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tcp: refine tcp_write_queue_empty() implementation

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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>
This commit is contained in:
Eric Dumazet
2019-12-12 12:55:30 -08:00
committed by Jakub Kicinski
parent 1f85e6267c
commit ee2aabd3fc
2 changed files with 13 additions and 3 deletions
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11
include/net/tcp.h
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@@ -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)