mptcp: add subtype matching

MPTCP multiplexes the various mptcp signalling data using the
first 4 bits of the mptcp option.

This allows to match on the mptcp subtype via:

   tcp option mptcp subtype 1

This misses delinearization support. mptcp subtype is the first tcp
option field that has a length of less than one byte.

Serialization processing will add a binop for this, but netlink
delinearization can't remove them, yet.

Also misses a new datatype/symbol table to allow to use mnemonics like
'mp_join' instead of raw numbers.

For this reason, no tests are added yet.

Signed-off-by: Florian Westphal <fw@strlen.de>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/tcpopt.h b/include/tcpopt.h
index 22df69dc..bb5c1329 100644
--- a/include/tcpopt.h
+++ b/include/tcpopt.h
@@ -77,6 +77,7 @@ enum tcpopt_hdr_field_sack {
 enum tcpopt_hdr_mptcp_common {
 	TCPOPT_MPTCP_KIND,
 	TCPOPT_MPTCP_LENGTH,
+	TCPOPT_MPTCP_SUBTYPE,
 };
 
 extern const struct exthdr_desc *tcpopt_protocols[__TCPOPT_KIND_MAX];