[Babel-users] [PATCH] Allow routes with source ::/128 for SAS on Linux

[Steven Barth]

Linux uses the source-address :: (unspecified) to lookup routes in the
routing table for connections that are not bound to a specific source
address (e.g. ping6 2001:db8::1). If all default routes are
source-restricted a command like above will result in a "Permission
denied" error and no packets are being sent. Adding a default route with
source ::/128 avoids this issue.

This patch excludes ::/128 from the "martian_prefix" check for source
prefixes and thus allows such auxiliary routes to be distributed.

Signed-off-by: Steven Barth <cyrus at openwrt.org>
---
 kernel_netlink.c | 4 ++--
 route.c          | 4 ++--
 util.c           | 4 ++--
 util.h           | 2 +-
 xroute.c         | 2 +-
 5 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/kernel_netlink.c b/kernel_netlink.c
index 8b9099c..2e174af 100644
--- a/kernel_netlink.c
+++ b/kernel_netlink.c
@@ -1236,8 +1236,8 @@ filter_kernel_routes(struct nlmsghdr *nh, void *data)
     if(rc < 0)
         return 0;
 
-    if(martian_prefix(current_route->prefix, current_route->plen) ||
-       martian_prefix(current_route->src_prefix, current_route->src_plen))
+    if(martian_prefix(current_route->prefix, current_route->plen, 0) ||
+       martian_prefix(current_route->src_prefix, current_route->src_plen, 1))
         return 0;
 
     /* Ignore default unreachable routes; no idea where they come from. */
diff --git a/route.c b/route.c
index a97e8ed..c709303 100644
--- a/route.c
+++ b/route.c
@@ -1371,12 +1371,12 @@ update_route(const unsigned char *id,
     if(memcmp(id, myid, 8) == 0)
         return NULL;
 
-    if(martian_prefix(prefix, plen)) {
+    if(martian_prefix(prefix, plen, 0)) {
         fprintf(stderr, "Rejecting martian route to %s through %s.\n",
                 format_prefix(prefix, plen), format_address(id));
         return NULL;
     }
-    if(src_plen != 0 && martian_prefix(src_prefix, src_plen)) {
+    if(src_plen != 0 && martian_prefix(src_prefix, src_plen, 1)) {
         fprintf(stderr, "Rejecting martian route to %s from %s through %s.\n",
                 format_prefix(prefix, plen),
                 format_prefix(src_prefix, src_plen), format_address(id));
diff --git a/util.c b/util.c
index cdb4ab2..80930e4 100644
--- a/util.c
+++ b/util.c
@@ -425,13 +425,13 @@ wait_for_fd(int direction, int fd, int msecs)
 }
 
 int
-martian_prefix(const unsigned char *prefix, int plen)
+martian_prefix(const unsigned char *prefix, int plen, int is_source)
 {
     return
         (plen >= 8 && prefix[0] == 0xFF) ||
         (plen >= 10 && prefix[0] == 0xFE && (prefix[1] & 0xC0) == 0x80) ||
         (plen >= 128 && memcmp(prefix, zeroes, 15) == 0 &&
-         (prefix[15] == 0 || prefix[15] == 1)) ||
+         ((prefix[15] == 0 && !is_source) || prefix[15] == 1)) ||
         (plen >= 96 && v4mapped(prefix) &&
          ((plen >= 104 && (prefix[12] == 127 || prefix[12] == 0)) ||
           (plen >= 100 && (prefix[12] & 0xE0) == 0xE0)));
diff --git a/util.h b/util.h
index 935481f..f399b8a 100644
--- a/util.h
+++ b/util.h
@@ -95,7 +95,7 @@ int parse_net(const char *net, unsigned char *prefix_r, unsigned char *plen_r,
               int *af_r);
 int parse_eui64(const char *eui, unsigned char *eui_r);
 int wait_for_fd(int direction, int fd, int msecs);
-int martian_prefix(const unsigned char *prefix, int plen) ATTRIBUTE ((pure));
+int martian_prefix(const unsigned char *prefix, int plen, int is_source) ATTRIBUTE ((pure));
 int linklocal(const unsigned char *address) ATTRIBUTE ((pure));
 int v4mapped(const unsigned char *address) ATTRIBUTE ((pure));
 void v4tov6(unsigned char *dst, const unsigned char *src);
diff --git a/xroute.c b/xroute.c
index e8b3b11..e4bd12a 100644
--- a/xroute.c
+++ b/xroute.c
@@ -259,7 +259,7 @@ check_xroutes(int send_updates)
     /* Add any new routes */
 
     for(i = 0; i < numroutes; i++) {
-        if(martian_prefix(routes[i].prefix, routes[i].plen))
+        if(martian_prefix(routes[i].prefix, routes[i].plen, 0))
             continue;
         metric = redistribute_filter(routes[i].prefix, routes[i].plen,
                                      routes[i].src_prefix, routes[i].src_plen,
-- 
1.8.3.2