problems some people have with bindings not being established fast enough at boot time; sometimes amd is started in /etc/rc after ypbind has run but before it gets a binding set up. The automounter gets annoyed at this and tends to exit. By pausing ther YP calls until a binding is ready, we avoid this situation. - Another _yp_dobind() change: if we determine that our binding files are unlocked or nonexistent, jump directly to code that pokes ypbind into restablishing the binding. Again, if it fails, we'll time out eventually and return.
1995-04-26 19:03:16 +00:00
assumes that the server is no longer running and resumes its network
1995-04-09 21:59:06 +00:00
broadcasts until another binding is established.
.Nm Ypbind
1997-04-15 07:15:47 +00:00
will also log warning messages using the
.Xr syslog 3
facility each time it detects that a server has stopped responding,
as well as when it has bound to a new server.
2000-01-23 20:32:24 +00:00
.Pp
The following options are available:
.Bl -tag -width indent
1995-04-09 21:59:06 +00:00
.It Fl ypset
It is possible to force
1997-04-15 07:15:47 +00:00
.Nm
1995-04-09 21:59:06 +00:00
to bind to a particular NIS server host for a given domain by using the
.Xr ypset 8
command.
However,
1997-04-15 07:15:47 +00:00
.Nm
1995-04-09 21:59:06 +00:00
refuses YPBINDPROC_SETDOM requests by default since it has no way of
knowing exactly who is sending them.
Using the
1995-04-09 21:59:06 +00:00
.Fl ypset
flag causes
1997-04-15 07:15:47 +00:00
.Nm
to accept YPBINDPROC_SETDOM requests from any host.
This option should only
1995-04-09 21:59:06 +00:00
be used for diagnostic purposes and only for limited periods since allowing
ypbind.c: Major overhaul. - Moved to a more client-driven model. We aggressively attempt to keep the default domain bound (as before) but we give up on non-default domains if we lose contact with a server and fail to get a response after one round of broadcasting. This helps drastically reduce the amount of network bandwitdh that ypbind consumes: if a client references the secondary domain at some later point, this will prod ypbind into establishing a new binding anyway, so continuously broadcasting without need is pointless. Note that we still actively seek out a binding for our default domain even if no client program has queried us yet. I'm not exactly sure if this matches SunOS's behavior or not, but I decided to do it this way since we can get into all sorts of trouble if our default domain comes unbound. Even so, we're still much quieter than we used to be. - Removed a bunch of no-longer pertinent comments and a couple of chunks of #ifdef 0'ed code that no longer fit in to the new layout. - Theo deRaadt must have become frustrated with the callback mechanism in clnt_broadcast(), because he shamelessly stole the clnt_broadcast() code right out of the RPC library and hacked it up to suit his needs. (Comments and all! :) I can understand why: clnt_broadcast() blocks while awaiting replies. Changing this behavior requires surgery. However, you can work around this: fork the broadcast into a child process and relay the results back to the parent via a pipe. (Careful obervation has shown that the SunOS ypbind forks children for broadcasting too, though I can only guess what sort of interprocess communication it uses. pipe() seems to do the job well enough.) This may seem like the long way around, but it's not really that hard to implement, and I'd prefer to use documented RPC library functions wherever possible. We're careful to limit the number of simultaneous broadcasters to avoid swamping the system (the current limit is 5). Each clnt_broadcast() call only sends out a small number of packets at increasing intervals. We're also careful not to spawn more than one bradcaster for a given domain. - Used clntudp_bufcreate() and clnt_call() to implement a ping() function for directly querying a particular server so that we can check if it's still alive. This lets me completely remove the old bradcasting code and use actual RPC library calls instead, at the cost of more than a few handfulls of torn-out hair. (Make no mistake folks: I *HATE* RPC.) Currently, the ping interval is one minute. - Fixed another potential 'nfds too big for select()' bug: use _rpc_dtablesize() instead of getdtablesize(). - Quieted gcc -Wall a bit. - Probably a bunch of other stuff that I've forgotten. ypbind.8: - Updated man page to reflect modifications. ypwhich.c: - Small mind-o fix from last time: decode error results from ypbind correctly (*groan*) yplib.c: - same as above - Change behavior of _yp_dobind() a little: if we get back a 'Domain not bound' error for a given domain, retry a few times before giving up and passing the error back to the caller. We have to sleep for a few seconds between tries since the 'Domain not bound' error comes back immediately (by repeatedly looping, we end up pounding on ypbind). We retry at most 20 times at 5 second intervals. This gives us a full minute to get a response. This seems to deviate a bit from SunOS behavior -- it appears to wait forever -- but I don't like the idea of perpetually hanging inside a library call. Note that this should fix the problems some people have with bindings not being established fast enough at boot time; sometimes amd is started in /etc/rc after ypbind has run but before it gets a binding set up. The automounter gets annoyed at this and tends to exit. By pausing ther YP calls until a binding is ready, we avoid this situation. - Another _yp_dobind() change: if we determine that our binding files are unlocked or nonexistent, jump directly to code that pokes ypbind into restablishing the binding. Again, if it fails, we'll time out eventually and return.
