Commit 563f8e97 authored by Guillaume Nault's avatar Guillaume Nault Committed by Jakub Kicinski
Browse files

ipv4: Stop taking ECN bits into account in fib4-rules 



Use the new dscp_t type to replace the tos field of struct fib4_rule,
so that fib4-rules consistently ignore ECN bits.

Before this patch, fib4-rules did accept rules with the high order ECN
bit set (but not the low order one). Also, it relied on its callers
masking the ECN bits of ->flowi4_tos to prevent those from influencing
the result. This was brittle and a few call paths still do the lookup
without masking the ECN bits first.

After this patch fib4-rules only compare the DSCP bits. ECN can't
influence the result anymore, even if the caller didn't mask these
bits. Also, fib4-rules now must have both ECN bits cleared or they will
be rejected.

Signed-off-by: default avatarGuillaume Nault <gnault@redhat.com>
Acked-by: default avatarDavid Ahern <dsahern@kernel.org>
Reviewed-by: default avatarToke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent a410a0cf

net/ipv4/fib_rules.c

+10 −8
Original line number Diff line number Diff line
@@ -23,6 +23,7 @@ 
#include <linux/list.h>

#include <linux/rcupdate.h>

#include <linux/export.h>

#include <net/inet_dscp.h>

#include <net/ip.h>

#include <net/route.h>

#include <net/tcp.h>
@@ -35,7 +36,7 @@ struct fib4_rule { 
	struct fib_rule		common;

	u8			dst_len;

	u8			src_len;

	u8			tos;

	dscp_t			dscp;

	__be32			src;

	__be32			srcmask;

	__be32			dst;
@@ -49,7 +50,7 @@ static bool fib4_rule_matchall(const struct fib_rule *rule) 
{

	struct fib4_rule *r = container_of(rule, struct fib4_rule, common);



	if (r->dst_len || r->src_len || r->tos)

	if (r->dst_len || r->src_len || r->dscp)

		return false;

	return fib_rule_matchall(rule);

}
@@ -185,7 +186,7 @@ INDIRECT_CALLABLE_SCOPE int fib4_rule_match(struct fib_rule *rule, 
	    ((daddr ^ r->dst) & r->dstmask))

		return 0;



	if (r->tos && (r->tos != fl4->flowi4_tos))

	if (r->dscp && r->dscp != inet_dsfield_to_dscp(fl4->flowi4_tos))

		return 0;



	if (rule->ip_proto && (rule->ip_proto != fl4->flowi4_proto))
@@ -225,10 +226,12 @@ static int fib4_rule_configure(struct fib_rule *rule, struct sk_buff *skb, 
	int err = -EINVAL;

	struct fib4_rule *rule4 = (struct fib4_rule *) rule;



	if (frh->tos & ~IPTOS_TOS_MASK) {

		NL_SET_ERR_MSG(extack, "Invalid tos");

	if (!inet_validate_dscp(frh->tos)) {

		NL_SET_ERR_MSG(extack,

			       "Invalid dsfield (tos): ECN bits must be 0");

		goto errout;

	}

	rule4->dscp = inet_dsfield_to_dscp(frh->tos);



	/* split local/main if they are not already split */

	err = fib_unmerge(net);
@@ -270,7 +273,6 @@ static int fib4_rule_configure(struct fib_rule *rule, struct sk_buff *skb, 
	rule4->srcmask = inet_make_mask(rule4->src_len);

	rule4->dst_len = frh->dst_len;

	rule4->dstmask = inet_make_mask(rule4->dst_len);

	rule4->tos = frh->tos;



	net->ipv4.fib_has_custom_rules = true;
@@ -313,7 +315,7 @@ static int fib4_rule_compare(struct fib_rule *rule, struct fib_rule_hdr *frh, 
	if (frh->dst_len && (rule4->dst_len != frh->dst_len))

		return 0;



	if (frh->tos && (rule4->tos != frh->tos))

	if (frh->tos && inet_dscp_to_dsfield(rule4->dscp) != frh->tos)

		return 0;



#ifdef CONFIG_IP_ROUTE_CLASSID
@@ -337,7 +339,7 @@ static int fib4_rule_fill(struct fib_rule *rule, struct sk_buff *skb, 


	frh->dst_len = rule4->dst_len;

	frh->src_len = rule4->src_len;

	frh->tos = rule4->tos;

	frh->tos = inet_dscp_to_dsfield(rule4->dscp);



	if ((rule4->dst_len &&

	     nla_put_in_addr(skb, FRA_DST, rule4->dst)) ||

tools/testing/selftests/net/fib_rule_tests.sh

+29 −1
Original line number Diff line number Diff line
@@ -215,10 +215,25 @@ fib_rule4_test_match_n_redirect() 
	log_test $? 0 "rule4 del by pref: $description"

}



fib_rule4_test_reject()

{

	local match="$1"

	local rc



	$IP rule add $match table $RTABLE 2>/dev/null

	rc=$?

	log_test $rc 2 "rule4 check: $match"



	if [ $rc -eq 0 ]; then

		$IP rule del $match table $RTABLE

	fi

}



fib_rule4_test()

{

	local getmatch

	local match

	local cnt



	# setup the fib rule redirect route

	$IP route add table $RTABLE default via $GW_IP4 dev $DEV onlink
@@ -234,8 +249,21 @@ fib_rule4_test() 
	fib_rule4_test_match_n_redirect "$match" "$match" "iif redirect to table"

	ip netns exec testns sysctl -qw net.ipv4.ip_forward=0



	# Reject dsfield (tos) options which have ECN bits set

	for cnt in $(seq 1 3); do

		match="dsfield $cnt"

		fib_rule4_test_reject "$match"

	done



	# Don't take ECN bits into account when matching on dsfield

	match="tos 0x10"

	fib_rule4_test_match_n_redirect "$match" "$match" "tos redirect to table"

	for cnt in "0x10" "0x11" "0x12" "0x13"; do

		# Using option 'tos' instead of 'dsfield' as old iproute2

		# versions don't support 'dsfield' in ip rule show.

		getmatch="tos $cnt"

		fib_rule4_test_match_n_redirect "$match" "$getmatch" \

						"$getmatch redirect to table"

	done



	match="fwmark 0x64"

	getmatch="mark 0x64"