BUG/MEDIUM: servers: Use a refcount for port_range and free it properly

port_range was never freed. That used not to be a problem, but now that
we can dynamically add and remove servers, it becomes one, as that leads
to a memory leak each time a server with a "source" directive is destroyed.
However, just adding a free() is not enough. We have to add a refcount,
because the server is not the only one with a reference to it. We may
also have one in fdinfo, so that we know which port to release when we
finally close the fd.
So add a refcount, and make sure to call port_range_release() when a
server is destroyed.

This should be backported up to 3.0.

include/haproxy/port_range-t.h

@@ -27,6 +27,7 @@
 
 struct port_range {
 	int size, get, put_h, put_t;	/* range size, and get/put positions */
+	int refcount;
 	uint16_t ports[VAR_ARRAY];	/* array of <size> ports, in host byte order */
 };
 

include/haproxy/port_range.h

@@ -28,6 +28,17 @@
 
 #define GET_NEXT_OFF(range, off) ((off) == (range)->size - 1 ? 0 : (off) + 1)
 
+static inline void port_range_release(struct port_range *range)
+{
+	if (range) {
+		int refcount = _HA_ATOMIC_SUB_FETCH(&range->refcount, 1);
+
+		BUG_ON(refcount < 0);
+		if (refcount == 0)
+			free(range);
+	}
+}
+
 /* return an available port from range <range>, or zero if none is left */
 static inline int port_range_alloc_port(struct port_range *range)
 {
@@ -44,6 +55,7 @@ static inline int port_range_alloc_port(struct port_range *range)
 			return 0;
 		ret = range->ports[get];
 	} while (!(_HA_ATOMIC_CAS(&range->get, &get, GET_NEXT_OFF(range, get))));
+	_HA_ATOMIC_INC(&range->refcount);
 	return ret;
 }
 
@@ -77,6 +89,7 @@ static inline void port_range_release_port(struct port_range *range, int port)
 	 * can use that port.
 	 */
 	_HA_ATOMIC_STORE(&range->put_t, GET_NEXT_OFF(range, put));
+	port_range_release(range);
 }
 
 /* return a new initialized port range of N ports. The ports are not
@@ -90,6 +103,7 @@ static inline struct port_range *port_range_alloc_range(int n)
 	if (!ret)
 		return NULL;
 	ret->size = n + 1;
+	ret->refcount = 1;
 	/* Start at the first free element */
 	ret->put_h = ret->put_t = n;
 	return ret;

src/server.c

@@ -3245,6 +3245,7 @@ void srv_free_params(struct server *srv)
 		ha_free(&srv_tlv->fmt_string);
 		ha_free(&srv_tlv);
 	}
+	port_range_release(srv->conn_src.sport_range);
 }
 
 /* Deallocate a server <srv> and its member. <srv> must be allocated. For