From: Guillaume Nault <gnault@xxxxxxxxxx>
[ Upstream commit 1ebf179037cb46c19da3a9c1e2ca16e7a754b75e ]
When inet_rtm_getroute() was converted to use the RCU variants of
ip_route_input() and ip_route_output_key(), the TOS parameters
stopped being masked with IPTOS_RT_MASK before doing the route lookup.
As a result, "ip route get" can return a different route than what
would be used when sending real packets.
For example:
$ ip route add 192.0.2.11/32 dev eth0
$ ip route add unreachable 192.0.2.11/32 tos 2
$ ip route get 192.0.2.11 tos 2
RTNETLINK answers: No route to host
But, packets with TOS 2 (ECT(0) if interpreted as an ECN bit) would
actually be routed using the first route:
$ ping -c 1 -Q 2 192.0.2.11
PING 192.0.2.11 (192.0.2.11) 56(84) bytes of data.
64 bytes from 192.0.2.11: icmp_seq=1 ttl=64 time=0.173 ms
--- 192.0.2.11 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.173/0.173/0.173/0.000 ms
This patch re-applies IPTOS_RT_MASK in inet_rtm_getroute(), to
return results consistent with real route lookups.
Fixes: 3765d35ed8b9 ("net: ipv4: Convert inet_rtm_getroute to rcu versions of route lookup")
Signed-off-by: Guillaume Nault <gnault@xxxxxxxxxx>
Reviewed-by: David Ahern <dsahern@xxxxxxxxxx>
Link: https://lore.kernel.org/r/b2d237d08317ca55926add9654a48409ac1b8f5b.1606412894.git.gnault@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/ipv4/route.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2788,7 +2788,7 @@ static int inet_rtm_getroute(struct sk_b
memset(&fl4, 0, sizeof(fl4));
fl4.daddr = dst;
fl4.saddr = src;
- fl4.flowi4_tos = rtm->rtm_tos;
+ fl4.flowi4_tos = rtm->rtm_tos & IPTOS_RT_MASK;
fl4.flowi4_oif = tb[RTA_OIF] ? nla_get_u32(tb[RTA_OIF]) : 0;
fl4.flowi4_mark = mark;
fl4.flowi4_uid = uid;
@@ -2807,8 +2807,9 @@ static int inet_rtm_getroute(struct sk_b
skb->protocol = htons(ETH_P_IP);
skb->dev = dev;
skb->mark = mark;
- err = ip_route_input_rcu(skb, dst, src, rtm->rtm_tos,
- dev, &res);
+ err = ip_route_input_rcu(skb, dst, src,
+ rtm->rtm_tos & IPTOS_RT_MASK, dev,
+ &res);
rt = skb_rtable(skb);
if (err == 0 && rt->dst.error)
