[PATCH RFC v2 0/3] dhclient: add --prefix-len option

H. Peter Anvin hpa at zytor.com
Wed Dec 2 19:21:14 UTC 2015


I have a regular need for setting a request for a specific prefix
length delegation in the IPv6 client.  This adds this feature as a new
command line option (just as the number of prefixes are requested via
possibly multiple -P options.)

In the process, I found a fair bit of duplicated or near-duplicated
code, and so I ended up refactoring some of the code, with the result
that the total patchset is actually a fair bit of reduction in total
code.

I have the following questions with regards to the protocol and
desired behavior:

- The current patch will only emit a null prefix for a SOLICIT
  message, but are there other messages where a null prefix is also
  appropriate?
- The current patch specifies a global prefix length, but would it be
  better if that prefix length was settable for each IA_PD IAID?  In
  that case, what do people think of any of the following command line
  syntaxes (where # is the number of bits):

  -P#
  -P=#
  --prefix=#
  -P #

  The last one would break if it is possible for a purely numeric
  argument to follow a -P option on the current command line (I don't
  know if there are any systems that use numbers for interface names,
  perhaps?)

Changes in version 2:

- Add a patch to support more than 256 IAIDs, theoretically possible.
- Don't omit expired prefixes for a SOLICIT message.

 client/dhc6.c     | 1082 +++++++++++++++++++++--------------------------------
 client/dhclient.8 |    7 +
 client/dhclient.c |   13 +-
 includes/dhcpd.h  |    1 +
 4 files changed, 441 insertions(+), 662 deletions(-)

H. Peter Anvin (3):
      dhclient: IPv6: factor common code in dhc6.c
      dhclient: IPv6: support more than 256 IAIDs
      dhclient: IPv6: add support for setting prefix length for IA_PD



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