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ipv4: Restore accept_local behaviour in fib_validate_source()

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Commit 7a9bc9b81a ("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 7a9bc9b81a 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>
This commit is contained in:
Sébastien Barré 2014-08-17 09:19:54 +02:00 committed by David S. Miller
parent 14462b6e8c
commit 1dced6a854
1 changed files with 8 additions and 6 deletions
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14
net/ipv4/fib_frontend.c
View File

@ -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)
goto e_inval;
}
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;