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Date: Wed, 01 Aug 2007 18:21:29 +0800
From: Wei Yongjun <yjwei@...fujitsu.com>
To: Vlad Yasevich <vladislav.yasevich@...com>
CC: Sridhar Samudrala <sri@...ibm.com>, netdev@...r.kernel.org,
lksctp-developers@...ts.sourceforge.net,
Neil Horman <nhorman@...driver.com>
Subject: Re: [PATCH] SCTP: drop SACK if ctsn is not less than the next tsn
of assoc
> Sorry, coming in late due to list issues...
>
> Wei Yongjun wrote:
>
>>> On Tue, 2007-07-31 at 07:37 -0400, Neil Horman wrote:
>>>
>>>
>>>> On Tue, Jul 31, 2007 at 12:44:27PM +0800, Wei Yongjun wrote:
>>>>
>>>>
>>>>> If SCTP data sender received a SACK which contains Cumulative TSN Ack is
>>>>> not less than the Cumulative TSN Ack Point, and if this Cumulative TSN
>>>>> Ack is not used by the data sender, SCTP data sender still accept this
>>>>> SACK , and next SACK which send correctly to DATA sender be dropped,
>>>>> because it is less than the new Cumulative TSN Ack Point.
>>>>> After received this SACK, data will be retrans again and again even if
>>>>> correct SACK is received.
>>>>> So I think this SACK must be dropped to let data transmit correctly.
>>>>>
>>>>> Following is the tcpdump of my test. And patch in this mail can avoid
>>>>> this problem.
>>>>>
>>>>> 02:19:38.233278 sctp (1) [INIT] [init tag: 1250461886] [rwnd: 54784] [OS: 10] [MIS: 65535] [init TSN: 217114040]
>>>>> 02:19:39.782160 sctp (1) [INIT ACK] [init tag: 1] [rwnd: 54784] [OS: 100] [MIS: 65535] [init TSN: 100]
>>>>> 02:19:39.798583 sctp (1) [COOKIE ECHO]
>>>>> 02:19:40.082125 sctp (1) [COOKIE ACK]
>>>>> 02:19:40.097859 sctp (1) [DATA] (B)(E) [TSN: 217114040] [SID: 0] [SSEQ 0] [PPID 0xf192090b]
>>>>> 02:19:40.100162 sctp (1) [DATA] (B)(E) [TSN: 217114041] [SID: 0] [SSEQ 1] [PPID 0x3e467007]
>>>>> 02:19:40.100779 sctp (1) [DATA] (B)(E) [TSN: 217114042] [SID: 0] [SSEQ 2] [PPID 0x11b12a0a]
>>>>> 02:19:40.101200 sctp (1) [DATA] (B)(E) [TSN: 217114043] [SID: 0] [SSEQ 3] [PPID 0x30e7d979]
>>>>> 02:19:40.561147 sctp (1) [SACK] [cum ack 217114040] [a_rwnd 54784] [#gap acks 0] [#dup tsns 0]
>>>>> 02:19:40.568498 sctp (1) [DATA] (B)(E) [TSN: 217114044] [SID: 0] [SSEQ 4] [PPID 0x251ff86f]
>>>>> 02:19:40.569308 sctp (1) [DATA] (B)(E) [TSN: 217114045] [SID: 0] [SSEQ 5] [PPID 0xe5d5da5d]
>>>>> 02:19:40.700584 sctp (1) [SACK] [cum ack 290855864] [a_rwnd 54784] [#gap acks 0] [#dup tsns 0]
>>>>> 02:19:40.701562 sctp (1) [DATA] (B)(E) [TSN: 217114046] [SID: 0] [SSEQ 6] [PPID 0x87d8b423]
>>>>> 02:19:40.701567 sctp (1) [DATA] (B)(E) [TSN: 217114047] [SID: 0] [SSEQ 7] [PPID 0xca47e645]
>>>>> 02:19:40.701569 sctp (1) [DATA] (B)(E) [TSN: 217114048] [SID: 0] [SSEQ 8] [PPID 0x6c0ea150]
