when I came up with this idea weren't strong enough to help me see it
through. If this was a self-contained application and I had complete
control over what data got sent through what socket and when, I might
be able to get everything to work right without blocking, but instead
I have RPC/XDR in between me and the socket layer, and they have their
own ideas about what to do.
Maybe one day I'll go totally mad and figure out the right way to do
this; in the meantime this mess goes on the back burner.
_without_ using fork().
The problem with YPPROC_ALL is that it transmits an entire map through
a TCP pipe as the result of a single RPC call. First of all, this requires
certain hackery in the XDR filter. Second, if the map being sent is
large, the server can end up spending lots of time in the XDR filter
sending to just the one client, while requests for other clients will
go unanswered.
My original solution for this was to fork() the request into a child
process which terminates after the map has been transmitted (or the
transfer is interrupted due to an error). This leaves the parent free
to handle other requests. But this solution is kind of lame: fork()
is relatively expensive, and we have to keep a cap on the number of
child processes to keep from swamping the system.
What we do now is grab control of the service transport handle and XDR
handle from the RPC library and send the records one at a time ourselves
instead of letting the RPC library do it. We send a record, then go
back to the svc_run() loop and select() on the socket. If select() says
we can still write data, we send the next record. Then we call
svc_getreqset() and handle other RPCs and loop around again. This way,
we can handle other RPCs between records.
We manage multiple YPPROC_ALL requests using a circular queue. When a
request is done, we dequeue it and destroy the handle. We also tag
each request with a ttl which is decremented whevever we run the queue
and a handle isn't serviced. This lets us nuke requests that have sat
idle for too long (if we didn't do this, we might run out of socket
descriptors.)
Now all I have to do is come up with an async resolver, and ypserv
won't need to fork() at all. :)
Note: these changes should not go into 2.2 unless they get a very
throrough shakedown before the final cutoff date.
and set the B and S variables here, but I forgot to actually add them to
the master.passwd and hosts.* targets. In other words, they weren't being
passed to yp_mkdb as needed.
This needs to go into 2.2; it doesn't break things a lot, but it leaves
your master.passwd maps available to unprivileged users without you
realizing it.
any maps that may have them. If the YP_SECURE key is present, ypserv
will only allow access to the map from clients on reserved ports.
If the YP_INTERDOMAIN key is present, the server will do DNS lookups
for hostnames that it can't find in hosts.byname or hosts.byaddr.
This is the same as the -d flag (which is retained for backwards
compatibility) but it can be set on a per-map/per-domain basis.
Also modified /var/yp/Makefile to add YP_INTERDOMAIN to the hosts.*
maps and YP_SECURE to master.passwd.* maps by default.
the callback is a fatal error for this function; return immediatlely if
this happens. Also make the "failed to establish callback handle" error
mesaage print the IP address of the target callback host.
have it check to see that it doesn't contain any '/' characters. This
prevents possible silliness like ypcat "../../../kernel". We already
test the domain name for this in yp_validdomain(), and ypserv itself
tests the map name in yp_open_db(), but it doesn't hurt to be paranoid
and test for it in the generic access routine too. rpc.ypxfrd does not
test the map name for slashes, but it does call yp_access() with the
map name, so this removes a potential vulnerability from there.
Also make the tests for IPPORT_RESERVED a little more selective: make
sure it trips when map == master.passwd.*, prog == YPPROC and proc ==
YPPROC_XFR, and prog == YPXFRD_FREEBSD_PROG and proc == YPXFRD_GETMAP.
Also use IPPORT_RESERVED instead of hard-coded value.
aliases of the "official" names as well, because now that getportbyname()
does a yp match, it no longer found the entries under the alias.
This broke rsh(1), because it looks up "shell/tcp" while the official
name in /etc/services is "cmd/tcp".
of line.
Also, fix existing bug in ethers.byname, it was passing an unknown option
to yppush. This appears to have been a cut/paste slip intended for a
$(DBLOAD) command above it.
the FreeBSD Makefile.yp structure by me. This allows you to have a single
amd map for all machines in a cluster.
In /etc/sysconfig, it would look something like:
amdflags="-p -a /net -c 1800 -l syslog /host amd.host"
it with the CIRCLEQ macros. This simplifies the code a little, makes
it somewhat easier to read, and may be a little faster. (Actually I think
the performace is about the same.)
