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Virtio interfaces do not currently allow the user to specify a particular Maximum Transmission Unit (MTU). Consequently, the MTU of Virtio interfaces is typically set to the Ethernet default value of 1500. This is problematic in the case of cloud deployments, in which a specific (and potentially non-standard) MTU needs to be set by a DHCP server, which needs to be honored by all interfaces across the traffic path.To acheive this Virtio interfaces should support setting of MTU. In case when GRE/VXLAN tunneling is used for internal communication, there will be an overhead added by the infrastructure in the packet over and above the ETHER MTU of 1518. So to take care of this overhead in these cases the DHCP server corrects the L3 MTU to 1454. But since virtio interfaces was not having the MTU set functionality that MTU sent by the DHCP server was ignored and the instance will still send packets with 1500 MTU which after encapsulation will become more than 1518 and eventually gets dropped in the infrastructure. By adding an additional 'set_mtu' function to the Virtio driver, we can honor the MTU sent by the DHCP server. The dhcp server/controller can then leverage this 'set_mtu' functionality to resolve the above mentioned issue of packets getting dropped due to incorrect size. Signed-off-by: Souvik Dey <sodey@sonusnet.com> Reviewed-by: Mark Kavanagh <mark.b.kavanagh@intel.com> Acked-by: Yuanhan Liu <yuanhan.liu@linux.intel.com> |
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DPDK is a set of libraries and drivers for fast packet processing. It supports many processor architectures and both FreeBSD and Linux. The DPDK uses the Open Source BSD license for the core libraries and drivers. The kernel components are GPLv2 licensed. Please check the doc directory for release notes, API documentation, and sample application information. For questions and usage discussions, subscribe to: users@dpdk.org Report bugs and issues to the development mailing list: dev@dpdk.org