Checksum offloading for SCTP is not currently specified for virtio. If the hypervisor announces checksum offloading support, it means TCP and UDP checksum offload. If an SCTP packet is sent and the host announced checksum offload support, the hypervisor inserts the IP checksum (16-bit) at the correct offset, but this is not the right checksum, which is a CRC32c. This results in all outgoing packets having the wrong checksum and therefore breaking SCTP based communications.
This patch removes SCTP checksum offloading support from the virtio network interface.
Thanks to Felix Weinrank for making me aware of the issue.