1995-04-26 19:03:16 +00:00
arbitrary users to reset the binding of an NIS client poses a severe
1995-04-09 21:59:06 +00:00
security risk.
.It Fl ypsetme
This is similar to the
.Fl ypset
flag, except that it only permits YPBINDPROC_SETDOM requests to be processed
if they originated from the local host.
.It Fl s
Cause
1997-04-15 07:15:47 +00:00
.Nm
1995-04-09 21:59:06 +00:00
to run in secure mode: it will refuse to bind to any NIS server
that is not running as root (i.e. that is not using privileged
TCP ports).
.It Fl S Xo
.Sm off
.Ar domainname , server1 , server2 , server3 , ...
.Sm on
.Xc
Allow the system administrator to lock
.Nm
to a particular
domain and group of NIS servers.
Up to ten servers can be specified.
There must not be any spaces between the commas in the domain/server
specification.
This option is used to insure that the system binds
2001-07-15 08:06:20 +00:00
only to one domain and only to one of the specified servers, which
is useful for systems that are both NIS servers and NIS
clients: it provides a way to restrict what machines the system can
bind to without the need for specifying the
.Fl ypset
or
.Fl ypsetme
options, which are often considered to be security holes.
The specified
servers must have valid entries in the local
.Pa /etc/hosts
file. IP addresses may be specified in place of hostnames.
If
1997-04-15 07:15:47 +00:00
.Nm
can't make sense ouf of the arguments, it will ignore
the
.Fl S
flag and continue running normally.
.Pp
Note that
1997-04-15 07:15:47 +00:00
.Nm
will consider the domainname specified with the
.Fl S
flag to be the system default domain.
This commit adds support to ypbind(8) for binding to non-local servers. The standard SunOS ypbind(8) (and, until now, the FreeBSD ypbind) only selects servers based on whether or not they respond to clnt_broadcast(). Ypbind(8) broadcasts to the YPPROC_DOMAIN_NONACK procedure and waits for answers; whichever server answers first is the one ypbind uses for the local client binding. This mechanism fails when binding across subnets is desired. In order for a client on one subnet to bind to a server on another subnet, the gateway(s) between the client and server must be configured to forward broadcasts. If this is not possible, then a slave server must be installed on the remote subnet. If this is also not possible, you have to force the client to bind to the remote server with ypset(8). Unfortunately, this last option is less than ideal. If the remote server becomes unavailable, ypbind(8) will lose its binding and revert to its broadcast-based search behavior. Even if there are other servers available, or even if the original server comes back up, ypbind(8) will not be able to create a new binding since all the servers are on remote subnets where its broadcasts won't be heard. If the administrator isn't around to run ypset(8) again, the system is hosed. In some Linux NIS implementations, there exists a yp.conf file where you can explicitly specify a server address and avoid the use of ypbind altogether. This is not desireable since it removes the possibility of binding to an alternate server in the event that the one specified in yp.conf crashes. Some people have mentioned to me how they though the 'restricted mode' operation (using the -S flag) could be used as a solution for this problem since it allows one to specify a list of servers. In fact, this is not the case: the -S flag just tells ypbind(8) that when it listens for replies to its broadcasts, it should only honor them if the replying hosts appear in the specified restricted list. This behavior has now been changed. If you use the -m flag in conjunction with the -S flag, ypbind(8) will use a 'many-cast' instead of a broadcast for choosing a server. In many-cast mode, ypbind(8) will transmit directly to the YPPROC_DOMAIN_NONACK