Unordered user message is not delivered if two FORWARD-TSN-Chunks are bundled

[TheAomx]

In the following test-case three unordered user messages with two fragments are outstanding and only the DATA-Chunk with E-Flag set has arrived the IUT. Then the third user message is completed with a DATA-Chunk and the first and second user message is abandoned by sending two bundled FORWARD-TSN-Chunks.

After that the sctp_recvmsg call fails and does not deliver the third message to the userland application. See the following test case for more details:

• https://github.com/nplab/PR_SCTP_Testsuite/blob/master/forward-tsn/receiver-side-implementation/packet-loss/unordered/unordered-packet-loss-13.pkt