[ovs-dev] [PATCH] datapath: Rehash 16-bit skbuff hashes into 32 bits.

Thomas Graf tgraf at noironetworks.com
Wed Jun 25 08:30:59 UTC 2014


On 06/24/14 at 06:46pm, Jesse Gross wrote:
> Currently, if the network stack provides skb->rxhash then we use it,
> otherwise we compute our own. However, on at least some versions of
> RHEL/CentOS, the stack provides a hash but it is 16 bits rather than
> 32 bits. In cases where we use the upper most bits of the hash this
> is particularly bad because we detect that a hash is present and we
> use it rather than computing our own but the result is always zero.
> 
> This is particularly noticible with tunnel ports that use the hash
> to generate a source port, such as VXLAN. On these kernels the source
> port is always zero when using VXLAN. To solve this problem while
> still taking advantage of the procomputed hash, this rehashes the
> hash so that the entropy is spread throughout 32 bits.
> 
> Signed-off-by: Jesse Gross <jesse at nicira.com>

Acked-by: Thomas Graf <tgraf at noironetworks.com>




More information about the dev mailing list