[PATCH] bpf/sockmap: read psock ingress_msg before sk_receive_queue

[Lingpeng Chen <forrest0579@gmail.com>]

Right now in tcp_bpf_recvmsg, sock read data first from sk_receive_queue
if not empty than psock->ingress_msg otherwise. If a FIN packet arrives
and there's also some data in psock->ingress_msg, the data in
psock->ingress_msg will be purged. It is always happen when request to a
HTTP1.0 server like python SimpleHTTPServer since the server send FIN
packet after data is sent out.

Fixes: 604326b41a6fb ("bpf, sockmap: convert to generic sk_msg interface")
Reported-by: Arika Chen <eaglesora@gmail.com>
Suggested-by: Arika Chen <eaglesora@gmail.com>
Signed-off-by: Lingpeng Chen <forrest0579@gmail.com>
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
---
 net/ipv4/tcp_bpf.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
index e38705165ac9..f7e902868fce 100644
--- a/net/ipv4/tcp_bpf.c
+++ b/net/ipv4/tcp_bpf.c
@@ -123,12 +123,13 @@ int tcp_bpf_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 
 	if (unlikely(flags & MSG_ERRQUEUE))
 		return inet_recv_error(sk, msg, len, addr_len);
-	if (!skb_queue_empty(&sk->sk_receive_queue))
-		return tcp_recvmsg(sk, msg, len, nonblock, flags, addr_len);
 
 	psock = sk_psock_get(sk);
 	if (unlikely(!psock))
 		return tcp_recvmsg(sk, msg, len, nonblock, flags, addr_len);
+	if (!skb_queue_empty(&sk->sk_receive_queue) &&
+	    sk_psock_queue_empty(psock))
+		return tcp_recvmsg(sk, msg, len, nonblock, flags, addr_len);
 	lock_sock(sk);
 msg_bytes_ready:
 	copied = __tcp_bpf_recvmsg(sk, psock, msg, len, flags);
@@ -139,7 +140,7 @@ int tcp_bpf_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 		timeo = sock_rcvtimeo(sk, nonblock);
 		data = tcp_bpf_wait_data(sk, psock, flags, timeo, &err);
 		if (data) {
-			if (skb_queue_empty(&sk->sk_receive_queue))
+			if (!sk_psock_queue_empty(psock))
 				goto msg_bytes_ready;
 			release_sock(sk);
 			sk_psock_put(sk, psock);
-- 
2.17.1