[DCCP]: Increment sequence numbers on retransmitted Response packets

Problem:

diff --git a/net/dccp/minisocks.c b/net/dccp/minisocks.c
index d3de696fe4bf487e60f0949d6362754359cee836..5b2773efd7c7a6b289c90f3e206f35e89c71c098 100644 (file)
--- a/net/dccp/minisocks.c
+++ b/net/dccp/minisocks.c
@@ -196,15 +196,17 @@ struct sock *dccp_check_req(struct sock *sk, struct sk_buff *skb,
 
        /* Check for retransmitted REQUEST */
        if (dccp_hdr(skb)->dccph_type == DCCP_PKT_REQUEST) {
-               if (after48(DCCP_SKB_CB(skb)->dccpd_seq,
-                           dccp_rsk(req)->dreq_isr)) {
-                       struct dccp_request_sock *dreq = dccp_rsk(req);
+               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");
-                       /* Send another RESPONSE packet */
-                       dccp_set_seqno(&dreq->dreq_iss, dreq->dreq_iss + 1);
-                       dccp_set_seqno(&dreq->dreq_isr,
-                                      DCCP_SKB_CB(skb)->dccpd_seq);
+                       dreq->dreq_isr = DCCP_SKB_CB(skb)->dccpd_seq;
+                       /*
+                        * Send another RESPONSE packet
+                        * To protect against Request floods, increment retrans
+                        * counter (backoff, monitored by dccp_response_timer).
+                        */
+                       req->retrans++;
                        req->rsk_ops->rtx_syn_ack(sk, req, NULL);
                }
                /* Network Duplicate, discard packet */

diff --git a/net/dccp/output.c b/net/dccp/output.c
index 992caedd772545016be413bf4835c985f264d144..08ee5547a2f21259a520a1f7ba9443eb08d77b0f 100644 (file)
--- a/net/dccp/output.c
+++ b/net/dccp/output.c
@@ -332,6 +332,8 @@ struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
        skb->dst = dst_clone(dst);
 
        dreq = dccp_rsk(req);
+       if (inet_rsk(req)->acked)       /* increase ISS upon retransmission */
+               dccp_inc_seqno(&dreq->dreq_iss);
        DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESPONSE;
        DCCP_SKB_CB(skb)->dccpd_seq  = dreq->dreq_iss;
 
@@ -354,6 +356,8 @@ struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
 
        dccp_csum_outgoing(skb);
 
+       /* We use `acked' to remember that a Response was already sent. */
+       inet_rsk(req)->acked = 1;
        DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
        return skb;
 }