tcp: add tcp_ooo_try_coalesce() helper

In case skb in out_or_order_queue is the result of
multiple skbs coalescing, we would like to get a proper gso_segs
counter tracking, so that future tcp_drop() can report an accurate
number.

I chose to not implement this tracking for skbs in receive queue,
since they are not dropped, unless socket is disconnected.

Signed-off-by: Eric Dumazet <edumazet@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>

1 files changed, 21 insertions, 4 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index b062a7692238..3bcd30a2ba06 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4358,6 +4358,23 @@ static bool tcp_try_coalesce(struct sock *sk,
         return true;
 }
 
+static bool tcp_ooo_try_coalesce(struct sock *sk,
+                             struct sk_buff *to,
+                             struct sk_buff *from,
+                             bool *fragstolen)
+{
+        bool res = tcp_try_coalesce(sk, to, from, fragstolen);
+
+        /* In case tcp_drop() is called later, update to->gso_segs */
+        if (res) {
+                u32 gso_segs = max_t(u16, 1, skb_shinfo(to)->gso_segs) +
+                               max_t(u16, 1, skb_shinfo(from)->gso_segs);
+
+                skb_shinfo(to)->gso_segs = min_t(u32, gso_segs, 0xFFFF);
+        }
+        return res;
+}
+
 static void tcp_drop(struct sock *sk, struct sk_buff *skb)
 {
         sk_drops_add(sk, skb);
@@ -4481,8 +4498,8 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
         /* In the typical case, we are adding an skb to the end of the list.
          * Use of ooo_last_skb avoids the O(Log(N)) rbtree lookup.
          */
-        if (tcp_try_coalesce(sk, tp->ooo_last_skb,
-                             skb, &fragstolen)) {
+        if (tcp_ooo_try_coalesce(sk, tp->ooo_last_skb,
+                                 skb, &fragstolen)) {
 coalesce_done:
                 tcp_grow_window(sk, skb);
                 kfree_skb_partial(skb, fragstolen);
@@ -4532,8 +4549,8 @@ coalesce_done:
                                 tcp_drop(sk, skb1);
                                 goto merge_right;
                         }
-                } else if (tcp_try_coalesce(sk, skb1,
-                                            skb, &fragstolen)) {
+                } else if (tcp_ooo_try_coalesce(sk, skb1,
+                                                skb, &fragstolen)) {
                         goto coalesce_done;
                 }
                 p = &parent->rb_right;