Re: [PATCH] openvswitch: Make IPv6 packet parsing dependent on IPv6 config

On 11/16/2012 12:26 PM, Jesse Gross wrote:

On Fri, Nov 16, 2012 at 7:40 AM, Vlad Yasevich [off-list ref] wrote:

quoted

Openvswitch attempts to use IPv6 packet parsing functions without
any dependency on IPv6 (unlike every other place in kernel).  Pull
the IPv6 code in openvswitch togeter and put a conditional that's
dependent on CONFIG_IPV6.

Resolves:
net/built-in.o: In function `ovs_flow_extract':
(.text+0xbf5d5): undefined reference to `ipv6_skip_exthdr'

Signed-off-by: Vlad Yasevich <redacted>

Doesn't this move in the opposite direction of your patches to make IPv6
GSO/GRO always available?  The packets being processed here
are generally created by the guest but with Open vSwitch running on the
host.  Also, ipv6_skip_exthdr() is in exthdrs_core.c, so it actually is
always available.  I suspect that the real problem is that the dependency
on the ipv6 directory changed to CONFIG_INET and Open vSwitch should now
depend on this.

Yes and no... :)  IPv6 uses a bunch of IPv4 code all over.  IPv4 is 
enabled with CONFIG_INET and IPv6 with CONFIG_NET.  So creates a strange 
imbalance.  By shifting IPv6 to CONFIG_INET (which is where it
lives and what enables its selection during config process), we now have 
a dependency with openvswitch.

All other users of ipv6_skip_exthdr have it either under the IS_ENABLED 
conditional or through some other means that don't build it when INET is
completely turned off.  This patch does the same for openvswitch.

I see 2 alternatives to this:
  1) Make openvswitch depend on CONFIG_INET.
  2) Pull a ton of code out of CONFIG_INET (v4 and v6) and into 
CONFIG_NET.  This could start with IPv6 header parsing and maybe even
include GSO/TSO (but not sure how much sense that would be).

What's your take?

-vlad