linux-kernel - Re: [PATCH] RDMA/cma: fix IPv6 address resolution

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Date:	Fri, 14 Aug 2015 22:05:46 -0400
From:	Doug Ledford <dledford@...hat.com>
To:	Roland Dreier <roland@...nel.org>,
	Spencer Baugh <sbaugh@...ern.com>
Cc:	Sean Hefty <sean.hefty@...el.com>,
	Spencer Baugh <spencer.baugh@...estorage.com>,
	Joern Engel <joern@...estorage.com>,
	"open list:INFINIBAND SUBSYSTEM" <linux-rdma@...r.kernel.org>,
	Hal Rosenstock <hal.rosenstock@...il.com>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] RDMA/cma: fix IPv6 address resolution

On 08/13/2015 03:21 PM, Roland Dreier wrote:
> Reviewed-by: Roland Dreier <roland@...estorage.com
> <mailto:roland@...estorage.com>>
> 
> On Aug 13, 2015 12:19 PM, "Spencer Baugh" <sbaugh@...ern.com
> <mailto:sbaugh@...ern.com>> wrote:
>>
>> Resolving a link-local IPv6 address with an unspecified source address
>> was broken by commit 5462eddd7a, which prevented the IPv6 stack from
>> learning the scope id of the link-local IPv6 address, causing random
>> failures as the IP stack chose a random link to resolve the address on.
>>
>> This commit 5462eddd7a made us bail out of cma_check_linklocal early if
>> the address passed in was not an IPv6 link-local address. On the address
>> resolution path, the address passed in is the source address; if the
>> source address is the unspecified address, which is not link-local, we
>> will bail out early.
>>
>> This is mostly correct, but if the destination address is a link-local
>> address, then we will be following a link-local route, and we'll need to
>> tell the IPv6 stack what the scope id of the destination address is.
>> This used to be done by last line of cma_check_linklocal, which is
>> skipped when bailing out early:
>>
>>         dev_addr->bound_dev_if = sin6->sin6_scope_id;
>>
>> (In cma_bind_addr, the sin6_scope_id of the source address is set to the
>> sin6_scope_id of the destination address, so this is correct)
>> This line is required in turn for the following line, L279 of
>> addr6_resolve, to actually inform the IPv6 stack of the scope id:
>>
>>       fl6.flowi6_oif = addr->bound_dev_if;
>>
>> Since we can only know we are in this failure case when we have access
>> to both the source IPv6 address and destination IPv6 address, we have to
>> deal with this further up the stack. So detect this failure case in
>> cma_bind_addr, and set bound_dev_if to the destination address scope id
>> to correct it.
>>
>> Signed-off-by: Spencer Baugh <sbaugh@...ern.com
> <mailto:sbaugh@...ern.com>>
>> ---
>>  drivers/infiniband/core/cma.c | 7 +++++--
>>  1 file changed, 5 insertions(+), 2 deletions(-)

I've picked this up, thanks.


-- 
Doug Ledford <dledford@...hat.com>
              GPG KeyID: 0E572FDD



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