[RFC PATCH v3 net-next 2/3] tcp: Handle eor bit when coalescing skb

[Martin KaFai Lau]

This patch:
1. Prevent next_skb from coalescing to the prev_skb if
   TCP_SKB_CB(prev_skb)->eor is set
2. Update the TCP_SKB_CB(prev_skb)->eor if coalescing is
   allowed

Signed-off-by: Martin KaFai Lau <ka...@fb.com>
Cc: Eric Dumazet <eduma...@google.com>
Cc: Neal Cardwell <ncardw...@google.com>
Cc: Soheil Hassas Yeganeh <soh...@google.com>
Cc: Willem de Bruijn <will...@google.com>
Cc: Yuchung Cheng <ych...@google.com>
---
 net/ipv4/tcp_input.c  | 4 ++++
 net/ipv4/tcp_output.c | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 75e8336..68c55e5 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1303,6 +1303,7 @@ static bool tcp_shifted_skb(struct sock *sk, struct 
sk_buff *skb,
        }
 
        TCP_SKB_CB(prev)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
+       TCP_SKB_CB(prev)->eor = TCP_SKB_CB(skb)->eor;
        if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
                TCP_SKB_CB(prev)->end_seq++;
 
@@ -1368,6 +1369,9 @@ static struct sk_buff *tcp_shift_skb_data(struct sock 
*sk, struct sk_buff *skb,
        if ((TCP_SKB_CB(prev)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED)
                goto fallback;
 
+       if (TCP_SKB_CB(prev)->eor)
+               goto fallback;
+
        in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
                  !before(end_seq, TCP_SKB_CB(skb)->end_seq);
 
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index a6e4a83..96bdf98 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2494,6 +2494,7 @@ static void tcp_collapse_retrans(struct sock *sk, struct 
sk_buff *skb)
         * packet counting does not break.
         */
        TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked & 
TCPCB_EVER_RETRANS;
+       TCP_SKB_CB(skb)->eor = TCP_SKB_CB(next_skb)->eor;
 
        /* changed transmit queue under us so clear hints */
        tcp_clear_retrans_hints_partial(tp);
@@ -2545,6 +2546,9 @@ static void tcp_retrans_try_collapse(struct sock *sk, 
struct sk_buff *to,
                if (!tcp_can_collapse(sk, skb))
                        break;
 
+               if (TCP_SKB_CB(to)->eor)
+                       break;
+
                space -= skb->len;
 
                if (first) {
-- 
2.5.1