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Commit 5bdac418 authored by Florian Westphal's avatar Florian Westphal Committed by Pablo Neira Ayuso
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netfilter: nat: fix icmp id randomization 



Sven Auhagen reported that a 2nd ping request will fail if 'fully-random'
mode is used.

Reason is that if no proto information is given, min/max are both 0,
so we set the icmp id to 0 instead of chosing a random value between
0 and 65535.

Update test case as well to catch this, without fix this yields:
[..]
ERROR: cannot ping ns1 from ns2 with ip masquerade fully-random (attempt 2)
ERROR: cannot ping ns1 from ns2 with ipv6 masquerade fully-random (attempt 2)

... becaus 2nd ping clashes with existing 'id 0' icmp conntrack and gets
dropped.

Fixes: 203f2e78 ("netfilter: nat: remove l4proto->unique_tuple")
Reported-by: default avatarSven Auhagen <sven.auhagen@voleatech.de>
Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent 33d1c018

net/netfilter/nf_nat_core.c

+8 −3
Original line number Diff line number Diff line
@@ -415,9 +415,14 @@ static void nf_nat_l4proto_unique_tuple(struct nf_conntrack_tuple *tuple, 
	case IPPROTO_ICMPV6:

		/* id is same for either direction... */

		keyptr = &tuple->src.u.icmp.id;

		min = range->min_proto.icmp.id;

		if (!(range->flags & NF_NAT_RANGE_PROTO_SPECIFIED)) {

			min = 0;

			range_size = 65536;

		} else {

			min = ntohs(range->min_proto.icmp.id);

			range_size = ntohs(range->max_proto.icmp.id) -

				     ntohs(range->min_proto.icmp.id) + 1;

		}

		goto find_free_id;

#if IS_ENABLED(CONFIG_NF_CT_PROTO_GRE)

	case IPPROTO_GRE:

tools/testing/selftests/netfilter/nft_nat.sh

+27 −9
Original line number Diff line number Diff line
@@ -321,6 +321,7 @@ EOF 


test_masquerade6()

{

	local natflags=$1

	local lret=0



	ip netns exec ns0 sysctl net.ipv6.conf.all.forwarding=1 > /dev/null
@@ -354,13 +355,13 @@ ip netns exec ns0 nft -f - <<EOF 
table ip6 nat {

	chain postrouting {

		type nat hook postrouting priority 0; policy accept;

		meta oif veth0 masquerade

		meta oif veth0 masquerade $natflags

	}

}

EOF

	ip netns exec ns2 ping -q -c 1 dead:1::99 > /dev/null # ping ns2->ns1

	if [ $? -ne 0 ] ; then

		echo "ERROR: cannot ping ns1 from ns2 with active ipv6 masquerading"

		echo "ERROR: cannot ping ns1 from ns2 with active ipv6 masquerade $natflags"

		lret=1

	fi
@@ -397,19 +398,26 @@ EOF 
		fi

	done



	ip netns exec ns2 ping -q -c 1 dead:1::99 > /dev/null # ping ns2->ns1

	if [ $? -ne 0 ] ; then

		echo "ERROR: cannot ping ns1 from ns2 with active ipv6 masquerade $natflags (attempt 2)"

		lret=1

	fi



	ip netns exec ns0 nft flush chain ip6 nat postrouting

	if [ $? -ne 0 ]; then

		echo "ERROR: Could not flush ip6 nat postrouting" 1>&2

		lret=1

	fi



	test $lret -eq 0 && echo "PASS: IPv6 masquerade for ns2"

	test $lret -eq 0 && echo "PASS: IPv6 masquerade $natflags for ns2"



	return $lret

}



test_masquerade()

{

	local natflags=$1

	local lret=0



	ip netns exec ns0 sysctl net.ipv4.conf.veth0.forwarding=1 > /dev/null
@@ -417,7 +425,7 @@ test_masquerade() 


	ip netns exec ns2 ping -q -c 1 10.0.1.99 > /dev/null # ping ns2->ns1

	if [ $? -ne 0 ] ; then

		echo "ERROR: canot ping ns1 from ns2"

		echo "ERROR: cannot ping ns1 from ns2 $natflags"

		lret=1

	fi
@@ -443,13 +451,13 @@ ip netns exec ns0 nft -f - <<EOF 
table ip nat {

	chain postrouting {

		type nat hook postrouting priority 0; policy accept;

		meta oif veth0 masquerade

		meta oif veth0 masquerade $natflags

	}

}

EOF

	ip netns exec ns2 ping -q -c 1 10.0.1.99 > /dev/null # ping ns2->ns1

	if [ $? -ne 0 ] ; then

		echo "ERROR: cannot ping ns1 from ns2 with active ip masquerading"

		echo "ERROR: cannot ping ns1 from ns2 with active ip masquere $natflags"

		lret=1

	fi
@@ -485,13 +493,19 @@ EOF 
		fi

	done



	ip netns exec ns2 ping -q -c 1 10.0.1.99 > /dev/null # ping ns2->ns1

	if [ $? -ne 0 ] ; then

		echo "ERROR: cannot ping ns1 from ns2 with active ip masquerade $natflags (attempt 2)"

		lret=1

	fi



	ip netns exec ns0 nft flush chain ip nat postrouting

	if [ $? -ne 0 ]; then

		echo "ERROR: Could not flush nat postrouting" 1>&2

		lret=1

	fi



	test $lret -eq 0 && echo "PASS: IP masquerade for ns2"

	test $lret -eq 0 && echo "PASS: IP masquerade $natflags for ns2"



	return $lret

}
@@ -750,8 +764,12 @@ test_local_dnat 
test_local_dnat6



reset_counters

test_masquerade

test_masquerade6

test_masquerade ""

test_masquerade6 ""



reset_counters

test_masquerade "fully-random"

test_masquerade6 "fully-random"



reset_counters

test_redirect