From 8accd04eb9a4123e65b4a17d411edea8d83e7de8 Mon Sep 17 00:00:00 2001 From: Soheil Hassas Yeganeh Date: Wed, 6 Mar 2019 13:01:36 -0500 Subject: [PATCH] tcp: do not report TCP_CM_INQ of 0 for closed connections [ 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 Acked-by: Neal Cardwell Signed-off-by: Eric Dumazet Acked-by: Yuchung Cheng Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv4/tcp.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 432dc9a..30c6e94 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -1901,6 +1901,11 @@ 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; } -- 2.7.4