Backport Linux changes for proper TCP EOF handling

Notably when remote eagerly sends a RST: we want to return EOF to the
application, not EPIPE.

* pfinet/linux-src/net/ipv4/tcp_output.c (tcp_connect): Set sk->done to 0.
* pfinet/linux-src/net/ipv4/tcp_input.c (tcp_fin): Set RCV_SHUTDOWN, and
sk->done to 1.
* pfinet/linux-src/net/ipv4/tcp.c (tcp_recv_urg): Only return ENOTCONN when
we never actually connect.  Always return 0 when reception is closed.
(tcp_recvmsg): When any data is available, ignore errors and EOF.  When no
data is available, first check for reception being closed, then for errors.

3 files changed, 31 insertions, 32 deletions

diff --git a/pfinet/linux-src/net/ipv4/tcp.c b/pfinet/linux-src/net/ipv4/tcp.c
index 8cde3854..1a057439 100644
--- a/pfinet/linux-src/net/ipv4/tcp.c
+++ b/pfinet/linux-src/net/ipv4/tcp.c
@@ -1059,13 +1059,11 @@ static int tcp_recv_urg(struct sock * sk, int nonblock,
 	if (sk->err)
 		return sock_error(sk);
 
-	if (sk->done)
+	if (sk->state == TCP_CLOSE && !sk->done)
 		return -ENOTCONN;
 
-	if (sk->state == TCP_CLOSE || (sk->shutdown & RCV_SHUTDOWN)) {
-		sk->done = 1;
+	if (sk->state == TCP_CLOSE || (sk->shutdown & RCV_SHUTDOWN))
 		return 0;
-	}
 
 	lock_sock(sk);
 	if (tp->urg_data & URG_VALID) {
@@ -1177,9 +1175,6 @@ int tcp_recvmsg(struct sock *sk, struct msghdr *msg,
 	int err = 0;
 	int target = 1;		/* Read at least this many bytes */
 
-	if (sk->err)
-		return sock_error(sk);
-
 	if (sk->state == TCP_LISTEN)
 		return -ENOTCONN;
 
@@ -1261,36 +1256,36 @@ int tcp_recvmsg(struct sock *sk, struct msghdr *msg,
 		if (copied >= target)
 			break;
 
-		/*
-		   These three lines and clause if (sk->state == TCP_CLOSE)
-		   are unlikely to be correct, if target > 1.
-		   I DO NOT FIX IT, because I have no idea, what
-		   POSIX prescribes to make here. Probably, it really
-		   wants to lose data 8), if not all target is received.
-		                                                 --ANK
-		 */
-		if (sk->err && !(flags&MSG_PEEK)) {
-			copied = sock_error(sk);
-			break;
-		}
+		if (copied) {
+			if (sk->err ||
+			    sk->state == TCP_CLOSE ||
+			    (sk->shutdown & RCV_SHUTDOWN) ||
+			    nonblock)
+				break;
+		} else {
+			if (sk->done)
+				break;
 
-		if (sk->shutdown & RCV_SHUTDOWN) {
-			sk->done = 1;
-			break;
-		}
+			if (sk->err) {
+				copied = sock_error(sk);
+				break;
+			}
+
+			if (sk->shutdown & RCV_SHUTDOWN)
+				break;
 
-		if (sk->state == TCP_CLOSE) {
-			if (!sk->done) {
-				sk->done = 1;
+			if (sk->state == TCP_CLOSE) {
+				if (!sk->done) {
+					copied = -ENOTCONN;
+					break;
+				}
 				break;
 			}
-			copied = -ENOTCONN;
-			break;
-		}
 
-		if (nonblock) {
-			copied = -EAGAIN;
-			break;
+			if (nonblock) {
+				copied = -EAGAIN;
+				break;
+			}
 		}
 
 		cleanup_rbuf(sk, copied);
diff --git a/pfinet/linux-src/net/ipv4/tcp_input.c b/pfinet/linux-src/net/ipv4/tcp_input.c
index e84eaf43..e2dfc156 100644
--- a/pfinet/linux-src/net/ipv4/tcp_input.c
+++ b/pfinet/linux-src/net/ipv4/tcp_input.c
@@ -1129,6 +1129,9 @@ static void tcp_fin(struct sk_buff *skb, struct sock *sk, struct tcphdr *th)
 
 	tcp_send_ack(sk);
 
+	sk->shutdown |= RCV_SHUTDOWN;
+	sk->done = 1;
+
 	if (!sk->dead) {
 		sk->state_change(sk);
 		sock_wake_async(sk->socket, 1);
diff --git a/pfinet/linux-src/net/ipv4/tcp_output.c b/pfinet/linux-src/net/ipv4/tcp_output.c
index 9ea4b7ad..a15b7b30 100644
--- a/pfinet/linux-src/net/ipv4/tcp_output.c
+++ b/pfinet/linux-src/net/ipv4/tcp_output.c
@@ -922,6 +922,7 @@ void tcp_connect(struct sock *sk, struct sk_buff *buff, int mtu)
 	tp->rcv_nxt = 0;
 
 	sk->err = 0;
+	sk->done = 0;
 	
 	/* We'll fix this up when we get a response from the other end.
 	 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.