>>>>> 02:19:40.701576 sctp (1) [DATA] (B)(E) [TSN: 217114049] [SID: 0] [SSEQ 9] [PPID 0x9cc1994f]
>>>>> 02:19:40.701585 sctp (1) [DATA] (B)(E) [TSN: 217114050] [SID: 0] [SSEQ 10] [PPID 0xb1df4129]
>>>>> 02:19:41.098201 sctp (1) [SACK] [cum ack 217114041] [a_rwnd 54784] [#gap acks 0] [#dup tsns 0]
>>>>> 02:19:41.283257 sctp (1) [SACK] [cum ack 217114042] [a_rwnd 54784] [#gap acks 0] [#dup tsns 0]
>>>>> 02:19:41.457217 sctp (1) [SACK] [cum ack 217114043] [a_rwnd 54784] [#gap acks 0] [#dup tsns 0]
>>>>> 02:19:41.691528 sctp (1) [SACK] [cum ack 217114044] [a_rwnd 54784] [#gap acks 0] [#dup tsns 0]
>>>>> 02:19:41.849636 sctp (1) [SACK] [cum ack 217114045] [a_rwnd 54784] [#gap acks 0] [#dup tsns 0]
>>>>> 02:19:41.975473 sctp (1) [DATA] (B)(E) [TSN: 217114046] [SID: 0] [SSEQ 6] [PPID 0x87d8b423]
>>>>> 02:19:42.021229 sctp (1) [SACK] [cum ack 217114046] [a_rwnd 54784] [#gap acks 0] [#dup tsns 0]
>>>>> 02:19:42.196495 sctp (1) [SACK] [cum ack 217114047] [a_rwnd 54784] [#gap acks 0] [#dup tsns 0]
>>>>> 02:19:42.424319 sctp (1) [SACK] [cum ack 217114048] [a_rwnd 54784] [#gap acks 0] [#dup tsns 0]
>>>>> 02:19:42.586924 sctp (1) [SACK] [cum ack 217114049] [a_rwnd 54784] [#gap acks 0] [#dup tsns 0]
>>>>> 02:19:42.744810 sctp (1) [SACK] [cum ack 217114050] [a_rwnd 54784] [#gap acks 0] [#dup tsns 0]
>>>>> 02:19:42.965536 sctp (1) [SACK] [cum ack 217114046] [a_rwnd 54784] [#gap acks 0] [#dup tsns 0]
>>>>> 02:19:43.106385 sctp (1) [DATA] (B)(E) [TSN: 217114046] [SID: 0] [SSEQ 6] [PPID 0x87d8b423]
>>>>> 02:19:43.218969 sctp (1) [SACK] [cum ack 217114046] [a_rwnd 54784] [#gap acks 0] [#dup tsns 0]
>>>>> 02:19:45.374101 sctp (1) [DATA] (B)(E) [TSN: 217114046] [SID: 0] [SSEQ 6] [PPID 0x87d8b423]
>>>>> 02:19:45.489258 sctp (1) [SACK] [cum ack 217114046] [a_rwnd 54784] [#gap acks 0] [#dup tsns 0]
>>>>> 02:19:49.830116 sctp (1) [DATA] (B)(E) [TSN: 217114046] [SID: 0] [SSEQ 6] [PPID 0x87d8b423]
>>>>> 02:19:49.984577 sctp (1) [SACK] [cum ack 217114046] [a_rwnd 54784] [#gap acks 0] [#dup tsns 0]
>>>>> 02:19:58.760300 sctp (1) [DATA] (B)(E) [TSN: 217114046] [SID: 0] [SSEQ 6] [PPID 0x87d8b423]
>>>>> 02:19:58.931690 sctp (1) [SACK] [cum ack 217114046] [a_rwnd 54784] [#gap acks 0] [#dup tsns 0]
>>>>>
>
>
> This is an interesting case, but I am not sure that simply discarding
> the SACK is the right thing.
>
> The peer in this case is violating the protocol whereby he is trying to
> advance the cumulative tsn ack to a point beyond the max tsn currently
> sent. I would vote for terminating the association in this case since
> either the peer is a mis-behaved implementation, or the association is
> under attack.
