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[Tim Hartrick <1205741@xxxxxxxxxxxxxxxxxx>]

Public bug reported:

There is a bug in the the management of inet peers which prevents route metrics like initcwnd from being inherited by route
cache entries.  An example:

$ ip route show
default via 172.16.231.2 dev eth0  metric 100 
172.16.231.0/24 dev eth0  proto kernel  scope link  src 172.16.231.26

$ ip route show cache
local 172.16.231.26 from 172.16.231.1 dev lo  src 172.16.231.26 
    cache <local,src-direct>  iif eth0
172.16.231.1 from 172.16.231.26 dev eth0 
    cache  ipid 0xa13f

$ ip route change 172.16.231.0/24 dev eth0  proto kernel  scope link
src 172.16.231.26 initcwnd lock 100

$ ip route show
default via 172.16.231.2 dev eth0  metric 100 
172.16.231.0/24 dev eth0  proto kernel  scope link  src 172.16.231.26  initcwnd 
lock 100

$ ip route show cache
172.16.231.1 from 172.16.231.26 dev eth0 
    cache  ipid 0xa13f rtt 4ms rttvar 4ms cwnd 40
local 172.16.231.26 from 172.16.231.1 dev lo  src 172.16.231.26 
    cache <local,src-direct>  iif eth0

Note that the initcwnd metric is not being inherited by the cache entry for 172.16.231.1.  The problem is that the
inetpeer cache is not flushed when the "ip route change" occurs.  Without this the metrics in the inetpeer are used
to build the metrics of the route cache entry even though they are stale.

A fix for this bug is in the 3.5.0 kernel from quantal.  It is a simple
fix and could be easily applied to the 3.2.0 line of kernels.

** Affects: linux (Ubuntu)
     Importance: Undecided
         Status: New

** Package changed: ubuntu => linux (Ubuntu)

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https://bugs.launchpad.net/bugs/1205741

Title:
  The route metrics added "ip route" are not being inherited by route
  cache entries

Status in “linux” package in Ubuntu:
  New

Bug description:
  There is a bug in the the management of inet peers which prevents route metrics like initcwnd from being inherited by route
  cache entries.  An example:

  $ ip route show
  default via 172.16.231.2 dev eth0  metric 100 
  172.16.231.0/24 dev eth0  proto kernel  scope link  src 172.16.231.26

  $ ip route show cache
  local 172.16.231.26 from 172.16.231.1 dev lo  src 172.16.231.26 
      cache <local,src-direct>  iif eth0
  172.16.231.1 from 172.16.231.26 dev eth0 
      cache  ipid 0xa13f

  $ ip route change 172.16.231.0/24 dev eth0  proto kernel  scope link
  src 172.16.231.26 initcwnd lock 100

  $ ip route show
  default via 172.16.231.2 dev eth0  metric 100 
  172.16.231.0/24 dev eth0  proto kernel  scope link  src 172.16.231.26  initcwnd 
  lock 100

  $ ip route show cache
  172.16.231.1 from 172.16.231.26 dev eth0 
      cache  ipid 0xa13f rtt 4ms rttvar 4ms cwnd 40
  local 172.16.231.26 from 172.16.231.1 dev lo  src 172.16.231.26 
      cache <local,src-direct>  iif eth0

  Note that the initcwnd metric is not being inherited by the cache entry for 172.16.231.1.  The problem is that the
  inetpeer cache is not flushed when the "ip route change" occurs.  Without this the metrics in the inetpeer are used
  to build the metrics of the route cache entry even though they are stale.

  A fix for this bug is in the 3.5.0 kernel from quantal.  It is a
  simple fix and could be easily applied to the 3.2.0 line of kernels.

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