Commit beb1afac authored by David Ahern's avatar David Ahern Committed by David S. Miller
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net: ipv6: Add support to dump multipath routes via RTA_MULTIPATH attribute 



IPv6 returns multipath routes as a series of individual routes making
their display and handling by userspace different and more complicated
than IPv4, putting the burden on the user to see that a route is part of
a multipath route and internally creating a multipath route if desired
(e.g., libnl does this as of commit 29b71371e764). This patch addresses
this difference, allowing multipath routes to be returned using the
RTA_MULTIPATH attribute.

The end result is that IPv6 multipath routes can be treated and displayed
in a format similar to IPv4:

    $ ip -6 ro ls vrf red
    2001:db8:1::/120 dev eth1 proto kernel metric 256  pref medium
    2001:db8:2::/120 dev eth2 proto kernel metric 256  pref medium
    2001:db8:200::/120 metric 1024
	    nexthop via 2001:db8:1::2  dev eth1 weight 1
	    nexthop via 2001:db8:2::2  dev eth2 weight 1

Signed-off-by: default avatarDavid Ahern <dsa@cumulusnetworks.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 0ae81335

net/ipv6/ip6_fib.c

+10 −0
Original line number Diff line number Diff line
@@ -318,6 +318,16 @@ static int fib6_dump_node(struct fib6_walker *w) 
			w->leaf = rt;

			return 1;

		}



		/* Multipath routes are dumped in one route with the

		 * RTA_MULTIPATH attribute. Jump 'rt' to point to the

		 * last sibling of this route (no need to dump the

		 * sibling routes again)

		 */

		if (rt->rt6i_nsiblings)

			rt = list_last_entry(&rt->rt6i_siblings,

					     struct rt6_info,

					     rt6i_siblings);

	}

	w->leaf = NULL;

	return 0;

net/ipv6/route.c

+95 −17
Original line number Diff line number Diff line
@@ -3195,8 +3195,20 @@ static int inet6_rtm_newroute(struct sk_buff *skb, struct nlmsghdr *nlh) 
		return ip6_route_add(&cfg);

}



static inline size_t rt6_nlmsg_size(struct rt6_info *rt)

static size_t rt6_nlmsg_size(struct rt6_info *rt)

{

	int nexthop_len = 0;



	if (rt->rt6i_nsiblings) {

		nexthop_len = nla_total_size(0)	 /* RTA_MULTIPATH */

			    + NLA_ALIGN(sizeof(struct rtnexthop))

			    + nla_total_size(16) /* RTA_GATEWAY */

			    + nla_total_size(4)  /* RTA_OIF */

			    + lwtunnel_get_encap_size(rt->dst.lwtstate);



		nexthop_len *= rt->rt6i_nsiblings;

	}



	return NLMSG_ALIGN(sizeof(struct rtmsg))

	       + nla_total_size(16) /* RTA_SRC */

	       + nla_total_size(16) /* RTA_DST */
@@ -3210,7 +3222,62 @@ static inline size_t rt6_nlmsg_size(struct rt6_info *rt) 
	       + nla_total_size(sizeof(struct rta_cacheinfo))

	       + nla_total_size(TCP_CA_NAME_MAX) /* RTAX_CC_ALGO */

	       + nla_total_size(1) /* RTA_PREF */

	       + lwtunnel_get_encap_size(rt->dst.lwtstate);

	       + lwtunnel_get_encap_size(rt->dst.lwtstate)

	       + nexthop_len;

}



static int rt6_nexthop_info(struct sk_buff *skb, struct rt6_info *rt,

			    unsigned int *flags)

{

	if (!netif_running(rt->dst.dev) || !netif_carrier_ok(rt->dst.dev)) {

		*flags |= RTNH_F_LINKDOWN;

		if (rt->rt6i_idev->cnf.ignore_routes_with_linkdown)

			*flags |= RTNH_F_DEAD;

	}



	if (rt->rt6i_flags & RTF_GATEWAY) {

		if (nla_put_in6_addr(skb, RTA_GATEWAY, &rt->rt6i_gateway) < 0)

			goto nla_put_failure;

