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authorGuillaume Nault <gnault@redhat.com>2020-11-26 19:09:22 +0100
committerJakub Kicinski <kuba@kernel.org>2020-11-28 13:14:23 -0800
commit1ebf179037cb46c19da3a9c1e2ca16e7a754b75e (patch)
treea3d0283da4cf5f694e9fb2a79c34db27bd39c302
parent3771b822422fd999fbcd30c7e8302d251be0bb75 (diff)
ipv4: Fix tos mask in inet_rtm_getroute()
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.1606412894.git.gnault@redhat.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
-rw-r--r--net/ipv4/route.c7
1 files 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)