Define a dscp_t type and its appropriate helpers that ensure ECN bits are not taken into account when handling DSCP.
Use this new type to replace the tclass field of struct fib6_rule, so that fib6-rules don't get influenced by ECN bits anymore.
Before this patch, fib6-rules didn't make any distinction between the DSCP and ECN bits. Therefore, rules specifying a DSCP (tos or dsfield options in iproute2) stopped working as soon a packets had at least one of its ECN bits set (as a work around one could create four rules for each DSCP value to match, one for each possible ECN value).
After this patch fib6-rules only compare the DSCP bits. ECN doesn't influence the result anymore. Also, fib6-rules now must have the ECN bits cleared or they will be rejected.
Signed-off-by: Guillaume Nault gnault@redhat.com --- include/net/inet_dscp.h | 57 +++++++++++++++++++ include/net/ipv6.h | 6 ++ net/ipv6/fib6_rules.c | 19 +++++-- tools/testing/selftests/net/fib_rule_tests.sh | 30 +++++++++- 4 files changed, 105 insertions(+), 7 deletions(-) create mode 100644 include/net/inet_dscp.h
diff --git a/include/net/inet_dscp.h b/include/net/inet_dscp.h new file mode 100644 index 000000000000..72f250dffada --- /dev/null +++ b/include/net/inet_dscp.h @@ -0,0 +1,57 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +/* + * inet_dscp.h: helpers for handling differentiated services codepoints (DSCP) + * + * DSCP is defined in RFC 2474: + * + * 0 1 2 3 4 5 6 7 + * +---+---+---+---+---+---+---+---+ + * | DSCP | CU | + * +---+---+---+---+---+---+---+---+ + * + * DSCP: differentiated services codepoint + * CU: currently unused + * + * The whole DSCP + CU bits form the DS field. + * The DS field is also commonly called TOS or Traffic Class (for IPv6). + * + * Note: the CU bits are now used for Explicit Congestion Notification + * (RFC 3168). + */ + +#ifndef _INET_DSCP_H +#define _INET_DSCP_H + +#include <linux/types.h> + +/* Special type for storing DSCP values. + * + * A dscp_t variable stores a DS field with the CU (ECN) bits cleared. + * Using dscp_t allows to strictly separate DSCP and ECN bits, thus avoiding + * bugs where ECN bits are erroneously taken into account during FIB lookups + * or policy routing. + * + * Note: to get the real DSCP value contained in a dscp_t variable one would + * have to do a bit shift after calling inet_dscp_to_dsfield(). We could have + * a helper for that, but there's currently no users. + */ +typedef u8 __bitwise dscp_t; + +#define INET_DSCP_MASK 0xfc + +static inline dscp_t inet_dsfield_to_dscp(__u8 dsfield) +{ + return (__force dscp_t)(dsfield & INET_DSCP_MASK); +} + +static inline __u8 inet_dscp_to_dsfield(dscp_t dscp) +{ + return (__force __u8)dscp; +} + +static inline bool inet_validate_dscp(__u8 val) +{ + return !(val & ~INET_DSCP_MASK); +} + +#endif /* _INET_DSCP_H */ diff --git a/include/net/ipv6.h b/include/net/ipv6.h index 082f30256f59..3d898eb6df9c 100644 --- a/include/net/ipv6.h +++ b/include/net/ipv6.h @@ -18,6 +18,7 @@ #include <net/ndisc.h> #include <net/flow.h> #include <net/flow_dissector.h> +#include <net/inet_dscp.h> #include <net/snmp.h> #include <net/netns/hash.h>
@@ -975,6 +976,11 @@ static inline u8 ip6_tclass(__be32 flowinfo) return ntohl(flowinfo & IPV6_TCLASS_MASK) >> IPV6_TCLASS_SHIFT; }
+static inline dscp_t ip6_dscp(__be32 flowinfo) +{ + return inet_dsfield_to_dscp(ip6_tclass(flowinfo)); +} + static inline __be32 ip6_make_flowinfo(unsigned int tclass, __be32 flowlabel) { return htonl(tclass << IPV6_TCLASS_SHIFT) | flowlabel; diff --git a/net/ipv6/fib6_rules.c b/net/ipv6/fib6_rules.c index ec029c86ae06..e2a7b0059669 100644 --- a/net/ipv6/fib6_rules.c +++ b/net/ipv6/fib6_rules.c @@ -16,6 +16,7 @@ #include <linux/indirect_call_wrapper.h>
