Re: [PATCH] sctp: send abort chunk when max_retrans exceeded

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On 11/20/2012 12:59 PM, Neil Horman wrote:
In the event that an association exceeds its max_retrans attempts, we should
send an ABORT chunk indicating that we are closing the assocation as a result.
Because of the nature of the error, its unlikely to be received, but its a nice
clean way to close the association if it does make it through, and it will give
anyone watching via tcpdump a clue as to what happened.

Signed-off-by: Neil Horman <nhorman@xxxxxxxxxxxxx>
CC: Vlad Yasevich <vyasevich@xxxxxxxxx>
CC: "David S. Miller" <davem@xxxxxxxxxxxxx>
CC: linux-sctp@xxxxxxxxxxxxxxx
---
  include/net/sctp/sm.h    |  2 ++
  net/sctp/sm_make_chunk.c | 26 +++++++++++++++++++++-----
  net/sctp/sm_sideeffect.c |  9 ++++++++-
  3 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/include/net/sctp/sm.h b/include/net/sctp/sm.h
index b5887e1..2a82d13 100644
--- a/include/net/sctp/sm.h
+++ b/include/net/sctp/sm.h
@@ -234,6 +234,8 @@ struct sctp_chunk *sctp_make_abort_violation(const struct sctp_association *,
  struct sctp_chunk *sctp_make_violation_paramlen(const struct sctp_association *,
  				   const struct sctp_chunk *,
  				   struct sctp_paramhdr *);
+struct sctp_chunk *sctp_make_violation_max_retrans(const struct sctp_association *,
+						   const struct sctp_chunk *);
  struct sctp_chunk *sctp_make_heartbeat(const struct sctp_association *,
  				  const struct sctp_transport *);
  struct sctp_chunk *sctp_make_heartbeat_ack(const struct sctp_association *,
diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index fbe1636..d6a8c80 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -1074,17 +1074,33 @@ struct sctp_chunk *sctp_make_violation_paramlen(
  {
  	struct sctp_chunk *retval;
  	static const char error[] = "The following parameter had invalid length:";
-	size_t payload_len = sizeof(error) + sizeof(sctp_errhdr_t) +
-				sizeof(sctp_paramhdr_t);
+	size_t payload_len = sizeof(error) + sizeof(sctp_errhdr_t);

  	retval = sctp_make_abort(asoc, chunk, payload_len);
  	if (!retval)
  		goto nodata;

-	sctp_init_cause(retval, SCTP_ERROR_PROTO_VIOLATION,
-			sizeof(error) + sizeof(sctp_paramhdr_t));
+	sctp_init_cause(retval, SCTP_ERROR_PROTO_VIOLATION, sizeof(error));
+	sctp_addto_chunk(retval, sizeof(error), error);
+
+nodata:
+	return retval;
+}

Neil

You ended dropping the parameter information of the parameter that caused the violation. Was that intentional?

-vlad

+
+struct sctp_chunk *sctp_make_violation_max_retrans(
+	const struct sctp_association *asoc,
+	const struct sctp_chunk *chunk)
+{
+	struct sctp_chunk *retval;
+	static const char error[] = "Association exceeded its max_retans count";
+	size_t payload_len = sizeof(error) + sizeof(sctp_errhdr_t);
+
+	retval = sctp_make_abort(asoc, chunk, payload_len);
+	if (!retval)
+		goto nodata;
+
+	sctp_init_cause(retval, SCTP_ERROR_PROTO_VIOLATION, sizeof(error));
  	sctp_addto_chunk(retval, sizeof(error), error);
-	sctp_addto_param(retval, sizeof(sctp_paramhdr_t), param);

  nodata:
  	return retval;
diff --git a/net/sctp/sm_sideeffect.c b/net/sctp/sm_sideeffect.c
index 6eecf7e..c076956 100644
--- a/net/sctp/sm_sideeffect.c
+++ b/net/sctp/sm_sideeffect.c
@@ -577,7 +577,7 @@ static void sctp_cmd_assoc_failed(sctp_cmd_seq_t *commands,
  				  unsigned int error)
  {
  	struct sctp_ulpevent *event;
-
+	struct sctp_chunk *abort;
  	/* Cancel any partial delivery in progress. */
  	sctp_ulpq_abort_pd(&asoc->ulpq, GFP_ATOMIC);

@@ -593,6 +593,13 @@ static void sctp_cmd_assoc_failed(sctp_cmd_seq_t *commands,
  		sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP,
  				SCTP_ULPEVENT(event));

+	if (asoc->overall_error_count >= asoc->max_retrans) {
+		abort = sctp_make_violation_max_retrans(asoc, chunk);
+		if (abort)
+			sctp_add_cmd_sf(commands, SCTP_CMD_REPLY,
+					SCTP_CHUNK(abort));
+	}
+
  	sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
  			SCTP_STATE(SCTP_STATE_CLOSED));



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