udp, tcp: Tweak handling of no_udp and no_tcp flags

We abort the UDP socket handler if the no_udp flag is set.  But if UDP
was disabled we should never have had a UDP socket to trigger the handler
in the first place.  If we somehow did, ignoring it here isn't really going
to help because aborting without doing anything is likely to lead to an
epoll loop.  The same is the case for the TCP socket and timer handlers and
the no_tcp flag.

Change these checks on the flag to ASSERT()s.  Similarly add ASSERT()s to
several other entry points to the protocol specific code which should never
be called if the protocol is disabled.

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

tcp.c

@@ -2326,7 +2326,9 @@ void tcp_listen_handler(struct ctx *c, union epoll_ref ref,
 	union flow *flow;
 	int s;
 
-	if (c->no_tcp || !(flow = flow_alloc()))
+	ASSERT(!c->no_tcp);
+
+	if (!(flow = flow_alloc()))
 		return;
 
 	s = accept4(ref.fd, &sa.sa, &sl, SOCK_NONBLOCK);
@@ -2379,8 +2381,7 @@ void tcp_timer_handler(struct ctx *c, union epoll_ref ref)
 	struct itimerspec check_armed = { { 0 }, { 0 } };
 	struct tcp_tap_conn *conn = CONN(ref.flow);
 
-	if (c->no_tcp)
+	ASSERT(!c->no_tcp);
-		return;
 
 	/* We don't reset timers on ~ACK_FROM_TAP_DUE, ~ACK_TO_TAP_DUE. If the
 	 * timer is currently armed, this event came from a previous setting,
@@ -2442,6 +2443,7 @@ void tcp_sock_handler(struct ctx *c, union epoll_ref ref, uint32_t events)
 {
 	struct tcp_tap_conn *conn = CONN(ref.flowside.flow);
 
+	ASSERT(!c->no_tcp);
 	ASSERT(conn->f.type == FLOW_TCP);
 	ASSERT(conn->f.pif[ref.flowside.side] != PIF_TAP);
 
@@ -2541,6 +2543,8 @@ int tcp_sock_init(const struct ctx *c, sa_family_t af, const void *addr,
 {
 	int r4 = FD_REF_MAX + 1, r6 = FD_REF_MAX + 1;
 
+	ASSERT(!c->no_tcp);
+
 	if (af == AF_UNSPEC && c->ifi4 && c->ifi6)
 		/* Attempt to get a dual stack socket */
 		if (tcp_sock_init_af(c, AF_UNSPEC, port, addr, ifname) >= 0)
@@ -2618,6 +2622,8 @@ static void tcp_ns_sock_init6(const struct ctx *c, in_port_t port)
  */
 void tcp_ns_sock_init(const struct ctx *c, in_port_t port)
 {
+	ASSERT(!c->no_tcp);
+
 	if (c->ifi4)
 		tcp_ns_sock_init4(c, port);
 	if (c->ifi6)
@@ -2706,6 +2712,8 @@ int tcp_init(struct ctx *c)
 	unsigned int b, optv = 0;
 	int s;
 
+	ASSERT(!c->no_tcp);
+
 	for (b = 0; b < TCP_HASH_TABLE_SIZE; b++)
 		tc_hash[b] = FLOW_SIDX_NONE;
 

udp.c

@@ -749,7 +749,9 @@ static int udp_sock_recv(const struct ctx *c, int s, uint32_t events,
 	 */
 	int n = (c->mode == MODE_PASTA ? 1 : UDP_MAX_FRAMES);
 
-	if (c->no_udp || !(events & EPOLLIN))
+	ASSERT(!c->no_udp);
+
+	if (!(events & EPOLLIN))
 		return 0;
 
 	n = recvmmsg(s, mmh, n, 0, NULL);
@@ -849,10 +851,11 @@ int udp_tap_handler(struct ctx *c, uint8_t pif,
 	in_port_t src, dst;
 	socklen_t sl;
 
-	(void)c;
 	(void)saddr;
 	(void)pif;
 
+	ASSERT(!c->no_udp);
+
 	uh = packet_get(p, idx, 0, sizeof(*uh), NULL);
 	if (!uh)
 		return 1;
@@ -1026,6 +1029,8 @@ int udp_sock_init(const struct ctx *c, int ns, sa_family_t af,
 				     .orig = true, .port = port };
 	int s, r4 = FD_REF_MAX + 1, r6 = FD_REF_MAX + 1;
 
+	ASSERT(!c->no_udp);
+
 	if (ns)
 		uref.pif = PIF_SPLICE;
 	else
@@ -1214,6 +1219,8 @@ void udp_timer(struct ctx *c, const struct timespec *now)
 	unsigned int i;
 	long *word, tmp;
 
+	ASSERT(!c->no_udp);
+
 	if (c->mode == MODE_PASTA) {
 		if (c->udp.fwd_out.f.mode == FWD_AUTO) {
 			fwd_scan_ports_udp(&c->udp.fwd_out.f, &c->udp.fwd_in.f,
@@ -1257,6 +1264,8 @@ v6:
  */
 int udp_init(struct ctx *c)
 {
+	ASSERT(!c->no_udp);
+
 	udp_iov_init(c);
 
 	udp_invert_portmap(&c->udp.fwd_in);