Allow router advertisements to have the "off-link" bit set.

src/dnsmasq.h

@@ -868,6 +868,7 @@ struct dhcp_context {
 #define CONTEXT_USED           (1u<<15)
 #define CONTEXT_OLD            (1u<<16)
 #define CONTEXT_V6             (1u<<17)
+#define CONTEXT_RA_OFF_LINK    (1u<<18)
 
 struct ping_result {
   struct in_addr addr;

src/option.c

@@ -2699,6 +2699,8 @@ static int one_opt(int option, char *arg, char *errstr, char *gen_err, int comma
 		  new->flags |= CONTEXT_RA_ROUTER | CONTEXT_RA;
 		else if (strcmp(a[leasepos], "ra-stateless") == 0)
 		  new->flags |= CONTEXT_RA_STATELESS | CONTEXT_DHCP | CONTEXT_RA;
+		else if (strcmp(a[leasepos], "off-link") == 0)
+		  new->flags |= CONTEXT_RA_OFF_LINK;
 		else if (leasepos == 1 && inet_pton(AF_INET6, a[leasepos], &new->end6))
 		  new->flags |= CONTEXT_DHCP; 
 		else if (strstr(a[leasepos], "constructor:") == a[leasepos])

src/radv.c

@@ -313,8 +313,10 @@ static void send_ra(time_t now, int iface, char *iface_name, struct in6_addr *de
 		  opt->type = ICMP6_OPT_PREFIX;
 		  opt->len = 4;
 		  opt->prefix_len = context->prefix;
-		  /* autonomous only if we're not doing dhcp, always set "on-link" */
-		  opt->flags = do_slaac ? 0xC0 : 0x80;
+		  /* autonomous only if we're not doing dhcp, set
+                     "on-link" unless "off-link" was specified */
+		  opt->flags = (do_slaac ? 0x40 : 0) |
+                    ((context->flags & CONTEXT_RA_OFF_LINK) ? 0 : 0x80);
 		  opt->valid_lifetime = htonl(context->saved_valid - old);
 		  opt->preferred_lifetime = htonl(0);
 		  opt->reserved = 0; 
@@ -514,6 +516,7 @@ static int add_prefixes(struct in6_addr *local,  int prefix,
 	  int deprecate  = 0;
 	  int constructed = 0;
 	  int adv_router = 0;
+	  int off_link = 0;
 	  unsigned int time = 0xffffffff;
 	  struct dhcp_context *context;
 	  
@@ -586,6 +589,7 @@ static int add_prefixes(struct in6_addr *local,  int prefix,
 		      context->ra_time = 0;
 		    context->flags |= CONTEXT_RA_DONE;
 		    real_prefix = context->prefix;
+                    off_link = (context->flags & CONTEXT_RA_OFF_LINK);
 		  }
 
 		param->first = 0;	
@@ -636,8 +640,9 @@ static int add_prefixes(struct in6_addr *local,  int prefix,
 		  opt->type = ICMP6_OPT_PREFIX;
 		  opt->len = 4;
 		  opt->prefix_len = real_prefix;
-		  /* autonomous only if we're not doing dhcp, always set "on-link" */
-		  opt->flags = 0x80;
+		  /* autonomous only if we're not doing dhcp, set
+                     "on-link" unless "off-link" was specified */
+		  opt->flags = (off_link ? 0 : 0x80);
 		  if (do_slaac)
 		    opt->flags |= 0x40;
 		  if (adv_router)