[DCCP]: Fix default sequence window size

When using the default sequence window size (100) I got the following in
my logs:

Jun 22 14:24:09 localhost kernel: [ 1492.114775] DCCP: Step 6 failed for
DATA packet, (LSWL(6279674225) <= P.seqno(6279674749) <=
S.SWH(6279674324)) and (P.ackno doesn't exist or LAWL(18798206530) <=
P.ackno(1125899906842620) <= S.AWH(18798206548), sending SYNC...
Jun 22 14:24:09 localhost kernel: [ 1492.115147] DCCP: Step 6 failed for
DATA packet, (LSWL(6279674225) <= P.seqno(6279674750) <=
S.SWH(6279674324)) and (P.ackno doesn't exist or LAWL(18798206530) <=
P.ackno(1125899906842620) <= S.AWH(18798206549), sending SYNC...

I went to alter the default sysctl and it didn't take for new sockets.
Below patch fixes this.

I think the default is too low but it is what the DCCP spec specifies.

As a side effect of this my rx speed using iperf goes from about 2.8 Mbits/sec
to 3.5. This is still far too slow but it is a step in the right direction.

Compile tested only for IPv6 but not particularly complex change.

Signed off by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dccp/feat.h

@@ -26,4 +26,6 @@ extern void dccp_feat_clean(struct dccp_minisock *dmsk);
 extern int  dccp_feat_clone(struct sock *oldsk, struct sock *newsk);
 extern int  dccp_feat_init(struct dccp_minisock *dmsk);
 
+extern int  dccp_feat_default_sequence_window;
+
 #endif /* _DCCP_FEAT_H */

net/dccp/ipv4.c

@@ -504,8 +504,7 @@ int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
 	ireq = inet_rsk(req);
 	ireq->loc_addr = daddr;
 	ireq->rmt_addr = saddr;
-	req->rcv_wnd	= 100; /* Fake, option parsing will get the
-				  right value */
+	req->rcv_wnd	= dccp_feat_default_sequence_window;
 	ireq->opt	= NULL;
 
 	/* 

net/dccp/ipv6.c

@@ -31,6 +31,7 @@
 
 #include "dccp.h"
 #include "ipv6.h"
+#include "feat.h"
 
 /* Socket used for sending RSTs and ACKs */
 static struct socket *dccp_v6_ctl_socket;
@@ -707,8 +708,7 @@ static int dccp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
 	ireq = inet_rsk(req);
 	ipv6_addr_copy(&ireq6->rmt_addr, &skb->nh.ipv6h->saddr);
 	ipv6_addr_copy(&ireq6->loc_addr, &skb->nh.ipv6h->daddr);
-	req->rcv_wnd	= 100; /* Fake, option parsing will get the
-				  right value */
+	req->rcv_wnd	= dccp_feat_default_sequence_window;
 	ireq6->pktopts	= NULL;
 
 	if (ipv6_opt_accepted(sk, skb) ||

net/dccp/options.c

@@ -29,6 +29,8 @@ int dccp_feat_default_ack_ratio	      = DCCPF_INITIAL_ACK_RATIO;
 int dccp_feat_default_send_ack_vector = DCCPF_INITIAL_SEND_ACK_VECTOR;
 int dccp_feat_default_send_ndp_count  = DCCPF_INITIAL_SEND_NDP_COUNT;
 
+EXPORT_SYMBOL_GPL(dccp_feat_default_sequence_window);
+
 void dccp_minisock_init(struct dccp_minisock *dmsk)
 {
 	dmsk->dccpms_sequence_window = dccp_feat_default_sequence_window;