epmd: Support 32-bit creation values in local node

* Increase distribution version from 5 to 6
* Introduce new ALIVE2_X_RESP with 32-bit creation
  as reply to ALIVE2_REQ when sender dist version >= 6
* Still reply old ALIVE2_RESP with tiny creation 1..3
  if sender dist version < 6.

3 files changed, 58 insertions, 40 deletions

diff --git a/erts/epmd/src/epmd.h b/erts/epmd/src/epmd.h
index cffcd4ae7a..7332294d3d 100644
--- a/erts/epmd/src/epmd.h
+++ b/erts/epmd/src/epmd.h
@@ -26,6 +26,7 @@
 #define EPMD_ALIVE2_REQ 'x'
 #define EPMD_PORT2_REQ 'z'
 #define EPMD_ALIVE2_RESP 'y'
+#define EPMD_ALIVE2_X_RESP 'v'
 #define EPMD_PORT2_RESP 'w'
 #define EPMD_NAMES_REQ 'n'
 
diff --git a/erts/epmd/src/epmd_int.h b/erts/epmd/src/epmd_int.h
index ed9bbdb8cd..a5156a142e 100644
--- a/erts/epmd/src/epmd_int.h
+++ b/erts/epmd/src/epmd_int.h
@@ -277,6 +277,12 @@ static const struct in6_addr in6addr_loopback =
 #define put_int16(i, s) {((unsigned char*)(s))[0] = ((i) >> 8) & 0xff; \
                         ((unsigned char*)(s))[1] = (i)         & 0xff;}
 
+#define put_int32(i, s) do {((char*)(s))[0] = (char)((i) >> 24) & 0xff;   \
+                            ((char*)(s))[1] = (char)((i) >> 16) & 0xff;   \
+                            ((char*)(s))[2] = (char)((i) >> 8)  & 0xff;   \
+                            ((char*)(s))[3] = (char)(i)         & 0xff;} \
+                        while (0)
+
 #if defined(__GNUC__)
 #  define EPMD_INLINE __inline__
 #elif defined(__WIN32__)
@@ -307,10 +313,10 @@ struct enode {
   int fd;			/* The socket in use */
   unsigned short port;		/* Port number of Erlang node */
   char symname[MAXSYMLEN+1];	/* Name of the Erlang node */
-  short creation;		/* Started as a random number 1..3 */
+  unsigned int cr_counter;	/* Used to generate 'creation' numbers */
   char nodetype;                /* 77 = normal erlang node 72 = hidden (c-node */
   char protocol;                /* 0 = tcp/ipv4 */
-  unsigned short highvsn;       /* 0 = OTP-R3 erts-4.6.x, 1 = OTP-R4 erts-4.7.x*/
+  unsigned short highvsn;       /* 5: creation=1..3, 6: creation=1..(2^32-1)*/
   unsigned short lowvsn;
   int extralen;
   char extra[MAXSYMLEN+1];
diff --git a/erts/epmd/src/epmd_srv.c b/erts/epmd/src/epmd_srv.c
index 1f2326d241..633ec71e5f 100644
--- a/erts/epmd/src/epmd_srv.c
+++ b/erts/epmd/src/epmd_srv.c
@@ -665,6 +665,21 @@ static int do_accept(EpmdVars *g,int listensock)
     return conn_open(g,msgsock);
 }
 
+static void bump_creation(Node* node)
+{
+    if (++node->cr_counter == 0)
+        node->cr_counter = 1;
+}
+static unsigned int get_creation(Node* node)
+{
+    if (node->highvsn >= 6) {
+        return node->cr_counter;  /* 1..(2^32-1)*/
+    }
+    else {
+        return (node->cr_counter - 1) % 3 + 1;   /* 1..3 */
+    }
+}
+
 /* buf is actually one byte larger than bsize,
    giving place for null termination */
 static void do_request(g, fd, s, buf, bsize)
@@ -706,8 +721,10 @@ static void do_request(g, fd, s, buf, bsize)
 	unsigned char protocol;
 	unsigned short highvsn;
 	unsigned short lowvsn;
+        unsigned int creation;
 	int namelen;
 	int extralen;
+        int replylen;
 	char *name; 
 	char *extra;
 	eport = get_int16(&buf[1]);
@@ -737,15 +754,20 @@ static void do_request(g, fd, s, buf, bsize)
 
 	extra = &buf[11+namelen+2];
 	extra[extralen]='\000';
-	wbuf[0] = EPMD_ALIVE2_RESP;
-	if ((node = node_reg2(g, namelen, name, fd, eport, nodetype, protocol,
-			      highvsn, lowvsn, extralen, extra)) == NULL) {
-	    wbuf[1] = 1; /* error */
-	    put_int16(99, wbuf+2);
-	} else {
-	    wbuf[1] = 0; /* ok */
-	    put_int16(node->creation, wbuf+2);
-	}
+        node = node_reg2(g, namelen, name, fd, eport, nodetype, protocol,
+                         highvsn, lowvsn, extralen, extra);
+        creation = node ? get_creation(node) :  99;
+        wbuf[1] = node ? 0 : 1; /* ok | error */
+        if (highvsn >= 6) {
+            wbuf[0] = EPMD_ALIVE2_X_RESP;
+            put_int32(creation, wbuf+2);
+            replylen = 6;
+        }
+        else {
+            wbuf[0] = EPMD_ALIVE2_RESP;
+            put_int16(creation, wbuf+2);
+            replylen = 4;
+        }
   
