f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricaCopyright (C) 2000, 2001 Internet Software Consortium.

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricaSee COPYRIGHT in the source root or http://isc.org/copyright.html for terms.

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01rica

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01rica BIND 8 to BIND 9 Migration Notes

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01rica

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricaBIND 9 is designed to be mostly upwards compatible with BIND 8, but

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricathere is still a number of caveats you should be aware of when

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricaupgrading an existing BIND 8 installation to use BIND 9.

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01rica

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01rica

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01rica1. Configuration File Compatibility

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01rica

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01rica1.1. Unimplemented Options and Changed Defaults

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01rica

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricaBIND 9 supports most, but not all of the named.conf options of BIND 8.

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricaFor a complete list of implemented options, see doc/misc/options.

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01rica

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricaIf your named.conf file uses an unimplemented option, named will log a

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricawarning message. A message is also logged about each option whose

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricadefault has changed unless the option is set explicitly in named.conf.

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01rica

5d3b8cb7141cfa596d20cdc5043b8a6df635938dBill SommerfeldThe default of the "transfer-format" option has changed from

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01rica"one-answer" to "many-answers". If you have slave servers that do not

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricaunderstand the many-answers zone transfer format (e.g., BIND 4.9.5 or

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricaolder) you need to explicitly specify "transfer-format one-answer;" in

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricaeither the options block or a server statement.

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01rica

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01rica1.2. Handling of Configuration File Errors

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01rica

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricaIn BIND 9, named refuses to start if it detects an error in

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricanamed.conf. Earlier versions would start despite errors, causing the

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricaserver to run with a partial configuration. Errors detected during

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricasubsequent reloads do not cause the server to exit.

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01rica

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricaErrors in master files do not cause the server to exit, but they

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricado cause the zone not to load.

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01rica

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01rica1.3. Logging

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01rica

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricaThe set of logging categories in BIND 9 is different from that

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricain BIND 8. If you have customized your logging on a per-category

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricabasis, you need to modify your logging statement to use the

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricanew categories.

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01rica

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricaAnother difference is that the "logging" statement only takes effect

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricaafter the entire named.conf file has been read. This means that when

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricathe server starts up, any messages about errors in the configuration

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricafile are always logged to the default destination (syslog) when the

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricaserver first starts up, regardless of the contents of the "logging"

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricastatement. In BIND 8, the new logging configuration took effect

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricaimmediately after the "logging" statement was read.

5d3b8cb7141cfa596d20cdc5043b8a6df635938dBill Sommerfeld

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01rica1.4. Notify messages and Refesh queries

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01rica

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricaThe source address and port for these is now controlled by

5d3b8cb7141cfa596d20cdc5043b8a6df635938dBill Sommerfeld"notify-source" and "transfer-source", respectively, rather that

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01ricaquery-source as in BIND 8.

f875b4ebb1dd9fdbeb043557cab38ab3bf7f6e01rica

5d3b8cb7141cfa596d20cdc5043b8a6df635938dBill Sommerfeld1.5. Multiple Classes.

Multiple classes have to be put into explicit views for each class.

2. Zone File Compatibility

2.1. Strict RFC1035 Interpretation of TTLs in Zone Files

BIND 9 strictly complies with the RFC1035 and RFC2308 rules regarding

omitted TTLs in zone files. Omitted TTLs are replaced by the value

specified with the $TTL directive, or by the previous explicit TTL if

there is no $TTL directive.

If there is no $TTL directive and the first RR in the file does not

have an explicit TTL field, the zone file is illegal according to

RFC1035 since the TTL of the first RR is undefined. Unfortunately,

BIND 4 and many versions of BIND 8 accept such files without warning

and use the value of the SOA MINTTL field as a default for missing TTL

values.

BIND 9.0 and 9.1 completely refused to load such files. BIND 9.2

emulates the nonstandard BIND 4/8 SOA MINTTL behavior and loads the

files anyway (provided the SOA is the first record in the file), but

will issue the warning message "no TTL specified; using SOA MINTTL

instad".

To avoid problems, we recommend that you use a $TTL directive in each

zone file.

2.2. Periods in SOA Serial Numbers Deprecated

Some versions of BIND allow SOA serial numbers with an embedded

period, like "3.002", and convert them into integers in a rather

unintuitive way. This feature is not supported by BIND 9; serial

numbers must be integers.

2.3. Handling of Unbalanced Quotes

TXT records with unbalanced quotes, like 'host TXT "foo', were not

treated as errors in some versions of BIND. If your zone files

contain such records, you will get potentially confusing error

messages like "unexpected end of file" because BIND 9 will interpret

everything up to the next quote character as a literal string.

2.4. Handling of Line Breaks

Some versions of BIND accept RRs containing line breaks that are not

properly quoted with parentheses, like the following SOA:

@ IN SOA ns.example. hostmaster.example.

