~ubuntu-branches/ubuntu/oneiric/isc-dhcp/oneiric-security

	      Internet Systems Consortium DHCP Distribution

			     Version 4.1.1-P1

			       17 May 2010

			      Release Notes

			      NEW FEATURES

ISC DHCP 4.1.x includes several new DHCPv6 features that were not included

in DHCP 4.0.x.  These include:

- Support for the rapid-commit option on the client side

- Prefix Delegation support

- IA_TA address support

- A basic DHCPv6 relay agent

- Basic and partial DHCPv6 leasequery support

There are a number of DHCPv6 limitations and features missing in this

release, which will be addressed in the future:

- Only Solaris, Linux, FreeBSD, NetBSD, and OpenBSD are supported.

- Only a single address is supported per IA.

- DHCPv6 includes human-readable text in status code messages. These

  should be configurable, and probably localized via gettext() or the

  like.

- The "host-identifier" option is limited to a simple token.

- The client and server can only operate DHCPv4 or DHCPv6 at a time,

  not both.  To use both protocols simultaneously, two instances of the

  relevant daemon are required, one with the '-6' command line option.

For information on how to install, configure and run this software, as

well as how to find documentation and report bugs, please consult the

README file.

ISC DHCP uses standard GNU configure for installation. Please review the

output of "./configure --help" to see what options are available.

The system has only been tested on Linux, FreeBSD, and Solaris, and may not

work on other platforms. Please report any problems and suggested fixes to

<dhcp-users@isc.org>.

                        Changes since 4.1.1

- A bug was fixed that could cause the DHCPv6 server to advertise/assign a

  previously allocated (active) lease to a client that has changed subnets,

  despite being on different shared networks.  Dynamic prefixes specifically

  allocated in shared networks also now are not offered if the client has

  moved.  [ISC-Bugs #21152]

! Accept a client id of length 0 while hashing.  Previously the server would

  exit if it attempted to hash a zero length client id, providing attackers

  with a simple denial of service attack.  [ISC-Bugs #21253]

                        Changes since 4.1.1rc1

- When using 'ignore client-updates;', the FQDN returned to the client

  is no longer truncated to one octet.

                        Changes since 4.1.1b3

- None.

			Changes since 4.1.1b2

- Fix test in dhcp_interface_signal_handler to check that the inner handler

  has a signal_handler before calling it.

- Both host and subnet6 configuration groups are now included whether a

  fixed-address6 (DHCPv6) is in use or not.  Host scoped configuration takes

  precedence.  This fixes two bugs, one where host scoped configuration

  would not be included from a non-fixed-address6 host record, and the equal

  and opposite bug where subnet6 scoped configuration would not be used when

  over-riding values were not present in a matching fixed-address6 host

  configuration.

- ./configure now checks to ensure the intX_t and u_intX_t types are defined,

  correcting a compilation failure when using Sun's compiler.

- Modified the handling of a connection to avoid releasing the omapi io

  object for the connection while it is still in use.  One symptom from

  this error was a segfault when a failover secondary attempted to connect

  to the failover primary if their clocks were not synchronized.

			Changes since 4.1.1b1

- Remove infinite loop in token_print_indent_concat().

- Memory leak in the load_balance_mine() function is fixed.  This would

  leak ~20-30 octets per DHCPDISCOVER packet while failover was in use

  and in normal state.

- Various compilation fixes have been included for the memory related

  DEBUG #defines in includes/site.h.

- Fixed Linux client script 'unary operator expected' errors with DHCPv6.

- Fixed setting hostname in Linux hosts that require hostname argument

  to be double-quoted.  Also allow server-provided hostname to

  override hostnames 'localhost' and '(none)'.

- Added client support for setting interface MTU and metric, thanks to

  Roy "UberLord" Marples <roy@marples.name>.

- Fixed failover reconnection retry code to continue to retry to reconnect

  rather than restarting the listener.

- Compilation on Solaris with USE_SOCKETS defined in includes/site.h has

  been repaired.  Other USE_ overrides should work better.

- A check for the local flavor of IFNAMSIZ had a broken 'else' condition,

  that probably still resulted in the correct behaviour (but wouldn't use

  a larger defined value provided by the host OS).

- Fixed a bug where an OMAPI socket disconnection message would not result

  in scheduling a failover reconnection, if the link had not negotiated a

  failover connect yet (e.g.: connection refused, asynch socket connect()

  timeouts).

