From: Guillaume Nault gnault@redhat.com
stable inclusion from linux-4.19.162 commit dbd97d579e60fae91a2db06e7b02b8f3a4a0872a
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[ 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@redhat.com Reviewed-by: David Ahern dsahern@kernel.org Link: https://lore.kernel.org/r/b2d237d08317ca55926add9654a48409ac1b8f5b.160641289... Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Yang Yingliang yangyingliang@huawei.com Signed-off-by: Cheng Jian cj.chengjian@huawei.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 f74b7513d607..106c97002088 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -2871,7 +2871,7 @@ static int inet_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh, 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; @@ -2895,8 +2895,9 @@ 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)