[RFC PATCH]sctp: handle ASCONF-ACK which contains Request Refused

[Shan Wei <shanwei@cn.fujitsu.com>]

If Host-A sends an ASCONF request for adding IP-A address, Host-Z may sent ASCONF-ACK
which contains Error Cause: Request Refused(error = 0x00A4), for the local security 
policy or other problems. See below chart:

Host-A                                Host-Z
   -------ASCONF(ADDIP[IP-A])---------->

   <------ASCONF-ACK(error=0x00A4)------


Host-Z would thought the operation of adding IP-A at Host-A is fail, and the IP-A address
is not part of this association. So, If Host-Z sends HEARBEAT to check the IP-A path, 
Host-A should treat this chunk as OOTB.

However, because there is no implementation of local security policy settings in sctp protocol,
ASCONF-ACK chunk which contains Request Refused error never be sent, and  will be ignored 
by the receiver.(when received ASCONF-ACK, no more further treatment.) 
So, If Host-Z sends HEARBEAT to check the IP-A path, Host-A doesn't treat this chunk as OOTB,
and sends HEARTBEAT-ACK from primary address.

Although Freebsd and Linux still does not send ASCONF-ACK (error = 0x00A4), but we can not
guarantee that other systems will not too. Therefore, It's necessary to do something when
receiving ASCONF-ACK(error = 0x00A4).

The current handle is to send ABORT terminates the association, but this will lead to termination
of other paths in the association. 

Is there better way to fix it?


Signed-off-by: Shan Wei <shanwei@cn.fujitsu.com>
---
 net/sctp/sm_make_chunk.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index 246f929..147cca4 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -3344,6 +3344,10 @@ int sctp_process_asconf_ack(struct sctp_association *asoc,
 			break;
 
 		case SCTP_ERROR_REQ_REFUSED:
+			if (asconf_param->param_hdr.type = SCTP_PARAM_ADD_IP)
+				retval = 1;
+			break;
+
 		case SCTP_ERROR_DEL_LAST_IP:
 		case SCTP_ERROR_DEL_SRC_IP:
 		default:
-- 
1.6.3.3