Prevent memory drain for long lasting floating sessions

For every float event we generate prefix, which allocates 256 + 64 bytes. That memory is reclaimed when client disconnects, so long lasting and constantly floating sessions drain memory.

As a fix use preallocated buffer inside multi_instance for storing multi_prefix.

Signed-off-by Lev Stipakov <[email protected]...>

---
 src/openvpn/mudp.c  |  4 ++++
 src/openvpn/multi.c | 14 ++++++++++----
 src/openvpn/multi.h |  8 +++++---
 3 files changed, 19 insertions(+), 7 deletions(-)

src/openvpn/mudp.c +4 -0

index 853c08c..3e3f750 100644
@@ -111,6 +111,10 @@ multi_get_create_instance_udp (struct multi_context *m, bool *floated)
 			      break;
 			    }
 			}
+
+		      /* should not really end up here, since multi_create_instance returns null
+		       * if amount of clients exceeds max_clients */
+		      ASSERT(i < m->max_clients);
 		    }
 		}
 	      else

src/openvpn/multi.c +10 -4

index 538f4f1..fd0d0fe 100644
@@ -403,7 +403,7 @@ multi_instance_string (const struct multi_instance *mi, bool null, struct gc_are
 {
   if (mi)
     {
-      struct buffer out = alloc_buf_gc (256, gc);
+      struct buffer out = alloc_buf_gc (MULTI_PREFIX_MAX_LENGTH, gc);
       const char *cn = tls_common_name (mi->context.c2.tls_multi, true);
 
       if (cn)

@@ -420,21 +420,27 @@ multi_instance_string (const struct multi_instance *mi, bool null, struct gc_are
 void
 generate_prefix (struct multi_instance *mi)
 {
-  mi->msg_prefix = multi_instance_string (mi, true, &mi->gc);
+  struct gc_arena gc = gc_new();
+  const char *prefix = multi_instance_string (mi, true, &gc);
+  if (prefix)
+    strncpynt(mi->msg_prefix, prefix, sizeof(mi->msg_prefix));
+  else
+    mi->msg_prefix[0] = '\0';
   set_prefix (mi);
+  gc_free(&gc);
 }
 
 void
 ungenerate_prefix (struct multi_instance *mi)
 {
-  mi->msg_prefix = NULL;
+  mi->msg_prefix[0] = '\0';
   set_prefix (mi);
 }
 
 static const char *
 mi_prefix (const struct multi_instance *mi)
 {
-  if (mi && mi->msg_prefix)
+  if (mi && mi->msg_prefix[0])
     return mi->msg_prefix;
   else
     return "UNDEF_I";

src/openvpn/multi.h +5 -3

index ad7f700..32b89d2 100644
@@ -42,6 +42,8 @@
 #include "mtcp.h"
 #include "perf.h"
 
+#define MULTI_PREFIX_MAX_LENGTH 256
+
 /*
  * Walk (don't run) through the routing table,
  * deleting old entries, and possibly multi_instance

@@ -80,7 +82,7 @@ struct multi_instance {
   struct mroute_addr real;      /**< External network address of the
                                  *   remote peer. */
   ifconfig_pool_handle vaddr_handle;
-  const char *msg_prefix;
+  char msg_prefix[MULTI_PREFIX_MAX_LENGTH];
 
   /* queued outgoing data in Server/TCP mode */
   unsigned int tcp_rwflags;

@@ -445,10 +447,10 @@ static inline void
 set_prefix (struct multi_instance *mi)
 {
 #ifdef MULTI_DEBUG_EVENT_LOOP
-  if (mi->msg_prefix)
+  if (mi->msg_prefix[0])
     printf ("[%s]\n", mi->msg_prefix);
 #endif
-  msg_set_prefix (mi->msg_prefix);
+  msg_set_prefix (mi->msg_prefix[0] ? mi->msg_prefix : NULL);
 }
 
 static inline void