- A bug was fixed that caused the 'conflict-done' state to fail to be parsed

  in failover state records.

! A stack overflow vulnerability was fixed in dhclient that could allow

  remote attackers to execute arbitrary commands as root on the system,

  or simply terminate the client, by providing an over-long subnet-mask

  option.  CERT VU#410676 - CVE-2009-0692

- Versions 3.0.x syntax with multiple name->code option definitions is now

  supported.  Note that, similarly to 3.0.x, for by-code lookups only the

  last option definition is used.

- Fixed a bug where a time difference of greater than 60 seconds between a

  failover pair could cause the primary to crash on contact with the

  secondary.  Thanks to a patch from Steinar Haug.

- Don't look for IPv6 interfaces on Linux when running in DHCPv4 mode.

  Thanks to patches from Matthew Newton and David Cantrell.

- Secondary servers in a failover pair will now perform ddns removals if

  they had performed ddns updates on a lease that is expiring, or was

  released through the primary.  As part of the same fix, stale binding scopes

  will now be removed if a change in identity of a lease's active client is

  detected, rather than simply if a lease is noticed to have expired (which it

  may have expired without a failover server noticing in some situations).

- A patch supplied by David Cantrell at RedHat was applied that detects

  invalid calling parameters given to the ns_name_ntop() function.

  Specifically, it detects if the caller passed a pointer and size pair

  that causes the pointer to integer-wrap past zero.

! Fixed a fenceposting bug when a client had two host records configured,

  one using 'uid' and the other using 'hardware ethernet'.  CVE-2009-1892

			Changes since 4.1.0

- Validate the argument to the -p option.

- The notorious 'option <unknown> ... larger than buffer' log line,

  which is seen in some malformed DHCP client packets, was modified.

  It now logs the universe name, and does not log the length values

  (which are bogus corruption read from the packet anyway).  It also

  carries a hopefully more useful explanation.

- A bug was fixed that caused the server not to answer some valid Solicit

  and Request packets, if the dynamic range covering any requested addresses

  had been deleted from configuration.

- Suppress spurious warnings from configure about --datarootdir

- Update the code to deal with GCC 4.3.  This included two sets of changes.

  The first is to the configuration files to include the use of

  AC_USE_SYSTEM_EXTENSIONS.  The second is to deal with return values that

  were being ignored.

- The db-time-format option was documented in manpages.

- Using reserved leases no longer results in 'lease with binding state

  free not on its queue' error messages, thanks to a patch from Frode

  Nordahl.

- DDNS removal routines were updated so that the DHCID is not removed until

  the client has been deprived of all A and AAAA records (not only the last

  one of either of those).  This resolves a bug where dual stack clients

  would not be able to regain their names after either expiration event.

- Fix a build error in dhcrelay, using older versions of gcc with

  dhcpv6 disabled.

- Two uninitialized stack structures are now memset to zero, thanks to

  patch from David Cantrell at Red Hat.

- Fixed a cosmetic bug where pretty-printing valid domain-search options would

  result in an erroneous error log message ('garbage in format string').

- A bug in DLPI packet transmission (Solaris, HP/UX) that caused the server

  to stop receiving packets is fixed.  The same fix also means that the MAC

  address will no longer appear 'bogus' on DLPI-based systems.

- A bug in select handling was discovered where the results of one select()

  call were discarded, causing the server to process the next select() call

  and use more system calls than required.  This has been repaired - the

  sockets will be handled after the first return from select(), resulting in

  fewer system calls.

- The update-conflict-detection feature would leave an FQDN updated without

  a DHCID (still currently implemented as a TXT RR).  This would cause later

  expiration or release events to fail to remove the domain name.  The feature

  now also inserts the client's up to date DHCID record, so records may safely

  be removed at expiration or release time.  Thanks to a patch submitted by

  Christof Chen.

                        Changes since 4.1.0b1

- A missing "else" in dhcrelay.c could have caused an interface not to

  be recognized.

			Changes since 4.1.0a2

- A cosmetic bug in DHCPDECLINE processing was fixed which caused all

  successful DHCPDECLINEs to be logged as "not found" rather than

  "abandoned".

- Added configuration file examples for DHCPv6.

- Some failover debugging #defines have been better defined and some

  high frequency messages moved to a deeper debugging symbol.

