3 files changed, 20 insertions, 1 deletions

diff --git a/include/linux/snmp.h b/include/linux/snmp.h
index 8ee8af4e6da9..2e68f5ba0389 100644
--- a/include/linux/snmp.h
+++ b/include/linux/snmp.h
@@ -233,6 +233,7 @@ enum
         LINUX_MIB_TCPREQQFULLDOCOOKIES,         /* TCPReqQFullDoCookies */
         LINUX_MIB_TCPREQQFULLDROP,              /* TCPReqQFullDrop */
         LINUX_MIB_TCPRETRANSFAIL,               /* TCPRetransFail */
+        LINUX_MIB_TCPRCVCOALESCE,                       /* TCPRcvCoalesce */
         __LINUX_MIB_MAX
 };
 
diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index 02d61079f08b..8af0d44e4e22 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -257,6 +257,7 @@ static const struct snmp_mib snmp4_net_list[] = {
         SNMP_MIB_ITEM("TCPReqQFullDoCookies", LINUX_MIB_TCPREQQFULLDOCOOKIES),
         SNMP_MIB_ITEM("TCPReqQFullDrop", LINUX_MIB_TCPREQQFULLDROP),
         SNMP_MIB_ITEM("TCPRetransFail", LINUX_MIB_TCPRETRANSFAIL),
+        SNMP_MIB_ITEM("TCPRcvCoalesce", LINUX_MIB_TCPRCVCOALESCE),
         SNMP_MIB_SENTINEL
 };
 
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index fa7de12c4a52..e886e2f7fa8d 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4484,7 +4484,24 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
         end_seq = TCP_SKB_CB(skb)->end_seq;
 
         if (seq == TCP_SKB_CB(skb1)->end_seq) {
-                __skb_queue_after(&tp->out_of_order_queue, skb1, skb);
+                /* Packets in ofo can stay in queue a long time.
+                 * Better try to coalesce them right now
+                 * to avoid future tcp_collapse_ofo_queue(),
+                 * probably the most expensive function in tcp stack.
+                 */
+                if (skb->len <= skb_tailroom(skb1) && !tcp_hdr(skb)->fin) {
+                        NET_INC_STATS_BH(sock_net(sk),
+                                         LINUX_MIB_TCPRCVCOALESCE);
+                        BUG_ON(skb_copy_bits(skb, 0,
+                                             skb_put(skb1, skb->len),
+                                             skb->len));
+                        TCP_SKB_CB(skb1)->end_seq = end_seq;
+                        TCP_SKB_CB(skb1)->ack_seq = TCP_SKB_CB(skb)->ack_seq;
+                        __kfree_skb(skb);
+                        skb = NULL;
+                } else {
+                        __skb_queue_after(&tp->out_of_order_queue, skb1, skb);
+                }
 
                 if (!tp->rx_opt.num_sacks ||
                     tp->selective_acks[0].end_seq != seq)