[PATCH net] openvswitch: take into account de-fragmentation in execute_check_pkt_len

[PATCH net] openvswitch: take into account de-fragmentation in execute_check_pkt_len

[Lorenzo Bianconi]

ovs connection tracking module performs de-fragmentation on incoming
fragmented traffic. Take info account if traffic has been de-fragmented
in execute_check_pkt_len action otherwise we will perform the wrong
nested action considering the original packet size. This issue typically
occurs if ovs-vswitchd adds a rule in the pipeline that requires connection
tracking (e.g. OVN stateful ACLs) before execute_check_pkt_len action.

Fixes: 4d5ec89fc8d14 ("net: openvswitch: Add a new action check_pkt_len")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
---
 net/openvswitch/actions.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
index fc0efd8833c8..9f4dd64e53bb 100644
--- a/net/openvswitch/actions.c
+++ b/net/openvswitch/actions.c
@@ -1169,9 +1169,10 @@ static int execute_check_pkt_len(struct datapath *dp, struct sk_buff *skb,
 				 struct sw_flow_key *key,
 				 const struct nlattr *attr, bool last)
 {
+	struct ovs_skb_cb *ovs_cb = OVS_CB(skb);
 	const struct nlattr *actions, *cpl_arg;
 	const struct check_pkt_len_arg *arg;
-	int rem = nla_len(attr);
+	int len, rem = nla_len(attr);
 	bool clone_flow_key;
 
 	/* The first netlink attribute in 'attr' is always
@@ -1180,7 +1181,8 @@ static int execute_check_pkt_len(struct datapath *dp, struct sk_buff *skb,
 	cpl_arg = nla_data(attr);
 	arg = nla_data(cpl_arg);
 
-	if (skb->len <= arg->pkt_len) {
+	len = ovs_cb->mru ? ovs_cb->mru : skb->len;
+	if (len <= arg->pkt_len) {
 		/* Second netlink attribute in 'attr' is always
 		 * 'OVS_CHECK_PKT_LEN_ATTR_ACTIONS_IF_LESS_EQUAL'.
 		 */
-- 
2.26.2

Re: [PATCH net] openvswitch: take into account de-fragmentation in execute_check_pkt_len

[Pravin Shelar]

On Fri, Jun 19, 2020 at 4:48 AM Lorenzo Bianconi <lorenzo@kernel.org> wrote:
>
> ovs connection tracking module performs de-fragmentation on incoming
> fragmented traffic. Take info account if traffic has been de-fragmented
> in execute_check_pkt_len action otherwise we will perform the wrong
> nested action considering the original packet size. This issue typically
> occurs if ovs-vswitchd adds a rule in the pipeline that requires connection
> tracking (e.g. OVN stateful ACLs) before execute_check_pkt_len action.
>
> Fixes: 4d5ec89fc8d14 ("net: openvswitch: Add a new action check_pkt_len")
> Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
> ---
>  net/openvswitch/actions.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
> index fc0efd8833c8..9f4dd64e53bb 100644
> --- a/net/openvswitch/actions.c
> +++ b/net/openvswitch/actions.c
> @@ -1169,9 +1169,10 @@ static int execute_check_pkt_len(struct datapath *dp, struct sk_buff *skb,
>                                  struct sw_flow_key *key,
>                                  const struct nlattr *attr, bool last)
>  {
> +       struct ovs_skb_cb *ovs_cb = OVS_CB(skb);
>         const struct nlattr *actions, *cpl_arg;
>         const struct check_pkt_len_arg *arg;
> -       int rem = nla_len(attr);
> +       int len, rem = nla_len(attr);
>         bool clone_flow_key;
>
>         /* The first netlink attribute in 'attr' is always
> @@ -1180,7 +1181,8 @@ static int execute_check_pkt_len(struct datapath *dp, struct sk_buff *skb,
>         cpl_arg = nla_data(attr);
>         arg = nla_data(cpl_arg);
>
> -       if (skb->len <= arg->pkt_len) {
> +       len = ovs_cb->mru ? ovs_cb->mru : skb->len;
> +       if (len <= arg->pkt_len) {

We could also check for the segmented packet and use  segment length
for this check.

Re: [PATCH net] openvswitch: take into account de-fragmentation in execute_check_pkt_len

[Lorenzo Bianconi]