- The CLTT parameter in failover is now only updated by client activity,

  and not by failover binding updates (taking on the peer's CLTT).

- Failover BNDUPD messages are now discarded if they conflict with an

  update that has been transmitted, but not acknowledged.

- A bug cleaning up unknown-xxx temporary option definitions was fixed.

- Delayed-ack is now a compile-time option, compiled out by default.

  This feature is simply too experimental for right now, and causes

  some problems to some failover installations.  We will revisit this

  in future releases.

- The !inet_pton() call in res_mkupdrec was adjusted to '<= 0' as

  inet_pton returns either 1, 0, or -1.

- A dhclient-script for MacOS X has been included, which enables

  'dhclient -6' support.

			Changes since 4.1.0a1

- Corrected list of failover state values in dhcpd man page.

- Fixed a bug that caused some request types to be logged incorrectly.

- Clients that sent a parameter request list containing the

  routers option before the subnet mask option were receiving

  only the latter.  Fixed.

- The server wasn't always sending the FQDN option when it should.

- A partner-down failover server no longer emits 'peer holds all free leases'

  if it is able to newly-allocate one of the peer's leases.

- Fixed a coredump when adding a class via OMAPI.

- Check whether files are zero length before trying to parse them.

- Ari Edelkind's PARANOIA patch has been included and may be compiled in

  via two ./configure parameters, --enable-paranoia and

  --enable-early-chroot.

- ./configure was extended to cover many optional build features, such

  as failover, server tracing, debugging, and the execute() command.

- There is now a default 1/4 of a second scheduled delay between delayed

  fsync()'s, it can be configured by the max-ack-delay configuration

  parameter.

- A bug was fixed where the length of a hostname was miscalculated, so that

  hosts were given odd-looking domain names ("foo.bar.ba.example.com").

- Shared network selection should be done from the innermost relay

  valid link-address field, rather than the outermost.

- Prefix pools are attached to shared network scopes.

- Merged IA_XX related structures.

- Add DHCPv6 files in configure.

- A memory leak when using omapi has been fixed.

- DHCPv6 vendor-class options (VSIO) are now only sent when they appear

  on the DHCPv6 ORO.  This resolves a bug where VSIO options were placed

  in IA_NA encapsulated options fields.

- Integrated client with stateless, temporary address and prefix delegation

  support.

- A double-dereference in dhclient transmission of DHCPDECLINEs was

  repaired.

- Fix handling of format code 'Z'.

- Support "-1" argument in DHCPv6.

- Merge DHCPv6-only "dhcrelay6" into general-purpose "dhcrelay" (use

  "-6" option to select DHCPv6 mode).

- Fix handling of -A and -a flags in dhcrelay; it was failing to expand

  packet size as needed to add relay agent options.

- A bug in subnet6 parsing where options contained in subnet6 clauses would

  not be applied to clients addressed within that network was repaired.

- When configuring a "subnet {}" or "subnet6 {}" without an explicit

  shared-network enclosing it, the DHCP software would synthesize a

  shared-network to contain the subnet.  However, all configuration

  parameters within the subnet more intuitively belong "to any client

  on that interface", or rather the synthesized shared-network.  So,

  when a shared-network is synthesized, it is used to contain the

  configuration present inside the subnet {} clause.  This means that

  the configuration will be valid for all clients on that network, not

  just those addressed out of the stated subnet.  If you intended the

  opposite, the workaround is to explicitly configure an empty

  shared-network.

- A bug was fixed where Information-Request processing was not sourcing

  configured option values.

- A warning was added since the DHCPv6 processing software does not yet

  support class statements.

- Compliation warnings on GCC 4.3 relating to bootp source address

  selection were repaired.

- The v6 BSD socket method was updated to use a single UDP BSD socket

  no matter how many interfaces are involved, differentiating the

  interfaces the packets were received on by the interface index supplied

  by the OS.

- The relay agent no longer listens to the All DHCP Servers Multicast

  address.

- A bug was fixed in data_string_sprintfa() where va_start was only called

  once for two invocations of vsprintf() variants.

- ERO (RFC 4994) server support.

- Basic and partial DHCPv6 leasequery support.

- Reliable DHCPv6 release (previous behavior, send release and exit, is

  still available with dhclient -6 -1 -r).

