[SCTP]: Fix protocol violation when receiving an error lenght INIT-ACK

When receiving an error length INIT-ACK during COOKIE-WAIT,
a 0-vtag ABORT will be responsed. This action violates the
protocol apparently. This patch achieves the following things.
1 If the INIT-ACK contains all the fixed parameters, use init-tag
  recorded from INIT-ACK as vtag.
2 If the INIT-ACK doesn't contain all the fixed parameters,
  just reflect its vtag.

Signed-off-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 18 insertions, 0 deletions

diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index f2ed6473feef..3ef97499df0d 100644
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c
@@ -4144,6 +4144,24 @@ static sctp_disposition_t sctp_sf_abort_violation(
                 goto nomem;
 
         if (asoc) {
+                /* Treat INIT-ACK as a special case during COOKIE-WAIT. */
+                if (chunk->chunk_hdr->type == SCTP_CID_INIT_ACK &&
+                    !asoc->peer.i.init_tag) {
+                        sctp_initack_chunk_t *initack;
+
+                        initack = (sctp_initack_chunk_t *)chunk->chunk_hdr;
+                        if (!sctp_chunk_length_valid(chunk,
+                                                     sizeof(sctp_initack_chunk_t)))
+                                abort->chunk_hdr->flags |= SCTP_CHUNK_FLAG_T;
+                        else {
+                                unsigned int inittag;
+
+                                inittag = ntohl(initack->init_hdr.init_tag);
+                                sctp_add_cmd_sf(commands, SCTP_CMD_UPDATE_INITTAG,
+                                                SCTP_U32(inittag));
+                        }
+                }
+
                 sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(abort));
                 SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);