From: Sabrina Dubroca <sd@queasysnail.net>
Date: Thu, 16 Jul 2020 10:09:02 +0200
Subject: espintcp: recv() should return 0 when the peer socket is closed
Patch-mainline: v5.8
Git-commit: e229c877cde141a4c46cb603a341ce8c909e9a98
References: bsc#1176447

man 2 recv says:

    RETURN VALUE

    When a stream socket peer has performed an orderly shutdown, the
    return value will be 0 (the traditional "end-of-file" return).

Currently, this works for blocking reads, but non-blocking reads will
return -EAGAIN. This patch overwrites that return value when the peer
won't send us any more data.

Fixes: e27cca96cd68 ("xfrm: add espintcp (RFC 8229)")
Reported-by: Andrew Cagney <cagney@libreswan.org>
Tested-by: Andrew Cagney <cagney@libreswan.org>
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 net/xfrm/espintcp.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/net/xfrm/espintcp.c
+++ b/net/xfrm/espintcp.c
@@ -109,8 +109,11 @@ static int espintcp_recvmsg(struct sock
 	flags |= nonblock ? MSG_DONTWAIT : 0;
 
 	skb = __skb_recv_datagram(sk, &ctx->ike_queue, flags, &off, &err);
-	if (!skb)
+	if (!skb) {
+		if (err == -EAGAIN && sk->sk_shutdown & RCV_SHUTDOWN)
+			return 0;
 		return err;
+	}
 
 	copied = len;
 	if (copied > skb->len)