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authorDavid S. Miller <davem@davemloft.net>2012-06-28 03:59:11 -0700
committerDavid S. Miller <davem@davemloft.net>2012-06-28 03:59:11 -0700
commit35ebf65e851c6d9731abc6362b189858eb59f4d3 (patch)
tree2e78c2c81bc72aeeb172484996cdff268f0111a2 /net/ipv4/fib_frontend.c
parent70e7341673a47fb1525cfc7d6651cc98b5348928 (diff)
ipv4: Create and use fib_compute_spec_dst() helper.
The specific destination is the host we direct unicast replies to. Usually this is the original packet source address, but if we are responding to a multicast or broadcast packet we have to use something different. Specifically we must use the source address we would use if we were to send a packet to the unicast source of the original packet. The routing cache precomputes this value, but we want to remove that precomputation because it creates a hard dependency on the expensive rpfilter source address validation which we'd like to make cheaper. There are only three places where this matters: 1) ICMP replies. 2) pktinfo CMSG 3) IP options Now there will be no real users of rt->rt_spec_dst and we can simply remove it altogether. Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/fib_frontend.c')
-rw-r--r--net/ipv4/fib_frontend.c29
1 files changed, 29 insertions, 0 deletions
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index 3854411fa37c..451939b60c54 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -180,6 +180,35 @@ unsigned int inet_dev_addr_type(struct net *net, const struct net_device *dev,
}
EXPORT_SYMBOL(inet_dev_addr_type);
+__be32 fib_compute_spec_dst(struct sk_buff *skb)
+{
+ struct net_device *dev = skb->dev;
+ struct in_device *in_dev;
+ struct fib_result res;
+ struct flowi4 fl4;
+ struct net *net;
+
+ if (skb->pkt_type != PACKET_BROADCAST &&
+ skb->pkt_type != PACKET_MULTICAST)
+ return ip_hdr(skb)->daddr;
+
+ in_dev = __in_dev_get_rcu(dev);
+ BUG_ON(!in_dev);
+ fl4.flowi4_oif = 0;
+ fl4.flowi4_iif = 0;
+ fl4.daddr = ip_hdr(skb)->saddr;
+ fl4.saddr = ip_hdr(skb)->daddr;
+ fl4.flowi4_tos = RT_TOS(ip_hdr(skb)->tos);
+ fl4.flowi4_scope = RT_SCOPE_UNIVERSE;
+ fl4.flowi4_mark = IN_DEV_SRC_VMARK(in_dev) ? skb->mark : 0;
+
+ net = dev_net(dev);
+ if (!fib_lookup(net, &fl4, &res))
+ return FIB_RES_PREFSRC(net, res);
+ else
+ return inet_select_addr(dev, 0, RT_SCOPE_UNIVERSE);
+}
+
/* Given (packet source, input interface) and optional (dst, oif, tos):
* - (main) check, that source is valid i.e. not broadcast or our local
* address.