tcp_splice: Register fds with epoll at flow creation

Register both splice connection sockets with epoll using empty events
(events=0) in tcp_splice_connect(), before initiating the connection.

This allows tcp_splice_epoll_ctl() to always use EPOLL_CTL_MOD, removing
the need to check whether fds are already registered. As a result, the
conditional ADD/MOD logic is no longer needed, simplifying the function.

If the second flow_epoll_set() fails after the first succeeds, we don't
need explicit rollback: tcp_splice_conn_from_sock() sets the CLOSING
flag on error, and conn_flag() handles it by calling epoll_del() for
both sockets.

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

1 files changed, 10 insertions, 10 deletions

diff --git a/tcp_splice.c b/tcp_splice.c
index a7c04ca..cb81e01 100644
--- a/tcp_splice.c
+++ b/tcp_splice.c
@@ -142,20 +142,12 @@ static uint32_t tcp_splice_conn_epoll_events(uint16_t events, unsigned sidei)
 static int tcp_splice_epoll_ctl(struct tcp_splice_conn *conn)
 {
 	uint32_t events[2];
-	int m;
-
-	if (flow_in_epoll(&conn->f)) {
-		m = EPOLL_CTL_MOD;
-	} else {
-		flow_epollid_set(&conn->f, EPOLLFD_ID_DEFAULT);
-		m = EPOLL_CTL_ADD;
-	}
 
 	events[0] = tcp_splice_conn_epoll_events(conn->events, 0);
 	events[1] = tcp_splice_conn_epoll_events(conn->events, 1);
 
-	if (flow_epoll_set(&conn->f, m, events[0], conn->s[0], 0) ||
-	    flow_epoll_set(&conn->f, m, events[1], conn->s[1], 1)) {
+	if (flow_epoll_set(&conn->f, EPOLL_CTL_MOD, events[0], conn->s[0], 0) ||
+	    flow_epoll_set(&conn->f, EPOLL_CTL_MOD, events[1], conn->s[1], 1)) {
 		int ret = -errno;
 		flow_perror(conn, "ERROR on epoll_ctl()");
 		return ret;
@@ -368,6 +360,14 @@ static int tcp_splice_connect(const struct ctx *c, struct tcp_splice_conn *conn)
 
 	pif_sockaddr(c, &sa, tgtpif, &tgt->eaddr, tgt->eport);
 
+	flow_epollid_set(&conn->f, EPOLLFD_ID_DEFAULT);
+	if (flow_epoll_set(&conn->f, EPOLL_CTL_ADD, 0, conn->s[0], 0) ||
+	    flow_epoll_set(&conn->f, EPOLL_CTL_ADD, 0, conn->s[1], 1)) {
+		int ret = -errno;
+		flow_perror(conn, "Cannot register to epollfd");
+		return ret;
+	}
+
 	conn_event(conn, SPLICE_CONNECT);
 
 	if (connect(conn->s[1], &sa.sa, socklen_inany(&sa))) {