$Id: Release-Notes-1.1.txt,v 1.8 1996/10/07 17:33:15 wessels Exp $
Release Notes for version 1.1 of the Squid cache.
TABLE OF CONTENTS:
Ident (RFC 931) lookups
Asynchronous Disk I/O
URL Redirector
Reverse IP Lookups, client hostname ACLs.
Cache directory structure changes
Getting true DNS TTL info into Squid's IP cache
Using a neighbor as both a parent and a sibling
Forcing your neighbors to use you as a sibling
Ident (RFC 931) lookups
==============================================================================
Squid will make an RFC931/ident request for client connections if
'ident_lookup' is enabled in the config file. Currently, the ident
value is only logged with the request in the access.log. It is not
currently (1.1.alpha6) possible to use the ident return value for
access control purposes.
Asynchronous Disk I/O
==============================================================================
Pete Bentley <pete@demon.net> has contributed a module for asynchronous
disk I/O. To enable, you must define USE_ASYNC_IO (e.g. in the
Makefile, or include/config.h). It should compile for both IRIX 5.3
and Solaris 2.x.
However, due to some of the underlying routines and structures in
disk.[ch], asynchronous I/O is not be efficiently implemented yet.
There can only be one outstanding aio_write() call per return from
the select loop. The standard disk I/O routines write all pending
blocks per return from select(). I do NOT recommend using these aio
with Squid just yet.
URL Redirector
==============================================================================
Squid now has the ability to rewrite requested URLs. This is implemented
as an external process, much like the dnsservers. Every incoming URL
is written to a 'redirector' process which then returns a new URL, or
a blank line to inidicate no change.
The redirector program is NOT provided in the Squid package. Currently,
it is up to the individual users to write their own implementation. For
testing, this very simple Perl script can be used:
#!/usr/local/bin/perl
$|=1;
print while (<>);
The redirector program must read URLs (one per line) on standard input,
and write rewritten URLs or blank lines on standard output. Note that
the redirector program can not use buffered I/O. Additional information
is written after the URL which a redirector can use to make a decision.
The input line consists of four fields:
URL ip-address/fqdn ident method
The ip-address is always written, the fqdn will be provided if
available (otherwise it will be "-"). Similarly, the user ident will
be provided if available (i.e. 'ident_lookup on' in config file). The
method is GET, POST, etc..
Note that when used in conjunction with the -V option (on a virtual hosted
machine) this provides a mechanism to use a single Squid cache as a front
end to numerous servers on different machines. URLs written to the
redirector will look like:
http://192.0.0.1/foo
http://192.0.0.2/foo
The redirector program might be this Perl script:
#!/usr/local/bin/perl
$|=1;
while (<>) {
s@http://192\.0\.0\.1@http://www1.foo.org@;
s@http://192\.0\.0\.2@http://www2.foo.org@;
print;
}
You may receive statistics on the redirector usage by requesting the
following 'cache_object' URL:
% client cache_object://localhost/stats/redirector
Reverse IP Lookups, client hostname ACLs.
==============================================================================
Squid now has a address-to-hostname cache ("fqdncache") much like the
name-to-address cache ("ipcache"). This means Squid can now write
client hostnames in the access log, and that client domain names can
be used in ACL expressions.
If you would like to log hostnames instead of addresses, enable
'log_fqdn' in your config file. This causes a reverse-lookup to be
started just after the client connection has been accepted. If the
reverse lookup has completed by the time the entry gets logged, the
fully qualified domain name will be used, otherwise the IP address
is still logged. Squid does not wait for the reverse lookup before
logging the access (but this may be changed in the future).
A new ACL type has been added for matching client hostnames:
acl Myusers srcdomain foo.org
The use of this ACL type may cause noticable delay in serving objects
through the cache. However, so long as allowed clients are local, the
reverse lookup should not take very long and the delay may not be
noticed.
Only the FQDN (i.e. the h_name field) is used for the comparison,
host aliases are *not* checked.
If a reverse lookup fails, the word "none" will be used for the
comparison. If you wanted to deny access to clients which did not
map back to valid names, you could use
acl BadClients srcdomain none
http_access deny BadClients
NOTE: DNS has a number of known security problems. Squid does not make
any effort to guarantee the validity of data returned from gethostbyname()
or gethostbyaddr() calls.
Cache directory structure changes
==============================================================================
Squid-1.1 uses a different directory structure for cache files.
