[dpdk-dev] ip_frag: handle MTU sizes not aligned to 8 bytes
thomas at monjalon.net
Thu Jun 22 18:00:25 CEST 2017
> > The rte_ipv4_fragment_packet API expects that the link/interface MTU value
> > passed in be divisible by 8 bytes. Given the name of the parameter is
> > "mtu" rather than "frag_size" it is not necessarily the case that it will
> > be divisible by 8. An MTU of 1500 happens to produce a max fragment size
> > of 1480 (1500 - sizeof(ipv4_hdr)) which is divisible by 8 but other MTU
> > values such as 1600 or 9000 do not produce values that are divisible by 8.
> > Unfortunately, the API checks that the frag_size value produced is
> > divisible by 8 with a call to RTE_ASSERT which is only enabled when the
> > RTE_LOG_LEVEL >= RTE_LOG_DEBUG. In cases where the log level is set
> > normally the code silently continues and produces IP fragments that have
> > invalid fragment offset values.
> > An application may not have control over what MTU a user selects and rather
> > than have each application adjust the MTU to pass a suitable value to the
> > fragmentation API this change modifies the fragmentation API to handle
> > cases where the "mtu" argument is not divisible by 8 and automatically
> > adjust the internal "frag_size".
> > Signed-off-by: Allain Legacy <allain.legacy at windriver.com>
> Acked-by: Konstantin Ananyev <konstantin.ananyev at intel.com>
More information about the dev