I have modify the patch to abort the association with protocol violation
error cause, and new patch is come on. May be this patch is correct.^_^
Signed-off-by: Wei Yongjun <yjwei@...fujitsu.com>
--- net/sctp/sm_statefuns.c.orig 2007-07-29 18:11:01.000000000 -0400
+++ net/sctp/sm_statefuns.c 2007-07-31 00:29:16.000000000 -0400
@@ -104,6 +104,13 @@ static sctp_disposition_t sctp_sf_violat
void *arg,
sctp_cmd_seq_t *commands);
+static sctp_disposition_t sctp_sf_violation_ctsn(
+ const struct sctp_endpoint *ep,
+ const struct sctp_association *asoc,
+ const sctp_subtype_t type,
+ void *arg,
+ sctp_cmd_seq_t *commands);
+
/* Small helper function that checks if the chunk length
* is of the appropriate length. The 'required_length' argument
* is set to be the size of a specific chunk we are testing.
@@ -2880,6 +2887,13 @@ sctp_disposition_t sctp_sf_eat_sack_6_2(
return SCTP_DISPOSITION_DISCARD;
}
+ /* If Cumulative TSN Ack beyond the max tsn currently
+ * send, terminating the association and respond to the
+ * sender with an ABORT.
+ */
+ if (!TSN_lt(ctsn, asoc->next_tsn))
+ return sctp_sf_violation_ctsn(ep, asoc, type, arg, commands);
+
/* Return this SACK for further processing. */
sctp_add_cmd_sf(commands, SCTP_CMD_PROCESS_SACK, SCTP_SACKH(sackh));
@@ -3756,6 +3770,68 @@ nomem:
return SCTP_DISPOSITION_NOMEM;
}
+/*
+ * Handle a protocol violation when the peer trying to advance the
+ * cumulative tsn ack to a point beyond the max tsn currently sent.
+ *
+ * We inform the other end by sending an ABORT with a Protocol Violation
+ * error code.
+ *
+ * Section: Not specified
+ * Verification Tag: Nothing to do
+ * Inputs
+ * (endpoint, asoc, chunk)
+ *
+ * Outputs
+ * (reply_msg, msg_up, counters)
+ *
+ * Generate an ABORT chunk and terminate the association.
+ */
+static sctp_disposition_t sctp_sf_violation_ctsn(
+ const struct sctp_endpoint *ep,
+ const struct sctp_association *asoc,
+ const sctp_subtype_t type,
+ void *arg,
+ sctp_cmd_seq_t *commands)
+{
+ struct sctp_chunk *chunk = arg;
+ struct sctp_chunk *abort = NULL;
+ char err_str[] = "The cumulative tsn ack beyond the max tsn currently sent:";
+
+ /* Make the abort chunk. */
+ abort = sctp_make_abort_violation(asoc, chunk, err_str,
+ sizeof(err_str));
+ if (!abort)
+ goto nomem;
+
+ sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(abort));
+ SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);
+
+ if (asoc->state <= SCTP_STATE_COOKIE_ECHOED) {
+ sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
+ SCTP_TO(SCTP_EVENT_TIMEOUT_T1_INIT));
+ sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR,
+ SCTP_ERROR(ECONNREFUSED));
+ sctp_add_cmd_sf(commands, SCTP_CMD_INIT_FAILED,
+ SCTP_PERR(SCTP_ERROR_PROTO_VIOLATION));
+ } else {
+ sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR,
+ SCTP_ERROR(ECONNABORTED));
+ sctp_add_cmd_sf(commands, SCTP_CMD_ASSOC_FAILED,
+ SCTP_PERR(SCTP_ERROR_PROTO_VIOLATION));
+ SCTP_DEC_STATS(SCTP_MIB_CURRESTAB);
+ }
+
+ sctp_add_cmd_sf(commands, SCTP_CMD_DISCARD_PACKET, SCTP_NULL());
+
+ SCTP_INC_STATS(SCTP_MIB_ABORTEDS);
+
+ return SCTP_DISPOSITION_ABORT;
+
+nomem:
+ return SCTP_DISPOSITION_NOMEM;
+}
+
/***************************************************************************
* These are the state functions for handling primitive (Section 10) events.
***************************************************************************/
--
A new email address of FJWAN is launched from Apr.1 2007.
The updated address is: yjwei@...fujitsu.com
--------------------------------------------------
Wei Yongjun
Development Dept.I
Nanjing Fujitsu Nanda Software Tech. Co., Ltd.(FNST)
8/F., Civil Defense Building, No.189 Guangzhou Road,
Nanjing, 210029, China
TEL: +86+25-86630523-858
COINS: 79955-858
FAX: +86+25-83317685
MAIL: yjwei@...fujitsu.com
--------------------------------------------------
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