[DCCP]: Increment sequence numbers on retransmitted Response packets

Problem:

2 files changed, 13 insertions, 7 deletions

diff --git a/net/dccp/minisocks.c b/net/dccp/minisocks.c
index d3de696fe4bf..5b2773efd7c7 100644
--- 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 992caedd7725..08ee5547a2f2 100644
--- 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;
 }