[PATCH net 0/2] ipv6: fix sticky pktinfo behaviour

Currently:

ip addr add dev eth0 2001:0010::1/64
ip addr add dev eth1 2001:0020::1/64
ping6 -I eth0 2001:0020::2

do not leads to the expected results, i.e. eth1 is used as the
egress interface.

This is due to two related issues in handling sticky pktinfo,
used by ping6 to enforce the device binding:

- ip6_dst_lookup_flow()/ip6_dst_lookup_tail() do not really enforce
flowi6_oif match
- ipv6 udp connect() just ignore flowi6_oif

These patches address each issue individually.

Paolo Abeni (2):
  ipv6: enforce flowi6_oif usage in ip6_dst_lookup_tail()
  ipv6/udp: use sticky pktinfo egress ifindex on connect()

 include/net/ip6_route.h |  2 ++
 net/ipv6/datagram.c     |  3 +++
 net/ipv6/ip6_output.c   |  6 +++++-
 net/ipv6/route.c        | 12 +++++++++---
 4 files changed, 19 insertions(+), 4 deletions(-)

-- 
1.8.3.1

The current implementation of ip6_dst_lookup_tail() basically
ignore the egress ifindex match: if the saddr is set,
ip6_route_output() purposefully ignores flowi6_oif, due
to the commit d46a9d678e4c ("net: ipv6: Dont add RT6_LOOKUP_F_IFACE
flag if saddr set"), if the saddr is 'any' the first route lookup
in ip6_dst_lookup_tail fails, but upon failure a second lookup will
be performed with saddr set, thus ignoring the ifindex constraint.

This commit adds an output route lookup function variant, which
allows the caller to specify additional lookup flags, and modify
ip6_dst_lookup_tail() to enforce the ifindex match on the second
lookup via said helper.

Fixes: d46a9d678e4c ("net: ipv6: Dont add RT6_LOOKUP_F_IFACE flag if saddr set")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
 include/net/ip6_route.h |  2 ++
 net/ipv6/ip6_output.c   |  6 +++++-
 net/ipv6/route.c        | 12 +++++++++---
 3 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
index 877f682..c221e36 100644
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h

@@ -66,6 +66,8 @@ void ip6_route_input(struct sk_buff *skb);
 
 struct dst_entry *ip6_route_output(struct net *net, const struct sock *sk,
 				   struct flowi6 *fl6);
+struct dst_entry *ip6_route_output_flags(struct net *net, const struct sock *sk,
+					 struct flowi6 *fl6, int flags);
 struct dst_entry *ip6_route_lookup(struct net *net, struct flowi6 *fl6,
 				   int flags);
 

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 23de98f..a163102 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c

@@ -909,6 +909,7 @@ static int ip6_dst_lookup_tail(struct net *net, const struct sock *sk,
 	struct rt6_info *rt;
 #endif
 	int err;
+	int flags = 0;
 
 	/* The correct way to handle this would be to do
 	 * ip6_route_get_saddr, and then ip6_route_output; however,

@@ -940,10 +941,13 @@ static int ip6_dst_lookup_tail(struct net *net, const struct sock *sk,
 			dst_release(*dst);
 			*dst = NULL;
 		}
+
+		if (fl6->flowi6_oif)
+			flags |= RT6_LOOKUP_F_IFACE;
 	}
 
 	if (!*dst)
-		*dst = ip6_route_output(net, sk, fl6);
+		*dst = ip6_route_output_flags(net, sk, fl6, flags);
 
 	err = (*dst)->error;
 	if (err)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 3c8834b..973cb73 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c

@@ -1183,11 +1183,10 @@ static struct rt6_info *ip6_pol_route_output(struct net *net, struct fib6_table
 	return ip6_pol_route(net, table, fl6->flowi6_oif, fl6, flags);
 }
 
-struct dst_entry *ip6_route_output(struct net *net, const struct sock *sk,
-				    struct flowi6 *fl6)
+struct dst_entry *ip6_route_output_flags(struct net *net, const struct sock *sk,
+					 struct flowi6 *fl6, int flags)
 {
 	struct dst_entry *dst;
-	int flags = 0;
 	bool any_src;
 
 	dst = l3mdev_rt6_dst_by_oif(net, fl6);