procedure of all the servers specified in the restricted mode list and then wait for a reply. As with the broadcast method, whichever server from the list answers first is used for the local binding. All other behavior is the same: ypbind(8) continues to ping its bound server every 60 seconds to insure it's still alive and will many-cast again if the server fails to respond. The code used to achieve this is in yp_ping.c; it includes a couple of modified RPC library routines. Note that it is not possible to use this mechanism without using the restricted list since we need to know the addresses of the available NIS servers ahead of time in order to transmit to them. Most-recently-requested by: Tom Samplonius
1997-05-25 19:49:33 +00:00
.It Fl m
Cause
.Nm
This commit adds support to ypbind(8) for binding to non-local servers. The standard SunOS ypbind(8) (and, until now, the FreeBSD ypbind) only selects servers based on whether or not they respond to clnt_broadcast(). Ypbind(8) broadcasts to the YPPROC_DOMAIN_NONACK procedure and waits for answers; whichever server answers first is the one ypbind uses for the local client binding. This mechanism fails when binding across subnets is desired. In order for a client on one subnet to bind to a server on another subnet, the gateway(s) between the client and server must be configured to forward broadcasts. If this is not possible, then a slave server must be installed on the remote subnet. If this is also not possible, you have to force the client to bind to the remote server with ypset(8). Unfortunately, this last option is less than ideal. If the remote server becomes unavailable, ypbind(8) will lose its binding and revert to its broadcast-based search behavior. Even if there are other servers available, or even if the original server comes back up, ypbind(8) will not be able to create a new binding since all the servers are on remote subnets where its broadcasts won't be heard. If the administrator isn't around to run ypset(8) again, the system is hosed. In some Linux NIS implementations, there exists a yp.conf file where you can explicitly specify a server address and avoid the use of ypbind altogether. This is not desireable since it removes the possibility of binding to an alternate server in the event that the one specified in yp.conf crashes. Some people have mentioned to me how they though the 'restricted mode' operation (using the -S flag) could be used as a solution for this problem since it allows one to specify a list of servers. In fact, this is not the case: the -S flag just tells ypbind(8) that when it listens for replies to its broadcasts, it should only honor them if the replying hosts appear in the specified restricted list. This behavior has now been changed. If you use the -m flag in conjunction with the -S flag, ypbind(8) will use a 'many-cast' instead of a broadcast for choosing a server. In many-cast mode, ypbind(8) will transmit directly to the YPPROC_DOMAIN_NONACK procedure of all the servers specified in the restricted mode list and then wait for a reply. As with the broadcast method, whichever server from the list answers first is used for the local binding. All other behavior is the same: ypbind(8) continues to ping its bound server every 60 seconds to insure it's still alive and will many-cast again if the server fails to respond. The code used to achieve this is in yp_ping.c; it includes a couple of modified RPC library routines. Note that it is not possible to use this mechanism without using the restricted list since we need to know the addresses of the available NIS servers ahead of time in order to transmit to them. Most-recently-requested by: Tom Samplonius
1997-05-25 19:49:33 +00:00
to use a 'many-cast' rather than a broadcast for choosing a server
from the restricted mode server list.