Squid-1.0 used 100 directories for each 'cache_dir'. Squid-1.1 uses a
two level structure with 16 first-level directories, and 256 second
level directories. In addition, directory and file names are in
hexadecimal, and fixed length. These changes mean that Squid-1.1 will
fail to reload metadata from a Squid-1.0 swap log.
Getting true DNS TTL info into Squid's IP cache
==============================================================================
If you have source for BIND, you can modify it as indicated in the diff
below. It causes the global variable _dns_ttl_ to be set with the TTL
of the most recent lookup. Then, when you compile Squid, the configure
script will look for the _dns_ttl_ symbol in libresolv.a. If found,
dnsserver will return the TTL value for every lookup.
This hack was contributed by Endre Balint Nagy <bne@CareNet.hu>
diff -ru bind-4.9.4-orig/res/gethnamaddr.c bind-4.9.4/res/gethnamaddr.c
--- bind-4.9.4-orig/res/gethnamaddr.c Mon Aug 5 02:31:35 1996
+++ bind-4.9.4/res/gethnamaddr.c Tue Aug 27 15:33:11 1996
@@ -133,6 +133,7 @@
} align;
extern int h_errno;
+int _dns_ttl_;
#ifdef DEBUG
static void
@@ -223,6 +224,7 @@
host.h_addr_list = h_addr_ptrs;
haveanswer = 0;
had_error = 0;
+ _dns_ttl_ = -1;
while (ancount-- > 0 && cp < eom && !had_error) {
n = dn_expand(answer->buf, eom, cp, bp, buflen);
if ((n < 0) || !(*name_ok)(bp)) {
@@ -232,8 +234,11 @@
cp += n; /* name */
type = _getshort(cp);
cp += INT16SZ; /* type */
- class = _getshort(cp);
- cp += INT16SZ + INT32SZ; /* class, TTL */
+ class = _getshort(cp);
+ cp += INT16SZ; /* class */
+ if (qtype == T_A && type == T_A)
+ _dns_ttl_ = _getlong(cp);
+ cp += INT32SZ; /* TTL */
n = _getshort(cp);
cp += INT16SZ; /* len */
if (class != C_IN) {
Using a neighbor as both a parent and a sibling
==============================================================================
Prior to version 1.1.beta5, a neighbor cache was always treated as
either a sibling or a parent for all requests. In some cases, it is
desirable to use a neighbor as a parent for some domains and as a
sibling for others. This can now be accomplished by adding either the
'parent' or 'sibling' keywords in the cache_host_domain config lines.
For example, consider these configuration lines
cache_host cache.foo.org sibling 3128 3130
cache_host_domain cache.foo.org parent foo.org
cache_host_domain cache.foo.org sibling !foo.org
These have the effect that cache.foo.org is queried for all requests.
If the URL host domain is foo.org, then cache.foo.org is treated as a
parent (and MISSES will be fetched through cache.foo.org). Otherwise
it will be treated as a sibling (and only HITS will be fetched from
cache.foo.org). Note that the third line is needed because when
cache_host_domain rules are present, the neighbor is only used when one
of the rules is matched.
Note that the parent/sibling modifiers apply to all domains appearing
after them on the same line. In other words,
cache_host_domain cache.foo.org parent foo.org bar.org
Is equivalent to
cache_host_domain cache.foo.org parent foo.org
cache_host_domain cache.foo.org parent bar.org
If a cache_host_domain line does not have a parent/sibling modifier,
then it defaults to the neighbor type specified in the cache_host
line.
Forcing your neighbors to use you as a sibling
==============================================================================
In a distributed cache hierarchy, you may need to force your peer caches
to use you as a sibling and not a parent. I.e., its okay for them to
fetch HITs from you, but not okay to resolve MISSes through your
cache (using your resources).
This can be accomplished by using the 'miss_access' config line. The
miss_access ACL list is very similar to the 'http_access' list. This
functionality is implemented as a separate access list because when we
check the http_access list, we don't yet know if the request will be a
hit or miss. The sequence of events goes something like this:
1. accept new connection
2. read request
3. check http_access
4. process request, check for hit or miss (IMS, etc)
5. check miss_access
Note that in order to get to the point where miss_access is checked, the
request must have also passed the http_access check.
You probably only want to use 'src' type ACL's with miss_access, although
you can use any of the access control types.
If you are restricting your neighbors, be sure to allow miss_access
to your local clients (e.g. users at browsers)!