tcp: add data bytes retransmitted stats

Introduce a new TCP stat to record the number of bytes retransmitted
(RFC4898 tcpEStatsPerfOctetsRetrans) and expose it in both tcp_info
(TCP_INFO) and opt_stats (SOF_TIMESTAMPING_OPT_STATS).

Signed-off-by: Wei Wang <weiwan@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 11 insertions, 0 deletions

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index d0798dcd2cab..fb67f9a51b95 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -333,6 +333,9 @@ struct tcp_sock {
                                  * the first SYN. */
         u32     undo_marker;    /* snd_una upon a new recovery episode. */
         int     undo_retrans;   /* number of undoable retransmissions. */
+        u64     bytes_retrans;  /* RFC4898 tcpEStatsPerfOctetsRetrans
+                                 * Total data bytes retransmitted
+                                 */
         u32     total_retrans;  /* Total retransmits for entire connection */
 
         u32     urg_seq;        /* Seq of received urgent pointer */
diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
index 1c70ed287c3b..c31f5100b744 100644
--- a/include/uapi/linux/tcp.h
+++ b/include/uapi/linux/tcp.h
@@ -237,6 +237,7 @@ struct tcp_info {
         __u32   tcpi_delivered_ce;
 
         __u64   tcpi_bytes_sent;     /* RFC4898 tcpEStatsPerfHCDataOctetsOut */
+        __u64   tcpi_bytes_retrans;  /* RFC4898 tcpEStatsPerfOctetsRetrans */
 };
 
 /* netlink attributes types for SCM_TIMESTAMPING_OPT_STATS */
@@ -260,6 +261,7 @@ enum {
         TCP_NLA_DELIVERED,      /* Data pkts delivered incl. out-of-order */
         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 */
 };
 
 /* for TCP_MD5SIG socket option */
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 873cb9968ff5..5ed1be88e922 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2595,6 +2595,7 @@ int tcp_disconnect(struct sock *sk, int flags)
         tcp_saved_syn_free(tp);
         tp->compressed_ack = 0;
         tp->bytes_sent = 0;
+        tp->bytes_retrans = 0;
 
         /* Clean up fastopen related fields */
         tcp_free_fastopen_req(tp);
@@ -3203,6 +3204,7 @@ void tcp_get_info(struct sock *sk, struct tcp_info *info)
         info->tcpi_delivered = tp->delivered;
         info->tcpi_delivered_ce = tp->delivered_ce;
         info->tcpi_bytes_sent = tp->bytes_sent;
+        info->tcpi_bytes_retrans = tp->bytes_retrans;
         unlock_sock_fast(sk, slow);
 }
 EXPORT_SYMBOL_GPL(tcp_get_info);
@@ -3228,6 +3230,7 @@ static size_t tcp_opt_stats_get_size(void)
                 nla_total_size(sizeof(u32)) + /* TCP_NLA_DELIVERED */
                 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 */
                 0;
 }
 
@@ -3277,6 +3280,8 @@ struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk)
 
         nla_put_u64_64bit(stats, TCP_NLA_BYTES_SENT, tp->bytes_sent,
                           TCP_NLA_PAD);
+        nla_put_u64_64bit(stats, TCP_NLA_BYTES_RETRANS, tp->bytes_retrans,
+                          TCP_NLA_PAD);
 
         return stats;
 }
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 861531fe0e97..50cabf7656f3 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2871,6 +2871,7 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
         if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
                 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
         tp->total_retrans += segs;
+        tp->bytes_retrans += skb->len;
 
         /* make sure skb->data is aligned on arches that require it
          * and check if ack-trimming & collapsing extended the headroom