4.20-stable review patch. If anyone has any objections, please let me know.
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From: Soheil Hassas Yeganeh soheil@google.com
[ Upstream commit 6466e715651f9f358e60c5ea4880e4731325827f ]
Returning 0 as inq to userspace indicates there is no more data to read, and the application needs to wait for EPOLLIN. For a connection that has received FIN from the remote peer, however, the application must continue reading until getting EOF (return value of 0 from tcp_recvmsg) or an error, if edge-triggered epoll (EPOLLET) is being used. Otherwise, the application will never receive a new EPOLLIN, since there is no epoll edge after the FIN.
Return 1 when there is no data left on the queue but the connection has received FIN, so that the applications continue reading.
Fixes: b75eba76d3d72 (tcp: send in-queue bytes in cmsg upon read) Signed-off-by: Soheil Hassas Yeganeh soheil@google.com Acked-by: Neal Cardwell ncardwell@google.com Signed-off-by: Eric Dumazet edumazet@google.com Acked-by: Yuchung Cheng ycheng@google.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv4/tcp.c | 5 +++++ 1 file changed, 5 insertions(+)
--- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -1914,6 +1914,11 @@ static int tcp_inq_hint(struct sock *sk) inq = tp->rcv_nxt - tp->copied_seq; release_sock(sk); } + /* After receiving a FIN, tell the user-space to continue reading + * by returning a non-zero inq. + */ + if (inq == 0 && sock_flag(sk, SOCK_DONE)) + inq = 1; return inq; }