Commit 8109616e authored Dec 13, 2007 by Gerrit Renker Committed by David S. Miller Jan 28, 2008

[DCCP]: Add (missing) option parsing to request_sock processing



This adds option-parsing code to processing of Acks in the listening state
on request_socks on the server, serving two purposes
 (i)  resolves a FIXME (removed);
 (ii) paves the way for feature-negotiation during connection-setup.

There is an intended subtlety here with regard to dccp_check_req:

 Parsing options happens only after testing whether the received packet is
 a retransmitted Request.  Otherwise, if the Request contained (a possibly
 large number of) feature-negotiation options, recomputing state would have to
 happen each time a retransmitted Request arrives, which opens the door to an
 easy DoS attack.  Since in a genuine retransmission the options should not be
 different from the original, reusing the already computed state seems better.

 The other point is - if there are timestamp options on the Request, they will
 not be answered; which means that in the presence of retransmission (likely
 due to loss and/or other problems), the use of Request/Response RTT sampling
 is suspended, so that startup problems here do not propagate.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 8b819412

net/dccp/minisocks.c

+6 −6

Original line number	Diff line number	Diff line
		@@ -200,10 +200,10 @@ struct sock dccp_check_req(struct sock sk, struct sk_buff *skb,
		struct request_sock **prev)
		{
		struct sock *child = NULL;
		struct dccp_request_sock *dreq = dccp_rsk(req);

		/* Check for retransmitted REQUEST */
		if (dccp_hdr(skb)->dccph_type == DCCP_PKT_REQUEST) {
		struct dccp_request_sock *dreq = dccp_rsk(req);

		if (after48(DCCP_SKB_CB(skb)->dccpd_seq, dreq->dreq_isr)) {
		dccp_pr_debug("Retransmitted REQUEST\n");
		@@ -227,22 +227,22 @@ struct sock dccp_check_req(struct sock sk, struct sk_buff *skb,
		goto drop;

		/* Invalid ACK */
		if (DCCP_SKB_CB(skb)->dccpd_ack_seq != dccp_rsk(req)->dreq_iss) {
		if (DCCP_SKB_CB(skb)->dccpd_ack_seq != dreq->dreq_iss) {
		dccp_pr_debug("Invalid ACK number: ack_seq=%llu, "
		"dreq_iss=%llu\n",
		(unsigned long long)
		DCCP_SKB_CB(skb)->dccpd_ack_seq,
		(unsigned long long)
		dccp_rsk(req)->dreq_iss);
		(unsigned long long) dreq->dreq_iss);
		goto drop;
		}

		if (dccp_parse_options(sk, dreq, skb))
		goto drop;

		child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL);
		if (child == NULL)
		goto listen_overflow;

		/* FIXME: deal with options */

		inet_csk_reqsk_queue_unlink(sk, req, prev);
		inet_csk_reqsk_queue_removed(sk, req);
		inet_csk_reqsk_queue_add(sk, req, child);