sctp: implement validate_ftsn for sctp_stream_interleave

validate_ftsn is added as a member of sctp_stream_interleave, used to
validate ssn/chunk type for fwdtsn or mid (message id)/chunk type for
ifwdtsn, called in sctp_sf_eat_fwd_tsn, just as validate_data.

If this check fails, an abort packet will be sent, as said in section
2.3.1 of RFC8260.

As ifwdtsn and fwdtsn chunks have different length, it also defines
ftsn_chunk_len for sctp_stream_interleave to describe the chunk size.
Then it replaces all sizeof(struct sctp_fwdtsn_chunk) with
sctp_ftsnchk_len.

It also adds the process for ifwdtsn in rx path. As Marcelo pointed
out, there's no need to add event table for ifwdtsn, but just share
prsctp_chunk_event_table with fwdtsn's. It would drop fwdtsn chunk
for ifwdtsn and drop ifwdtsn chunk for fwdtsn by calling validate_ftsn
in sctp_sf_eat_fwd_tsn.

After this patch, the ifwdtsn can be accepted.

Note that this patch also removes the sctp.intl_enable check for
idata chunks in sctp_chunk_event_lookup, as it will do this check
in validate_data later.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo R. Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/net/sctp/stream_interleave.h b/include/net/sctp/stream_interleave.h
index 66267dbcecba..0db15b50c5e6 100644
--- a/include/net/sctp/stream_interleave.h
+++ b/include/net/sctp/stream_interleave.h
@@ -33,6 +33,7 @@
 
 struct sctp_stream_interleave {
 	__u16	data_chunk_len;
+	__u16	ftsn_chunk_len;
 	/* (I-)DATA process */
 	struct sctp_chunk *(*make_datafrag)(const struct sctp_association *asoc,
 					    const struct sctp_sndrcvinfo *sinfo,
@@ -49,6 +50,7 @@ struct sctp_stream_interleave {
 	void	(*abort_pd)(struct sctp_ulpq *ulpq, gfp_t gfp);
 	/* (I-)FORWARD-TSN process */
 	void	(*generate_ftsn)(struct sctp_outq *q, __u32 ctsn);
+	bool	(*validate_ftsn)(struct sctp_chunk *chunk);
 };
 
 void sctp_stream_interleave_init(struct sctp_stream *stream);