Commit a1dd2cf2 authored by Xin Long's avatar Xin Long Committed by Jakub Kicinski
Browse files

sctp: allow changing transport encap_port by peer packets 



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: default avatarXin Long <lucien.xin@gmail.com>
Acked-by: default avatarMarcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 8dba2960

include/net/sctp/sm.h

+1 −0
Original line number Diff line number Diff line
@@ -380,6 +380,7 @@ sctp_vtag_verify(const struct sctp_chunk *chunk, 
        if (ntohl(chunk->sctp_hdr->vtag) == asoc->c.my_vtag)

                return 1;



	chunk->transport->encap_port = SCTP_INPUT_CB(chunk->skb)->encap_port;

	return 0;

}

include/net/sctp/structs.h

+1 −6
Original line number Diff line number Diff line
@@ -1120,14 +1120,9 @@ static inline void sctp_outq_cork(struct sctp_outq *q) 
 * sctp_input_cb is currently used on rx and sock rx queue

 */

struct sctp_input_cb {

	union {

		struct inet_skb_parm	h4;

#if IS_ENABLED(CONFIG_IPV6)

		struct inet6_skb_parm	h6;

#endif

	} header;

	struct sctp_chunk *chunk;

	struct sctp_af *af;

	__be16 encap_port;

};

#define SCTP_INPUT_CB(__skb)	((struct sctp_input_cb *)&((__skb)->cb[0]))

net/sctp/ipv6.c

+1 −0
Original line number Diff line number Diff line
@@ -1053,6 +1053,7 @@ static struct inet_protosw sctpv6_stream_protosw = { 


static int sctp6_rcv(struct sk_buff *skb)

{

	memset(skb->cb, 0, sizeof(skb->cb));

	return sctp_rcv(skb) ? -1 : 0;

}

net/sctp/protocol.c

+10 −1
Original line number Diff line number Diff line
@@ -843,6 +843,9 @@ static int sctp_ctl_sock_init(struct net *net) 


static int sctp_udp_rcv(struct sock *sk, struct sk_buff *skb)

{

	memset(skb->cb, 0, sizeof(skb->cb));

	SCTP_INPUT_CB(skb)->encap_port = udp_hdr(skb)->source;



	skb_set_transport_header(skb, sizeof(struct udphdr));

	sctp_rcv(skb);

	return 0;
@@ -1139,9 +1142,15 @@ static struct inet_protosw sctp_stream_protosw = { 
	.flags      = SCTP_PROTOSW_FLAG

};



static int sctp4_rcv(struct sk_buff *skb)

{

	memset(skb->cb, 0, sizeof(skb->cb));

	return sctp_rcv(skb);

}



/* Register with IP layer.  */

static const struct net_protocol sctp_protocol = {

	.handler     = sctp_rcv,

	.handler     = sctp4_rcv,

	.err_handler = sctp_v4_err,

	.no_policy   = 1,

	.netns_ok    = 1,

net/sctp/sm_make_chunk.c

+1 −0
Original line number Diff line number Diff line
@@ -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;

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