			Changes since 4.0.0 (new features)

- Added DHCPv6 rapid commit support.

- Added explicit parser support for zero-length DHCP options, such as

  rapid-commit, via format code 'Z'.

- It's now possible to update the "ends" field of a lease with OMAPI.

  This is useful if you want not only to release a lease, but also make

  it available for reuse right away.  Hat tip to Christof Chen.

- Fixed definition of the iaaddr hash functions to use the correct 

  functions when referencing and dereferencing memory.

- Some definitions not in phase with the IANA registry were updated.

- Allocated interface IDs are better controlled ('u' bit set to zero,

  reserved IDs avoided).

- Unicast options are taken into account only for RENEWs.

- NoAddrsAvail answers to SOLICITs are always ADVERTISEs even when a SOLICIT

  carries a rapid-commit option.

- Return in place of raise an impossible condition when one tries to release

  an empty active lease.

- Timer granularity is now 1/100s in the DHCPv6 client.

- The dhclient-script was updated to create a host route for the default

  gateway if the supplied subnet mask for an IPv4 address was a /32.  This

  allows the client to work in 'captive' network environments, where the

  operator does not want clients to crosstalk directly.

- MINUS tokens should be parseable again.

- Multiple (up to "delayed-ack x;" maximum) DHCPv4 packets are now queued and

  released in bursts after single fsync() events when the upper limit is

  reached or if the receiving sockets go dry.  The practical upshot is

  that fsync-coupled server performance is now multiplicitively increased.

  The default delayed ack limit is 28.  Thanks entirely to a patch from

  Christof Chen.

			Changes since 4.0.0 (bug fixes)

- DHCP now builds on AIX.

- Exit with warning when DHCPv6-specific statements are used in the

  config file but -6 is not specified.

- Fixed "--version" flag in dhcrelay

- The 'min-secs' configuration parameter's log message has been updated to

  be more helpful.

- The warning logged when an address range doesn't fit in the subnets

  they were declared has been updated to be more helpful and identify the

  typo in configuration that created the spanning addresses.

- A bug in failover pool rebalancing that caused POOLREQ message ping-pongs

  was repaired.

- A flaw in failover pool rebalancing that could cause POOLREQ messages to

  be sent outside of the min-balance/max-balance scheduled intervals has

  been repaired.

- A cosmetic bug during potential-conflict recovery that caused the peer's

  'conflict-done' state message to be logged as 'unknown-state' has been

  repaired.  It is now logged correctly.

- A bug was fixed where the 'giaddr' may be used to find the client's subnet

  rather than its own 'ciaddr'.

- A log message was introduced to clarify the situation where a failover

  'address' parameter (the server's local address) did not resolve to an

  IPv4 address.

- The minimum site code value was set to 224 in 3.1.0 to track RFC3942.  This

  broke a lot of legacy site local configurations.  The new code in place will

  track site local space minimum option codes and logs a warning to encourage

  updates and exploration of site local code migration problems.  Option

  codes less than 128 in site local spaces remain inaccessible.

- A possible relay agent option bug was repaired where random server

  initialization state may have been used to signal the relay agent

  information options sub-option code for the 'END' of the option space.

- Fixes to allow code to compile and run on Solaris 9.

- Fixes to allow code to compile on Mac OS X Leopard (10.5).

- When server is configured with options that it overrides, a warning is

  issued when the configuration file is read, rather than at the time the

  option is overridden. This was important, because the warning was given

  every time the option was overridden, which could create a lot of 

  unnecessary logging.

- Fixed a compilation problems on platforms that define a value for FDDI,

  which conflicts with a dhcp configuration syntax token by the same name.

- When a failover server suspects it has encountered a peer running a

  version 3.0.x failover server, a warning that the failover wire protocol

  is incompatible is printed.

- The failover server no longer issues a floating point error if it encounters

  a previously undefined option code.

- Fix startup error messages to report a missing "subnet6 declaration", rather

  than a missing "subnet declaration", when running as a DHCPv6 server.

- DHCPv6 client timestamp in DUID was based on the year 1970 rather 

  than the year 2000.

- Warn when attempting to use a hardware parameter in DHCPv6.

- DHCPv6 released resources are now marked as released by the client.

- 'Soft' bindings have no more side-effects.

			Changes since 4.0.0b3

- The reverse dns name for PTR updates on IPv6 addresses has been fixed to

  use ip6.arpa. rather than default to in-addr.arpa and require user

  configuration.

