flow: Move flow_count from context structure to a global

In general, the passt code is a bit haphazard about what's a true global
variable and what's in the quasi-global 'context structure'.  The
flow_count field is one such example: it's in the context structure,
although it's really part of the same data structure as flowtab[], which
is a genuine global.

Move flow_count to be a regular global to match.  For now it needs to be
public, rather than static, but we expect to be able to change that in
future.

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

flow.c

@@ -26,6 +26,7 @@ static_assert(ARRAY_SIZE(flow_type_str) == FLOW_NUM_TYPES,
 	      "flow_type_str[] doesn't match enum flow_type");
 
 /* Global Flow Table */
+unsigned flow_count;
 union flow flowtab[FLOW_MAX];
 
 /* Last time the flow timers ran */
@@ -54,18 +55,18 @@ void flow_log_(const struct flow_common *f, int pri, const char *fmt, ...)
  * @c:		Execution context
  * @hole:	Pointer to recently closed flow
  */
-void flow_table_compact(struct ctx *c, union flow *hole)
+void flow_table_compact(const struct ctx *c, union flow *hole)
 {
 	union flow *from;
 
-	if (FLOW_IDX(hole) == --c->flow_count) {
+	if (FLOW_IDX(hole) == --flow_count) {
 		debug("flow: table compaction: maximum index was %u (%p)",
 		      FLOW_IDX(hole), (void *)hole);
 		memset(hole, 0, sizeof(*hole));
 		return;
 	}
 
-	from = flowtab + c->flow_count;
+	from = flowtab + flow_count;
 	memcpy(hole, from, sizeof(*hole));
 
 	switch (from->f.type) {
@@ -93,7 +94,7 @@ void flow_table_compact(struct ctx *c, union flow *hole)
  * @c:		Execution context
  * @now:	Current timestamp
  */
-void flow_defer_handler(struct ctx *c, const struct timespec *now)
+void flow_defer_handler(const struct ctx *c, const struct timespec *now)
 {
 	bool timer = false;
 	union flow *flow;
@@ -103,7 +104,7 @@ void flow_defer_handler(struct ctx *c, const struct timespec *now)
 		flow_timer_run = *now;
 	}
 
-	for (flow = flowtab + c->flow_count - 1; flow >= flowtab; flow--) {
+	for (flow = flowtab + flow_count - 1; flow >= flowtab; flow--) {
 		switch (flow->f.type) {
 		case FLOW_TCP:
 			tcp_flow_defer(c, flow);

flow.h

@@ -68,8 +68,8 @@ static inline bool flow_sidx_eq(flow_sidx_t a, flow_sidx_t b)
 
 union flow;
 
-void flow_table_compact(struct ctx *c, union flow *hole);
+void flow_table_compact(const struct ctx *c, union flow *hole);
-void flow_defer_handler(struct ctx *c, const struct timespec *now);
+void flow_defer_handler(const struct ctx *c, const struct timespec *now);
 
 void flow_log_(const struct flow_common *f, int pri, const char *fmt, ...)
 	__attribute__((format(printf, 3, 4)));

flow_table.h

@@ -22,6 +22,7 @@ union flow {
 };
 
 /* Global Flow Table */
+extern unsigned flow_count;
 extern union flow flowtab[];
 
 

passt.h

@@ -224,7 +224,6 @@ struct ip6_ctx {
  * @pasta_conf_ns:	Configure namespace after creating it
  * @no_copy_routes:	Don't copy all routes when configuring target namespace
  * @no_copy_addrs:	Don't copy all addresses when configuring namespace
- * @flow_count:		Number of tracked packet flows (connections etc.)
  * @no_tcp:		Disable TCP operation
  * @tcp:		Context for TCP protocol handler
  * @no_tcp:		Disable UDP operation
@@ -284,8 +283,6 @@ struct ctx {
 	int no_copy_routes;
 	int no_copy_addrs;
 
-	unsigned flow_count;
-
 	int no_tcp;
 	struct tcp_ctx tcp;
 	int no_udp;

tcp.c

@@ -1307,7 +1307,7 @@ static struct tcp_tap_conn *tcp_hash_lookup(const struct ctx *c,
  * @c:		Execution context
  * @flow:	Flow table entry for this connection
  */
-void tcp_flow_defer(struct ctx *c, union flow *flow)
+void tcp_flow_defer(const struct ctx *c, union flow *flow)
 {
 	const struct tcp_tap_conn *conn = &flow->tcp;
 
@@ -1949,7 +1949,7 @@ static void tcp_conn_from_tap(struct ctx *c,
 
 	(void)saddr;
 
-	if (c->flow_count >= FLOW_MAX)
+	if (flow_count >= FLOW_MAX)
 		return;
 
 	if ((s = tcp_conn_pool_sock(pool)) < 0)
@@ -1975,7 +1975,7 @@ static void tcp_conn_from_tap(struct ctx *c,
 		}
 	}
 
-	conn = CONN(c->flow_count++);
+	conn = CONN(flow_count++);
 	conn->f.type = FLOW_TCP;
 	conn->sock = s;
 	conn->timer = -1;
@@ -2724,14 +2724,14 @@ void tcp_listen_handler(struct ctx *c, union epoll_ref ref,
 	union flow *flow;
 	int s;
 
-	if (c->no_tcp || c->flow_count >= FLOW_MAX)
+	if (c->no_tcp || flow_count >= FLOW_MAX)
 		return;
 
 	s = accept4(ref.fd, (struct sockaddr *)&sa, &sl, SOCK_NONBLOCK);
 	if (s < 0)
 		return;
 
-	flow = flowtab + c->flow_count++;
+	flow = flowtab + flow_count++;
 
 	if (c->mode == MODE_PASTA &&
 	    tcp_splice_conn_from_sock(c, ref.tcp_listen, &flow->tcp_splice,

tcp_conn.h

@@ -158,8 +158,8 @@ extern int init_sock_pool6	[TCP_SOCK_POOL_SIZE];
 void tcp_tap_conn_update(const struct ctx *c, struct tcp_tap_conn *old,
 			 struct tcp_tap_conn *new);
 void tcp_splice_conn_update(const struct ctx *c, struct tcp_splice_conn *new);
-void tcp_flow_defer(struct ctx *c, union flow *flow);
+void tcp_flow_defer(const struct ctx *c, union flow *flow);
-void tcp_splice_flow_defer(struct ctx *c, union flow *flow);
+void tcp_splice_flow_defer(const struct ctx *c, union flow *flow);
 void tcp_splice_timer(const struct ctx *c, union flow *flow);
 int tcp_conn_pool_sock(int pool[]);
 int tcp_conn_new_sock(const struct ctx *c, sa_family_t af);

tcp_splice.c

@@ -247,7 +247,7 @@ void tcp_splice_conn_update(const struct ctx *c, struct tcp_splice_conn *new)
  * @c:		Execution context
  * @flow:	Flow table entry for this connection
  */
-void tcp_splice_flow_defer(struct ctx *c, union flow *flow)
+void tcp_splice_flow_defer(const struct ctx *c, union flow *flow)
 {
 	struct tcp_splice_conn *conn = &flow->tcp_splice;
 	unsigned side;