[net-next PATCH RFC 0/3] Preserve skb->mark through VTI tunnels

[net-next PATCH RFC 0/3] Preserve skb->mark through VTI tunnels

[Alexander Duyck]

These patches are meant to try and address the fact the VTI tunnels are
currently overwriting the skb->mark value.  I am generally happy with the
first two patches, however the third patch still modifies the skb->mark,
though it undoes after the fact.

The main problem I am trying to address is the fact that currently if I use
an v6 over v6 VTI tunnel I cannot receive any traffic on the interface as
the skb->mark is bleeding through and causing the traffic to be dropped.

---

Alexander Duyck (3):
      ip_vti/ip6_vti: Do not touch skb->mark on xmit
      xfrm: Override skb->mark with tunnel->parm.i_key in xfrm_input
      ip_vti/ip6_vti: Preserve skb->mark after rcv_cb call


 net/ipv4/ip_vti.c     |    9 ++++++---
 net/ipv6/ip6_vti.c    |    8 ++++++--
 net/xfrm/xfrm_input.c |   17 ++++++++++++++++-
 3 files changed, 28 insertions(+), 6 deletions(-)

--

[net-next PATCH RFC 1/3] ip_vti/ip6_vti: Do not touch skb->mark on xmit

[Alexander Duyck]

Instead of modifying skb->mark we can simply modify the flowi_mark that is
generated as a result of the xfrm_decode_session.  By doing this we don't
need to actually touch the skb->mark and it can be preserved as it passes
out through the tunnel.

Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
---
 net/ipv4/ip_vti.c  |    5 +++--
 net/ipv6/ip6_vti.c |    4 +++-
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/ip_vti.c b/net/ipv4/ip_vti.c
index 9f7269f3c54a..4c318e1c13c8 100644
--- a/net/ipv4/ip_vti.c
+++ b/net/ipv4/ip_vti.c
@@ -216,8 +216,6 @@ static netdev_tx_t vti_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
 
 	memset(&fl, 0, sizeof(fl));
 
-	skb->mark = be32_to_cpu(tunnel->parms.o_key);
-
 	switch (skb->protocol) {
 	case htons(ETH_P_IP):
 		xfrm_decode_session(skb, &fl, AF_INET);
@@ -233,6 +231,9 @@ static netdev_tx_t vti_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
 		return NETDEV_TX_OK;
 	}
 
+	/* override mark with tunnel output key */
+	fl.flowi_mark = be32_to_cpu(tunnel->parms.o_key);
+
 	return vti_xmit(skb, dev, &fl);
 }
 
diff --git a/net/ipv6/ip6_vti.c b/net/ipv6/ip6_vti.c
index ed9d681207fa..104de4da3ff3 100644
--- a/net/ipv6/ip6_vti.c
+++ b/net/ipv6/ip6_vti.c
@@ -495,7 +495,6 @@ vti6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
 	int ret;
 
 	memset(&fl, 0, sizeof(fl));
-	skb->mark = be32_to_cpu(t->parms.o_key);
 
 	switch (skb->protocol) {
 	case htons(ETH_P_IPV6):
@@ -516,6 +515,9 @@ vti6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
 		goto tx_err;
 	}
 
+	/* override mark with tunnel output key */
+	fl.flowi_mark = be32_to_cpu(t->parms.o_key);
+
 	ret = vti6_xmit(skb, dev, &fl);
 	if (ret < 0)
 		goto tx_err;

[net-next PATCH RFC 2/3] xfrm: Override skb->mark with tunnel->parm.i_key in xfrm_input

[Alexander Duyck]

This change makes it so that if a tunnel is defined we just use the mark
from the tunnel instead of the mark from the skb header.  By doing this we
can avoid the need to set skb->mark inside of the tunnel receive functions.

Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
---
 net/xfrm/xfrm_input.c |   17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/net/xfrm/xfrm_input.c b/net/xfrm/xfrm_input.c
index 526c4feb3b50..b58286ecd156 100644
--- a/net/xfrm/xfrm_input.c
+++ b/net/xfrm/xfrm_input.c
@@ -13,6 +13,8 @@
 #include <net/dst.h>
 #include <net/ip.h>
 #include <net/xfrm.h>
+#include <net/ip_tunnels.h>
+#include <net/ip6_tunnel.h>
 
 static struct kmem_cache *secpath_cachep __read_mostly;
 
@@ -186,6 +188,7 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type)
 	struct xfrm_state *x = NULL;
 	xfrm_address_t *daddr;
 	struct xfrm_mode *inner_mode;
+	u32 mark = skb->mark;
 	unsigned int family;
 	int decaps = 0;
 	int async = 0;
@@ -203,6 +206,18 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type)
 				   XFRM_SPI_SKB_CB(skb)->daddroff);
 	family = XFRM_SPI_SKB_CB(skb)->family;
 
+	/* if tunnel is present override skb->mark value with tunnel i_key */
+	if (XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip4) {
+		switch (family) {
+		case AF_INET:
+			mark = be32_to_cpu(XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip4->parms.i_key);
+			break;
+		case AF_INET6:
+			mark = be32_to_cpu(XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip6->parms.i_key);
+			break;
+		}
+	}
+
 	/* Allocate new secpath or COW existing one. */
 	if (!skb->sp || atomic_read(&skb->sp->refcnt) != 1) {
 		struct sec_path *sp;
@@ -229,7 +244,7 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type)
 			goto drop;
 		}
 
-		x = xfrm_state_lookup(net, skb->mark, daddr, spi, nexthdr, family);
+		x = xfrm_state_lookup(net, mark, daddr, spi, nexthdr, family);
 		if (x == NULL) {
 			XFRM_INC_STATS(net, LINUX_MIB_XFRMINNOSTATES);
 			xfrm_audit_state_notfound(skb, family, spi, seq);

[net-next PATCH RFC 3/3] ip_vti/ip6_vti: Preserve skb->mark after rcv_cb call

[Alexander Duyck]

The vti6_rcv_cb and vti_rcv_cb calls were leaving the skb->mark modified
after completing the function.  This resulted in the original skb->mark
value being lost.  Since we only need skb->mark to be set for
xfrm_policy_check we can pull the assignment into the rcv_cb calls and then
just restore the original mark after xfrm_policy_check has been completed.

Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
---
 net/ipv4/ip_vti.c  |    9 +++++++--
 net/ipv6/ip6_vti.c |    9 +++++++--
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/ip_vti.c b/net/ipv4/ip_vti.c
index 4c318e1c13c8..0c152087ca15 100644
--- a/net/ipv4/ip_vti.c
+++ b/net/ipv4/ip_vti.c
@@ -65,7 +65,6 @@ static int vti_input(struct sk_buff *skb, int nexthdr, __be32 spi,
 			goto drop;
 
 		XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip4 = tunnel;
-		skb->mark = be32_to_cpu(tunnel->parms.i_key);
 
 		return xfrm_input(skb, nexthdr, spi, encap_type);
 	}
@@ -91,6 +90,8 @@ static int vti_rcv_cb(struct sk_buff *skb, int err)
 	struct pcpu_sw_netstats *tstats;
 	struct xfrm_state *x;
 	struct ip_tunnel *tunnel = XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip4;
+	u32 orig_mark = skb->mark;
+	int ret;
 
 	if (!tunnel)
 		return 1;
@@ -107,7 +108,11 @@ static int vti_rcv_cb(struct sk_buff *skb, int err)
 	x = xfrm_input_state(skb);
 	family = x->inner_mode->afinfo->family;
 
-	if (!xfrm_policy_check(NULL, XFRM_POLICY_IN, skb, family))
+	skb->mark = be32_to_cpu(tunnel->parms.i_key);
+	ret = xfrm_policy_check(NULL, XFRM_POLICY_IN, skb, family);
+	skb->mark = orig_mark;
+
+	if (!ret)
 		return -EPERM;
 
 	skb_scrub_packet(skb, !net_eq(tunnel->net, dev_net(skb->dev)));
diff --git a/net/ipv6/ip6_vti.c b/net/ipv6/ip6_vti.c
index 104de4da3ff3..ff3bd863fa03 100644
--- a/net/ipv6/ip6_vti.c
+++ b/net/ipv6/ip6_vti.c
@@ -322,7 +322,6 @@ static int vti6_rcv(struct sk_buff *skb)
 		}
 
 		XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip6 = t;
-		skb->mark = be32_to_cpu(t->parms.i_key);
 
 		rcu_read_unlock();
 
@@ -342,6 +341,8 @@ static int vti6_rcv_cb(struct sk_buff *skb, int err)
 	struct pcpu_sw_netstats *tstats;
 	struct xfrm_state *x;
 	struct ip6_tnl *t = XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip6;
+	u32 orig_mark = skb->mark;
+	int ret;
 
 	if (!t)
 		return 1;
@@ -358,7 +359,11 @@ static int vti6_rcv_cb(struct sk_buff *skb, int err)
 	x = xfrm_input_state(skb);
 	family = x->inner_mode->afinfo->family;
 
-	if (!xfrm_policy_check(NULL, XFRM_POLICY_IN, skb, family))
+	skb->mark = be32_to_cpu(t->parms.i_key);
+	ret = xfrm_policy_check(NULL, XFRM_POLICY_IN, skb, family);
+	skb->mark = orig_mark;
+
+	if (!ret)
 		return -EPERM;
 
 	skb_scrub_packet(skb, !net_eq(t->net, dev_net(skb->dev)));

Re: [net-next PATCH RFC 0/3] Preserve skb->mark through VTI tunnels

[Steffen Klassert]

On Tue, May 26, 2015 at 03:41:10PM -0700, Alexander Duyck wrote:
> These patches are meant to try and address the fact the VTI tunnels are
> currently overwriting the skb->mark value.  I am generally happy with the
> first two patches, however the third patch still modifies the skb->mark,
> though it undoes after the fact.

I don't see any better solution, so I think this should be ok for now.
On the long run we need to replace this gre key/mark matching with
a separate interface.

> 
> The main problem I am trying to address is the fact that currently if I use
> an v6 over v6 VTI tunnel I cannot receive any traffic on the interface as
> the skb->mark is bleeding through and causing the traffic to be dropped.

This is broken in the current mainline, so it should go into the ipsec
tree as a bugfix. I'd merge this patchset if you submit it to that tree.

Thanks!

Re: [net-next PATCH RFC 0/3] Preserve skb->mark through VTI tunnels

[Herbert Xu]

On Tue, May 26, 2015 at 03:41:10PM -0700, Alexander Duyck wrote:
> These patches are meant to try and address the fact the VTI tunnels are
> currently overwriting the skb->mark value.  I am generally happy with the
> first two patches, however the third patch still modifies the skb->mark,
> though it undoes after the fact.
> 
> The main problem I am trying to address is the fact that currently if I use
> an v6 over v6 VTI tunnel I cannot receive any traffic on the interface as
> the skb->mark is bleeding through and causing the traffic to be dropped.

Looks good to me.  Thanks for following up on this!
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt