Load Sharing using IP Network Address Translation (RFC 2391, LSNAT).

LSNAT links are first created by either PacketAliasRedirectPort() or
PacketAliasRedirectAddress() and then set up by one or more calls to
PacketAliasAddServer().

1 files changed, 85 insertions, 27 deletions

diff --git a/lib/libalias/alias_db.c b/lib/libalias/alias_db.c
index 431a757..bc020f3 100644
--- a/lib/libalias/alias_db.c
+++ b/lib/libalias/alias_db.c
@@ -237,6 +237,13 @@ struct tcp_dat
     int fwhole;             /* Which firewall record is used for this hole? */
 };
 
+struct server              /* LSNAT server pool (circular list) */
+{
+    struct in_addr addr;
+    u_short port;
+    struct server *next;
+};
+
 struct alias_link                /* Main data structure */
 {
     struct in_addr src_addr;     /* Address and port information        */
@@ -247,6 +254,7 @@ struct alias_link                /* Main data structure */
     u_short dst_port;
     u_short alias_port;
     u_short proxy_port;
+    struct server *server;
 
     int link_type;               /* Type of link: TCP, UDP, ICMP, PPTP, frag */
 
@@ -778,6 +786,17 @@ DeleteLink(struct alias_link *link)
     ClearFWHole(link);
 #endif
 
+/* Free memory allocated for LSNAT server pool */
+    if (link->server != NULL) {
+	struct server *head, *curr, *next;
+
+	head = curr = link->server;
+	do {
+	    next = curr->next;
+	    free(curr);
+	} while ((curr = next) != head);
+    }
+
 /* Adjust output table pointers */
     link_last = link->last_out;
     link_next = link->next_out;
@@ -871,6 +890,7 @@ AddLink(struct in_addr  src_addr,
         link->src_port          = src_port;
         link->dst_port          = dst_port;
         link->proxy_port        = 0;
+        link->server            = NULL;
         link->link_type         = link_type;
         link->sockfd            = -1;
         link->flags             = 0;
@@ -1044,6 +1064,7 @@ _FindLinkOut(struct in_addr src_addr,
     while (link != NULL)
     {
         if (link->src_addr.s_addr == src_addr.s_addr
+         && link->server          == NULL
          && link->dst_addr.s_addr == dst_addr.s_addr
          && link->dst_port        == dst_port
          && link->src_port        == src_port
@@ -1207,39 +1228,39 @@ _FindLinkIn(struct in_addr dst_addr,
     if (link_fully_specified != NULL)
     {
         link_fully_specified->timestamp = timeStamp;
-        return link_fully_specified;
+        link = link_fully_specified;
     }
     else if (link_unknown_dst_port != NULL)
-    {
-        return replace_partial_links
-          ? ReLink(link_unknown_dst_port,
-                   link_unknown_dst_port->src_addr, dst_addr, alias_addr,
-                   link_unknown_dst_port->src_port, dst_port, alias_port,
-                   link_type)
-          : link_unknown_dst_port;
-    }
+	link = link_unknown_dst_port;
     else if (link_unknown_dst_addr != NULL)
-    {
-        return replace_partial_links
-          ? ReLink(link_unknown_dst_addr,
-                   link_unknown_dst_addr->src_addr, dst_addr, alias_addr,
-                   link_unknown_dst_addr->src_port, dst_port, alias_port,
-                   link_type)
-          : link_unknown_dst_addr;
-    }
+	link = link_unknown_dst_addr;
     else if (link_unknown_all != NULL)
-    {
-        return replace_partial_links
-          ? ReLink(link_unknown_all,
-                   link_unknown_all->src_addr, dst_addr, alias_addr,
-                   link_unknown_all->src_port, dst_port, alias_port,
-                   link_type)
-          : link_unknown_all;
-    }
+	link = link_unknown_all;
     else
+        return (NULL);
+
+    if (replace_partial_links &&
+	(link->flags & LINK_PARTIALLY_SPECIFIED || link->server != NULL))
     {
-        return(NULL);
+	struct in_addr src_addr;
+	u_short src_port;
+
+	if (link->server != NULL) {		/* LSNAT link */
+	    src_addr = link->server->addr;
+	    src_port = link->server->port;
+	    link->server = link->server->next;
+	} else {
+	    src_addr = link->src_addr;
+	    src_port = link->src_port;
+	}
+
+	link = ReLink(link,
+		      src_addr, dst_addr, alias_addr,
+		      src_port, dst_port, alias_port,
+		      link_type);
     }
+
+    return (link);
 }
 
 static struct alias_link *
@@ -1527,7 +1548,13 @@ FindOriginalAddress(struct in_addr alias_addr)
     }
     else
     {
-        if (link->src_addr.s_addr == INADDR_ANY)
+	if (link->server != NULL) {		/* LSNAT link */
+	    struct in_addr src_addr;
+
+	    src_addr = link->server->addr;
+	    link->server = link->server->next;
+	    return (src_addr);
+        } else if (link->src_addr.s_addr == INADDR_ANY)
             return aliasAddress;
         else
             return link->src_addr;
@@ -2035,6 +2062,7 @@ UninitPacketAliasLog(void)
 -- "outside world" means other than alias*.c routines --
 
     PacketAliasRedirectPort()
+    PacketAliasAddServer()
     PacketAliasRedirectPptp()
     PacketAliasRedirectAddr()
     PacketAliasRedirectDelete()
@@ -2092,6 +2120,36 @@ PacketAliasRedirectPort(struct in_addr src_addr,   u_short src_port,
     return link;
 }
 
+/* Add server to the pool of servers */
+int
+PacketAliasAddServer(struct alias_link *link, struct in_addr addr, u_short port)
+{
+    struct server *server;
+
+    server = malloc(sizeof(struct server));
+
+    if (server != NULL) {
+	struct server *head;
+
+	server->addr = addr;
+	server->port = port;
+
+	head = link->server;
+	if (head == NULL)
+	    server->next = server;
+	else {
+	    struct server *s;
+
+	    for (s = head; s->next != head; s = s->next);
+	    s->next = server;
+	    server->next = head;
+	}
+	link->server = server;
+	return (0);
+    } else
+	return (-1);
+}
+
 /* Translate PPTP packets to a machine on the inside
  * XXX This function is made obsolete by PacketAliasRedirectPptp().
  */