udp: Split spliced forwarding path from udp_buf_reply_sock_data()

udp_buf_reply_sock_data() can handle forwarding data either from socket
to socket ("splicing") or from socket to tap.  It has a test on each
datagram for which case we're in, but that will be the same for everything
in the batch.

Split out the spliced path into a separate udp_sock_to_sock() function.
This leaves udp_{buf,vu}_reply_sock_data() handling only forwards from
socket to tap, so rename and simplify them accordingly.

This makes the code slightly longer for now, but will allow future cleanups
to shrink it back down again.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
[sbrivio: Fix typos in comments to udp_sock_recv() and
 udp_vu_listen_sock_data()]
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

udp.c

@@ -670,6 +670,49 @@ static int udp_sock_recv(const struct ctx *c, int s, struct mmsghdr *mmh, int n)
 	return n;
 }
 
+/**
+ * udp_sock_to_sock() - Forward datagrams from socket to socket
+ * @c:		Execution context
+ * @from_s:	Socket to receive datagrams from
+ * @n:		Maximum number of datagrams to forward
+ * @tosidx:	Flow & side to forward datagrams to
+ */
+static void udp_sock_to_sock(const struct ctx *c, int from_s, int n,
+			     flow_sidx_t tosidx)
+{
+	int i;
+
+	if ((n = udp_sock_recv(c, from_s, udp_mh_recv, n)) <= 0)
+		return;
+
+	for (i = 0; i < n; i++)
+		udp_splice_prepare(udp_mh_recv, i);
+
+	udp_splice_send(c, 0, n, tosidx);
+}
+
+/**
+ * udp_buf_sock_to_tap() - Forward datagrams from socket to tap
+ * @c:		Execution context
+ * @s:		Socket to read data from
+ * @n:		Maximum number of datagrams to forward
+ * @tosidx:	Flow & side to forward data from @s to
+ */
+static void udp_buf_sock_to_tap(const struct ctx *c, int s, int n,
+				flow_sidx_t tosidx)
+{
+	const struct flowside *toside = flowside_at_sidx(tosidx);
+	int i;
+
+	if ((n = udp_sock_recv(c, s, udp_mh_recv, n)) <= 0)
+		return;
+
+	for (i = 0; i < n; i++)
+		udp_tap_prepare(udp_mh_recv, i, toside, false);
+
+	tap_send_frames(c, &udp_l2_iov[0][0], UDP_NUM_IOVS, n);
+}
+
 /**
  * udp_buf_listen_sock_data() - Handle new data from socket
  * @c:		Execution context
@@ -737,43 +780,6 @@ void udp_listen_sock_handler(const struct ctx *c,
 	}
 }
 
-/**
- * udp_buf_reply_sock_data() - Handle new data from flow specific socket
- * @c:		Execution context
- * @s:		Socket to read data from
- * @n:		Maximum number of datagrams to forward
- * @tosidx:	Flow & side to forward data from @s to
- *
- * Return: true on success, false if can't forward from socket to flow's pif
- */
-static bool udp_buf_reply_sock_data(const struct ctx *c, int s, int n,
-				    flow_sidx_t tosidx)
-{
-	const struct flowside *toside = flowside_at_sidx(tosidx);
-	uint8_t topif = pif_at_sidx(tosidx);
-	int i;
-
-	if ((n = udp_sock_recv(c, s, udp_mh_recv, n)) <= 0)
-		return true;
-
-	for (i = 0; i < n; i++) {
-		if (pif_is_socket(topif))
-			udp_splice_prepare(udp_mh_recv, i);
-		else if (topif == PIF_TAP)
-			udp_tap_prepare(udp_mh_recv, i, toside, false);
-	}
-
-	if (pif_is_socket(topif)) {
-		udp_splice_send(c, 0, n, tosidx);
-	} else if (topif == PIF_TAP) {
-		tap_send_frames(c, &udp_l2_iov[0][0], UDP_NUM_IOVS, n);
-	} else {
-		return false;
-	}
-
-	return true;
-}
-
 /**
  * udp_sock_handler() - Handle new data from flow specific socket
  * @c:		Execution context
@@ -805,21 +811,26 @@ void udp_sock_handler(const struct ctx *c, union epoll_ref ref,
 		 */
 		size_t n = (c->mode == MODE_PASTA ? 1 : UDP_MAX_FRAMES);
 		flow_sidx_t tosidx = flow_sidx_opposite(ref.flowside);
+		uint8_t topif = pif_at_sidx(tosidx);
 		int s = ref.fd;
-		bool ret;
 
 		flow_trace(uflow, "Received data on reply socket");
 		uflow->ts = now->tv_sec;
 
-		if (c->mode == MODE_VU) {
-			ret = udp_vu_reply_sock_data(c, s, UDP_MAX_FRAMES,
-						     tosidx);
+		if (pif_is_socket(topif)) {
+			udp_sock_to_sock(c, ref.fd, n, tosidx);
+		} else if (topif == PIF_TAP) {
+			if (c->mode == MODE_VU) {
+				udp_vu_sock_to_tap(c, s, UDP_MAX_FRAMES,
+						   tosidx);
+			} else {
+				udp_buf_sock_to_tap(c, s, n, tosidx);
+			}
 		} else {
-			ret = udp_buf_reply_sock_data(c, s, n, tosidx);
-		}
-
-		if (!ret) {
-			flow_err(uflow, "Unable to forward UDP");
+			flow_err(uflow,
+				 "No support for forwarding UDP from %s to %s",
+				 pif_name(pif_at_sidx(ref.flowside)),
+				 pif_name(topif));
 			goto fail;
 		}
 	}

udp_vu.c

@@ -254,16 +254,13 @@ void udp_vu_listen_sock_data(const struct ctx *c, union epoll_ref ref,
 }
 
 /**
- * udp_vu_reply_sock_data() - Handle new data from flow specific socket
+ * udp_vu_sock_to_tap() - Forward datagrams from socket to tap
  * @c:		Execution context
  * @s:		Socket to read data from
  * @n:		Maximum number of datagrams to forward
  * @tosidx:	Flow & side to forward data from @s to
- *
- * Return: true on success, false if can't forward from socket to flow's pif
  */
-bool udp_vu_reply_sock_data(const struct ctx *c, int s, int n,
-			    flow_sidx_t tosidx)
+void udp_vu_sock_to_tap(const struct ctx *c, int s, int n, flow_sidx_t tosidx)
 {
 	const struct flowside *toside = flowside_at_sidx(tosidx);
 	bool v6 = !(inany_v4(&toside->eaddr) && inany_v4(&toside->oaddr));
@@ -271,9 +268,6 @@ bool udp_vu_reply_sock_data(const struct ctx *c, int s, int n,
 	struct vu_virtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE];
 	int i;
 
-	if (pif_at_sidx(tosidx) != PIF_TAP)
-		return false;
-
 	for (i = 0; i < n; i++) {
 		ssize_t dlen;
 		int iov_used;
@@ -290,6 +284,4 @@ bool udp_vu_reply_sock_data(const struct ctx *c, int s, int n,
 		}
 		vu_flush(vdev, vq, elem, iov_used);
 	}
-
-	return true;
 }

udp_vu.h

@@ -8,7 +8,6 @@
 
 void udp_vu_listen_sock_data(const struct ctx *c, union epoll_ref ref,
 			     const struct timespec *now);
-bool udp_vu_reply_sock_data(const struct ctx *c, int s, int n,
-			    flow_sidx_t tosidx);
+void udp_vu_sock_to_tap(const struct ctx *c, int s, int n, flow_sidx_t tosidx);
 
 #endif /* UDP_VU_H */