[DCCP]: Support inserting options during the 3-way handshake

This provides a separate routine to insert options during the initial handshake.
The main purpose is to conduct feature negotiation, for the moment the only user
is the timestamp echo needed for the (CCID3) handshake RTT sample.

Padding of options has been put into a small separate routine, to be shared among
the two functions. This could also be used as a generic routine to finish inserting
options.

Also removed an `XXX' comment since its content was obvious.

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>

3 files changed, 24 insertions, 11 deletions

diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index 3af3320194f0..b138e2019d78 100644
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -428,6 +428,7 @@ static inline int dccp_ack_pending(const struct sock *sk)
 }
 
 extern int dccp_insert_options(struct sock *sk, struct sk_buff *skb);
+extern int dccp_insert_options_rsk(struct dccp_request_sock*, struct sk_buff*);
 extern int dccp_insert_option_elapsed_time(struct sock *sk,
                                             struct sk_buff *skb,
                                             u32 elapsed_time);
diff --git a/net/dccp/options.c b/net/dccp/options.c
index 0c996d8c79a3..bedb5daaa3c5 100644
--- a/net/dccp/options.c
+++ b/net/dccp/options.c
@@ -537,6 +537,18 @@ static int dccp_insert_options_feat(struct sock *sk, struct sk_buff *skb)
         return 0;
 }
 
+/* The length of all options needs to be a multiple of 4 (5.8) */
+static void dccp_insert_option_padding(struct sk_buff *skb)
+{
+        int padding = DCCP_SKB_CB(skb)->dccpd_opt_len % 4;
+
+        if (padding != 0) {
+                padding = 4 - padding;
+                memset(skb_push(skb, padding), 0, padding);
+                DCCP_SKB_CB(skb)->dccpd_opt_len += padding;
+        }
+}
+
 int dccp_insert_options(struct sock *sk, struct sk_buff *skb)
 {
         struct dccp_sock *dp = dccp_sk(sk);
@@ -580,18 +592,18 @@ int dccp_insert_options(struct sock *sk, struct sk_buff *skb)
             dccp_insert_option_timestamp_echo(dp, NULL, skb))
                 return -1;
 
-        /* XXX: insert other options when appropriate */
+        dccp_insert_option_padding(skb);
+        return 0;
+}
 
-        if (DCCP_SKB_CB(skb)->dccpd_opt_len != 0) {
-                /* The length of all options has to be a multiple of 4 */
-                int padding = DCCP_SKB_CB(skb)->dccpd_opt_len % 4;
+int dccp_insert_options_rsk(struct dccp_request_sock *dreq, struct sk_buff *skb)
+{
+        DCCP_SKB_CB(skb)->dccpd_opt_len = 0;
 
-                if (padding != 0) {
-                        padding = 4 - padding;
-                        memset(skb_push(skb, padding), 0, padding);
-                        DCCP_SKB_CB(skb)->dccpd_opt_len += padding;
-                }
-        }
+        if (dreq->dreq_timestamp_echo != 0 &&
+            dccp_insert_option_timestamp_echo(NULL, dreq, skb))
+                return -1;
 
+        dccp_insert_option_padding(skb);
         return 0;
 }
diff --git a/net/dccp/output.c b/net/dccp/output.c
index b2e17910930d..5589a5e581f4 100644
--- a/net/dccp/output.c
+++ b/net/dccp/output.c
@@ -303,7 +303,7 @@ struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
         DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESPONSE;
         DCCP_SKB_CB(skb)->dccpd_seq  = dreq->dreq_iss;
 
-        if (dccp_insert_options(sk, skb)) {
+        if (dccp_insert_options_rsk(dreq, skb)) {
                 kfree_skb(skb);
                 return NULL;
         }