On 6/2/15, 2:13 PM, Eric W. Biederman wrote:
So I just stopped and looked at what is happening. When you originally
reported this you said (or at least I understood) that rtm_scope was not
being set in iproute. I assumed that meant it was not being touched
and it was taking a default value of zero (or else it was possibly
floating). Having looked neither is true. iproute sets rtm_scope
to RT_SCOPE_NOWHERE during delete deliberately to act as a wild card.
In the kernel in other protocols currently ipv4 treats RT_SCOPE_NOWHERE
as a wild card during delete, decnet treats RT_SCOPE_NOWHERE as a wild
card during delete, the remaining protocols (ipv6, phonet, and can) that
implement RTM_DELROUTE do not look at rtm_scope at all. Further ipv6
and phonet set rtm_scope to RT_SCOPE_UNIVERSE when dumped.
Which says to me that we have semantics in the kernel that no one has
let userspace know about, and that scares me when there is a
misunderstanding between the kernel and userspace about what fields
mean. That inevitabily leads to bugs. The kind of bugs that I have
to create security fixes for recently.
So I really think we should fix this in userspace so that that someone
reading iproute will have a chance at knowing that this scopes do not
exist in ipv6 and mpls and that scope logic is just noise in those
cases.
ack, i did start with handling both type and scope
in iproute2. I misunderstood you when you said you did not care
abt the scope in earlier comments. so i made the kernel not care abt the
scope. :) but only handled type in 'iproute2' in v2. now its clear. I
do have a similar patch like below.
sorry abt the iterations. I will respin (If you prefer to post your
below patch yourself, pls do. I am ok either way. Thanks.
Something like:
From 837dddea49af874fe750ab0712b3ef8066a2f55a Mon Sep 17 00:00:00 2001
From: "Eric W. Biederman" <[email protected]>
Date: Tue, 2 Jun 2015 15:51:31 -0500
Subject: [PATCH] iproute: When deleting routes don't always set the scope to
RT_SCOPE_NOWHERE
IPv6 and MPLS do not implement scopes on addresses and using
RT_SCOPE_NOWHERE is just confusing noise. Use RT_SCOPE_UNIVERSE
instead so that it is clear what is actually happening in the code.
Signed-off-by: "Eric W. Biederman" <[email protected]>
---
ip/iproute.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/ip/iproute.c b/ip/iproute.c
index fba475f65314..e9b991fdf62f 100644
--- a/ip/iproute.c
+++ b/ip/iproute.c
@@ -1136,6 +1136,9 @@ static int iproute_modify(int cmd, unsigned flags, int
argc, char **argv)
if (nhs_ok)
parse_nexthops(&req.n, &req.r, argc, argv);
+ if (req.r.rtm_family == AF_UNSPEC)
+ req.r.rtm_family = AF_INET;
+
if (!table_ok) {
if (req.r.rtm_type == RTN_LOCAL ||
req.r.rtm_type == RTN_BROADCAST ||
@@ -1144,7 +1147,10 @@ static int iproute_modify(int cmd, unsigned flags, int
argc, char **argv)
req.r.rtm_table = RT_TABLE_LOCAL;
}
if (!scope_ok) {
- if (req.r.rtm_type == RTN_LOCAL ||
+ if (req.r.rtm_family == AF_INET6 ||
+ req.r.rtm_family == AF_MPLS)
+ req.r.rtm_scope = RT_SCOPE_UNIVERSE;
+ else if (req.r.rtm_type == RTN_LOCAL ||
req.r.rtm_type == RTN_NAT)
req.r.rtm_scope = RT_SCOPE_HOST;
else if (req.r.rtm_type == RTN_BROADCAST ||
@@ -1160,9 +1166,6 @@ static int iproute_modify(int cmd, unsigned flags, int
argc, char **argv)
}
}
- if (req.r.rtm_family == AF_UNSPEC)
- req.r.rtm_family = AF_INET;
-
if (rtnl_talk(&rth, &req.n, NULL, 0) < 0)
return -2;
--
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