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[94.130.216.23]) by smtp.gmail.com with ESMTPSA id m6sm9918244edc.36.2021.12.30.11.17.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Dec 2021 11:17:51 -0800 (PST) From: Matthieu Baerts To: mptcp@lists.linux.dev Cc: Matthieu Baerts Subject: [PATCH mptcp-next v7 3/4] mptcp: clarify when options can be used Date: Thu, 30 Dec 2021 20:16:50 +0100 Message-Id: <20211230191651.1831507-4-matthieu.baerts@tessares.net> X-Mailer: git-send-email 2.33.1 In-Reply-To: <20211230191651.1831507-1-matthieu.baerts@tessares.net> References: <20211230191651.1831507-1-matthieu.baerts@tessares.net> Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" RFC8684 doesn't seem to clearly specify which MPTCP options can be used together. Some options are mutually exclusive -- e.g. MP_CAPABLE and MP_JOIN --, some can be used together -- e.g. DSS + MP_PRIO --, some can but we prefer not to -- e.g. DSS + ADD_ADDR -- and some have to be used together at some points -- e.g. MP_FAIL and DSS. We need to clarify this as a base before allowing other modifications. For example, does it make sense to send a RM_ADDR with an MPC or MPJ? This remains open for possible future discussions. Signed-off-by: Matthieu Baerts --- net/mptcp/options.c | 23 +++++++++++++++++++++-- 1 file changed, 21 insertions(+), 2 deletions(-) diff --git a/net/mptcp/options.c b/net/mptcp/options.c index 3427b31c0da7..d06855e66007 100644 --- a/net/mptcp/options.c +++ b/net/mptcp/options.c @@ -1263,8 +1263,27 @@ static u16 mptcp_make_csum(const struct mptcp_ext *m= pext) void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp, struct mptcp_out_options *opts) { - /* DSS, MPC, MPJ, ADD_ADDR, FASTCLOSE and FAIL are mutually exclusive, - * see mptcp_established_options*() + /* Which options can be used together? + * + * X: mutually exclusive + * O: often used together + * C: can be used together in some cases + * P: could be used together but we prefer not to (optimisations) + * + * Opt: | MPC | MPJ | DSS | ADD | RM | PRIO | FAIL | FC | + * ------|------|------|------|------|------|------|------|------| + * MPC |------|------|------|------|------|------|------|------| + * MPJ | X |------|------|------|------|------|------|------| + * DSS | X | X |------|------|------|------|------|------| + * ADD | X | X | P |------|------|------|------|------| + * RM | C | C | C | C |------|------|------|------| + * PRIO | X | C | C | C | C |------|------|------| + * FAIL | X | X | C | X | X | X |------|------| + * FC | X | X | X | X | X | X | X |------| + * RST | X | X | X | X | X | X | O | O | + * ------|------|------|------|------|------|------|------|------| + * + * The same applies in mptcp_established_options() function. */ if (likely(OPTION_MPTCP_DSS & opts->suboptions)) { struct mptcp_ext *mpext =3D &opts->ext_copy; --=20 2.33.1