Also, in the non DB_CACHE case, save copies of data returned from
the database library in a static buffer, just in case we decide to use
it after the database has been closed. Technically, the memory that the
data pointers refer to belongs to the DB package and we can't count on
it being there after the database has been closed -- the DB package
frees its buffers. (With DB_CACHE #defined the databases are held
open so the buffers remain valid.) I don't think any of the utilities
that use the dblookup module have had any problems with this yet, but
there's no sense in taking any chances.
- Add a 'pushpw' target that only yppushes the various passwd maps
and sends a YPPROC_CLEAR to the local ypserv. This will be used by
rpc.yppasswdd once I merge in the in-place update changes.
yp_access.c:
- Make the yp_access() function print RPC program and procedure numbers
that it doesn't know about in literal form. This will allow it to work
with other prgrams that it doesn't know about, like rpc.ypxfrd I'm going
to import shortly.
yp_dblookup.c:
- Take out the __inline keywords. They weren't really helping me anyway.
- Somehow I broke yp_next() when DB_CACHE wasn't #defined. Fix it.
- Also fix potential case where yp_next() might loop forever; make sure
it checks the return values of all the (dbp->seq)()/R_NEXT calls that
it does as well as comparing keys.
Fix some comments to reflect reality (in some cases I made changes
to code but not to the comments).
Change some instances of 'inline' to '__inline' to pacify
gcc -ansi -pedantic.
Use rcsid strings more consistently.
Make 'oldaddr' static in yp_access().
Use strcpy()/strcat() in yp_open_db_cache() instead of snprintf().
(Seems to be a little faster this way.)
yp_dblookup.c:
- Implement database handle caching. What this means is that instead
of opening and closing map databases for each request, we open a
database and save the handle (and, if requested, the key index)
in an array. This saves a bit of overhead on things like repeated
YPPROC_NEXT calls, such as you'd get from getpwent(). Normally,
each YPPROC_NEXT would require open()ing the database, seeking
to the location supplied by the caller (which is time consuming with
hash databases as the R_CURSOR flag doesn't work), reading the
data, close()ing the database and then shipping the data off to
the caller. The system call overhead is prohibitive, especially
with very large maps. By caching the handle to an open database,
we elimitate at least the open()/close() system calls, as well
as the associated DB setup and tear-down operations, for a large
percentage of the time. This improves performance substantially at
the cost of consuming a little more memory than before.
Note that all the caching support is surrounded by #ifdef DB_CACHE
so that this same source module can still be used by other programs
that don't need it.
- Make yp_open_db() call yp_validdomain(). Doing it here saves cycles
when caching is enabled since a hit on the map cache list by
definition means that the domain being referenced is valid.
- Also make yp_open_db() check for exhaustion of file descriptors,
just in case.
yp_server.c:
- Reorganize things a little to take advantage of the database
handle caching. Add a call to yp_flush_all() in ypproc_clear_2_svc().
- Remove calls to yp_validdomain() from some of the service procedures.
yp_validdomain() is called inside yp_open_db() now, so procedures that
call into the database package don't need to use yp_validdomain()
themselves.
- Fix a bogosity in ypproc_maplist_2_svc(): don't summarily initiallize
the result.maps pointer to NULL. This causes yp_maplist_free()
to fail and leaks memory.
- Make ypproc_master_2_svc() copy the string it gets from the database
package into a private static buffer before trying to NUL terminate it.
This is necessary with the DB handle caching: stuffing a NUL into the
data returned by DB package will goof it up internally.
yp_main.c:
- Stuff for DB handle caching: call yp_init_dbs() to clear the
handle array and add call to yp_flush_all() to the SIGHUP
signal handler.
Makefile.yp:
- Reorganize to deal with database caching. yp_mkdb(8) can now be used
to send a YPPROC_CLEAR signal to ypserv(8). Call it after each map
is created to refresh ypserv's cache.
- Add support for mail.alias map.
Contributed by Mike Murphy (mrm@sceard.com).
- Make default location for the netgroups source file be /var/yp/netgroup
instead of /etc/netgroup.
mkaliases:
- New file: script to generate mail.alias map.
Contributed by Mike Murphy (mrm@sceard.com).
Makefile:
- Install Makefile.yp as /var/yp/Makefile.dist and link it to
/var/yp/Makefile only if /var/yp/Makefile doesn't already exist.
Suggested by Peter Wemm.
- Install new mkaliases script in /usr/libexec along with mknetid.
- Use somewhat saner approach to generating rpcgen-dependent files
as suggested by Garrett Wollman.
dbopen() to open an NIS map.
