[PATCH] XDMCP: For IPv6 add IPv6 link local addresses to the end of the list

[Egbert Eich]

From: Reinhard Max <max at suse.de>

For IPv6 add a link local addresses to the end of the list passed to
the XDMCP servers.
Reason: for link local addresses the XDMCP server would need to either
know the interface thru a scope identifier or try all available interfaces.
If they don't this address will fail in which case the XDMCP server
could still try the other addresses passed - however some only try
the first address and then give up.
Even if this seems to be the wrong place to fix this it seems to be
easier than fixing all display servers.

Signed-off-by: Egbert Eich <eich at freedesktop.org>
---
 os/access.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/os/access.c b/os/access.c
index 88a44d9..2767fe3 100644
--- a/os/access.c
+++ b/os/access.c
@@ -505,6 +505,12 @@ DefineSelf(int fd)
     unsigned char *addr;
     int family;
     register HOST *host;
+    struct ipv6_locallink {
+        unsigned char *addr;
+        int len;
+    } *linklocal_list = NULL;
+    int num_linklocals = 0;
+    int i;
 
 #ifndef HAVE_GETIFADDRS
 
@@ -602,6 +608,20 @@ DefineSelf(int fd)
             else if (family == FamilyInternet6 &&
                      IN6_IS_ADDR_LOOPBACK((struct in6_addr *) addr))
                 continue;
+            /* Register IPv6 link local addresses (fe80::/10) at the end,
+             * because they need a scope identifier, which we have no way
+             * of telling to the other end.
+             */
+
+            if (family == FamilyInternet6 &&
+                IN6_IS_ADDR_LINKLOCAL((struct in6_addr *)addr)) {
+                linklocal_list = realloc(linklocal_list,
+                                         sizeof(struct ipv6_locallink)
+                                         * ++num_linklocals);
+                linklocal_list[num_linklocals - 1].len = len;
+                linklocal_list[num_linklocals - 1].addr = addr;
+                continue;
+            }
 #endif
 
             /*
@@ -667,6 +687,11 @@ DefineSelf(int fd)
         }
 #endif                          /* XDMCP */
     }
+    for (i = 0; i < num_linklocals; i++)
+        XdmcpRegisterConnection (FamilyInternet6,
+                                 (char *)linklocal_list[i].addr,
+                                 linklocal_list[i].len);
+
     if (bufptr != buf)
         free(bufptr);
 #else                           /* HAVE_GETIFADDRS */
@@ -735,6 +760,19 @@ DefineSelf(int fd)
             else if (family == FamilyInternet6 &&
                      IN6_IS_ADDR_LOOPBACK((struct in6_addr *) addr))
                 continue;
+            /* Register IPv6 link local addresses (fe80::/10) at the end,
+             * because they need a scope identifier, which we have no way
+             * of telling to the other end.
+             */
+            if (family == FamilyInternet6 &&
+                +IN6_IS_ADDR_LINKLOCAL((struct in6_addr *)addr)) {
+                linklocal_list = realloc(linklocal_list,
+                                         sizeof(struct ipv6_locallink)
+                                         * ++num_linklocals);
+                linklocal_list[num_linklocals - 1].len = len;
+                linklocal_list[num_linklocals - 1].addr = addr;
+                continue;
+            }
 #endif
             XdmcpRegisterConnection(family, (char *) addr, len);
 #if defined(IPv6) && defined(AF_INET6)
@@ -752,9 +790,16 @@ DefineSelf(int fd)
 #endif                          /* XDMCP */
 
     }                           /* for */
+
+    for (i = 0; i < num_linklocals; i++)
+        XdmcpRegisterConnection (FamilyInternet6,
+                                 (char *)linklocal_list[i].addr,
+                                 linklocal_list[i].len);
     freeifaddrs(ifap);
 #endif                          /* HAVE_GETIFADDRS */
 
+    free(linklocal_list);
+
     /*
      * add something of FamilyLocalHost
      */
-- 
1.8.1.4