In many-cast mode,
.Nm
This commit adds support to ypbind(8) for binding to non-local servers. The standard SunOS ypbind(8) (and, until now, the FreeBSD ypbind) only selects servers based on whether or not they respond to clnt_broadcast(). Ypbind(8) broadcasts to the YPPROC_DOMAIN_NONACK procedure and waits for answers; whichever server answers first is the one ypbind uses for the local client binding. This mechanism fails when binding across subnets is desired. In order for a client on one subnet to bind to a server on another subnet, the gateway(s) between the client and server must be configured to forward broadcasts. If this is not possible, then a slave server must be installed on the remote subnet. If this is also not possible, you have to force the client to bind to the remote server with ypset(8). Unfortunately, this last option is less than ideal. If the remote server becomes unavailable, ypbind(8) will lose its binding and revert to its broadcast-based search behavior. Even if there are other servers available, or even if the original server comes back up, ypbind(8) will not be able to create a new binding since all the servers are on remote subnets where its broadcasts won't be heard. If the administrator isn't around to run ypset(8) again, the system is hosed. In some Linux NIS implementations, there exists a yp.conf file where you can explicitly specify a server address and avoid the use of ypbind altogether. This is not desireable since it removes the possibility of binding to an alternate server in the event that the one specified in yp.conf crashes. Some people have mentioned to me how they though the 'restricted mode' operation (using the -S flag) could be used as a solution for this problem since it allows one to specify a list of servers. In fact, this is not the case: the -S flag just tells ypbind(8) that when it listens for replies to its broadcasts, it should only honor them if the replying hosts appear in the specified restricted list. This behavior has now been changed. If you use the -m flag in conjunction with the -S flag, ypbind(8) will use a 'many-cast' instead of a broadcast for choosing a server. In many-cast mode, ypbind(8) will transmit directly to the YPPROC_DOMAIN_NONACK procedure of all the servers specified in the restricted mode list and then wait for a reply. As with the broadcast method, whichever server from the list answers first is used for the local binding. All other behavior is the same: ypbind(8) continues to ping its bound server every 60 seconds to insure it's still alive and will many-cast again if the server fails to respond. The code used to achieve this is in yp_ping.c; it includes a couple of modified RPC library routines. Note that it is not possible to use this mechanism without using the restricted list since we need to know the addresses of the available NIS servers ahead of time in order to transmit to them. Most-recently-requested by: Tom Samplonius
1997-05-25 19:49:33 +00:00
will transmit directly to the YPPROC_DOMAIN_NONACK procedure of the
servers specified in the restricted list and bind to the server that
responds the fastest.
This mode of operation is useful for NIS clients on remote subnets
where no local NIS servers are available.
The
.Fl m
flag can only be used in conjunction with the
.Fl S
flag above (if used without the
.Fl S
flag, it has no effect).
This commit adds support to ypbind(8) for binding to non-local servers. The standard SunOS ypbind(8) (and, until now, the FreeBSD ypbind) only selects servers based on whether or not they respond to clnt_broadcast(). Ypbind(8) broadcasts to the YPPROC_DOMAIN_NONACK procedure and waits for answers; whichever server answers first is the one ypbind uses for the local client binding. This mechanism fails when binding across subnets is desired. In order for a client on one subnet to bind to a server on another subnet, the gateway(s) between the client and server must be configured to forward broadcasts. If this is not possible, then a slave server must be installed on the remote subnet. If this is also not possible, you have to force the client to bind to the remote server with ypset(8). Unfortunately, this last option is less than ideal. If the remote server becomes unavailable, ypbind(8) will lose its binding and revert to its broadcast-based search behavior. Even if there are other servers available, or even if the original server comes back up, ypbind(8) will not be able to create a new binding since all the servers are on remote subnets where its broadcasts won't be heard. If the administrator isn't around to run ypset(8) again, the system is hosed. In some Linux NIS implementations, there exists a yp.conf file where you can explicitly specify a server address and avoid the use of ypbind altogether. This is not desireable since it removes the possibility of binding to an alternate server in the event that the one specified in yp.conf crashes. Some people have mentioned to me how they though the 'restricted mode' operation (using the -S flag) could be used as a solution for this problem since it allows one to specify a list of servers. In fact, this is not the case: the -S flag just tells ypbind(8) that when it listens for replies to its broadcasts, it should only honor them if the replying hosts appear in the specified restricted list. This behavior has now been changed. If you use the -m