diff --git a/xdmcp.c b/xdmcp.c

index 7c91d1e..66a5e0f 100644

--- a/xdmcp.c

+++ b/xdmcp.c

@@ -791,8 +791,8 @@ forward_respond (

{

struct sockaddr_in6 in6_addr;

- if (clientAddress.length != 16 ||

- clientPort.length != 2)

+ if ((clientAddress.length != 16 && clientAddress.length != 4) ||

+ (clientPort.length != 2))

{

goto badAddress;

}

@@ -801,7 +801,24 @@ forward_respond (

in6_addr.sin6_len = sizeof(in6_addr);

# endif

in6_addr.sin6_family = AF_INET6;

- memmove(&in6_addr.sin6_addr,clientAddress.data,clientAddress.length);

+ if (clientAddress.length == 16) {

+ memmove(in6_addr.sin6_addr.s6_addr, clientAddress.data, 16);

+ } else {

+ /* If the client wants to forward the xdm server to an

+ ipv4 hosts it sends an ipv4 address in the forward

+ packet. On dual-stack hosts the packet arrives as a

+ ipv6 packet. To respond to the ipv4 host one has

+ to create an ipv4-mapped address of the form

+

+ ::ffff::xxx.xxx.xxx.xxx

+

+ One example where this is necessary is an ipv4-only

+ thin client that connects to a dual-stacked xdm.

+ */

+ in6_addr.sin6_addr.s6_addr[10] = 0xff;

+ in6_addr.sin6_addr.s6_addr[11] = 0xff;

+ memmove(in6_addr.sin6_addr.s6_addr + 12, clientAddress.data, 4);

+ }

memmove((char *) &in6_addr.sin6_port, clientPort.data, 2);

client = (struct sockaddr *) &in6_addr;

clientlen = sizeof (in6_addr);