tcp: Clarify allowed state for tcp_data_from_tap()

Comments suggest that this should only be called for an ESTABLISHED
connection.  However, it's non-trivial to ascertain that from the actual
control flow in the caller.  Add an ASSERT() to make it very clear that
this is only called in ESTABLISHED state.

In fact, there were some circumstances where it could be called on a CLOSED
connection.  In a sense that is "established", but with that assert this
does require specific (trivial) handling to avoid a spurious abort().

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

1 files changed, 5 insertions, 0 deletions

diff --git a/tcp.c b/tcp.c
index f156287..d82c62e 100644
--- a/tcp.c
+++ b/tcp.c
@@ -2337,6 +2337,11 @@ static void tcp_data_from_tap(struct ctx *c, struct tcp_tap_conn *conn,
 	size_t len;
 	ssize_t n;
 
+	if (conn->events == CLOSED)
+		return;
+
+	ASSERT(conn->events & ESTABLISHED);
+
 	for (i = 0, iov_i = 0; i < (int)p->count; i++) {
 		uint32_t seq, seq_offset, ack_seq;
 		struct tcphdr *th;