From: Guillaume Nault <gnault@redhat.com>
To: dccp@vger.kernel.org
Subject: [PATCH net-next 0/3] ipv4: First steps toward removing RTO_ONLINK
Date: Wed, 20 Apr 2022 23:21:19 +0000 [thread overview]
Message-ID: <cover.1650470610.git.gnault@redhat.com> (raw)
RTO_ONLINK is a flag that allows to reduce the scope of route lookups.
It's stored in a normally unused bit of the ->flowi4_tos field, in
struct flowi4. However it has several problems:
* This bit is also used by ECN. Although ECN bits are supposed to be
cleared before doing a route lookup, it happened that some code
paths didn't properly sanitise their ->flowi4_tos. So this mechanism
is fragile and we had bugs in the past where ECN bits slipped in and
could end up being erroneously interpreted as RTO_ONLINK.
* A dscp_t type was recently introduced to ensure ECN bits are cleared
during route lookups. ->flowi4_tos is the most important structure
field to convert, but RTO_ONLINK prevents such conversion, as dscp_t
mandates that ECN bits (where RTO_ONLINK is stored) be zero.
Therefore we need to stop using RTO_ONLINK altogether. Fortunately
RTO_ONLINK isn't a necessity. Instead of passing a flag in ->flowi4_tos
to tell the route lookup function to restrict the scope, we can simply
initialise the scope correctly.
Patch 1 does some preparatory work: it stops resetting ->flowi4_scope
automatically before a route lookup, thus allowing callers to set their
desired scope without having to rely on the RTO_ONLINK flag.
Patch 2-3 convert a few code paths to avoid relying on RTO_ONLINK.
More conversions will have to take place before we can eventually
remove this flag.
Guillaume Nault (3):
ipv4: Don't reset ->flowi4_scope in ip_rt_fix_tos().
ipv4: Avoid using RTO_ONLINK with ip_route_connect().
ipv4: Initialise ->flowi4_scope properly in ICMP handlers.
include/net/route.h | 36 ++++++++++++++++++++++++------------
net/dccp/ipv4.c | 5 ++---
net/ipv4/af_inet.c | 6 +++---
net/ipv4/datagram.c | 7 +++----
net/ipv4/route.c | 41 +++++++++++++++++++----------------------
net/ipv4/tcp_ipv4.c | 5 ++---
6 files changed, 53 insertions(+), 47 deletions(-)
--
2.21.3
next reply other threads:[~2022-04-20 23:21 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-20 23:21 Guillaume Nault [this message]
2022-04-22 3:10 ` [PATCH net-next 0/3] ipv4: First steps toward removing RTO_ONLINK David Ahern
2022-04-22 11:02 ` Guillaume Nault
2022-04-22 12:50 ` patchwork-bot+netdevbpf
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