flag in conjunction with the -S flag, ypbind(8) will use a 'many-cast' instead of a broadcast for choosing a server. In many-cast mode, ypbind(8) will transmit directly to the YPPROC_DOMAIN_NONACK procedure of all the servers specified in the restricted mode list and then wait for a reply. As with the broadcast method, whichever server from the list answers first is used for the local binding. All other behavior is the same: ypbind(8) continues to ping its bound server every 60 seconds to insure it's still alive and will many-cast again if the server fails to respond. The code used to achieve this is in yp_ping.c; it includes a couple of modified RPC library routines. Note that it is not possible to use this mechanism without using the restricted list since we need to know the addresses of the available NIS servers ahead of time in order to transmit to them. Most-recently-requested by: Tom Samplonius
1997-05-25 19:49:33 +00:00
.El
ypbind.c: Major overhaul. - Moved to a more client-driven model. We aggressively attempt to keep the default domain bound (as before) but we give up on non-default domains if we lose contact with a server and fail to get a response after one round of broadcasting. This helps drastically reduce the amount of network bandwitdh that ypbind consumes: if a client references the secondary domain at some later point, this will prod ypbind into establishing a new binding anyway, so continuously broadcasting without need is pointless. Note that we still actively seek out a binding for our default domain even if no client program has queried us yet. I'm not exactly sure if this matches SunOS's behavior or not, but I decided to do it this way since we can get into all sorts of trouble if our default domain comes unbound. Even so, we're still much quieter than we used to be. - Removed a bunch of no-longer pertinent comments and a couple of chunks of #ifdef 0'ed code that no longer fit in to the new layout. - Theo deRaadt must have become frustrated with the callback mechanism in clnt_broadcast(), because he shamelessly stole the clnt_broadcast() code right out of the RPC library and hacked it up to suit his needs. (Comments and all! :) I can understand why: clnt_broadcast() blocks while awaiting replies. Changing this behavior requires surgery. However, you can work around this: fork the broadcast into a child process and relay the results back to the parent via a pipe. (Careful obervation has shown that the SunOS ypbind forks children for broadcasting too, though I can only guess what sort of interprocess communication it uses. pipe() seems to do the job well enough.) This may seem like the long way around, but it's not really that hard to implement, and I'd prefer to use documented RPC library functions wherever possible. We're careful to limit the number of simultaneous broadcasters to avoid swamping the system (the current limit is 5). Each clnt_broadcast() call only sends out a small number of packets at increasing intervals. We're also careful not to spawn more than one bradcaster for a given domain. - Used clntudp_bufcreate() and clnt_call() to implement a ping() function for directly querying a particular server so that we can check if it's still alive. This lets me completely remove the old bradcasting code and use actual RPC library calls instead, at the cost of more than a few handfulls of torn-out hair. (Make no mistake folks: I *HATE* RPC.) Currently, the ping interval is one minute. - Fixed another potential 'nfds too big for select()' bug: use _rpc_dtablesize() instead of getdtablesize(). - Quieted gcc -Wall a bit. - Probably a bunch of other stuff that I've forgotten. ypbind.8: - Updated man page to reflect modifications. ypwhich.c: - Small mind-o fix from last time: decode error results from ypbind correctly (*groan*) yplib.c: - same as above - Change behavior of _yp_dobind() a little: if we get back a 'Domain not bound' error for a given domain, retry a few times before giving up and passing the error back to the caller. We have to sleep for a few seconds between tries since the 'Domain not bound' error comes back immediately (by repeatedly looping, we end up pounding on ypbind). We retry at most 20 times at 5 second intervals. This gives us a full minute to get a response. This seems to deviate a bit from SunOS behavior -- it appears to wait forever -- but I don't like the idea of perpetually hanging inside a library call. Note that this should fix the problems some people have with bindings not being established fast enough at boot time; sometimes amd is started in /etc/rc after ypbind has run but before it gets a binding set up. The automounter gets annoyed at this and tends to exit. By pausing ther YP calls until a binding is ready, we avoid this situation. - Another _yp_dobind() change: if we determine that our binding files are unlocked or nonexistent, jump directly to code that pokes ypbind into restablishing the binding. Again, if it fails, we'll time out eventually and return.
1995-04-26 19:03:16 +00:00
.Sh NOTES
1997-04-15 07:15:47 +00:00
The
.Nm
program will not make continuous attempts to keep secondary domains bound.
If a server for a secondary domain fails to respond to a ping,
.Nm
will broadcast for a new server only once before giving up.
If a
1997-04-15 07:15:47 +00:00
client program attempts to reference the unbound domain,
.Nm
will try broadcasting again.
