RAdv: Add custom options

Currently one can use only a predefined set of advertised options in RAdv
protocol, which are supported by BIRD configuration. It would be convenient
to be able to specify other possible options at least manually as a blob
so one should not wait until it is supported in the code, released, etc.

This idea is inspired by presentation by Ondřej Caletka at CSNOG, in which
he noticed the lack of either PREF64 option or possibility to add custom
options in various software.

The patch makes it possible to define such options with the syntax:

  other type <num> <bytestring>

1 files changed, 45 insertions, 0 deletions

diff --git a/proto/radv/packets.c b/proto/radv/packets.c
index 5cd8b2de..d1f86ec1 100644
--- a/proto/radv/packets.c
+++ b/proto/radv/packets.c
@@ -82,6 +82,13 @@ struct radv_opt_dnssl
   char domain[];
 };
 
+struct radv_opt_custom
+{
+  u8 type;
+  u8 length;
+  u8 payload[];
+};
+
 static int
 radv_prepare_route(struct radv_iface *ifa, struct radv_route *rt,
 		   char **buf, char *bufend)
@@ -255,6 +262,36 @@ radv_prepare_dnssl(struct radv_iface *ifa, list *dnssl_list, char **buf, char *b
 }
 
 static int
+radv_prepare_custom(struct radv_iface *ifa, list *custom_list, char **buf, char *bufend)
+{
+  struct radv_custom_config *ccf = HEAD(*custom_list);
+
+  while(NODE_VALID(ccf))
+  {
+    struct radv_opt_custom *op = (void *) *buf;
+    /* Add 2 octets for type and size and 8 - 1 for ceiling the division up to 8 octets */
+    int size = (ccf->payload->length + 2 + 8 - 1) / 8;
+    if (bufend - *buf < size * 8)
+      goto too_much;
+
+    memset(op, 0, size * 8); /* Clear buffer so there is no tail garbage */
+    op->type = ccf->type;
+    op->length = size;
+    memcpy(op->payload, ccf->payload->data, ccf->payload->length);
+
+    *buf += 8 * op->length;
+    ccf = NODE_NEXT(ccf);
+  }
+
+  return 0;
+
+ too_much:
+  log(L_WARN "%s: Too many RA options on interface %s",
+      ifa->ra->p.name, ifa->iface->name);
+  return -1;
+}
+
+static int
 radv_prepare_prefix(struct radv_iface *ifa, struct radv_prefix *px,
 		    char **buf, char *bufend)
 {
@@ -352,6 +389,14 @@ radv_prepare_ra(struct radv_iface *ifa)
   if (radv_prepare_dnssl(ifa, &ic->dnssl_list, &buf, bufend) < 0)
     goto done;
 
+  if (! ic->custom_local)
+    if (radv_prepare_custom(ifa, &cf->custom_list, &buf, bufend) < 0)
+      goto done;
+
+  if (radv_prepare_custom(ifa, &ic->custom_list, &buf, bufend) < 0)
+    goto done;
+
+
   if (p->fib_up)
   {
     FIB_WALK(&p->routes, struct radv_route, rt)