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sctp: allow changing transport encap_port by peer packets

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As rfc6951#section-5.4 says:

  "After finding the SCTP association (which
   includes checking the verification tag), the UDP source port MUST be
   stored as the encapsulation port for the destination address the SCTP
   packet is received from (see Section 5.1).

   When a non-encapsulated SCTP packet is received by the SCTP stack,
   the encapsulation of outgoing packets belonging to the same
   association and the corresponding destination address MUST be
   disabled."

transport encap_port should be updated by a validated incoming packet's
udp src port.

We save the udp src port in sctp_input_cb->encap_port, and then update
the transport in two places:

  1. right after vtag is verified, which is required by RFC, and this
     allows the existent transports to be updated by the chunks that
     can only be processed on an asoc.

  2. right before processing the 'init' where the transports are added,
     and this allows building a sctp over udp connection by client with
     the server not knowing the remote encap port.

  3. when processing ootb_pkt and creating the temporary transport for
     the reply pkt.

Note that sctp_input_cb->header is removed, as it's not used any more
in sctp.

v1->v2:
  - Change encap_port as __be16 for sctp_input_cb.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Xin Long 2020-10-29 15:05:03 +08:00 • committed by Jakub Kicinski
parent 8dba29603b
commit a1dd2cf2f1
6 changed files with 16 additions and 7 deletions
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1
net/sctp/sm_make_chunk.c
View file

@ -2321,6 +2321,7 @@ int sctp_process_init(struct sctp_association *asoc, struct sctp_chunk *chunk,
* added as the primary transport. The source address seems to
* be a better choice than any of the embedded addresses.
*/
asoc->encap_port = SCTP_INPUT_CB(chunk->skb)->encap_port;
if (!sctp_assoc_add_peer(asoc, peer_addr, gfp, SCTP_ACTIVE))
goto nomem;