	}



	if (rt->dst.dev &&

	    nla_put_u32(skb, RTA_OIF, rt->dst.dev->ifindex))

		goto nla_put_failure;



	if (rt->dst.lwtstate &&

	    lwtunnel_fill_encap(skb, rt->dst.lwtstate) < 0)

		goto nla_put_failure;



	return 0;



nla_put_failure:

	return -EMSGSIZE;

}



static int rt6_add_nexthop(struct sk_buff *skb, struct rt6_info *rt)

{

	struct rtnexthop *rtnh;

	unsigned int flags = 0;



	rtnh = nla_reserve_nohdr(skb, sizeof(*rtnh));

	if (!rtnh)

		goto nla_put_failure;



	rtnh->rtnh_hops = 0;

	rtnh->rtnh_ifindex = rt->dst.dev ? rt->dst.dev->ifindex : 0;



	if (rt6_nexthop_info(skb, rt, &flags) < 0)

		goto nla_put_failure;



	rtnh->rtnh_flags = flags;



	/* length of rtnetlink header + attributes */

	rtnh->rtnh_len = nlmsg_get_pos(skb) - (void *)rtnh;



	return 0;



nla_put_failure:

	return -EMSGSIZE;

}



static int rt6_fill_node(struct net *net,
@@ -3264,11 +3331,6 @@ static int rt6_fill_node(struct net *net, 
	else

		rtm->rtm_type = RTN_UNICAST;

	rtm->rtm_flags = 0;

	if (!netif_running(rt->dst.dev) || !netif_carrier_ok(rt->dst.dev)) {

		rtm->rtm_flags |= RTNH_F_LINKDOWN;

		if (rt->rt6i_idev->cnf.ignore_routes_with_linkdown)

			rtm->rtm_flags |= RTNH_F_DEAD;

	}

	rtm->rtm_scope = RT_SCOPE_UNIVERSE;

	rtm->rtm_protocol = rt->rt6i_protocol;

	if (rt->rt6i_flags & RTF_DYNAMIC)
@@ -3332,17 +3394,35 @@ static int rt6_fill_node(struct net *net, 
	if (rtnetlink_put_metrics(skb, metrics) < 0)

		goto nla_put_failure;



	if (rt->rt6i_flags & RTF_GATEWAY) {

		if (nla_put_in6_addr(skb, RTA_GATEWAY, &rt->rt6i_gateway) < 0)

	if (nla_put_u32(skb, RTA_PRIORITY, rt->rt6i_metric))

		goto nla_put_failure;

	}



	if (rt->dst.dev &&

	    nla_put_u32(skb, RTA_OIF, rt->dst.dev->ifindex))

	/* For multipath routes, walk the siblings list and add

	 * each as a nexthop within RTA_MULTIPATH.

	 */

	if (rt->rt6i_nsiblings) {

		struct rt6_info *sibling, *next_sibling;

		struct nlattr *mp;



		mp = nla_nest_start(skb, RTA_MULTIPATH);

		if (!mp)

			goto nla_put_failure;

	if (nla_put_u32(skb, RTA_PRIORITY, rt->rt6i_metric))



		if (rt6_add_nexthop(skb, rt) < 0)

			goto nla_put_failure;



		list_for_each_entry_safe(sibling, next_sibling,

					 &rt->rt6i_siblings, rt6i_siblings) {

			if (rt6_add_nexthop(skb, sibling) < 0)

				goto nla_put_failure;

		}



		nla_nest_end(skb, mp);

	} else {

		if (rt6_nexthop_info(skb, rt, &rtm->rtm_flags) < 0)

			goto nla_put_failure;

	}



	expires = (rt->rt6i_flags & RTF_EXPIRES) ? rt->dst.expires - jiffies : 0;



	if (rtnl_put_cacheinfo(skb, &rt->dst, 0, expires, rt->dst.error) < 0)
@@ -3351,8 +3431,6 @@ static int rt6_fill_node(struct net *net, 
	if (nla_put_u8(skb, RTA_PREF, IPV6_EXTRACT_PREF(rt->rt6i_flags)))

		goto nla_put_failure;



	if (lwtunnel_fill_encap(skb, rt->dst.lwtstate) < 0)

		goto nla_put_failure;



	nlmsg_end(skb, nlh);

	return 0;

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