Code change:
is running out of resources.  In these cases, MPTCP should send the MP_FASTCLOSE.  This option is illustrated in tcpm_fastclose. <del> If Host A wants to force the closure of an MPTCP connection, the MPTCP Fast Close procedure is as follows: </del> <ins> If Host A wants to force the closure of an MPTCP connection, it has two different options: </ins> <del> Host A sends an ACK containing the MP_FASTCLOSE option on one subflow, containing the key of Host B as declared in the initial connection handshake.  On all the other subflows, Host A sends a regular TCP RST to close these subflows, and tears them down. Host A now enters FASTCLOSE_WAIT state. </del> <ins> Option A (ACK) : Host A sends an ACK containing the MP_FASTCLOSE option on one subflow, containing the key of Host B as declared in the initial connection handshake.  On all the other subflows, Host A sends a regular TCP RST to close these subflows, and tears them down.  Host A now enters FASTCLOSE_WAIT state. </ins> <del> Upon receipt of an MP_FASTCLOSE, containing the valid key, Host B answers on the same subflow with a TCP RST and tears down all subflows.  Host B can now close the whole MPTCP connection (it transitions directly to CLOSED state). </del> <ins> Option R (RST) : Host A sends a RST containing the MP_FASTCLOSE option on all subflows, containing the key of Host B as declared in the initial connection handshake.  Host A can tear the subflows and the connection down immediately. If a host receives a packet with a valid MP_FASTCLOSE option, it shall process it as follows : Upon receipt of an ACK with MP_FASTCLOSE, containing the valid key, Host B answers on the same subflow with a TCP RST and tears down all subflows.  Host B can now close the whole MPTCP connection (it transitions directly to CLOSED state). </ins> As soon as Host A has received the TCP RST on the remaining subflow, it can close this subflow and tear down the whole

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text: 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +---------------+---------------+-------+-----------------------+ +---------------+---------------+-------+-----------------------+ +---------------------------------------------------------------+ Figure 14: Fast Close (MPFASTCLOSE) Option If Host A wants to force the closure of an MPTCP connection, it has two different options : Option A (ACK) : Host A sends an ACK containing the MPFASTCLOSE option on one subflow, containing the key of Host B as declared in the initial connection handshake. On all the other subflows, Host A sends a regular TCP RST to close these subflows, and tears them down. Host A now enters FASTCLOSEWAIT state. Option R (RST) : Host A sends a RST containing the MPFASTCLOSE option on all subflows, containing the key of Host B as declared in the initial connection handshake. Host A can tear the subflows and the connection down immediately. If a host receives a packet with a valid MPFASTCLOSE option, it shall process it as follows : o Upon receipt of an ACK with MPFASTCLOSE, containing the valid key, Host B answers on the same subflow with a TCP RST and tears down all subflows. Host B can now close the whole MPTCP connection (it transitions directly to CLOSED state). o As soon as Host A has received the TCP RST on the remaining subflow, it can close this subflow and tear down the whole connection (transition from FASTCLOSEWAIT to CLOSED states). If Host A receives an MPFASTCLOSE instead of a TCP RST, both hosts attempted fast closure simultaneously. Host A should reply with a TCP RST and tear down the connection. o If Host A does not receive a TCP RST in reply to its MPFASTCLOSE after one retransmission timeout (RTO) (the RTO of the subflow where the MPTCPRST has been sent), it SHOULD retransmit the MPFASTCLOSE.