- dhc6_lease_destroy() and dhc6_ia_destroy() now set lease and IA pointers

  to NULL after freeing, to prevent subsequent accesses to freed memory.

- The DHCPv6 server would not send the preference option unless the 

  client requested it, via the ORO. This has been fixed, so the DHCPv6

  server will always send the preference value if it is configured.

- When addresses were passed as hints to the server in an IA, they were 

  incorrectly handled, sometimes being treated as an error. Now the 

  server will treat these as hints and ignore them if it cannot supply

  a requested address.

- If the client had multiple addresses, and one expired (was not renewed

  by the server), the client would continue to attempt to renew the same

  old address over and over.  Now, the client will omit any expired

  addresses from future Confirm, Renew, or Rebind messages.

- dhclient -6 will now select renew/rebind timers based upon the longest

  address expiration time rather than the shortest expiration time, in

  order to avoid cascading renewals in the event a server elects not to

  extend one of multiple IAADDR leases.

- The server now limits clients that request multiple addresses to one

  address per IA by default, which can be adjusted through the

  "limit-addrs-per-ia" configuration option.

- The DHCPv6 client now issues fresh transaction IDs on Renew and Rebind

  message exchanges, rather than using the most recent ID.

- The DHCPv6 server now replies to Information-Request messages.

- A bug was fixed in the dhclient-script for BSDs to correctly carry error

  codes through some conditions.

- The parsing of some options in the dhclient lease file, in particular

  the success DHCPv6 status-code, was fixed.

- A bug was fixed that caused the DHCPv6 ORO option to be corrupted with

  seemingly random values.

- A reference overleak in DHCPv6 shared network processing was repaired.

- ./configure now autodetects local database locations rather than trying

  to put dhcpd.leases and dhclient.leases in /usr/local/var/db, which no

  one ever has.

- Regression fix for bug where server advertised a IPv6 address in 

  response to a SOLICIT but would not return the address in response 

  to a REQUEST.

- A bug was fixed where the DHCPv6 server puts the NoAddrsAvail status

  code in the IA_NA was fixed.  The status code now appears in the root

  level.

			Changes since 4.0.0b2

- Clarified error message when lease limit exceeded

- Relative time may now be used as a qualifier for 'allow' and 'deny' access

  control lists.  These directives may be used to assist in re-addressing

  address pools without having to constantly reconfigure the server.  Please

  see 'man dhcpd.conf' for more information on allow/deny 'after time' syntax.

  Thanks to a patch from Christof Chen.

- The server will now include multiple IA_NA's and multiple IAADDRs within

  them, if advertised by the client.  It still only seeks to allocate one

  new address.

			Changes since 4.0.0b1

- Use different paths for PID and lease files when running in DHCPv4

  or DHCPv6 mode, so that servers for both protcols can be run

  simultaneously on a single interface.

- Fixed a buffer overflow error which could have allowed a denial

  of service under unusual server configurations

- Eliminated a spurious error message from the client

- A number of bugs with the internal handling of lease state on the 

  server have been fixed. Some of these could cause server crashes.

- The peer_wants_leases() changes pulled up from 3.1.0 were corrected,

  'never used' leases will no longer consistently shift between servers

  on every pool rebalance run.

- sendmsg()/recvmsg() control buffers are now declared in such a way to

  ensure they are correctly aligned on all (esp. 64-bit) architectures.

- The client leasing subsystem was streamlined and corrected to account

  more closely for changes in client link attachment selection.

			Changes since 4.0.0a3

- The DHCP server no longer requires a "ddns-update-style" statement, 

  and now defaults to "none", which means DNS updates are disabled.

- Log messages when failover peer names mismatch have been improved to

  point out the problem.

- Bug where server advertised a IPv6 address in response to a SOLICIT 

  but would not return the address in response to a REQUEST. Thanks to

  Dennis Kou for finding the bug.

- Fixed an error causing the server to lock up on lease expiration,

  reported independently by Jothilingam Vasu and Dennis Kou.

- Fixed a ./configure bug where compile tests were failing due to

  "-Werror" (unused variable) rather than the actual test failure.  Lead

  to inconsistent and unworkable auto-configurations.

- Compilation with DLPI and -Werror has been repaired.

