[TCP]: Add total num retransmits accounting.

Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/tcp.h

@@ -186,6 +186,8 @@ struct tcp_info
 
 	__u32	tcpi_rcv_rtt;
 	__u32	tcpi_rcv_space;
+
+	__u32	tcpi_total_retrans;
 };
 
 #ifdef __KERNEL__
@@ -364,6 +366,8 @@ struct tcp_opt {
 	__u8	urg_mode;	/* In urgent mode		*/
 	__u32	snd_up;		/* Urgent pointer		*/
 
+	__u32	total_retrans;	/* Total retransmits for entire connection */
+
 	/* The syn_wait_lock is necessary only to avoid proc interface having
 	 * to grab the main lock sock while browsing the listening hash
 	 * (otherwise it's deadlock prone).

net/ipv4/tcp_diag.c

@@ -105,6 +105,8 @@ void tcp_get_info(struct sock *sk, struct tcp_info *info)
 
 	info->tcpi_rcv_rtt = jiffies_to_usecs(tp->rcv_rtt_est.rtt)>>3;
 	info->tcpi_rcv_space = tp->rcvq_space.space;
+
+	info->tcpi_total_retrans = tp->total_retrans;
 }
 
 static int tcpdiag_fill(struct sk_buff *skb, struct sock *sk,

net/ipv4/tcp_output.c

@@ -1106,6 +1106,8 @@ int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
 		/* Update global TCP statistics. */
 		TCP_INC_STATS(TCP_MIB_RETRANSSEGS);
 
+		tp->total_retrans++;
+
 #if FASTRETRANS_DEBUG > 0
 		if (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) {
 			if (net_ratelimit())