ipv6: add special mode accept_ra=2 to accept RA while configured as router (65e9b62d) · Commits · 戴 / test

The current IPv6 behavior is to not accept router advertisements while forwarding, i.e. configured as router. This does make sense, a router is typically not supposed to be auto configured. However there are exceptions and we should allow the current behavior to be overwritten. Therefore this patch enables the user to overrule the "if forwarding enabled then don't listen to RAs" rule by setting accept_ra to the special value of 2. An alternative would be to ignore the forwarding switch alltogether and solely accept RAs based on the value of accept_ra. However, I found that if not intended, accepting RAs as a router can lead to strange unwanted behavior therefore we it seems wise to only do so if the user explicitely asks for this behavior. Signed-off-by:

Thomas Graf <tgraf@infradead.org> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/ipv6/ndisc.c

+14 −4

Original line number	Diff line number	Diff line
		@@ -1105,6 +1105,18 @@ errout:
		rtnl_set_sk_err(net, RTNLGRP_ND_USEROPT, err);
		}

		static inline int accept_ra(struct inet6_dev *in6_dev)
		{
		/*
		* If forwarding is enabled, RA are not accepted unless the special
		* hybrid mode (accept_ra=2) is enabled.
		*/
		if (in6_dev->cnf.forwarding && in6_dev->cnf.accept_ra < 2)
		return 0;

		return in6_dev->cnf.accept_ra;
		}

		static void ndisc_router_discovery(struct sk_buff *skb)
		{
		struct ra_msg ra_msg = (struct ra_msg )skb_transport_header(skb);
		@@ -1158,8 +1170,7 @@ static void ndisc_router_discovery(struct sk_buff *skb)
		return;
		}

		/* skip route and link configuration on routers */
		if (in6_dev->cnf.forwarding \|\| !in6_dev->cnf.accept_ra)
		if (!accept_ra(in6_dev))
		goto skip_linkparms;

		#ifdef CONFIG_IPV6_NDISC_NODETYPE
		@@ -1309,8 +1320,7 @@ skip_linkparms:
		NEIGH_UPDATE_F_ISROUTER);
		}

		/* skip route and link configuration on routers */
		if (in6_dev->cnf.forwarding \|\| !in6_dev->cnf.accept_ra)
		if (!accept_ra(in6_dev))
		goto out;

		#ifdef CONFIG_IPV6_ROUTE_INFO

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