#include <net/fib_rules.h> +#include <net/inet_dscp.h> #include <net/ipv6.h> #include <net/addrconf.h> #include <net/ip6_route.h> @@ -25,14 +26,14 @@ struct fib6_rule { struct fib_rule common; struct rt6key src; struct rt6key dst; - u8 tclass; + dscp_t dscp; };
static bool fib6_rule_matchall(const struct fib_rule *rule) { struct fib6_rule *r = container_of(rule, struct fib6_rule, common);
- if (r->dst.plen || r->src.plen || r->tclass) + if (r->dst.plen || r->src.plen || r->dscp) return false; return fib_rule_matchall(rule); } @@ -323,7 +324,7 @@ INDIRECT_CALLABLE_SCOPE int fib6_rule_match(struct fib_rule *rule, return 0; }
- if (r->tclass && r->tclass != ip6_tclass(fl6->flowlabel)) + if (r->dscp && r->dscp != ip6_dscp(fl6->flowlabel)) return 0;
if (rule->ip_proto && (rule->ip_proto != fl6->flowi6_proto)) @@ -349,6 +350,13 @@ static int fib6_rule_configure(struct fib_rule *rule, struct sk_buff *skb, struct net *net = sock_net(skb->sk); struct fib6_rule *rule6 = (struct fib6_rule *) rule;
+ if (!inet_validate_dscp(frh->tos)) { + NL_SET_ERR_MSG(extack, + "Invalid dsfield (tos): ECN bits must be 0"); + goto errout; + } + rule6->dscp = inet_dsfield_to_dscp(frh->tos); + if (rule->action == FR_ACT_TO_TBL && !rule->l3mdev) { if (rule->table == RT6_TABLE_UNSPEC) { NL_SET_ERR_MSG(extack, "Invalid table"); @@ -369,7 +377,6 @@ static int fib6_rule_configure(struct fib_rule *rule, struct sk_buff *skb,
rule6->src.plen = frh->src_len; rule6->dst.plen = frh->dst_len; - rule6->tclass = frh->tos;
if (fib_rule_requires_fldissect(rule)) net->ipv6.fib6_rules_require_fldissect++; @@ -402,7 +409,7 @@ static int fib6_rule_compare(struct fib_rule *rule, struct fib_rule_hdr *frh, if (frh->dst_len && (rule6->dst.plen != frh->dst_len)) return 0;
- if (frh->tos && (rule6->tclass != frh->tos)) + if (frh->tos && inet_dscp_to_dsfield(rule6->dscp) != frh->tos) return 0;
if (frh->src_len && @@ -423,7 +430,7 @@ static int fib6_rule_fill(struct fib_rule *rule, struct sk_buff *skb,
frh->dst_len = rule6->dst.plen; frh->src_len = rule6->src.plen; - frh->tos = rule6->tclass; + frh->tos = inet_dscp_to_dsfield(rule6->dscp);
if ((rule6->dst.plen && nla_put_in6_addr(skb, FRA_DST, &rule6->dst.addr)) || diff --git a/tools/testing/selftests/net/fib_rule_tests.sh b/tools/testing/selftests/net/fib_rule_tests.sh index 3b0489910422..d7a9ab3be1d3 100755 --- a/tools/testing/selftests/net/fib_rule_tests.sh +++ b/tools/testing/selftests/net/fib_rule_tests.sh @@ -114,10 +114,25 @@ fib_rule6_test_match_n_redirect() log_test $? 0 "rule6 del by pref: $description" }
+fib_rule6_test_reject() +{ + local match="$1" + local rc + + $IP -6 rule add $match table $RTABLE 2>/dev/null + rc=$? + log_test $rc 2 "rule6 check: $match" + + if [ $rc -eq 0 ]; then + $IP -6 rule del $match table $RTABLE + fi +} + fib_rule6_test() { local getmatch local match + local cnt
# setup the fib rule redirect route $IP -6 route add table $RTABLE default via $GW_IP6 dev $DEV onlink @@ -128,8 +143,21 @@ fib_rule6_test() match="from $SRC_IP6 iif $DEV" fib_rule6_test_match_n_redirect "$match" "$match" "iif redirect to table"
+ # Reject dsfield (tos) options which have ECN bits set + for cnt in $(seq 1 3); do + match="dsfield $cnt" + fib_rule6_test_reject "$match" + done + + # Don't take ECN bits into account when matching on dsfield match="tos 0x10" - fib_rule6_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 $cnt" + fib_rule6_test_match_n_redirect "$match" "$getmatch" \ + "$getmatch redirect to table" + done
match="fwmark 0x64" getmatch="mark 0x64"