Merge branch 'ipv4-ensure-ecn-bits-don-t-influence-source-address-validation'

Guillaume Nault says:

====================
ipv4: Ensure ECN bits don't influence source address validation

Functions that end up calling fib_table_lookup() should clear the ECN
bits from the TOS, otherwise ECT(0) and ECT(1) packets can be treated
differently.

Most functions already clear the ECN bits, but there are a few cases
where this is not done. This series only fixes the ones related to
source address validation.
====================

Link: https://lore.kernel.org/r/cover.1610790904.git.gnault@redhat.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv4/netfilter/ipt_rpfilter.c

@@ -76,7 +76,7 @@ static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par)
 	flow.daddr = iph->saddr;
 	flow.saddr = rpfilter_get_saddr(iph->daddr);
 	flow.flowi4_mark = info->flags & XT_RPFILTER_VALID_MARK ? skb->mark : 0;
-	flow.flowi4_tos = RT_TOS(iph->tos);
+	flow.flowi4_tos = iph->tos & IPTOS_RT_MASK;
 	flow.flowi4_scope = RT_SCOPE_UNIVERSE;
 	flow.flowi4_oif = l3mdev_master_ifindex_rcu(xt_in(par));
 

net/ipv4/udp.c

@@ -2555,7 +2555,8 @@ int udp_v4_early_demux(struct sk_buff *skb)
 		 */
 		if (!inet_sk(sk)->inet_daddr && in_dev)
 			return ip_mc_validate_source(skb, iph->daddr,
-						     iph->saddr, iph->tos,
+						     iph->saddr,
+						     iph->tos & IPTOS_RT_MASK,
 						     skb->dev, in_dev, &itag);
 	}
 	return 0;