[DCCP]: Introduce dccp_get_info

And also hc_tx and hc_rx get_info functions for the CCIDs to fill in
information that is specific to them.

For now reusing struct tcp_info, later I'll try to figure out a better
solution, for now its really nice to get this kind of info:

[root@qemu ~]# ./ss -danemi
State       Recv-Q Send-Q  Local Addr:Port  Peer Addr:Port
LISTEN      0      0                *:5001          *:*     ino:628 sk:c1340040
         mem:(r0,w0,f0,t0) cwnd:0 ssthresh:0
ESTAB       0      0       172.20.0.2:5001 172.20.0.1:32785 ino:629 sk:c13409a0
         mem:(r0,w0,f0,t0) ts rto:1000 rtt:0.004/0 cwnd:0 ssthresh:0 rcv_rtt:61.377

This, for instance, shows that we're not congestion controlling ACKs,
as the above output is in the ttcp receiving host, and ttcp is a one
way app, i.e. the received never calls sendmsg, so
ccid_hc_tx_send_packet is never called, so the TX half connection
stays in TFRC_SSTATE_NO_SENT state and hctx_rtt is never calculated,
stays with the value set in ccid3_hc_tx_init, 4us, as show above in
milliseconds (0.004ms), upcoming patches will fix this.

rcv_rtt seems sane tho, matching ping results :-)
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dccp/ccid.h

@@ -50,6 +50,10 @@ struct ccid {
 						  struct sk_buff *skb, int len);
 	void		(*ccid_hc_tx_packet_sent)(struct sock *sk, int more,
 						  int len);
+	void		(*ccid_hc_rx_get_info)(struct sock *sk,
+					       struct tcp_info *info);
+	void		(*ccid_hc_tx_get_info)(struct sock *sk,
+					       struct tcp_info *info);
 };
 
 extern int	   ccid_register(struct ccid *ccid);
@@ -159,4 +163,18 @@ static inline void ccid_hc_rx_insert_options(struct ccid *ccid, struct sock *sk,
 	if (ccid->ccid_hc_rx_insert_options != NULL)
 		ccid->ccid_hc_rx_insert_options(sk, skb);
 }
+
+static inline void ccid_hc_rx_get_info(struct ccid *ccid, struct sock *sk,
+				       struct tcp_info *info)
+{
+	if (ccid->ccid_hc_rx_get_info != NULL)
+		ccid->ccid_hc_rx_get_info(sk, info);
+}
+
+static inline void ccid_hc_tx_get_info(struct ccid *ccid, struct sock *sk,
+				       struct tcp_info *info)
+{
+	if (ccid->ccid_hc_tx_get_info != NULL)
+		ccid->ccid_hc_tx_get_info(sk, info);
+}
 #endif /* _CCID_H */

net/dccp/ccids/ccid3.c

@@ -2020,6 +2020,31 @@ static void ccid3_hc_rx_exit(struct sock *sk)
 	dp->dccps_hc_rx_ccid_private = NULL;
 }
 
+static void ccid3_hc_rx_get_info(struct sock *sk, struct tcp_info *info)
+{
+	const struct dccp_sock *dp = dccp_sk(sk);
+	const struct ccid3_hc_rx_sock *hcrx = dp->dccps_hc_rx_ccid_private;
+
+	if (hcrx == NULL)
+		return;
+
+	info->tcpi_ca_state	= hcrx->ccid3hcrx_state;
+	info->tcpi_options	|= TCPI_OPT_TIMESTAMPS;
+	info->tcpi_rcv_rtt	= hcrx->ccid3hcrx_rtt;
+}
+
+static void ccid3_hc_tx_get_info(struct sock *sk, struct tcp_info *info)
+{
+	const struct dccp_sock *dp = dccp_sk(sk);
+	const struct ccid3_hc_tx_sock *hctx = dp->dccps_hc_tx_ccid_private;
+
+	if (hctx == NULL)
+		return;
+
+	info->tcpi_rto = hctx->ccid3hctx_t_rto;
+	info->tcpi_rtt = hctx->ccid3hctx_rtt;
+}
+
 static struct ccid ccid3 = {
 	.ccid_id		   = 3,
 	.ccid_name		   = "ccid3",
@@ -2037,6 +2062,8 @@ static struct ccid ccid3 = {
 	.ccid_hc_rx_exit	   = ccid3_hc_rx_exit,
 	.ccid_hc_rx_insert_options = ccid3_hc_rx_insert_options,
 	.ccid_hc_rx_packet_recv	   = ccid3_hc_rx_packet_recv,
+	.ccid_hc_rx_get_info	   = ccid3_hc_rx_get_info,
+	.ccid_hc_tx_get_info	   = ccid3_hc_tx_get_info,
 };
  
 module_param(ccid3_debug, int, 0444);

net/dccp/diag.c

@@ -14,19 +14,43 @@
 #include <linux/module.h>
 #include <linux/inet_diag.h>
 
+#include "ccid.h"
 #include "dccp.h"
 
+static void dccp_get_info(struct sock *sk, struct tcp_info *info)
+{
+	struct dccp_sock *dp = dccp_sk(sk);
+	const struct inet_connection_sock *icsk = inet_csk(sk);
+
+	memset(info, 0, sizeof(*info));
+
+	info->tcpi_state	= sk->sk_state;
+	info->tcpi_retransmits	= icsk->icsk_retransmits;
+	info->tcpi_probes	= icsk->icsk_probes_out;
+	info->tcpi_backoff	= icsk->icsk_backoff;
+	info->tcpi_pmtu		= dp->dccps_pmtu_cookie;
+
+	if (dp->dccps_options.dccpo_send_ack_vector)
+		info->tcpi_options |= TCPI_OPT_SACK;
+
+	ccid_hc_rx_get_info(dp->dccps_hc_rx_ccid, sk, info);
+	ccid_hc_tx_get_info(dp->dccps_hc_tx_ccid, sk, info);
+}
+
 static void dccp_diag_get_info(struct sock *sk, struct inet_diag_msg *r,
 			       void *_info)
 {
 	r->idiag_rqueue = r->idiag_wqueue = 0;
+
+	if (_info != NULL)
+		dccp_get_info(sk, _info);
 }
 
 static struct inet_diag_handler dccp_diag_handler = {
 	.idiag_hashinfo	 = &dccp_hashinfo,
 	.idiag_get_info	 = dccp_diag_get_info,
 	.idiag_type	 = DCCPDIAG_GETSOCK,
-	.idiag_info_size = 0,
+	.idiag_info_size = sizeof(struct tcp_info),
 };
 
 static int __init dccp_diag_init(void)