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authorMatthieu Baerts <matthieu.baerts@tessares.net>2022-02-02 17:03:39 -0800
committerDavid S. Miller <davem@davemloft.net>2022-02-03 11:44:08 +0000
commit8cca39e251718baec13a5999bf3d18c05af865be (patch)
treedb6fa9c3cd5d4cb98d49d712fce44eb64aea77d8 /net/mptcp
parent902c8f8648828c9293533cc54393f163fb594d06 (diff)
mptcp: clarify when options can be used
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 <matthieu.baerts@tessares.net> Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/mptcp')
-rw-r--r--net/mptcp/options.c23
1 files changed, 21 insertions, 2 deletions
diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index ab054c389a5f..7345f28f3de1 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -1267,8 +1267,27 @@ void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
const struct sock *ssk = (const struct sock *)tp;
struct mptcp_subflow_context *subflow;
- /* DSS, MPC, MPJ, ADD_ADDR, FASTCLOSE and RST 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 | P |------|------|------|------|
+ * 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 = &opts->ext_copy;