[DCCP]: Twice the wrong reset code in receiving connection-Requests

This fixes two bugs in processing of connection-Requests in
v{4,6}_conn_request:

 1. Due to using the variable `reset_code', the Reset code generated
    internally by dccp_parse_options() is overwritten with the
    initialised value ("Too Busy") of reset_code, which is not what is
    intended.

 2. When receiving a connection-Request on a multicast or broadcast
    address, no Reset should be generated, to avoid storms of such
    packets. Instead of jumping to the `drop' label, the
    v{4,6}_conn_request functions now return 0. Below is why in my
    understanding this is correct:

    When the conn_request function returns < 0, then the caller,
    dccp_rcv_state_process(), returns 1. In all instances where
    dccp_rcv_state_process is called (dccp_v4_do_rcv, dccp_v6_do_rcv,
    and dccp_child_process), a return value of != 0 from
    dccp_rcv_state_process() means that a Reset is generated.

    If on the other hand the conn_request function returns 0, the
    packet is discarded and no Reset is generated.

Note: There may be a related problem when sending the Response, due to
the following.

	if (dccp_v6_send_response(sk, req, NULL))
		goto drop_and_free;
	/* ... */
	drop_and_free:
		return -1;

In this case, if send_response fails due to transmission errors, the
next thing that is generated is a Reset with a code "Too Busy". I
haven't been able to conjure up such a condition, but it might be good
to change the behaviour here also (not done by this patch).

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>

1 files changed, 4 insertions, 7 deletions

diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index 2312b9f4d7af..44f6e17e105f 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -568,17 +568,14 @@ int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
         struct dccp_request_sock *dreq;
         const __be32 service = dccp_hdr_request(skb)->dccph_req_service;
         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
-        __u8 reset_code = DCCP_RESET_CODE_TOO_BUSY;
 
         /* Never answer to DCCP_PKT_REQUESTs send to broadcast or multicast */
         if (((struct rtable *)skb->dst)->rt_flags &
-            (RTCF_BROADCAST | RTCF_MULTICAST)) {
-                reset_code = DCCP_RESET_CODE_NO_CONNECTION;
-                goto drop;
-        }
+            (RTCF_BROADCAST | RTCF_MULTICAST))
+                return 0;       /* discard, don't send a reset here */
 
         if (dccp_bad_service_code(sk, service)) {
-                reset_code = DCCP_RESET_CODE_BAD_SERVICE_CODE;
+                dcb->dccpd_reset_code = DCCP_RESET_CODE_BAD_SERVICE_CODE;
                 goto drop;
         }
         /*
@@ -586,6 +583,7 @@ int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
          * limitations, they conserve resources and peer is
          * evidently real one.
          */
+        dcb->dccpd_reset_code = DCCP_RESET_CODE_TOO_BUSY;
         if (inet_csk_reqsk_queue_is_full(sk))
                 goto drop;
 
@@ -638,7 +636,6 @@ drop_and_free:
         reqsk_free(req);
 drop:
         DCCP_INC_STATS_BH(DCCP_MIB_ATTEMPTFAILS);
-        dcb->dccpd_reset_code = reset_code;
         return -1;
 }