By contrast,
1997-04-15 07:15:47 +00:00
.Nm
ypbind.c: Major overhaul. - Moved to a more client-driven model. We aggressively attempt to keep the default domain bound (as before) but we give up on non-default domains if we lose contact with a server and fail to get a response after one round of broadcasting. This helps drastically reduce the amount of network bandwitdh that ypbind consumes: if a client references the secondary domain at some later point, this will prod ypbind into establishing a new binding anyway, so continuously broadcasting without need is pointless. Note that we still actively seek out a binding for our default domain even if no client program has queried us yet. I'm not exactly sure if this matches SunOS's behavior or not, but I decided to do it this way since we can get into all sorts of trouble if our default domain comes unbound. Even so, we're still much quieter than we used to be. - Removed a bunch of no-longer pertinent comments and a couple of chunks of #ifdef 0'ed code that no longer fit in to the new layout. - Theo deRaadt must have become frustrated with the callback mechanism in clnt_broadcast(), because he shamelessly stole the clnt_broadcast() code right out of the RPC library and hacked it up to suit his needs. (Comments and all! :) I can understand why: clnt_broadcast() blocks while awaiting replies. Changing this behavior requires surgery. However, you can work around this: fork the broadcast into a child process and relay the results back to the parent via a pipe. (Careful obervation has shown that the SunOS ypbind forks children for broadcasting too, though I can only guess what sort of interprocess communication it uses. pipe() seems to do the job well enough.) This may seem like the long way around, but it's not really that hard to implement, and I'd prefer to use documented RPC library functions wherever possible. We're careful to limit the number of simultaneous broadcasters to avoid swamping the system (the current limit is 5). Each clnt_broadcast() call only sends out a small number of packets at increasing intervals. We're also careful not to spawn more than one bradcaster for a given domain. - Used clntudp_bufcreate() and clnt_call() to implement a ping() function for directly querying a particular server so that we can check if it's still alive. This lets me completely remove the old bradcasting code and use actual RPC library calls instead, at the cost of more than a few handfulls of torn-out hair. (Make no mistake folks: I *HATE* RPC.) Currently, the ping interval is one minute. - Fixed another potential 'nfds too big for select()' bug: use _rpc_dtablesize() instead of getdtablesize(). - Quieted gcc -Wall a bit. - Probably a bunch of other stuff that I've forgotten. ypbind.8: - Updated man page to reflect modifications. ypwhich.c: - Small mind-o fix from last time: decode error results from ypbind correctly (*groan*) yplib.c: - same as above - Change behavior of _yp_dobind() a little: if we get back a 'Domain not bound' error for a given domain, retry a few times before giving up and passing the error back to the caller. We have to sleep for a few seconds between tries since the 'Domain not bound' error comes back immediately (by repeatedly looping, we end up pounding on ypbind). We retry at most 20 times at 5 second intervals. This gives us a full minute to get a response. This seems to deviate a bit from SunOS behavior -- it appears to wait forever -- but I don't like the idea of perpetually hanging inside a library call. Note that this should fix the problems some people have with bindings not being established fast enough at boot time; sometimes amd is started in /etc/rc after ypbind has run but before it gets a binding set up. The automounter gets annoyed at this and tends to exit. By pausing ther YP calls until a binding is ready, we avoid this situation. - Another _yp_dobind() change: if we determine that our binding files are unlocked or nonexistent, jump directly to code that pokes ypbind into restablishing the binding. Again, if it fails, we'll time out eventually and return.
1995-04-26 19:03:16 +00:00
will automatically maintain a binding for the default domain whether
client programs reference it ot not.
1995-04-09 21:59:06 +00:00
.Sh FILES
.Bl -tag -width /etc/rc.conf -compact
1995-04-09 21:59:06 +00:00
.It Pa /var/yp/binding/[domainname].[version]
the files used to hold binding information for each NIS domain
.It Pa /etc/rc.conf
system configuration file where the system default domain and
ypbind startup options are specified
1995-04-09 21:59:06 +00:00
.El
.Sh SEE ALSO
.Xr domainname 1 ,
.Xr syslog 3 ,
2002-01-14 16:59:03 +00:00
.Xr yp 8 ,
1995-04-09 21:59:06 +00:00
.Xr ypserv 8 ,
.Xr ypset 8
.Sh AUTHORS
.An Theo de Raadt Aq deraadt@fsa.ca