path: root/include/net/tcp.h
diff options
authorEric Dumazet <edumazet@google.com>2019-12-12 12:55:30 -0800
committerJakub Kicinski <jakub.kicinski@netronome.com>2019-12-13 21:58:40 -0800
commitee2aabd3fc2eef4c1a0ebdadccc76fbff74b94fc (patch)
treeff49c797d50165533687b248d7531010a9b24339 /include/net/tcp.h
parenttcp: do not send empty skb from tcp_write_xmit() (diff)
tcp: refine tcp_write_queue_empty() implementation
Due to how tcp_sendmsg() is implemented, we can have an empty skb at the tail of the write queue. Most [1] tcp_write_queue_empty() callers want to know if there is anything to send (payload and/or FIN) Instead of checking if the sk_write_queue is empty, we need to test if tp->write_seq == tp->snd_nxt [1] tcp_send_fin() was the only caller that expected to see if an skb was in the write queue, I have changed the code to reuse the tcp_write_queue_tail() result. Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Neal Cardwell <ncardwell@google.com> Acked-by: Soheil Hassas Yeganeh <soheil@google.com> Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Diffstat (limited to '')
1 files changed, 10 insertions, 1 deletions
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 86b9a8766648..e460ea7f767b 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1766,9 +1766,18 @@ static inline bool tcp_skb_is_last(const struct sock *sk,
return skb_queue_is_last(&sk->sk_write_queue, skb);
+ * tcp_write_queue_empty - test if any payload (or FIN) is available in write queue
+ * @sk: socket
+ *
+ * Since the write queue can have a temporary empty skb in it,
+ * we must not use "return skb_queue_empty(&sk->sk_write_queue)"
+ */
static inline bool tcp_write_queue_empty(const struct sock *sk)
- return skb_queue_empty(&sk->sk_write_queue);
+ const struct tcp_sock *tp = tcp_sk(sk);
+ return tp->write_seq == tp->snd_nxt;
static inline bool tcp_rtx_queue_empty(const struct sock *sk)