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[2a01:cb05:8918:ce00:dd1a:5a4f:9908:f2d5]) by smtp.gmail.com with ESMTPSA id 90sm9875593wrl.60.2020.11.26.10.09.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 26 Nov 2020 10:09:24 -0800 (PST) Date: Thu, 26 Nov 2020 19:09:22 +0100 From: Guillaume Nault To: David Miller , Jakub Kicinski Cc: netdev@vger.kernel.org, David Ahern , Russell Strong Subject: [PATCH net] ipv4: Fix tos mask in inet_rtm_getroute() Message-ID: MIME-Version: 1.0 Content-Disposition: inline Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 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 Reviewed-by: David Ahern --- 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)