When one side of an association does not support PR-SCTP and does not announce the support with the FORWARD-TSN-Supported- Parameter in the INIT-Chunk or INIT-ACK chunk during the handshake there are two issues: If the peer does not include the FORWARD-TSN-Supported-Parameter in the INIT-Chunk and later sends an FORWARD-TSN-Chunk, then the linux kernel does not respond with an ERROR-Chunk like defined in https://tools.ietf.org/html/rfc3758#section-3.3.1. It instead silently discards the FORWARD-TSN-Chunk. Testscript available at: https://github.com/nplab/PR_SCTP_Testsuite/blob/master/forward-tsn/handshake-with-forward-tsn/handshake-with-forward-tsn-4.pkt If the peer does not include the FORWARD-TSN-Supported-Parameter in the INIT-ACK-Chunk but sends later an FORWARD-TSN-Chunk, then the behaviour is different. The Forward-TSN-Chunk is processed and an SACK-Chunk is sent by the linux kernel. This should also be an ERROR-Chunk, because the peer has not announced support for PR-SCTP. Testscript available at: https://github.com/nplab/PR_SCTP_Testsuite/blob/master/forward-tsn/handshake-with-forward-tsn/handshake-with-forward-tsn-5.pkt
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