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As suggested by Julian:
Simply, flowi4_iif must not contain 0, it does not
look logical to ignore all ip rules with specified iif.
because in fib_rule_match() we do:
if (rule->iifindex && (rule->iifindex != fl->flowi_iif))
goto out;
flowi4_iif should be LOOPBACK_IFINDEX by default.
We need to move LOOPBACK_IFINDEX to include/net/flow.h:
1) It is mostly used by flowi_iif
2) Fix the following compile error if we use it in flow.h
by the patches latter:
In file included from include/linux/netfilter.h:277:0,
from include/net/netns/netfilter.h:5,
from include/net/net_namespace.h:21,
from include/linux/netdevice.h:43,
from include/linux/icmpv6.h:12,
from include/linux/ipv6.h:61,
from include/net/ipv6.h:16,
from include/linux/sunrpc/clnt.h:27,
from include/linux/nfs_fs.h:30,
from init/do_mounts.c:32:
include/net/flow.h: In function ‘flowi4_init_output’:
include/net/flow.h:84:32: error: ‘LOOPBACK_IFINDEX’ undeclared (first use in this function)
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Julian Anastasov <ja@ssi.bg>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Cong Wang <cwang@twopensource.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Alex Efros reported rpfilter module doesn't match following packets:
IN=br.qemu SRC=192.168.2.1 DST=192.168.2.255 [ .. ]
(netfilter bugzilla #814).
Problem is that network stack arranges for the locally generated broadcasts
to appear on the interface they were sent out, so the IFF_LOOPBACK check
doesn't trigger.
As -m rpfilter is restricted to PREROUTING, we can check for existing
rtable instead, it catches locally-generated broad/multicast case, too.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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As pointed out, there are places, that access net->loopback_dev->ifindex
and after ifindex generation is made per-net this value becomes constant
equals 1. So go ahead and introduce the LOOPBACK_IFINDEX constant and use
it where appropriate.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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This tries to do the same thing as fib_validate_source(), but differs
in several aspects.
The most important difference is that the reverse path filter built into
fib_validate_source uses the oif as iif when performing the reverse
lookup. We do not do this, as the oif is not yet known by the time the
PREROUTING hook is invoked.
We can't wait until FORWARD chain because by the time FORWARD is invoked
ipv4 forward path may have already sent icmp messages is response
to to-be-discarded-via-rpfilter packets.
To avoid the such an additional lookup in PREROUTING, Patrick McHardy
suggested to attach the path information directly in the match
(i.e., just do what the standard ipv4 path does a bit earlier in PREROUTING).
This works, but it also has a few caveats. Most importantly, when using
marks in PREROUTING to re-route traffic based on the nfmark, -m rpfilter
would have to be used after the nfmark has been set; otherwise the nfmark
would have no effect (because the route is already attached).
Another problem would be interaction with -j TPROXY, as this target sets an
nfmark and uses ACCEPT instead of continue, i.e. such a version of
-m rpfilter cannot be used for the initial to-be-intercepted packets.
In case in turns out that the oif is required, we can add Patricks
suggestion with a new match option (e.g. --rpf-use-oif) to keep ruleset
compatibility.
Another difference to current builtin ipv4 rpfilter is that packets subject to ipsec
transformation are not automatically excluded. If you want this, simply
combine -m rpfilter with the policy match.
Packets arriving on loopback interfaces always match.
Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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