tcp, tcp_splice: Avoid double layered dispatch for connected TCP sockets

Currently connected TCP sockets have the same epoll type, whether they're
for a "tap" connection or a spliced connection.  This means that
tcp_sock_handler() has to do a secondary check on the type of the
connection to call the right function.  We can avoid this by adding a new
epoll type and dispatching directly to the right thing.

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

passt.c

@@ -50,6 +50,7 @@
 #include "pasta.h"
 #include "arch.h"
 #include "log.h"
+#include "tcp_splice.h"
 
 #define EPOLL_EVENTS		8
 
@@ -61,6 +62,7 @@ char pkt_buf[PKT_BUF_BYTES]	__attribute__ ((aligned(PAGE_SIZE)));
 
 char *epoll_type_str[] = {
 	[EPOLL_TYPE_TCP]	= "connected TCP socket",
+	[EPOLL_TYPE_TCP_SPLICE]	= "connected spliced TCP socket",
 	[EPOLL_TYPE_TCP_LISTEN]	= "listening TCP socket",
 	[EPOLL_TYPE_TCP_TIMER]	= "TCP timer",
 	[EPOLL_TYPE_UDP]	= "UDP socket",
@@ -373,8 +375,10 @@ loop:
 			pasta_netns_quit_handler(&c, quit_fd);
 			break;
 		case EPOLL_TYPE_TCP:
-			if (!c.no_tcp)
+			tcp_sock_handler(&c, ref, eventmask);
-				tcp_sock_handler(&c, ref, eventmask);
+			break;
+		case EPOLL_TYPE_TCP_SPLICE:
+			tcp_splice_sock_handler(&c, ref, eventmask);
 			break;
 		case EPOLL_TYPE_TCP_LISTEN:
 			tcp_listen_handler(&c, ref, &now);

passt.h

@@ -51,6 +51,8 @@ enum epoll_type {
 	EPOLL_TYPE_NONE = 0,
 	/* Connected TCP sockets */
 	EPOLL_TYPE_TCP,
+	/* Connected TCP sockets (spliced) */
+	EPOLL_TYPE_TCP_SPLICE,
 	/* Listening TCP sockets */
 	EPOLL_TYPE_TCP_LISTEN,
 	/* timerfds used for TCP timers */

tcp.c

@@ -2804,14 +2804,18 @@ void tcp_timer_handler(struct ctx *c, union epoll_ref ref)
 }
 
 /**
- * tcp_tap_sock_handler() - Handle new data from non-spliced socket
+ * tcp_sock_handler() - Handle new data from non-spliced socket
  * @c:		Execution context
- * @conn:	Connection state
+ * @ref:	epoll reference
  * @events:	epoll events bitmap
  */
-static void tcp_tap_sock_handler(struct ctx *c, struct tcp_tap_conn *conn,
+void tcp_sock_handler(struct ctx *c, union epoll_ref ref, uint32_t events)
-				 uint32_t events)
 {
+	struct tcp_tap_conn *conn = CONN(ref.flowside.flow);
+
+	ASSERT(conn->f.type == FLOW_TCP);
+	ASSERT(ref.flowside.side == SOCKSIDE);
+
 	if (conn->events == CLOSED)
 		return;
 
@@ -2858,30 +2862,6 @@ static void tcp_tap_sock_handler(struct ctx *c, struct tcp_tap_conn *conn,
 	}
 }
 
-/**
- * tcp_sock_handler() - Handle new data from socket, or timerfd event
- * @c:		Execution context
- * @ref:	epoll reference
- * @events:	epoll events bitmap
- */
-void tcp_sock_handler(struct ctx *c, union epoll_ref ref, uint32_t events)
-{
-	union flow *flow = FLOW(ref.flowside.flow);
-
-	switch (flow->f.type) {
-	case FLOW_TCP:
-		tcp_tap_sock_handler(c, &flow->tcp, events);
-		break;
-	case FLOW_TCP_SPLICE:
-		tcp_splice_sock_handler(c, &flow->tcp_splice, ref.flowside.side,
-					events);
-		break;
-	default:
-		die("Unexpected %s in tcp_sock_handler_compact()",
-		    FLOW_TYPE(&flow->f));
-	}
-}
-
 /**
  * tcp_sock_init_af() - Initialise listening socket for a given af and port
  * @c:		Execution context

tcp_splice.c

@@ -127,9 +127,9 @@ static int tcp_splice_epoll_ctl(const struct ctx *c,
 {
 	int m = conn->in_epoll ? EPOLL_CTL_MOD : EPOLL_CTL_ADD;
 	const union epoll_ref ref[SIDES] = {
-		{ .type = EPOLL_TYPE_TCP, .fd = conn->s[0],
+		{ .type = EPOLL_TYPE_TCP_SPLICE, .fd = conn->s[0],
 		  .flowside = FLOW_SIDX(conn, 0) },
-		{ .type = EPOLL_TYPE_TCP, .fd = conn->s[1],
+		{ .type = EPOLL_TYPE_TCP_SPLICE, .fd = conn->s[1],
 		  .flowside = FLOW_SIDX(conn, 1) }
 	};
 	struct epoll_event ev[SIDES] = { { .data.u64 = ref[0].u64 },
@@ -484,18 +484,20 @@ bool tcp_splice_conn_from_sock(const struct ctx *c,
 /**
  * tcp_splice_sock_handler() - Handler for socket mapped to spliced connection
  * @c:		Execution context
- * @conn:	Connection state
+ * @ref:	epoll reference
- * @side:	Side of the connection on which an event has occurred
  * @events:	epoll events bitmap
  *
  * #syscalls:pasta splice
  */
-void tcp_splice_sock_handler(struct ctx *c, struct tcp_splice_conn *conn,
+void tcp_splice_sock_handler(struct ctx *c, union epoll_ref ref,
-			     int side, uint32_t events)
+			     uint32_t events)
 {
+	struct tcp_splice_conn *conn = CONN(ref.flowside.flow);
+	unsigned side = ref.flowside.side, fromside;
 	uint8_t lowat_set_flag, lowat_act_flag;
 	int eof, never_read;
-	unsigned fromside;
+
+	ASSERT(conn->f.type == FLOW_TCP_SPLICE);
 
 	if (conn->events == SPLICE_CLOSED)
 		return;

tcp_splice.h

@@ -8,8 +8,8 @@
 
 struct tcp_splice_conn;
 
-void tcp_splice_sock_handler(struct ctx *c, struct tcp_splice_conn *conn,
+void tcp_splice_sock_handler(struct ctx *c, union epoll_ref ref,
-			     int side, uint32_t events);
+			     uint32_t events);
 bool tcp_splice_conn_from_sock(const struct ctx *c,
 			       union tcp_listen_epoll_ref ref,
 			       struct tcp_splice_conn *conn, int s,