@@ -1208,6 +1207,13 @@ struct dst_entry *ip6_route_output(struct net *net, const struct sock *sk,
 
 	return fib6_rule_lookup(net, fl6, flags, ip6_pol_route_output);
 }
+EXPORT_SYMBOL_GPL(ip6_route_output_flags);
+
+struct dst_entry *ip6_route_output(struct net *net, const struct sock *sk,
+				   struct flowi6 *fl6)
+{
+	return ip6_route_output_flags(net, sk, fl6, 0);
+}
 EXPORT_SYMBOL(ip6_route_output);
 
 struct dst_entry *ip6_blackhole_route(struct net *net, struct dst_entry *dst_orig)

-- 
1.8.3.1

Currently, the egress interface index specified via IPV6_PKTINFO
is ignored by __ip6_datagram_connect(), so that RFC 3542 section 6.7
can be subverted when the user space application calls connect()
before sendmsg().
Fix it by initializing properly flowi6_oif in connect() before
performing the route lookup.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
 net/ipv6/datagram.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/ipv6/datagram.c b/net/ipv6/datagram.c
index 517c55b..4281621 100644
--- a/net/ipv6/datagram.c
+++ b/net/ipv6/datagram.c

@@ -162,6 +162,9 @@ ipv4_connected:
 	fl6.fl6_dport = inet->inet_dport;
 	fl6.fl6_sport = inet->inet_sport;
 
+	if (!fl6.flowi6_oif)
+		fl6.flowi6_oif = np->sticky_pktinfo.ipi6_ifindex;
+
 	if (!fl6.flowi6_oif && (addr_type&IPV6_ADDR_MULTICAST))
 		fl6.flowi6_oif = np->mcast_oif;
 

-- 
1.8.3.1

On 27.01.2016 14:45, Paolo Abeni wrote:

I think this can just be a static inline function.

Is it a lot of work to introduce the flags argument globally? Most other 
functions already have a flags parameter, maybe instead of just adding 
another wrapper just bite the bullet and add it everywhere?

Thanks,
Hannes

On Wed, 2016-01-27 at 19:38 +0100, Hannes Frederic Sowa wrote:

On 27.01.2016 14:45, Paolo Abeni wrote:

quoted

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 3c8834b..973cb73 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c

@@ -1183,11 +1183,10 @@ static struct rt6_info *ip6_pol_route_output(struct net *net, struct fib6_table
  	return ip6_pol_route(net, table, fl6->flowi6_oif, fl6, flags);
  }

-struct dst_entry *ip6_route_output(struct net *net, const struct sock *sk,
-				    struct flowi6 *fl6)
+struct dst_entry *ip6_route_output_flags(struct net *net, const struct sock *sk,
+					 struct flowi6 *fl6, int flags)
  {
  	struct dst_entry *dst;
-	int flags = 0;
  	bool any_src;

  	dst = l3mdev_rt6_dst_by_oif(net, fl6);

@@ -1208,6 +1207,13 @@ struct dst_entry *ip6_route_output(struct net *net, const struct sock *sk,

  	return fib6_rule_lookup(net, fl6, flags, ip6_pol_route_output);
  }
+EXPORT_SYMBOL_GPL(ip6_route_output_flags);
+
+struct dst_entry *ip6_route_output(struct net *net, const struct sock *sk,
+				   struct flowi6 *fl6)
+{
+	return ip6_route_output_flags(net, sk, fl6, 0);
+}
  EXPORT_SYMBOL(ip6_route_output);

I think this can just be a static inline function.

Is it a lot of work to introduce the flags argument globally? Most other 
functions already have a flags parameter, maybe instead of just adding 
another wrapper just bite the bullet and add it everywhere?

There are ~20 call sites for ip6_route_output(). Replacing them with
ip6_route_output_flags() should be trivial, but it sounds quite
invasive. Moving the new ip6_route_output() definition into the header
file as static inline function should be pretty much equivalent, may I
go with the latter option ?

