From 0075014c4075d10d2cc0fba2bd2052cde4534272 Mon Sep 17 00:00:00 2001
From: Heikki Hannikainen <hessu@hes.iki.fi>
Date: Sun, 23 Oct 2022 13:43:18 +0300
Subject: [PATCH] sctp: Buffer outgoing data, similar to TCP

Instead of sending one APRS-IS line per SCTP message, combine multiple
messages in a single SCTP message. This reduces the amount of system
calls a lot and improves eventual DTLS performance.
---
 src/sctp.c   | 56 +++++++++++++++++++++++++++++++++-------------------
 src/worker.c |  4 ++--
 src/worker.h |  1 +
 3 files changed, 39 insertions(+), 22 deletions(-)

diff --git a/src/sctp.c b/src/sctp.c
index df3b4ce..db14e7e 100644
--- a/src/sctp.c
+++ b/src/sctp.c
@@ -245,8 +245,6 @@ int sctp_readable(struct worker_t *self, struct client_t *c)
 	}
 	
 	//hlog_packet(LOG_DEBUG, iov.iov_base, e, "sctp_readable: got data: ");
-	c->ibuf[e++] = '\r';
-	c->ibuf[e++] = '\n';
 	
 	return client_postread(self, c, e);
 }
@@ -268,27 +266,45 @@ int sctp_writable(struct worker_t *self, struct client_t *c)
 
 int sctp_client_write(struct worker_t *self, struct client_t *c, char *p, int len)
 {
-	//hlog_packet(LOG_DEBUG, p, len, "client_write_sctp %d bytes: ", len);
+	//hlog_packet(LOG_DEBUG, p, len, "%s/%s: client_write_sctp %d bytes: ", c->addr_rem, c->username, len);
 	
-	if (len == 0)
-		return 0;
-		
-	clientaccount_add( c, IPPROTO_SCTP, 0, 0, len, 0, 0, 0);
-	
-	int i = send(c->fd, p, len-2, 0);
-	
-	if (i < 0) {
-		hlog(LOG_ERR, "SCTP transmit error to fd %d / %s: %s",
-			c->fd, c->addr_rem, strerror(errno));
-	} else if (i != len -2) {
-		hlog(LOG_ERR, "SCTP transmit incomplete to fd %d / %s: wrote %d of %d bytes, errno: %s",
-			c->fd, c->addr_rem, i, len-2, strerror(errno));
-	} else {
-		//hlog(LOG_DEBUG, "SCTP transmit ok to %s: %d bytes", c->addr_rem, i);
-		c->obuf_wtime = tick;
+	if (len > 0) {
+		c->obuf_writes++;
+		if (client_buffer_outgoing_data(self, c, p, len) == -12)
+			return -12;
+		clientaccount_add( c, IPPROTO_SCTP, 0, 0, len, 0, 0, 0);
 	}
 	
-	return i;
+	/* Is it over the flush size ? */
+	if (c->obuf_end > c->obuf_flushsize || ((len == 0) && (c->obuf_end > c->obuf_start))) {
+		int to_send = c->obuf_end - c->obuf_start;
+		int i = send(c->fd, c->obuf + c->obuf_start, to_send, 0);
+		
+		if (i < 0) {
+			hlog(LOG_ERR, "%s/%s: SCTP transmit error to fd %d: %s",
+				c->addr_rem, c->username, c->fd, strerror(errno));
+			client_close(self, c, errno);
+			return -9;
+		} else if (i != to_send) {
+			// Incomplete write with SCTP is not great, as we might not have ordered delivery.
+			hlog(LOG_ERR, "%s/%s: SCTP transmit incomplete to fd %d: wrote %d of %d bytes, errno: %s",
+				c->addr_rem, c->username, c->fd, i, to_send, strerror(errno));
+			client_close(self, c, errno);
+			return -9;
+		} else {
+			//hlog(LOG_DEBUG, "%s/%s: SCTP transmit ok: %d bytes", c->addr_rem, c->username, i);
+		}
+		c->obuf_start += i;
+		c->obuf_wtime = tick;
+	}
+
+	/* All done ? */
+	if (c->obuf_start >= c->obuf_end) {
+		hlog(LOG_DEBUG, "%s/%s: client_write obuf empty", c->addr_rem, c->username, c->addr_rem);
+		c->obuf_start = 0;
+		c->obuf_end   = 0;
+	}
+	return len;
 }
 
 
diff --git a/src/worker.c b/src/worker.c
index d40ec2e..354c9c8 100644
--- a/src/worker.c
+++ b/src/worker.c
@@ -960,7 +960,7 @@ static char *client_buffer_outgoing_allocate(struct client_t *c, int len)
 	return c->obuf + c->obuf_end;
 }
 
-static int client_buffer_outgoing_data(struct worker_t *self, struct client_t *c, char *p, int len)
+int client_buffer_outgoing_data(struct worker_t *self, struct client_t *c, char *p, int len)
 {
 	char *buf_tail = client_buffer_outgoing_allocate(c, len);
 	
@@ -1662,7 +1662,7 @@ static void send_keepalives(struct worker_t *self)
 			c->obuf_flushsize = flushlevel;
 		} else {
 			/* just fush if there was anything to write */
-			if (c->ai_protocol == IPPROTO_TCP) {
+			if (c->ai_protocol == IPPROTO_TCP || c->ai_protocol == IPPROTO_SCTP) {
 				rc = c->write(self, c, buf, 0);
 				if (rc < -2) continue; // destroyed..
 			}
diff --git a/src/worker.h b/src/worker.h
index ee31528..0eddcf6 100644
--- a/src/worker.h
+++ b/src/worker.h
@@ -491,6 +491,7 @@ extern void pbuf_dump(FILE *fp);
 extern void pbuf_dupe_dump(FILE *fp);
 
 extern int client_postread(struct worker_t *self, struct client_t *c, int r);
+extern int client_buffer_outgoing_data(struct worker_t *self, struct client_t *c, char *p, int len);
 
 extern int client_printf(struct worker_t *self, struct client_t *c, const char *fmt, ...);
 extern int client_write(struct worker_t *self, struct client_t *c, char *p, int len);