 	if (!reply(g, fd, wbuf, replylen))
 	  {
@@ -1200,8 +1222,8 @@ static int node_unreg(EpmdVars *g,char *name)
   for (; node; prev = &node->next, node = node->next)
     if (is_same_str(node->symname, name))
       {
-	dbg_tty_printf(g,1,"unregistering '%s:%d', port %d",
-		       node->symname, node->creation, node->port);
+	dbg_tty_printf(g,1,"unregistering '%s:%u', port %d",
+		       node->symname, get_creation(node), node->port);
 
 	*prev = node->next;	/* Link out from "reg" list */
 
@@ -1235,8 +1257,8 @@ static int node_unreg_sock(EpmdVars *g,int fd)
   for (; node; prev = &node->next, node = node->next)
     if (node->fd == fd)
       {
-	dbg_tty_printf(g,1,"unregistering '%s:%d', port %d",
-		       node->symname, node->creation, node->port);
+	dbg_tty_printf(g,1,"unregistering '%s:%u', port %d",
+		       node->symname, get_creation(node), node->port);
 
 	*prev = node->next;	/* Link out from "reg" list */
 
@@ -1264,19 +1286,8 @@ static int node_unreg_sock(EpmdVars *g,int fd)
 }
 
 /*
- *  Finding a node slot and a (name,creation) name is a bit tricky.
- *  We try in order
- *
- *  1. If the name was used before and we can reuse that slot but use
- *     a new "creation" digit in the range 1..3.
- *
- *  2. We try to find a new unused slot.
- *
- *  3. We try to use an used slot this isn't used any longer.
- *     FIXME: The criteria for *what* slot to steal should be improved.
- *     Perhaps use the oldest or something.
+ * Register a new node
  */
-
 static Node *node_reg2(EpmdVars *g,
 		       int namelen,
 		       char* name,
@@ -1346,7 +1357,7 @@ static Node *node_reg2(EpmdVars *g,
       }
 
   /* Try to find the name in the used queue so that we
-     can change "creation" number 1..3 */
+     can change "creation" number */
 
   prev = NULL;
 
@@ -1375,9 +1386,8 @@ static Node *node_reg2(EpmdVars *g,
 
 	g->nodes.unreg_count--;
 
-	/* When reusing we change the "creation" number 1..3 */
-
-	node->creation = node->creation % 3 + 1;
+	/* When reusing we change the "creation" number */
+	bump_creation(node);
 
 	break;
       }
@@ -1404,7 +1414,8 @@ static Node *node_reg2(EpmdVars *g,
 	      exit(1);
 	    }
 
-	  node->creation = (current_time(g) % 3) + 1; /* "random" 1-3 */
+	  node->cr_counter = current_time(g); /* "random" */
+          bump_creation(node);
 	}
     }
 
@@ -1423,11 +1434,11 @@ static Node *node_reg2(EpmdVars *g,
   select_fd_set(g, fd);
 
   if (highvsn == 0) {
-    dbg_tty_printf(g,1,"registering '%s:%d', port %d",
-		   node->symname, node->creation, node->port);
+    dbg_tty_printf(g,1,"registering '%s:%u', port %d",
+		   node->symname, get_creation(node), node->port);
   } else {
-    dbg_tty_printf(g,1,"registering '%s:%d', port %d",
-		   node->symname, node->creation, node->port);
+    dbg_tty_printf(g,1,"registering '%s:%u', port %d",
+		   node->symname, get_creation(node), node->port);
     dbg_tty_printf(g,1,"type %d proto %d highvsn %d lowvsn %d",
 		   nodetype, protocol, highvsn, lowvsn);
   }      
@@ -1561,8 +1572,8 @@ static void print_names(EpmdVars *g)
 
   for (node = g->nodes.reg; node; node = node->next)
     {
-      fprintf(stderr,"*****     active name     \"%s#%d\" at port %d, fd = %d\r\n",
-	      node->symname, node->creation, node->port, node->fd);
+      fprintf(stderr,"*****     active name     \"%s#%u\" at port %d, fd = %d\r\n",
+	      node->symname, get_creation(node), node->port, node->fd);
       count ++;
     }
 
@@ -1572,8 +1583,8 @@ static void print_names(EpmdVars *g)
 
   for (node = g->nodes.unreg; node; node = node->next)
     {
-      fprintf(stderr,"*****     old/unused name \"%s#%d\"\r\n",
-	      node->symname, node->creation);
+      fprintf(stderr,"*****     old/unused name \"%s#%u\"\r\n",
+	      node->symname, get_creation(node));
       count ++;
     }