From 545103ff1c61fb766e6623e316c96d84be10142f Mon Sep 17 00:00:00 2001
From: Steffen Vogel <stvogel@eonerc.rwth-aachen.de>
Date: Sat, 10 Sep 2016 20:58:46 -0400
Subject: [PATCH] rewrote socket_read(): there ave been some misunderstandings

---
 lib/socket.c | 83 +++++++++++++++++++++++-----------------------------
 1 file changed, 37 insertions(+), 46 deletions(-)

diff --git a/lib/socket.c b/lib/socket.c
index 71f5a511c..ab08eebc2 100644
--- a/lib/socket.c
+++ b/lib/socket.c
@@ -212,70 +212,61 @@ int socket_read(struct node *n, struct sample *smps[], unsigned cnt)
 {
 	struct socket *s = n->_vd;
 
-	int samples, ret, received, smp_count;
+	int samples, ret, received;
 	ssize_t bytes;
 
-	if (s->header == SOCKET_HEADER_GTNET_SKT)
-		smp_count = cnt;
-	else
-		smp_count = 2*cnt;
-
-	struct msg msgs[cnt];
-	struct msg hdr;
-
-	float sample_value;
-	struct iovec iov[smp_count];
-	struct msghdr mhdr = {
-		.msg_iov = iov
-	};
-
 	if (s->header == SOCKET_HEADER_GTNET_SKT) {
-		bytes = recv(s->sd, &sample_value, SAMPLE_DATA_LEN(1), MSG_PEEK | MSG_TRUNC);
-		if (bytes < sizeof(float) || bytes % 4 != 0) {
-			warn("Packet size is invalid");
+		if (cnt < 1)
+			return 0;
+
+		/* The GTNETv2-SKT protocol send every sample in a single packet.
+		 * socket_read() receives a single packet. */
+		struct sample *smp = smps[0];
+
+		/* Receive next sample */
+		bytes = recv(s->sd, &smp->values[0], SAMPLE_DATA_LEN(smp->length), MSG_PEEK | MSG_TRUNC);
+		if (bytes == 0)
+			error("Remote node %s closed the connection", node_name(n)); /** @todo Should we really hard fail here? */
+		else if (bytes < 0)
+			serror("Failed recv from node %s", node_name(n));
+		else if (bytes % 4 != 0) {
+			warn("Packet size is invalid. Must be multiple of 4 bytes.");
+			recv(s->sd, NULL, 0, 0); /* empty receive buffer */
 			return -1;
 		}
 
-		samples = bytes / sizeof(sample_value);
+		received = bytes / sizeof(smp->values[0]);
+		if (received > smp->length) {
+			warn("Node %s received more samples than supported. Dropping %u samples", node_name(n), received - smp->length);
+			received = smp->length;
+		}
 
-		if (samples > cnt) {
-			warn("Received more samples than supported. Dropping %u samples", samples - cnt);
-			samples = cnt;
-		}
-		/* We add one value per sample */
-		for (int i = 0; i < samples; i++) {
-			iov[i].iov_base = SAMPLE_DATA_OFFSET(smps[i]);
-			iov[i].iov_len  = SAMPLE_DATA_LEN(1);			/** values per sample is 1 while reading */
-			mhdr.msg_iovlen += 1;
-		}
-		/* Receive message from socket */
-		bytes = recvmsg(s->sd, &mhdr, 0);
-		if (bytes == 0)
-			error("Remote node %s closed the connection", node_name(n));
-		else if (bytes < 0)
-			serror("Failed recv from node %s", node_name(n));
-
-		for (received = 0; received < samples; received++) {
-			struct sample *smp = smps[received];
-			smp->length = 1;
-			/** @todo see if s->sequence value is needed */
-			/** @todo see if s->ts.origin and smp->ts.received value is needed, essentially requiring a header */
-		}
+		/** @todo Should we generate sequence no here manually?
+		 *        Or maybe optinally use the first data value as a sequence?
+		 *        However this would require the RTDS model to be changed. */
+		smp->sequence = 0;
+		smp->length = received;
 	}
-
 	else {
+		struct msg msgs[cnt];
+		struct msg hdr;
+		struct iovec iov[2*cnt];
+		struct msghdr mhdr = {
+			.msg_iov = iov
+		};
+
 		/* Peak into message header of the first sample and to get total packet size. */
 		bytes = recv(s->sd, &hdr, sizeof(struct msg), MSG_PEEK | MSG_TRUNC);
 		if (bytes < sizeof(struct msg) || bytes % 4 != 0) {
-			warn("Packet size is invalid");
-			recv(s->sd, &hdr, sizeof(struct msg), 0);
+			warn("Packet size is invalid. Must be multiple of 4 bytes.");
+			recv(s->sd, &hdr, sizeof(struct msg), 0); /* empty receive buffer */
 			return -1;
 		}
 
 		ret = msg_verify(&hdr);
 		if (ret) {
 			warn("Invalid message received: reason=%d, bytes=%zd", ret, bytes);
-			recv(s->sd, &hdr, sizeof(struct msg), 0);
+			recv(s->sd, NULL, 0, 0); /* empty receive buffer */
 			return -1;
 		}