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> On Fri, Jun 19, 2020 at 4:48 AM Lorenzo Bianconi <lorenzo@kernel.org> wrote:
> >
> > ovs connection tracking module performs de-fragmentation on incoming
> > fragmented traffic. Take info account if traffic has been de-fragmented
> > in execute_check_pkt_len action otherwise we will perform the wrong
> > nested action considering the original packet size. This issue typically
> > occurs if ovs-vswitchd adds a rule in the pipeline that requires connection
> > tracking (e.g. OVN stateful ACLs) before execute_check_pkt_len action.
> >
> > Fixes: 4d5ec89fc8d14 ("net: openvswitch: Add a new action check_pkt_len")
> > Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
> > ---
> >  net/openvswitch/actions.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
> > index fc0efd8833c8..9f4dd64e53bb 100644
> > --- a/net/openvswitch/actions.c
> > +++ b/net/openvswitch/actions.c
> > @@ -1169,9 +1169,10 @@ static int execute_check_pkt_len(struct datapath *dp, struct sk_buff *skb,
> >                                  struct sw_flow_key *key,
> >                                  const struct nlattr *attr, bool last)
> >  {
> > +       struct ovs_skb_cb *ovs_cb = OVS_CB(skb);
> >         const struct nlattr *actions, *cpl_arg;
> >         const struct check_pkt_len_arg *arg;
> > -       int rem = nla_len(attr);
> > +       int len, rem = nla_len(attr);
> >         bool clone_flow_key;
> >
> >         /* The first netlink attribute in 'attr' is always
> > @@ -1180,7 +1181,8 @@ static int execute_check_pkt_len(struct datapath *dp, struct sk_buff *skb,
> >         cpl_arg = nla_data(attr);
> >         arg = nla_data(cpl_arg);
> >
> > -       if (skb->len <= arg->pkt_len) {
> > +       len = ovs_cb->mru ? ovs_cb->mru : skb->len;
> > +       if (len <= arg->pkt_len) {
> 
> We could also check for the segmented packet and use  segment length
> for this check.

Hi Pravin,

thx for review.
By 'segmented packet' and 'segment length', do you mean 'fragment' and
'fragment length'?
If so I guess we can't retrieve the original fragment length if we exec
OVS_ACTION_ATTR_CT before OVS_ACTION_ATTR_CHECK_PKT_LEN (e.g if we have a
stateful ACL in the ingress pipeline) since handle_fragments() will reconstruct
the whole IP datagram and it will store frag_max_size in OVS_CB(skb)->mru.
Am I missing something?

Regards,
Lorenzo


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Re: [PATCH net] openvswitch: take into account de-fragmentation in execute_check_pkt_len

[Pravin Shelar]

On Mon, Jun 22, 2020 at 5:02 AM Lorenzo Bianconi <lorenzo@kernel.org> wrote:
>
> > On Fri, Jun 19, 2020 at 4:48 AM Lorenzo Bianconi <lorenzo@kernel.org> wrote:
> > >
> > > ovs connection tracking module performs de-fragmentation on incoming
> > > fragmented traffic. Take info account if traffic has been de-fragmented
> > > in execute_check_pkt_len action otherwise we will perform the wrong
> > > nested action considering the original packet size. This issue typically
> > > occurs if ovs-vswitchd adds a rule in the pipeline that requires connection
> > > tracking (e.g. OVN stateful ACLs) before execute_check_pkt_len action.
> > >
> > > Fixes: 4d5ec89fc8d14 ("net: openvswitch: Add a new action check_pkt_len")
> > > Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
> > > ---
> > >  net/openvswitch/actions.c | 6 ++++--
> > >  1 file changed, 4 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
> > > index fc0efd8833c8..9f4dd64e53bb 100644
> > > --- a/net/openvswitch/actions.c
> > > +++ b/net/openvswitch/actions.c
> > > @@ -1169,9 +1169,10 @@ static int execute_check_pkt_len(struct datapath *dp, struct sk_buff *skb,
> > >                                  struct sw_flow_key *key,
> > >                                  const struct nlattr *attr, bool last)
> > >  {
> > > +       struct ovs_skb_cb *ovs_cb = OVS_CB(skb);
> > >         const struct nlattr *actions, *cpl_arg;
> > >         const struct check_pkt_len_arg *arg;
> > > -       int rem = nla_len(attr);
> > > +       int len, rem = nla_len(attr);
> > >         bool clone_flow_key;
> > >
> > >         /* The first netlink attribute in 'attr' is always
> > > @@ -1180,7 +1181,8 @@ static int execute_check_pkt_len(struct datapath *dp, struct sk_buff *skb,
> > >         cpl_arg = nla_data(attr);
> > >         arg = nla_data(cpl_arg);
> > >
> > > -       if (skb->len <= arg->pkt_len) {
> > > +       len = ovs_cb->mru ? ovs_cb->mru : skb->len;
> > > +       if (len <= arg->pkt_len) {
> >
> > We could also check for the segmented packet and use  segment length
> > for this check.
>
> Hi Pravin,
>
> thx for review.
> By 'segmented packet' and 'segment length', do you mean 'fragment' and
> 'fragment length'?

I am actually talking about GSO packets.

Thanks.

> If so I guess we can't retrieve the original fragment length if we exec
> OVS_ACTION_ATTR_CT before OVS_ACTION_ATTR_CHECK_PKT_LEN (e.g if we have a
> stateful ACL in the ingress pipeline) since handle_fragments() will reconstruct
> the whole IP datagram and it will store frag_max_size in OVS_CB(skb)->mru.
> