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DVMRP reporting missing last subnet that should be listed in report #14

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matthew-l-weber opened this issue Sep 1, 2015 · 5 comments
Closed

DVMRP reporting missing last subnet that should be listed in report #14

matthew-l-weber opened this issue Sep 1, 2015 · 5 comments

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@matthew-l-weber
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Based on some testing where we added a list of subnets to the DVMRP report coming from host A, it was determined that mrouted on host B (A and B are connected with a L2 switch) was always missing the last subnet reported in the DVMRP report. Some of the debug output from mrouted as well as its route dump was showing that it was processing this subnet, but wasn't transmitting it within the DVMRP report nor was it processing traffic originating from this subnet.

Reverting back to the 3.9-beta3 version of mrouted resolved this issue, while version 3.9.7 was the one exhibiting this behavior. Beyond that we haven't investigation as to where along the line the bug may have been introduced.

We are running a 3.12.19 Linux kernel.
@troglobit
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Thanks for the report! Sounds like an off-by-one bug has been introduced somewhere.

Do you plan to do some further investigation into this, e.g. narrowing down the release the bug appeared in?

@matthew-l-weber
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Yeah, hoping to investigate later this week.
On Sep 1, 2015 12:11 AM, "Joachim Nilsson" notifications@github.com wrote:

Thanks for the report! Sounds like an off-by-one bug has been introduced
somewhere.

Do you plan to do some further investigation into this, e.g. narrowing
down the release the bug appeared in?

—
Reply to this email directly or view it on GitHub
#14 (comment).

@troglobit
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Thx! 😃

@matthew-l-weber
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Found the fix and submitted #15

troglobit pushed a commit that referenced this issue Sep 12, 2015
@rc-matthew-l-weber @troglobit
DVMRP report missing subnet (off by one error)
2cb2d32 
A subnet is missing in the DVMRP report sent to it's neighbor after the
initial probe occurs.  The issue was with the traversal of a double
linked list from end to start.  Once the traversing pointer reaches the
start of routing table for loop (condition) it would break and always
drop the first subnet.

Fixes issue #14.

Signed-off-by: Matthew Weber <matthew.weber@rockwellcollins.com>
Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
@troglobit
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Merged PR #15, closing. Thanks again!

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@troglobit @matthew-l-weber