[PATCH ipsec 2/3] espintcp: recv() should return 0 when the peer socket is closed

[Sabrina Dubroca]

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 <cag...@libreswan.org>
Tested-by: Andrew Cagney <cag...@libreswan.org>
Signed-off-by: Sabrina Dubroca <s...@queasysnail.net>
---
 net/xfrm/espintcp.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/xfrm/espintcp.c b/net/xfrm/espintcp.c
index 5d3d2b98c62d..cb83e3664680 100644
--- a/net/xfrm/espintcp.c
+++ b/net/xfrm/espintcp.c
@@ -109,8 +109,11 @@ static int espintcp_recvmsg(struct sock *sk, struct msghdr 
*msg, size_t len,
        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)
-- 
2.27.0