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Commit f8126f1d authored Jul 13, 2012 by David S. Miller

ipv4: Adjust semantics of rt->rt_gateway.



In order to allow prefixed routes, we have to adjust how rt_gateway
is set and interpreted.

The new interpretation is:

1) rt_gateway == 0, destination is on-link, nexthop is iph->daddr

2) rt_gateway != 0, destination requires a nexthop gateway

Abstract the fetching of the proper nexthop value using a new
inline helper, rt_nexthop(), as suggested by Joe Perches.

Signed-off-by: David S. Miller <davem@davemloft.net>
Tested-by: Vijay Subramanian <subramanian.vijay@gmail.com>

parent f1ce3062

include/net/route.h

+7 −0

Original line number	Diff line number	Diff line
		@@ -70,6 +70,13 @@ static inline bool rt_is_output_route(const struct rtable *rt)
		return rt->rt_route_iif == 0;
		}

		static inline __be32 rt_nexthop(const struct rtable *rt, __be32 daddr)
		{
		if (rt->rt_gateway)
		return rt->rt_gateway;
		return daddr;
		}

		struct ip_rt_acct {
		__u32 o_bytes;
		__u32 o_packets;

net/ipv4/arp.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -475,8 +475,7 @@ int arp_find(unsigned char haddr, struct sk_buff skb)
		return 1;
		}

		paddr = skb_rtable(skb)->rt_gateway;

		paddr = rt_nexthop(skb_rtable(skb), ip_hdr(skb)->daddr);
		if (arp_set_predefined(inet_addr_type(dev_net(dev), paddr), haddr,
		paddr, dev))
		return 0;

net/ipv4/inet_connection_sock.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -389,7 +389,7 @@ struct dst_entry inet_csk_route_req(struct sock sk,
		rt = ip_route_output_flow(net, fl4, sk);
		if (IS_ERR(rt))
		goto no_route;
		if (opt && opt->opt.is_strictroute && fl4->daddr != rt->rt_gateway)
		if (opt && opt->opt.is_strictroute && rt->rt_gateway)
		goto route_err;
		return &rt->dst;

		@@ -422,7 +422,7 @@ struct dst_entry inet_csk_route_child_sock(struct sock sk,
		rt = ip_route_output_flow(net, fl4, sk);
		if (IS_ERR(rt))
		goto no_route;
		if (opt && opt->opt.is_strictroute && fl4->daddr != rt->rt_gateway)
		if (opt && opt->opt.is_strictroute && rt->rt_gateway)
		goto route_err;
		return &rt->dst;

net/ipv4/ip_gre.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -766,7 +766,7 @@ static netdev_tx_t ipgre_tunnel_xmit(struct sk_buff skb, struct net_device dev

		if (skb->protocol == htons(ETH_P_IP)) {
		rt = skb_rtable(skb);
		dst = rt->rt_gateway;
		dst = rt_nexthop(rt, old_iph->daddr);
		}
		#if IS_ENABLED(CONFIG_IPV6)
		else if (skb->protocol == htons(ETH_P_IPV6)) {

net/ipv4/ip_output.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -371,7 +371,7 @@ int ip_queue_xmit(struct sk_buff skb, struct flowi fl)
		skb_dst_set_noref(skb, &rt->dst);

		packet_routed:
		if (inet_opt && inet_opt->opt.is_strictroute && fl4->daddr != rt->rt_gateway)
		if (inet_opt && inet_opt->opt.is_strictroute && rt->rt_gateway)
		goto no_route;

		/* OK, we know where to send it, allocate and build IP header. */