| Message ID | 20240715142354.3697987-2-idosch@nvidia.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 338bb57e4c2a1c2c6fc92f9c0bd35be7587adca7 |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | ipv4: Fix incorrect TOS in route get reply | expand |
On 7/15/24 7:23 AM, Ido Schimmel wrote: > The TOS value that is returned to user space in the route get reply is > the one with which the lookup was performed ('fl4->flowi4_tos'). This is > fine when the matched route is configured with a TOS as it would not > match if its TOS value did not match the one with which the lookup was > performed. > > However, matching on TOS is only performed when the route's TOS is not > zero. It is therefore possible to have the kernel incorrectly return a > non-zero TOS: > > # ip link add name dummy1 up type dummy > # ip address add 192.0.2.1/24 dev dummy1 > # ip route get 192.0.2.2 tos 0xfc > 192.0.2.2 tos 0x1c dev dummy1 src 192.0.2.1 uid 0 > cache > > Fix by adding a DSCP field to the FIB result structure (inside an > existing 4 bytes hole), populating it in the route lookup and using it > when filling the route get reply. > > Output after the patch: > > # ip link add name dummy1 up type dummy > # ip address add 192.0.2.1/24 dev dummy1 > # ip route get 192.0.2.2 tos 0xfc > 192.0.2.2 dev dummy1 src 192.0.2.1 uid 0 > cache > > Fixes: 1a00fee4ffb2 ("ipv4: Remove rt_key_{src,dst,tos} from struct rtable.") > Signed-off-by: Ido Schimmel <idosch@nvidia.com> > --- > include/net/ip_fib.h | 1 + > net/ipv4/fib_trie.c | 1 + > net/ipv4/route.c | 14 +++++++------- > 3 files changed, 9 insertions(+), 7 deletions(-) > Reviewed-by: David Ahern <dsahern@kernel.org>
On Mon, Jul 15, 2024 at 05:23:53PM +0300, Ido Schimmel wrote: > The TOS value that is returned to user space in the route get reply is > the one with which the lookup was performed ('fl4->flowi4_tos'). This is > fine when the matched route is configured with a TOS as it would not > match if its TOS value did not match the one with which the lookup was > performed. > > However, matching on TOS is only performed when the route's TOS is not > zero. It is therefore possible to have the kernel incorrectly return a > non-zero TOS: > > # ip link add name dummy1 up type dummy > # ip address add 192.0.2.1/24 dev dummy1 > # ip route get 192.0.2.2 tos 0xfc > 192.0.2.2 tos 0x1c dev dummy1 src 192.0.2.1 uid 0 > cache > > Fix by adding a DSCP field to the FIB result structure (inside an > existing 4 bytes hole), populating it in the route lookup and using it > when filling the route get reply. > > Output after the patch: > > # ip link add name dummy1 up type dummy > # ip address add 192.0.2.1/24 dev dummy1 > # ip route get 192.0.2.2 tos 0xfc > 192.0.2.2 dev dummy1 src 192.0.2.1 uid 0 > cache Reviewed-by: Guillaume Nault <gnault@redhat.com>
diff --git a/include/net/ip_fib.h b/include/net/ip_fib.h index 9b2f69ba5e49..c29639b4323f 100644 --- a/include/net/ip_fib.h +++ b/include/net/ip_fib.h @@ -173,6 +173,7 @@ struct fib_result { unsigned char type; unsigned char scope; u32 tclassid; + dscp_t dscp; struct fib_nh_common *nhc; struct fib_info *fi; struct fib_table *table; diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c index f474106464d2..8f30e3f00b7f 100644 --- a/net/ipv4/fib_trie.c +++ b/net/ipv4/fib_trie.c @@ -1629,6 +1629,7 @@ int fib_table_lookup(struct fib_table *tb, const struct flowi4 *flp, res->nhc = nhc; res->type = fa->fa_type; res->scope = fi->fib_scope; + res->dscp = fa->fa_dscp; res->fi = fi; res->table = tb; res->fa_head = &n->leaf; diff --git a/net/ipv4/route.c b/net/ipv4/route.c index b3073d1c8f8f..7790a8347461 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -2868,9 +2868,9 @@ EXPORT_SYMBOL_GPL(ip_route_output_flow); /* called with rcu_read_lock held */ static int rt_fill_info(struct net *net, __be32 dst, __be32 src, - struct rtable *rt, u32 table_id, struct flowi4 *fl4, - struct sk_buff *skb, u32 portid, u32 seq, - unsigned int flags) + struct rtable *rt, u32 table_id, dscp_t dscp, + struct flowi4 *fl4, struct sk_buff *skb, u32 portid, + u32 seq, unsigned int flags) { struct rtmsg *r; struct nlmsghdr *nlh; @@ -2886,7 +2886,7 @@ static int rt_fill_info(struct net *net, __be32 dst, __be32 src, r->rtm_family = AF_INET; r->rtm_dst_len = 32; r->rtm_src_len = 0; - r->rtm_tos = fl4 ? fl4->flowi4_tos : 0; + r->rtm_tos = inet_dscp_to_dsfield(dscp); r->rtm_table = table_id < 256 ? table_id : RT_TABLE_COMPAT; if (nla_put_u32(skb, RTA_TABLE, table_id)) goto nla_put_failure; @@ -3036,7 +3036,7 @@ static int fnhe_dump_bucket(struct net *net, struct sk_buff *skb, goto next; err = rt_fill_info(net, fnhe->fnhe_daddr, 0, rt, - table_id, NULL, skb, + table_id, 0, NULL, skb, NETLINK_CB(cb->skb).portid, cb->nlh->nlmsg_seq, flags); if (err) @@ -3359,8 +3359,8 @@ static int inet_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh, err = fib_dump_info(skb, NETLINK_CB(in_skb).portid, nlh->nlmsg_seq, RTM_NEWROUTE, &fri, 0); } else { - err = rt_fill_info(net, dst, src, rt, table_id, &fl4, skb, - NETLINK_CB(in_skb).portid, + err = rt_fill_info(net, dst, src, rt, table_id, res.dscp, &fl4, + skb, NETLINK_CB(in_skb).portid, nlh->nlmsg_seq, 0); } if (err < 0)
The TOS value that is returned to user space in the route get reply is the one with which the lookup was performed ('fl4->flowi4_tos'). This is fine when the matched route is configured with a TOS as it would not match if its TOS value did not match the one with which the lookup was performed. However, matching on TOS is only performed when the route's TOS is not zero. It is therefore possible to have the kernel incorrectly return a non-zero TOS: # ip link add name dummy1 up type dummy # ip address add 192.0.2.1/24 dev dummy1 # ip route get 192.0.2.2 tos 0xfc 192.0.2.2 tos 0x1c dev dummy1 src 192.0.2.1 uid 0 cache Fix by adding a DSCP field to the FIB result structure (inside an existing 4 bytes hole), populating it in the route lookup and using it when filling the route get reply. Output after the patch: # ip link add name dummy1 up type dummy # ip address add 192.0.2.1/24 dev dummy1 # ip route get 192.0.2.2 tos 0xfc 192.0.2.2 dev dummy1 src 192.0.2.1 uid 0 cache Fixes: 1a00fee4ffb2 ("ipv4: Remove rt_key_{src,dst,tos} from struct rtable.") Signed-off-by: Ido Schimmel <idosch@nvidia.com> --- include/net/ip_fib.h | 1 + net/ipv4/fib_trie.c | 1 + net/ipv4/route.c | 14 +++++++------- 3 files changed, 9 insertions(+), 7 deletions(-)