| Message ID | 68bdd9383165b264dda2157cd4793d2b723d6438.1610790904.git.gnault@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | ipv4: Ensure ECN bits don't influence source address validation | expand |
diff --git a/net/ipv4/netfilter/ipt_rpfilter.c b/net/ipv4/netfilter/ipt_rpfilter.c index cc23f1ce239c..8cd3224d913e 100644 --- a/net/ipv4/netfilter/ipt_rpfilter.c +++ b/net/ipv4/netfilter/ipt_rpfilter.c @@ -76,7 +76,7 @@ static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par) flow.daddr = iph->saddr; flow.saddr = rpfilter_get_saddr(iph->daddr); flow.flowi4_mark = info->flags & XT_RPFILTER_VALID_MARK ? skb->mark : 0; - flow.flowi4_tos = RT_TOS(iph->tos); + flow.flowi4_tos = iph->tos & IPTOS_RT_MASK; flow.flowi4_scope = RT_SCOPE_UNIVERSE; flow.flowi4_oif = l3mdev_master_ifindex_rcu(xt_in(par));
RT_TOS() only masks one of the two ECN bits. Therefore rpfilter_mt() treats Not-ECT or ECT(1) packets in a different way than those with ECT(0) or CE. Reproducer: Create two netns, connected with a veth: $ ip netns add ns0 $ ip netns add ns1 $ ip link add name veth01 netns ns0 type veth peer name veth10 netns ns1 $ ip -netns ns0 link set dev veth01 up $ ip -netns ns1 link set dev veth10 up $ ip -netns ns0 address add 192.0.2.10/32 dev veth01 $ ip -netns ns1 address add 192.0.2.11/32 dev veth10 Add a route to ns1 in ns0: $ ip -netns ns0 route add 192.0.2.11/32 dev veth01 In ns1, only packets with TOS 4 can be routed to ns0: $ ip -netns ns1 route add 192.0.2.10/32 tos 4 dev veth10 Ping from ns0 to ns1 works regardless of the ECN bits, as long as TOS is 4: $ ip netns exec ns0 ping -Q 4 192.0.2.11 # TOS 4, Not-ECT ... 0% packet loss ... $ ip netns exec ns0 ping -Q 5 192.0.2.11 # TOS 4, ECT(1) ... 0% packet loss ... $ ip netns exec ns0 ping -Q 6 192.0.2.11 # TOS 4, ECT(0) ... 0% packet loss ... $ ip netns exec ns0 ping -Q 7 192.0.2.11 # TOS 4, CE ... 0% packet loss ... Now use iptable's rpfilter module in ns1: $ ip netns exec ns1 iptables-legacy -t raw -A PREROUTING -m rpfilter --invert -j DROP Not-ECT and ECT(1) packets still pass: $ ip netns exec ns0 ping -Q 4 192.0.2.11 # TOS 4, Not-ECT ... 0% packet loss ... $ ip netns exec ns0 ping -Q 5 192.0.2.11 # TOS 4, ECT(1) ... 0% packet loss ... But ECT(0) and ECN packets are dropped: $ ip netns exec ns0 ping -Q 6 192.0.2.11 # TOS 4, ECT(0) ... 100% packet loss ... $ ip netns exec ns0 ping -Q 7 192.0.2.11 # TOS 4, CE ... 100% packet loss ... After this patch, rpfilter doesn't drop ECT(0) and CE packets anymore. Fixes: 8f97339d3feb ("netfilter: add ipv4 reverse path filter match") Signed-off-by: Guillaume Nault <gnault@redhat.com> --- net/ipv4/netfilter/ipt_rpfilter.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)