4 files changed, 10 insertions, 0 deletions

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index fb67f9a51b95..da6281c549a5 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -188,6 +188,9 @@ struct tcp_sock {
                                  * sum(delta(snd_una)), or how many bytes
                                  * were acked.
                                  */
+        u32     dsack_dups;     /* RFC4898 tcpEStatsStackDSACKDups
+                                 * total number of DSACK blocks received
+                                 */
         u32     snd_una;        /* First byte we want an ack for        */
         u32     snd_sml;        /* Last byte of the most recently transmitted small packet */
         u32     rcv_tstamp;     /* timestamp of last received ACK (for keepalives) */
diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
index c31f5100b744..0e1c0aec0153 100644
--- a/include/uapi/linux/tcp.h
+++ b/include/uapi/linux/tcp.h
@@ -238,6 +238,7 @@ struct tcp_info {
 
         __u64   tcpi_bytes_sent;     /* RFC4898 tcpEStatsPerfHCDataOctetsOut */
         __u64   tcpi_bytes_retrans;  /* RFC4898 tcpEStatsPerfOctetsRetrans */
+        __u32   tcpi_dsack_dups;     /* RFC4898 tcpEStatsStackDSACKDups */
 };
 
 /* netlink attributes types for SCM_TIMESTAMPING_OPT_STATS */
@@ -262,6 +263,7 @@ enum {
         TCP_NLA_DELIVERED_CE,   /* Like above but only ones w/ CE marks */
         TCP_NLA_BYTES_SENT,     /* Data bytes sent including retransmission */
         TCP_NLA_BYTES_RETRANS,  /* Data bytes retransmitted */
+        TCP_NLA_DSACK_DUPS,     /* DSACK blocks received */
 };
 
 /* for TCP_MD5SIG socket option */
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 5ed1be88e922..d6232b598cae 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2596,6 +2596,7 @@ int tcp_disconnect(struct sock *sk, int flags)
         tp->compressed_ack = 0;
         tp->bytes_sent = 0;
         tp->bytes_retrans = 0;
+        tp->dsack_dups = 0;
 
         /* Clean up fastopen related fields */
         tcp_free_fastopen_req(tp);
@@ -3205,6 +3206,7 @@ void tcp_get_info(struct sock *sk, struct tcp_info *info)
         info->tcpi_delivered_ce = tp->delivered_ce;
         info->tcpi_bytes_sent = tp->bytes_sent;
         info->tcpi_bytes_retrans = tp->bytes_retrans;
+        info->tcpi_dsack_dups = tp->dsack_dups;
         unlock_sock_fast(sk, slow);
 }
 EXPORT_SYMBOL_GPL(tcp_get_info);
@@ -3231,6 +3233,7 @@ static size_t tcp_opt_stats_get_size(void)
                 nla_total_size(sizeof(u32)) + /* TCP_NLA_DELIVERED_CE */
                 nla_total_size_64bit(sizeof(u64)) + /* TCP_NLA_BYTES_SENT */
                 nla_total_size_64bit(sizeof(u64)) + /* TCP_NLA_BYTES_RETRANS */
+                nla_total_size(sizeof(u32)) + /* TCP_NLA_DSACK_DUPS */
                 0;
 }
 
@@ -3282,6 +3285,7 @@ struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk)
                           TCP_NLA_PAD);
         nla_put_u64_64bit(stats, TCP_NLA_BYTES_RETRANS, tp->bytes_retrans,
                           TCP_NLA_PAD);
+        nla_put_u32(stats, TCP_NLA_DSACK_DUPS, tp->dsack_dups);
 
         return stats;
 }
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index d51fa358b2b1..fbc85ff7d71d 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -874,6 +874,7 @@ static void tcp_dsack_seen(struct tcp_sock *tp)
 {
         tp->rx_opt.sack_ok |= TCP_DSACK_SEEN;
         tp->rack.dsack_seen = 1;
+        tp->dsack_dups++;
 }
 
 /* It's reordering when higher sequence was delivered (i.e. sacked) before