dccp: fix bug in sequence number validation during connection setup

This fixes a bug in the sequence number validation during the initial handshake.

The code did not treat the initial sequence numbers ISS and ISR as read-only and
did not keep state for GSR and GSS as required by the specification. This causes
problems with retransmissions during the initial handshake, causing the
budding connection to be reset.

This patch now treats ISS/ISR as read-only and tracks GSS/GSR as required.

Signed-off-by: Samuel Jero <sj323707@ohio.edu>
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>

1 files changed, 5 insertions, 5 deletions

diff --git a/net/dccp/output.c b/net/dccp/output.c
index dede3edb8849..787367308797 100644
--- a/net/dccp/output.c
+++ b/net/dccp/output.c
@@ -408,10 +408,10 @@ struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
         skb_dst_set(skb, dst_clone(dst));
 
         dreq = dccp_rsk(req);
-        if (inet_rsk(req)->acked)       /* increase ISS upon retransmission */
-                dccp_inc_seqno(&dreq->dreq_iss);
+        if (inet_rsk(req)->acked)       /* increase GSS upon retransmission */
+                dccp_inc_seqno(&dreq->dreq_gss);
         DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESPONSE;
-        DCCP_SKB_CB(skb)->dccpd_seq  = dreq->dreq_iss;
+        DCCP_SKB_CB(skb)->dccpd_seq  = dreq->dreq_gss;
 
         /* Resolve feature dependencies resulting from choice of CCID */
         if (dccp_feat_server_ccid_dependencies(dreq))
@@ -429,8 +429,8 @@ struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
                            DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
         dh->dccph_type  = DCCP_PKT_RESPONSE;
         dh->dccph_x     = 1;
-        dccp_hdr_set_seq(dh, dreq->dreq_iss);
-        dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dreq->dreq_isr);
+        dccp_hdr_set_seq(dh, dreq->dreq_gss);
+        dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dreq->dreq_gsr);
         dccp_hdr_response(skb)->dccph_resp_service = dreq->dreq_service;
 
         dccp_csum_outgoing(skb);