Now that we have SCTP offload capabilities in the kernel, we can add them to virtio as well. First step is SCTP checksum.
We need a new freature in virtio to negotiate this support since SCTP is excluded with the stardard checksum and requires a little bit extra. This series proposes VIRTIO_NET_F_SCTP_CSUM feature bit. As the "little bit extra", the kernel uses a new bit in the skb (skb->csum_not_inet) to determine whether to use standard inet checksum or the SCTP CRC32c checksum. This bit has to be communicated between the host and the guest. This bit is carried in the vnet header. Tap and macvtap support is added through an extra feature for the TUNSETOFFLOAD ioctl. Additionally macvtap will no correctly do sctp checksumming if the receive doesn't support SCTP offload. This also turns on sctp offloading for macvlan devices. As for the perf numbers, I am seeing about a 5% increase in vm-to-vm and vm-to-hos throughput which is the same as manually disabling sctp checksumming,since this is exactly what we are emulatting. Sending outside the host, the increase about 2.5-3%. As for GSO, the way sctp GSO is currently implemented buys us nothing in added support to virtio. To add true GSO, would require a lot of re-work inside of SCTP and would require extensions to the virtio net header to carry extra sctp data. Vladislav Yasevich (5): virtio: Add support for SCTP checksum offloading sctp: Handle sctp packets with CHECKSUM_PARTIAL sctp: Build sctp offload support into the base kernel tun: Add support for SCTP checksum offload macvlan/macvtap: Add support for SCTP checksum offload. drivers/net/macvlan.c | 5 +++-- drivers/net/tap.c | 8 +++++--- drivers/net/tun.c | 5 +++++ drivers/net/virtio_net.c | 10 +++++++--- include/linux/virtio_net.h | 6 ++++++ include/net/sctp/sctp.h | 5 ----- include/uapi/linux/if_tun.h | 1 + include/uapi/linux/virtio_net.h | 2 ++ net/Kconfig | 1 + net/sctp/Kconfig | 1 - net/sctp/Makefile | 3 ++- net/sctp/input.c | 11 ++++++++++- net/sctp/offload.c | 4 +++- net/sctp/protocol.c | 3 --- 14 files changed, 45 insertions(+), 20 deletions(-) -- 2.9.5
