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Date: Sat, 16 May 2015 17:13:28 -0400 (EDT)
From: David Miller <davem@...emloft.net>
To: herbert@...dor.apana.org.au
Cc: alexander.duyck@...il.com, alexander.h.duyck@...hat.com,
netdev@...r.kernel.org, steffen.klassert@...unet.com, tgraf@...g.ch
Subject: Re: [net PATCH] ip_vti/ip6_vti: Clear skb->mark when resetting
skb->dev in receive path
From: Herbert Xu <herbert@...dor.apana.org.au>
Date: Sat, 16 May 2015 20:34:58 +0800
> On Fri, May 15, 2015 at 12:14:43PM -0700, Alexander Duyck wrote:
>>
>> >Yeah, this mark handling via tunnel->parms.o_key looks not so good.
>>
>> So is there any recommendations for an alternative to make it so
>> that the ipsec endpoint is identified as needing to be encrypted or
>> decrypted? If needed I could probably take a day or two to try and
>> address it as I still have a few other minor things I want to try
>> and fix such as the MTU configuration for vti/vti6.
>
> I'd like to hear from Steffen as to whether there is anything
> in userspace that relies on the mark being used in this way by
> vti. If not it should be easy to get rid of it and use some
> field that's not exposed to user-space. If there is then this
> would be tricky to resolve.
The mark stuff comes from the commit below, and at the time I remember
pushing back a few times because I was uneasy about applying this
change:
====================
commit 7263a5187f9e9de45fcb51349cf0e031142c19a1
Author: Christophe Gouault <christophe.gouault@...nd.com>
Date: Tue Oct 8 17:21:22 2013 +0200
vti: get rid of nf mark rule in prerouting
This patch fixes and improves the use of vti interfaces (while
lightly changing the way of configuring them).
Currently:
- it is necessary to identify and mark inbound IPsec
packets destined to each vti interface, via netfilter rules in
the mangle table at prerouting hook.
- the vti module cannot retrieve the right tunnel in input since
commit b9959fd3: vti tunnels all have an i_key, but the tunnel lookup
is done with flag TUNNEL_NO_KEY, so there no chance to retrieve them.
- the i_key is used by the outbound processing as a mark to lookup
for the right SP and SA bundle.
This patch uses the o_key to store the vti mark (instead of i_key) and
enables:
- to avoid the need for previously marking the inbound skbuffs via a
netfilter rule.
- to properly retrieve the right tunnel in input, only based on the IPsec
packet outer addresses.
- to properly perform an inbound policy check (using the tunnel o_key
as a mark).
- to properly perform an outbound SPD and SAD lookup (using the tunnel
o_key as a mark).
- to keep the current mark of the skbuff. The skbuff mark is neither
used nor changed by the vti interface. Only the vti interface o_key
is used.
SAs have a wildcard mark.
SPs have a mark equal to the vti interface o_key.
The vti interface must be created as follows (i_key = 0, o_key = mark):
ip link add vti1 mode vti local 1.1.1.1 remote 2.2.2.2 okey 1
The SPs attached to vti1 must be created as follows (mark = vti1 o_key):
ip xfrm policy add dir out mark 1 tmpl src 1.1.1.1 dst 2.2.2.2 \
proto esp mode tunnel
ip xfrm policy add dir in mark 1 tmpl src 2.2.2.2 dst 1.1.1.1 \
proto esp mode tunnel
The SAs are created with the default wildcard mark. There is no
distinction between global vs. vti SAs. Just their addresses will
possibly link them to a vti interface:
ip xfrm state add src 1.1.1.1 dst 2.2.2.2 proto esp spi 1000 mode tunnel \
enc "cbc(aes)" "azertyuiopqsdfgh"
ip xfrm state add src 2.2.2.2 dst 1.1.1.1 proto esp spi 2000 mode tunnel \
enc "cbc(aes)" "sqbdhgqsdjqjsdfh"
To avoid matching "global" (not vti) SPs in vti interfaces, global SPs
should no use the default wildcard mark, but explicitly match mark 0.
To avoid a double SPD lookup in input and output (in global and vti SPDs),
the NOPOLICY and NOXFRM options should be set on the vti interfaces:
echo 1 > /proc/sys/net/ipv4/conf/vti1/disable_policy
echo 1 > /proc/sys/net/ipv4/conf/vti1/disable_xfrm
The outgoing traffic is steered to vti1 by a route via the vti interface:
ip route add 192.168.0.0/16 dev vti1
The incoming IPsec traffic is steered to vti1 because its outer addresses
match the vti1 tunnel configuration.
Signed-off-by: Christophe Gouault <christophe.gouault@...nd.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
diff --git a/net/ipv4/ip_vti.c b/net/ipv4/ip_vti.c
index e805e7b..6e87f85 100644
--- a/net/ipv4/ip_vti.c
+++ b/net/ipv4/ip_vti.c
@@ -125,8 +125,17 @@ static int vti_rcv(struct sk_buff *skb)
iph->saddr, iph->daddr, 0);
if (tunnel != NULL) {
struct pcpu_tstats *tstats;
+ u32 oldmark = skb->mark;
+ int ret;
- if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
+
+ /* temporarily mark the skb with the tunnel o_key, to
+ * only match policies with this mark.
+ */
+ skb->mark = be32_to_cpu(tunnel->parms.o_key);
+ ret = xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb);
+ skb->mark = oldmark;
+ if (!ret)
return -1;
tstats = this_cpu_ptr(tunnel->dev->tstats);
@@ -135,7 +144,6 @@ static int vti_rcv(struct sk_buff *skb)
tstats->rx_bytes += skb->len;
u64_stats_update_end(&tstats->syncp);
- skb->mark = 0;
secpath_reset(skb);
skb->dev = tunnel->dev;
return 1;
@@ -167,7 +175,7 @@ static netdev_tx_t vti_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
memset(&fl4, 0, sizeof(fl4));
flowi4_init_output(&fl4, tunnel->parms.link,
- be32_to_cpu(tunnel->parms.i_key), RT_TOS(tos),
+ be32_to_cpu(tunnel->parms.o_key), RT_TOS(tos),
RT_SCOPE_UNIVERSE,
IPPROTO_IPIP, 0,
dst, tiph->saddr, 0, 0);
--
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