Cheers,

Paolo

On 28.01.2016 13:27, Paolo Abeni wrote:

On Wed, 2016-01-27 at 19:38 +0100, Hannes Frederic Sowa wrote:

quoted

On 27.01.2016 14:45, Paolo Abeni wrote:

quoted

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 3c8834b..973cb73 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c

@@ -1183,11 +1183,10 @@ static struct rt6_info *ip6_pol_route_output(struct net *net, struct fib6_table
   	return ip6_pol_route(net, table, fl6->flowi6_oif, fl6, flags);
   }

-struct dst_entry *ip6_route_output(struct net *net, const struct sock *sk,
-				    struct flowi6 *fl6)
+struct dst_entry *ip6_route_output_flags(struct net *net, const struct sock *sk,
+					 struct flowi6 *fl6, int flags)
   {
   	struct dst_entry *dst;
-	int flags = 0;
   	bool any_src;

   	dst = l3mdev_rt6_dst_by_oif(net, fl6);

@@ -1208,6 +1207,13 @@ struct dst_entry *ip6_route_output(struct net *net, const struct sock *sk,

   	return fib6_rule_lookup(net, fl6, flags, ip6_pol_route_output);
   }
+EXPORT_SYMBOL_GPL(ip6_route_output_flags);
+
+struct dst_entry *ip6_route_output(struct net *net, const struct sock *sk,
+				   struct flowi6 *fl6)
+{
+	return ip6_route_output_flags(net, sk, fl6, 0);
+}
   EXPORT_SYMBOL(ip6_route_output);

I think this can just be a static inline function.

Is it a lot of work to introduce the flags argument globally? Most other
functions already have a flags parameter, maybe instead of just adding
another wrapper just bite the bullet and add it everywhere?

There are ~20 call sites for ip6_route_output(). Replacing them with
ip6_route_output_flags() should be trivial, but it sounds quite
invasive. Moving the new ip6_route_output() definition into the header
file as static inline function should be pretty much equivalent, may I
go with the latter option ?

I am not really a fan of such static inline wrappers all over the place, 
it doesnt't really help to evolve the code base.

But as a net/stable fix, go with the static inline first, IMHO.

Thanks,
Hannes

On 1/27/16 6:45 AM, Paolo Abeni wrote:

The current implementation of ip6_dst_lookup_tail() basically
ignore the egress ifindex match: if the saddr is set,
ip6_route_output() purposefully ignores flowi6_oif, due
to the commit d46a9d678e4c ("net: ipv6: Dont add RT6_LOOKUP_F_IFACE
flag if saddr set"), if the saddr is 'any' the first route lookup
in ip6_dst_lookup_tail fails, but upon failure a second lookup will
be performed with saddr set, thus ignoring the ifindex constraint.

This commit adds an output route lookup function variant, which
allows the caller to specify additional lookup flags, and modify
ip6_dst_lookup_tail() to enforce the ifindex match on the second
lookup via said helper.

Fixes: d46a9d678e4c ("net: ipv6: Dont add RT6_LOOKUP_F_IFACE flag if saddr set")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

I don't agree with that 'Fixes:' tag.

ip6_route_output did not add the RT6_LOOKUP_F_IFACE flag until 
741a11d9e410; d46a9d678e4c is a follow on to limit adding the flag only 
if no source address  is given.

Since ip6_dst_lookup_tail never considered the flowi6_oif this is a 
general bug fix rather than a fix of d46a9d678e4c.

On Thu, 2016-01-28 at 07:59 -0700, David Ahern wrote:

On 1/27/16 6:45 AM, Paolo Abeni wrote:

quoted

The current implementation of ip6_dst_lookup_tail() basically
ignore the egress ifindex match: if the saddr is set,
ip6_route_output() purposefully ignores flowi6_oif, due
to the commit d46a9d678e4c ("net: ipv6: Dont add RT6_LOOKUP_F_IFACE
flag if saddr set"), if the saddr is 'any' the first route lookup
in ip6_dst_lookup_tail fails, but upon failure a second lookup will
be performed with saddr set, thus ignoring the ifindex constraint.

This commit adds an output route lookup function variant, which
allows the caller to specify additional lookup flags, and modify
ip6_dst_lookup_tail() to enforce the ifindex match on the second
lookup via said helper.

Fixes: d46a9d678e4c ("net: ipv6: Dont add RT6_LOOKUP_F_IFACE flag if saddr set")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

I don't agree with that 'Fixes:' tag.

ip6_route_output did not add the RT6_LOOKUP_F_IFACE flag until 
741a11d9e410; d46a9d678e4c is a follow on to limit adding the flag only 
if no source address  is given.

Since ip6_dst_lookup_tail never considered the flowi6_oif this is a 
general bug fix rather than a fix of d46a9d678e4c.

Ok, I'll remove it in the v2, which will include Hannes feedback, too.

Regards,

Paolo