sctp: add pad chunk and its make function and event table

This chunk is defined in rfc4820#section-3, and used to pad an
SCTP packet. The receiver must discard this chunk and continue
processing the rest of the chunks in the packet.

Add it now, as it will be bundled with a heartbeat chunk to probe
pmtu in the following patches.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/sctp.h b/include/linux/sctp.h
index bb19265..a86e852 100644 (file)
--- a/include/linux/sctp.h
+++ b/include/linux/sctp.h
@@ -98,6 +98,7 @@ enum sctp_cid {
        SCTP_CID_I_FWD_TSN              = 0xC2,
        SCTP_CID_ASCONF_ACK             = 0x80,
        SCTP_CID_RECONF                 = 0x82,
+       SCTP_CID_PAD                    = 0x84,
 }; /* enum */
 
 
@@ -410,6 +411,12 @@ struct sctp_heartbeat_chunk {
 };
 
 
+/* PAD chunk could be bundled with heartbeat chunk to probe pmtu */
+struct sctp_pad_chunk {
+       struct sctp_chunkhdr uh;
+};
+
+
 /* For the abort and shutdown ACK we must carry the init tag in the
  * common header. Just the common header is all that is needed with a
  * chunk descriptor.

diff --git a/include/net/sctp/sm.h b/include/net/sctp/sm.h
index fd223c9..09c5915 100644 (file)
--- a/include/net/sctp/sm.h
+++ b/include/net/sctp/sm.h
@@ -230,6 +230,7 @@ struct sctp_chunk *sctp_make_heartbeat_ack(const struct sctp_association *asoc,
                                           const struct sctp_chunk *chunk,
                                           const void *payload,
                                           const size_t paylen);
+struct sctp_chunk *sctp_make_pad(const struct sctp_association *asoc, int len);
 struct sctp_chunk *sctp_make_op_error(const struct sctp_association *asoc,
                                      const struct sctp_chunk *chunk,
                                      __be16 cause_code, const void *payload,

diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index 5b44d22..e5d470c 100644 (file)
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -1218,6 +1218,32 @@ nodata:
        return retval;
 }
 
+/* RFC4820 3. Padding Chunk (PAD)
+ *  0                   1                   2                   3
+ *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | Type = 0x84   |   Flags=0     |             Length            |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                                                               |
+ * \                         Padding Data                          /
+ * /                                                               \
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ */
+struct sctp_chunk *sctp_make_pad(const struct sctp_association *asoc, int len)
+{
+       struct sctp_chunk *retval;
+
+       retval = sctp_make_control(asoc, SCTP_CID_PAD, 0, len, GFP_ATOMIC);
+       if (!retval)
+               return NULL;
+
+       skb_put_zero(retval->skb, len);
+       retval->chunk_hdr->length = htons(ntohs(retval->chunk_hdr->length) + len);
+       retval->chunk_end = skb_tail_pointer(retval->skb);
+
+       return retval;
+}
+
 /* Create an Operation Error chunk with the specified space reserved.
  * This routine can be used for containing multiple causes in the chunk.
  */

diff --git a/net/sctp/sm_statetable.c b/net/sctp/sm_statetable.c
index 88ea87f..c82c423 100644 (file)
--- a/net/sctp/sm_statetable.c
+++ b/net/sctp/sm_statetable.c
@@ -527,6 +527,26 @@ auth_chunk_event_table[SCTP_NUM_AUTH_CHUNK_TYPES][SCTP_STATE_NUM_STATES] = {
 }; /*state_fn_t auth_chunk_event_table[][] */
 
 static const struct sctp_sm_table_entry
+pad_chunk_event_table[SCTP_STATE_NUM_STATES] = {
+       /* SCTP_STATE_CLOSED */
+       TYPE_SCTP_FUNC(sctp_sf_discard_chunk),
+       /* SCTP_STATE_COOKIE_WAIT */
+       TYPE_SCTP_FUNC(sctp_sf_discard_chunk),
+       /* SCTP_STATE_COOKIE_ECHOED */
+       TYPE_SCTP_FUNC(sctp_sf_discard_chunk),
+       /* SCTP_STATE_ESTABLISHED */
+       TYPE_SCTP_FUNC(sctp_sf_discard_chunk),
+       /* SCTP_STATE_SHUTDOWN_PENDING */
+       TYPE_SCTP_FUNC(sctp_sf_discard_chunk),
+       /* SCTP_STATE_SHUTDOWN_SENT */
+       TYPE_SCTP_FUNC(sctp_sf_discard_chunk),
+       /* SCTP_STATE_SHUTDOWN_RECEIVED */
+       TYPE_SCTP_FUNC(sctp_sf_discard_chunk),
+       /* SCTP_STATE_SHUTDOWN_ACK_SENT */
+       TYPE_SCTP_FUNC(sctp_sf_discard_chunk),
+};     /* chunk pad */
+
+static const struct sctp_sm_table_entry
 chunk_event_table_unknown[SCTP_STATE_NUM_STATES] = {
        /* SCTP_STATE_CLOSED */
        TYPE_SCTP_FUNC(sctp_sf_ootb),
@@ -992,6 +1012,9 @@ static const struct sctp_sm_table_entry *sctp_chunk_event_lookup(
 
        case SCTP_CID_AUTH:
                return &auth_chunk_event_table[0][state];
+
+       case SCTP_CID_PAD:
+               return &pad_chunk_event_table[state];
        }
 
        return &chunk_event_table_unknown[state];