3 files changed, 32 insertions, 3 deletions

diff --git a/sys/netinet/libalias/alias.h b/sys/netinet/libalias/alias.h
index 671241212799..91351a9eb8b9 100644
--- a/sys/netinet/libalias/alias.h
+++ b/sys/netinet/libalias/alias.h
@@ -86,6 +86,7 @@ struct alias_link;
 /* Initialization and control functions. */
 struct libalias *LibAliasInit(struct libalias *);
 void		LibAliasSetAddress(struct libalias *, struct in_addr _addr);
+void		LibAliasSetAliasPortRange(struct libalias *la, u_short port_low, u_short port_hi);
 void		LibAliasSetFWBase(struct libalias *, unsigned int _base, unsigned int _num);
 void		LibAliasSetSkinnyPort(struct libalias *, unsigned int _port);
 unsigned int
diff --git a/sys/netinet/libalias/alias_db.c b/sys/netinet/libalias/alias_db.c
index 8da9a7fe683a..1f85a606b2d5 100644
--- a/sys/netinet/libalias/alias_db.c
+++ b/sys/netinet/libalias/alias_db.c
@@ -595,6 +595,11 @@ GetNewPort(struct libalias *la, struct alias_link *lnk, int alias_port_param)
 			 */
 			port_net = lnk->src_port;
 			port_sys = ntohs(port_net);
+		} else if (la->aliasPortLower) {
+			/* First trial is a random port in the aliasing range. */
+			port_sys = la->aliasPortLower +
+			    (arc4random() % la->aliasPortLength);
+			port_net = htons(port_sys);
 		} else {
 			/* First trial and all subsequent are random. */
 			port_sys = arc4random() & ALIAS_PORT_MASK;
@@ -647,9 +652,15 @@ GetNewPort(struct libalias *la, struct alias_link *lnk, int alias_port_param)
 			}
 #endif
 		}
-		port_sys = arc4random() & ALIAS_PORT_MASK;
-		port_sys += ALIAS_PORT_BASE;
-		port_net = htons(port_sys);
+		if (la->aliasPortLower) {
+			port_sys = la->aliasPortLower +
+			    (arc4random() % la->aliasPortLength);
+			port_net = htons(port_sys);
+		} else {
+			port_sys = arc4random() & ALIAS_PORT_MASK;
+			port_sys += ALIAS_PORT_BASE;
+			port_net = htons(port_sys);
+		}
 	}
 
 #ifdef LIBALIAS_DEBUG
@@ -2381,6 +2392,19 @@ LibAliasSetAddress(struct libalias *la, struct in_addr addr)
 	LIBALIAS_UNLOCK(la);
 }
 
+
+void
+LibAliasSetAliasPortRange(struct libalias *la, u_short port_low,
+    u_short port_high)
+{
+
+	LIBALIAS_LOCK(la);
+	la->aliasPortLower = port_low;
+	/* Add 1 to the aliasPortLength as modulo has range of 1 to n-1 */
+	la->aliasPortLength = port_high - port_low + 1;
+	LIBALIAS_UNLOCK(la);
+}
+
 void
 LibAliasSetTarget(struct libalias *la, struct in_addr target_addr)
 {
diff --git a/sys/netinet/libalias/alias_local.h b/sys/netinet/libalias/alias_local.h
index 5919851a4019..ba128638c1fe 100644
--- a/sys/netinet/libalias/alias_local.h
+++ b/sys/netinet/libalias/alias_local.h
@@ -163,6 +163,10 @@ struct libalias {
 	struct in_addr	true_addr;	/* in network byte order. */
 	u_short		true_port;	/* in host byte order. */
 
+	/* Port ranges for aliasing. */
+	u_short		aliasPortLower;
+	u_short		aliasPortLength;
+
 	/*
 	 * sctp code support
 	 */