- Error in decoding IA_NA option if multiple interfaces are present 

  fixed by Marcus Goller.

- DHCPv6 server Confirm message processing has been enhanced - it no

  longer replies only to clients with host {} records, it now replies

  as directed in RFC3315 section 18.2.2 - that is, to all clients

  regardless of the existence of bindings.

- A core dump during expired lease cleanup has been repaired.

- DDNS updates state information are now stored in 'binding scopes' that

  follow the leases through their lifecycles.  This enables DDNS teardowns

  on leases that are assigned and expired inbetween a server restart (the

  state is recovered from dhcpd.leases).  Arbitrary user-specified binding

  scopes ('set var = "value";') are not yet supported.

- Additional compilation problems on HP/UX have been repaired.

			Changes since 4.0.0a2

- Fix for startup where there are no IPv4 addresses on an interface.

  Thanks to Marcus Goller for reporting the bug.

- Fixed file descriptor leak on listen failure. Thanks to Tom Clark.

- Bug in server configuration parser caused server to get stuck on

  startup for certain bad pool declarations. Thanks to Guillaume 

  Knispel for the bug report and fix.

- Code cleaned to remove warnings reported by "gcc -Wall".

- DHCPv6 is now the default. You can disable DHCPv6 support using the

  "--disable-dhcpv6" flag when you run the configure script.

- An internal database inconsistency bug was repaired where the server

  would segfault if a client attempted to renew a lease that had been

  loaded from persistent storage.

- 'request' and 'also request' syntaxes have been added to accommodate

  the DHCPv6 client configuration.  'send dhcp6.oro' is no longer

  necessary.

- Bug fixed where configuration file parsing did not work with 

  zero-length options; this made it impossible to set the 

  rapid-commit option.

- Bogus messages about host records with IPv4 fixed-addresses being of

  non-128-bits in length were removed.

			Changes since 4.0.0a1

- Bug in octal parsing fixed. Thanks to Bernd Fuhrmann for the report

  and fix.

- Autoconf now supplies proper flags for Solaris DHCPv6 builds.

- Fix for parsing error on some IPv6 addresses.

- Invalid CIDR representation for IPv6 subnets or ranges now checked

  for when loading configuration.

- Compilation on HP/UX has been repaired.  The changes should generally

  apply to any architecture that supplies SIOCGLIFCONF but does not

  use 'struct lifconf' structures to pass values.

- Two new operators, ~= and ~~, have been integrated to implement

  boolean matches by regular expression (such as may be used in

  class matching statements).  Thanks to a patch by Alexandr S.

  Agranovsky, which underwent slight modification.

- Fix for icmp packets on 64-bit systems (bug introduced in 4.0).

- A bug was fixed in interface discovery wherein an error identifying

  a server-configured interface with no IPv4 addresses would SEGV.

- Fixed a bug in which write_lease() might report a failure incorrectly

- Added support for DHCPv6 Release messages

- Added -x option to dhclient, which triggers dhclient processes

  to exit gracefully without releasing leases first

- All binaries (client, server, relay) now change directories

  to / before going into daemon mode, so as not to hold $CWD open

- Fixed a bug parsing DHCPv6 client-id's in host-identifier statements

- Fixed a bug with the 'ddns-updates' boolean server configuration

  parameter, which caused the server to fail.

			Changes since 4.0.0-20070413

- Old (expired) leases are now cleaned.

- IPv6 subnets now have support for arbitrary allocation ranges via

  a new 'range6' configuration directive.

- An obviated option code hash lookup to find D6O_CLIENTID was removed.

- Corrected some situations where variables might be used without being

  initialized.

- Silenced several other compiler warnings.

- Include the more standard sys/uio.h rather than rely upon other

  header files to include it (fixes a BSD 4.2 compile failure).

- Duplicate dhclient-script updates for DHCPv6 to all provided scripts.

- DHCPv4 I/O methods that failed to sense hardware address were corrected.

- DHCPv4 is now the default (as documented) rather than DHCPv6.  The default

  was set to DHCPv6 to facilitate ease early development, and forgotten.

- Corrected a segmentation violation in DHCPv4 socket processing.

- dhclient will now fork() into the background once it binds to an

  IPv6 address, or immediately if the -n flag is supplied.

- -q is now the default behaviour on dhclient, with -d or -v enabling

  non-quiet (stderr logging) mode.