tcp_splice: Simplify selection of socket and pipe sides in socket handler

tcp_splice_sock_handler() uses the tcp_splice_dir() helper to select
which of the socket, pipe and counter fields to use depending on which
side of the connection the socket event is coming from.

Now that we are using arrays for the two sides, rather than separate named
fields, we can instead just use a variable indicating the side and use
that to index the arrays whever we need a particular side's field.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 22 insertions, 59 deletions

diff --git a/tcp_splice.c b/tcp_splice.c
index 9f84d4f..a5c1332 100644
--- a/tcp_splice.c
+++ b/tcp_splice.c
@@ -439,29 +439,6 @@ static int tcp_splice_new(const struct ctx *c, struct tcp_splice_conn *conn,
 }
 
 /**
- * tcp_splice_dir() - Set sockets/pipe pointers reflecting flow direction
- * @conn:	Connection pointers
- * @ref_sock:	Socket returned as reference from epoll
- * @reverse:	Reverse direction: @ref_sock is used as destination
- * @from:	Destination socket pointer to set
- * @to:		Source socket pointer to set
- * @pipes:	Pipe set, assigned on return
- */
-static void tcp_splice_dir(struct tcp_splice_conn *conn, int ref_sock,
-			   int reverse, int *from, int *to, int **pipes)
-{
-	if (!reverse) {
-		*from = ref_sock;
-		*to   = (*from == conn->s[0]) ? conn->s[1] : conn->s[0];
-	} else {
-		*to   = ref_sock;
-		*from = (*to   == conn->s[0]) ? conn->s[1] : conn->s[0];
-	}
-
-	*pipes = *from == conn->s[0] ? conn->pipe[0] : conn->pipe[1];
-}
-
-/**
  * tcp_splice_conn_from_sock() - Attempt to init state for a spliced connection
  * @c:		Execution context
  * @ref:	epoll reference of listening socket
@@ -521,8 +498,7 @@ void tcp_splice_sock_handler(struct ctx *c, struct tcp_splice_conn *conn,
 			     int s, uint32_t events)
 {
 	uint8_t lowat_set_flag, lowat_act_flag;
-	int from, to, *pipes, eof, never_read;
-	uint32_t *seq_read, *seq_write;
+	int fromside, eof, never_read;
 
 	if (conn->events == SPLICE_CLOSED)
 		return;
@@ -538,14 +514,15 @@ void tcp_splice_sock_handler(struct ctx *c, struct tcp_splice_conn *conn,
 	}
 
 	if (events & EPOLLOUT) {
-		if (s == conn->s[0])
+		if (s == conn->s[0]) {
 			conn_event(c, conn, ~OUT_WAIT_0);
-		else
+			fromside = 1;
+		} else {
 			conn_event(c, conn, ~OUT_WAIT_1);
-
-		tcp_splice_dir(conn, s, 1, &from, &to, &pipes);
+			fromside = 0;
+		}
 	} else {
-		tcp_splice_dir(conn, s, 0, &from, &to, &pipes);
+		fromside = s == conn->s[0] ? 0 : 1;
 	}
 
 	if (events & EPOLLRDHUP) {
@@ -566,24 +543,16 @@ swap:
 	eof = 0;
 	never_read = 1;
 
-	if (from == conn->s[0]) {
-		seq_read = &conn->read[0];
-		seq_write = &conn->written[0];
-		lowat_set_flag = RCVLOWAT_SET_0;
-		lowat_act_flag = RCVLOWAT_ACT_0;
-	} else {
-		seq_read = &conn->read[1];
-		seq_write = &conn->written[1];
-		lowat_set_flag = RCVLOWAT_SET_1;
-		lowat_act_flag = RCVLOWAT_ACT_1;
-	}
+	lowat_set_flag = fromside == 0 ? RCVLOWAT_SET_0 : RCVLOWAT_SET_1;
+	lowat_act_flag = fromside == 0 ? RCVLOWAT_ACT_0 : RCVLOWAT_ACT_1;
 
 	while (1) {
 		ssize_t readlen, to_write = 0, written;
 		int more = 0;
 
 retry:
-		readlen = splice(from, NULL, pipes[1], NULL, c->tcp.pipe_size,
+		readlen = splice(conn->s[fromside], NULL,
+				 conn->pipe[fromside][1], NULL, c->tcp.pipe_size,
 				 SPLICE_F_MOVE | SPLICE_F_NONBLOCK);
 		trace("TCP (spliced): %li from read-side call", readlen);
 		if (readlen < 0) {
@@ -608,7 +577,8 @@ retry:
 		}
 
 eintr:
-		written = splice(pipes[0], NULL, to, NULL, to_write,
+		written = splice(conn->pipe[fromside][0], NULL,
+				 conn->s[!fromside], NULL, to_write,
 				 SPLICE_F_MOVE | more | SPLICE_F_NONBLOCK);
 		trace("TCP (spliced): %li from write-side call (passed %lu)",
 		      written, to_write);
@@ -622,8 +592,8 @@ eintr:
 			    readlen > (long)c->tcp.pipe_size / 10) {
 				int lowat = c->tcp.pipe_size / 4;
 
-				setsockopt(from, SOL_SOCKET, SO_RCVLOWAT,
-					   &lowat, sizeof(lowat));
+				setsockopt(conn->s[fromside], SOL_SOCKET,
+					   SO_RCVLOWAT, &lowat, sizeof(lowat));
 
 				conn_flag(c, conn, lowat_set_flag);
 				conn_flag(c, conn, lowat_act_flag);
@@ -632,8 +602,8 @@ eintr:
 			break;
 		}
 
-		*seq_read  += readlen > 0 ? readlen : 0;
-		*seq_write += written > 0 ? written : 0;
+		conn->read[fromside]    += readlen > 0 ? readlen : 0;
+		conn->written[fromside] += written > 0 ? written : 0;
 
 		if (written < 0) {
 			if (errno == EINTR)
@@ -645,10 +615,8 @@ eintr:
 			if (never_read)
 				break;
 
-			if (to == conn->s[0])
-				conn_event(c, conn, OUT_WAIT_0);
-			else
-				conn_event(c, conn, OUT_WAIT_1);
+			conn_event(c, conn,
+				   fromside == 0 ? OUT_WAIT_1 : OUT_WAIT_0);
 			break;
 		}
 
@@ -665,14 +633,14 @@ eintr:
 	}
 
 	if ((conn->events & FIN_RCVD_0) && !(conn->events & FIN_SENT_1)) {
-		if (*seq_read == *seq_write && eof) {
+		if (conn->read[fromside] == conn->written[fromside] && eof) {
 			shutdown(conn->s[1], SHUT_WR);
 			conn_event(c, conn, FIN_SENT_1);
 		}
 	}
 
 	if ((conn->events & FIN_RCVD_1) && !(conn->events & FIN_SENT_0)) {
-		if (*seq_read == *seq_write && eof) {
+		if (conn->read[fromside] == conn->written[fromside] && eof) {
 			shutdown(conn->s[0], SHUT_WR);
 			conn_event(c, conn, FIN_SENT_0);
 		}
@@ -684,12 +652,7 @@ eintr:
 	if ((events & (EPOLLIN | EPOLLOUT)) == (EPOLLIN | EPOLLOUT)) {
 		events = EPOLLIN;
 
-		SWAP(from, to);
-		if (pipes == conn->pipe[0])
-			pipes = conn->pipe[1];
-		else
-			pipes = conn->pipe[0];
-
+		fromside = !fromside;
 		goto swap;
 	}