( 1 3600 1800 1814400 3600 )

This is not legal master file syntax and will be treated as an error

by BIND 9. The fix is to move the opening parenthesis to the first

line.

2.5. Unimplemented BIND 8 Extensions

$GENERATE: The "$$" construct for getting a literal $ into a domain

name is deprecated. Use \$ instead.

3. Interoperability Impact of New Protocol Features

3.1. EDNS0

BIND 9 uses EDNS0 (RFC2671) to advertise its receive buffer size. It

also sets an EDNS flag bit in queries to indicate that it wishes to

receive DNSSEC responses; this flag bit usage is not yet standardized,

but we hope it will be.

Most older servers that do not support EDNS0, including prior versions

of BIND, will send a FORMERR or NOTIMP response to these queries.

When this happens, BIND 9 will automatically retry the query without

EDNS0.

Unfortunately, there exists at least one non-BIND name server

implementation that silently ignores these queries instead of sending

an error response. Resolving names in zones where all or most

authoritative servers use this server will be very slow or fail

completely. We have contacted the manufacturer of the name server in

case, and they are working on a solution.

When BIND 9 communicates with a server that does support EDNS0, such as

another BIND 9 server, responses of up to 4096 bytes may be

transmitted as a single UDP datagram which is subject to fragmentation

at the IP level. If a firewall incorrectly drops IP fragments, it can

cause resolution to slow down dramatically or fail.

3.2. Zone Transfers

Outgoing zone transfers now use the "many-answers" format by default.

This format is not understood by certain old versions of BIND 4.

You can work around this problem using the option "transfer-format

one-answer;", but since these old versions all have known security

problems, the correct fix is to upgrade the slave servers.

Zone transfers to Windows 2000 DNS servers sometimes fail due to a bug

in the Windows 2000 DNS server where DNS messages larger than 16K are

not handled properly. There will be a hot fix available from

Microsoft to address this issue. In the meantime, the problem can

be worked around by setting "transfer-format one-answer;".

[As of May 4 2001 the hotfix was still being prepared]

4. Unrestricted Character Set

BIND 9 does not restrict the character set of domain names - it is

fully 8-bit clean in accordance with RFC2181 section 11.

It is strongly recommended that hostnames published in the DNS follow

the RFC952 rules, but BIND 9 will not enforce this restriction.

Historically, some applications have suffered from security flaws

where data originating from the network, such as names returned by

gethostbyaddr(), are used with insufficient checking and may cause a

breach of security when containing unexpected characters; see

<http://www.cert.org/advisories/CA-96.04.corrupt_info_from_servers.html>

for details. Some earlier versions of BIND attempt to protect these

flawed applications from attack by discarding data containing

characters deemed inappropriate in host names or mail addresses, under

the control of the "check-names" option in named.conf and/or "options

no-check-names" in resolv.conf. BIND 9 provides no such protection;

if applications with these flaws are still being used, they should

be upgraded.

5. Server Administration Tools

The "ndc" program has been replaced by "rndc", which is capable of

remote operation. Unlike ndc, rndc requires a configuration file;

see the man pages in bin/rndc/rndc.1 and bin/rndc/rndc.conf.5 for

details. Some of the ndc commands are still unimplemented in rndc.

6. No Information Leakage between Zones

BIND 9 stores the authoritative data for each zone in a separate data

structure, as recommended in RFC1035 and as required by DNSSEC and

IXFR. When a BIND 9 server is authoritative for both a child zone and

its parent, it will have two distinct sets of NS records at the

delegation point: the authoritative NS records at the child's apex,

and a set of glue NS records in the parent.

BIND 8 was unable to properly distinguish between these two sets of NS

records and would "leak" the child's NS records into the parent,

effectively causing the parent zone to be silently modified: responses

and zone transfers from the parent contained the child's NS records

rather than the glue configured into the parent (if any). In the case

of children of type "stub", this behavior was documented as a feature,

allowing the glue NS records to be omitted from the parent

configuration.

Sites that were relying on this BIND 8 behavior need to add any

omitted glue NS records, and any necessary glue A records, to the

parent zone.

Although stub zones can no longer be used as a mechanism for injecting

NS records into their parent zones, they are still useful as a way of

directing queries for a given domain to a particular set of name

servers.

7. Umask not Modified

The BIND 8 named unconditionally sets the umask to 022. BIND 9 does

not; the umask inherited from the parent process remains in effect.

This may cause files created by named, such as journal files, to be

created with different file permissions than they did in BIND 8. If

necessary, the umask should be set explicitly in the script used to

start the named process.

8. Nsupdate Differences

The BIND 8 implementation of nsupdate had an undocumented feature

where an update request would be broken down into multiple requests

based upon the discovered zones that contained the records. This

behaviour has not been implemented in BIND 9. Each update request

must pertain to a single zone, but it is still possible to do multiple

updates in a single invocation of nsupdate by terminating each update

with an empty line or a "send" command.

$Id: migration,v 1.40 2001/09/21 17:34:37 gson Exp $