Commit 1dced6a8 authored Aug 17, 2014 by Sébastien Barré Committed by David S. Miller Aug 22, 2014

ipv4: Restore accept_local behaviour in fib_validate_source()



Commit 7a9bc9b8 ("ipv4: Elide fib_validate_source() completely when possible.")
introduced a short-circuit to avoid calling fib_validate_source when not
needed. That change took rp_filter into account, but not accept_local.
This resulted in a change of behaviour: with rp_filter and accept_local
off, incoming packets with a local address in the source field should be
dropped.

Here is how to reproduce the change pre/post 7a9bc9b8 commit:
-configure the same IPv4 address on hosts A and B.
-try to send an ARP request from B to A.
-The ARP request will be dropped before that commit, but accepted and answered
after that commit.

This adds a check for ACCEPT_LOCAL, to maintain full
fib validation in case it is 0. We also leave __fib_validate_source() earlier
when possible, based on the same check as fib_validate_source(), once the
accept_local stuff is verified.

Cc: Gregory Detal <gregory.detal@uclouvain.be>
Cc: Christoph Paasch <christoph.paasch@uclouvain.be>
Cc: Hannes Frederic Sowa <hannes@redhat.com>
Cc: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Sébastien Barré <sebastien.barre@uclouvain.be>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 14462b6e

net/ipv4/fib_frontend.c

+8 −6

Original line number	Diff line number	Diff line
		@@ -243,7 +243,7 @@ static int __fib_validate_source(struct sk_buff *skb, __be32 src, __be32 dst,
		u8 tos, int oif, struct net_device *dev,
		int rpf, struct in_device idev, u32 itag)
		{
		int ret, no_addr, accept_local;
		int ret, no_addr;
		struct fib_result res;
		struct flowi4 fl4;
		struct net *net;
		@@ -258,16 +258,17 @@ static int __fib_validate_source(struct sk_buff *skb, __be32 src, __be32 dst,

		no_addr = idev->ifa_list == NULL;

		accept_local = IN_DEV_ACCEPT_LOCAL(idev);
		fl4.flowi4_mark = IN_DEV_SRC_VMARK(idev) ? skb->mark : 0;

		net = dev_net(dev);
		if (fib_lookup(net, &fl4, &res))
		goto last_resort;
		if (res.type != RTN_UNICAST) {
		if (res.type != RTN_LOCAL \|\| !accept_local)
		if (res.type != RTN_UNICAST &&
		(res.type != RTN_LOCAL \|\| !IN_DEV_ACCEPT_LOCAL(idev)))
		goto e_inval;
		}
		if (!rpf && !fib_num_tclassid_users(dev_net(dev)) &&
		(dev->ifindex != oif \|\| !IN_DEV_TX_REDIRECTS(idev)))
		goto last_resort;
		fib_combine_itag(itag, &res);
		dev_match = false;

		@@ -321,6 +322,7 @@ int fib_validate_source(struct sk_buff *skb, __be32 src, __be32 dst,
		int r = secpath_exists(skb) ? 0 : IN_DEV_RPFILTER(idev);

		if (!r && !fib_num_tclassid_users(dev_net(dev)) &&
		IN_DEV_ACCEPT_LOCAL(idev) &&
		(dev->ifindex != oif \|\| !IN_DEV_TX_REDIRECTS(idev))) {
		*itag = 0;
		return 0;

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