From: Guillaume Nault <gnault@redhat.com>
To: David Miller <davem@davemloft.net>, Jakub Kicinski <kuba@kernel.org>
Cc: netdev@vger.kernel.org, David Ahern <dsahern@gmail.com>,
Russell Strong <russell@strong.id.au>
Subject: [PATCH net] ipv4: Fix tos mask in inet_rtm_getroute()
Date: Thu, 26 Nov 2020 19:09:22 +0100 [thread overview]
Message-ID: <b2d237d08317ca55926add9654a48409ac1b8f5b.1606412894.git.gnault@redhat.com> (raw)
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@redhat.com>
---
net/ipv4/route.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index dc2a399cd9f4..9f43abeac3a8 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -3222,7 +3222,7 @@ static int inet_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh,
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;
@@ -3246,8 +3246,9 @@ static int inet_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh,
fl4.flowi4_iif = iif; /* for rt_fill_info */
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)
--
2.21.3
next reply other threads:[~2020-11-26 18:09 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-26 18:09 Guillaume Nault [this message]
2020-11-28 17:03 ` [PATCH net] ipv4: Fix tos mask in inet_rtm_getroute() David Ahern
2020-11-28 21:17 ` Jakub Kicinski
2020-11-29 12:54 ` Guillaume Nault
2020-11-30 16:51 ` Jakub Kicinski
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