If a client sends an ipv4 address to a dual-stacked xdm that is bound to a ipv6
socket in a forward request, then the packet was silently discarded. Now the
address is encapsulated as a ipv4-mapped address and a response is send back.
---
xdmcp.c | 23 ++++++++++++++++++++---
1 files changed, 20 insertions(+), 3 deletions(-)
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);
--
1.6.5.3
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