diff mbox

[net,v3,2/2] mpls: fix mpls route deletes to not check for route scope

Message ID 87a8wholtc.fsf@x220.int.ebiederm.org
State RFC, archived
Delegated to: stephen hemminger
Headers show

Commit Message

Eric W. Biederman June 2, 2015, 9:13 p.m. UTC 
Roopa Prabhu <roopa@cumulusnetworks.com> writes:

> From: Roopa Prabhu <roopa@cumulusnetworks.com>
>
> Ignore scope for route del messages

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.

Something like:

From 837dddea49af874fe750ab0712b3ef8066a2f55a Mon Sep 17 00:00:00 2001
From: "Eric W. Biederman" <ebiederm@xmission.com>
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" <ebiederm@xmission.com>
---
 ip/iproute.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

Comments

Roopa Prabhu June 2, 2015, 10:03 p.m. UTC | #1 
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" <ebiederm@xmission.com>
> 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" <ebiederm@xmission.com>
> ---
>   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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Eric W. Biederman June 2, 2015, 10:59 p.m. UTC | #2 
roopa <roopa@cumulusnetworks.com> writes:

> 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.

I don't have enough energy to follow through with more than review
today.

Eric
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diff mbox

Patch

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;