Testing with very large maps (e.g. a sample password database with 31,000+
entries) has shown that ypserv will leak memory (ps shows RSS and VSZ
growing to 4000 pages or more) when performing repeated yp_next()s or
a yp_all(). The problem with yp_all() is not immediately obvious since
the ypproc_all service is handled in a child process which exits once
the transfer is finished, but with repeated yp_next()s (like what you
get when you use getpwent() to scroll through the password database),
the parent ypserv grows to enormous size and never shrinks again.
It seems this is related to the HASHINFO parameters I used in yp_dblookup.c,
which I actually stole from pwd_mkdb. Calling dbopen() with the default
parameters (specifying openinfo as NULL) fixes the problem.
I still need to see how this impacts the other NIS tools. I'm also
considering changing from hash to btree databases: the hash database
method doesn't support R_CURSOR, which means yp_next_record() has to
do a lot of ugly work in order to reach an arbitrary location in the
database.
are currently implemented:
YPOLDPROC_NULL
YPOLDPROC_DOMAIN
YPOLDPROC_DOMAIN_NONACK
YPOLDPROC_FIRST
YPOLDPROC_NEXT
YPOLDPROC_MATCH
YPOLDPROC_POLL
These are all implemented as wrappers around their v2 counterparts.
The YPOLDPROC_PUSH, PULL and GET procedures are not implemented since
a) I couldn't figure out exactly what to have them do, and b) I
suspect they're used for doing map transfers between master and
slave servers, which we already do using the v2 protocol anyway.
This means we can server NIS v1 clients but can't be a master or
slave with NIS v1-only servers. I think I'll get over it. :)
The -k (sunos_4_kludge) flag and associated code has been removed
since it is no longer needed.
Also tweaked yp_access() to handle both sets of procedures and
updated the man page.
in the same was as the SunOS ypserv (same format, described in ypserv man
page). If the user wants tcpwrapper style access control, they can
recompile ypserv to use that instead. This way we get securenets without
having to ship libwrap.a and tcpd.h with core FreeBSD distribution.
If /var/yp/securenets doesn't exist, ypserv allows all connections.
- Improve support for multiple domains. (In preparation for new rpc.yppasswdd.)
yp_dblookup.c:
- Improve error reporting: be more selective as to what error code
we return when a (dbp->get) fails.
In yp_server.c:
- Modify ypproc_xfr_2_svc() so that it sends both a return status and
a yppush callback (if necessary: normally ypxfr is supposed to send the
callback once it's done transfering a map, but if we can't get ypxfr
off the ground for some reason, we have to send it here instead) and
do it in the right order: have to send the reply to the ypproc_xfr
request first, then send callback. This requires us to cheat a bit:
you're supposed to just return() and let the RPC dispatcher send
the reply for you, but we wouldn't be able to send the callback message
if we did that, so we have to call svc_sendreply() ourselves, then
send the callback, and then return NULL so that the RPC dispatcher
won't call svc_sendreply() itself.
- Also modify ypproc_xfr_2_svc() so that it doesn't invoke ypxfr with
the -f flag: this overrides the order number checks, which prevents
us from ever refusing maps that aren't newer than then ones we already
have.
In yp_access.c:
- Fix a typo in the TCP_WRAPPER support code (which is #ifdef'ed out
by default): a close paren somehow vanished into the ether.
- Add a ypxfr_callback() function that we can use to signal failure to
yppush(8) in the event that we can't fork()/exec() ypxfr(8). yppush
only checks the return status from YPPROC_XFR enough to determine
that the RPC succeded: it relies on its callback service to figure
out whether or not the transfer actually worked.
- Give yp_dblookup.c its own debug variable (ypdb_debug) so that DB
access debugging messages can be turned on or off independent of the
program's global debug messages.
- Have the Makefile rpcgen the ypushresp_xfr_1() client stub for us and
nuke the unneeded rule for yp_xdr.c that I left in by mistake (the XDR
filters live in libc now).
equivalent to the old ypserv, except that it doesn't support the
-p [port] option to force the server to use a particular port.
The server stubs and yp.h header file are auto-generated from the yp.x
protocol definition file. The auto-generated XDR routines in libc/yp
are also used. The database access code has been broken out into a
seperate module so that other NIS utilities (ypxfr in particular)
can use it.
Note that the old mknetid script is being temporarily moved here; it
will be replaced by an mknetid program which will eventually have
a home under /usr/src/libexec. (The existing script is actually
somewhat broken -- it doesn't handle hosts -- but this isn't a big
deal at this point since the netid.byname map is really only useful
fopr Secure RPC, which we don't have yet.)
