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authorGuillaume Nault <gnault@redhat.com>2020-12-24 20:01:09 +0100
committerDavid S. Miller <davem@davemloft.net>2020-12-28 14:44:32 -0800
commit21fdca22eb7df2a1e194b8adb812ce370748b733 (patch)
tree5a0470c0dab4bc23f2e17fb549f7c230998a5296 /net
parent4f374d2c43a9e5e773f1dee56db63bd6b8a36276 (diff)
ipv4: Ignore ECN bits for fib lookups in fib_compute_spec_dst()
RT_TOS() only clears one of the ECN bits. Therefore, when fib_compute_spec_dst() resorts to a fib lookup, it can return different results depending on the value of the second ECN bit. For example, ECT(0) and ECT(1) packets could be treated differently. $ 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 lo up $ ip -netns ns1 link set dev lo up $ ip -netns ns0 link set dev veth01 up $ ip -netns ns1 link set dev veth10 up $ ip -netns ns0 address add 192.0.2.10/24 dev veth01 $ ip -netns ns1 address add 192.0.2.11/24 dev veth10 $ ip -netns ns1 address add 192.0.2.21/32 dev lo $ ip -netns ns1 route add 192.0.2.10/32 tos 4 dev veth10 src 192.0.2.21 $ ip netns exec ns1 sysctl -wq net.ipv4.icmp_echo_ignore_broadcasts=0 With TOS 4 and ECT(1), ns1 replies using source address 192.0.2.21 (ping uses -Q to set all TOS and ECN bits): $ ip netns exec ns0 ping -c 1 -b -Q 5 192.0.2.255 [...] 64 bytes from 192.0.2.21: icmp_seq=1 ttl=64 time=0.544 ms But with TOS 4 and ECT(0), ns1 replies using source address 192.0.2.11 because the "tos 4" route isn't matched: $ ip netns exec ns0 ping -c 1 -b -Q 6 192.0.2.255 [...] 64 bytes from 192.0.2.11: icmp_seq=1 ttl=64 time=0.597 ms After this patch the ECN bits don't affect the result anymore: $ ip netns exec ns0 ping -c 1 -b -Q 6 192.0.2.255 [...] 64 bytes from 192.0.2.21: icmp_seq=1 ttl=64 time=0.591 ms Fixes: 35ebf65e851c ("ipv4: Create and use fib_compute_spec_dst() helper.") Signed-off-by: Guillaume Nault <gnault@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/fib_frontend.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index cdf6ec5aa45d..84bb707bd88d 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -292,7 +292,7 @@ __be32 fib_compute_spec_dst(struct sk_buff *skb)
.flowi4_iif = LOOPBACK_IFINDEX,
.flowi4_oif = l3mdev_master_ifindex_rcu(dev),
.daddr = ip_hdr(skb)->saddr,
- .flowi4_tos = RT_TOS(ip_hdr(skb)->tos),
+ .flowi4_tos = ip_hdr(skb)->tos & IPTOS_RT_MASK,
.flowi4_scope = scope,
.flowi4_mark = vmark ? skb->mark : 0,
};