tcp_splice, flow: Add socket to epoll set before connect(), drop assert2025_12_09.c3f1ba7

...otherwise, if we have a real error on connect() (that is, not
EINPROGRESS), we'll return early from tcp_splice_connect() and later
try to fetch the epoll file descriptor:

  ASSERTION FAILED in flow_epollfd (flow.c:362): f->epollid < ((1 << 8) - 1)

which is still (correctly) EPOLLFD_ID_INVALID.

Replace the ASSERT() in flow_epollfd() with a warning, as it looks
like there might be harmless cases where the socket is not in the
epoll set yet, and we'll just crash for nothing. We can turn this back
to an ASSERT() once we audit these paths in more detail.

Link: https://bodhi.fedoraproject.org/updates/FEDORA-2025-93b4eb64c3#comment-4473411
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

2 files changed, 8 insertions, 3 deletions

diff --git a/flow.c b/flow.c
index 8d72965..4f53486 100644
--- a/flow.c
+++ b/flow.c
@@ -359,7 +359,12 @@ bool flow_in_epoll(const struct flow_common *f)
  */
 int flow_epollfd(const struct flow_common *f)
 {
-	ASSERT(f->epollid < EPOLLFD_ID_MAX);
+	if (f->epollid >= EPOLLFD_ID_MAX) {
+		flow_log_(f, true, LOG_WARNING,
+			  "Invalid epollid %i for flow, assuming default",
+			  f->epollid);
+		return epoll_id_to_fd[EPOLLFD_ID_DEFAULT];
+	}
 
 	return epoll_id_to_fd[f->epollid];
 }
diff --git a/tcp_splice.c b/tcp_splice.c
index 717766a..4405224 100644
--- a/tcp_splice.c
+++ b/tcp_splice.c
@@ -381,14 +381,14 @@ static int tcp_splice_connect(const struct ctx *c, struct tcp_splice_conn *conn)
 
 	pif_sockaddr(c, &sa, tgtpif, &tgt->eaddr, tgt->eport);
 
+	conn_event(c, conn, SPLICE_CONNECT);
+
 	if (connect(conn->s[1], &sa.sa, socklen_inany(&sa))) {
 		if (errno != EINPROGRESS) {
 			flow_trace(conn, "Couldn't connect socket for splice: %s",
 				   strerror_(errno));
 			return -errno;
 		}
-
-		conn_event(c, conn, SPLICE_CONNECT);
 	} else {
 		conn_event(c, conn, SPLICE_ESTABLISHED);
 		return tcp_splice_connect_finish(c, conn);