[PATCH net v2 1/4] sctp: abort unordered partial delivery when its message is skipped

[Tim Budding <tim.budding@gmail.com>]

When an I-FORWARD-TSN skips unordered messages on a stream,
sctp_intl_skip() only aborts the stream's unordered partial delivery if
the MID being delivered is lower than the skipped MID. If the skipped
message is the one being partially delivered, partial delivery stays in
progress: no PARTIAL_DELIVERY_ABORTED is sent, and the next unordered
message on the stream is delivered as the rest of the abandoned one.

Abort the partial delivery when the MID being delivered is at or below
the skipped MID, as the ordered case already does.

Reproduced on an unmodified kernel with the uo_pd test of the
sctp_ifwdtsn.sh selftest added later in this series; its partial
delivery checks pass with this fix. Reproduction and fix done with AI
assistance.

Fixes: de60fe910543 ("sctp: implement handle_ftsn for sctp_stream_interleave")
Cc: stable@vger.kernel.org
Signed-off-by: Tim Budding <tim.budding@gmail.com>
---
 net/sctp/stream_interleave.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sctp/stream_interleave.c b/net/sctp/stream_interleave.c
index 840f24045ae2..869940001588 100644
--- a/net/sctp/stream_interleave.c
+++ b/net/sctp/stream_interleave.c
@@ -1255,7 +1255,7 @@ static void sctp_intl_skip(struct sctp_ulpq *ulpq, __u16 sid, __u32 mid,
 	struct sctp_stream *stream  = &ulpq->asoc->stream;
 
 	if (flags & SCTP_FTSN_U_BIT) {
-		if (sin->pd_mode_uo && MID_lt(sin->mid_uo, mid)) {
+		if (sin->pd_mode_uo && !MID_lt(mid, sin->mid_uo)) {
 			sin->pd_mode_uo = 0;
 			sctp_intl_stream_abort_pd(ulpq, sid, mid, 0x1,
 						  GFP_ATOMIC);
-- 
2.34.1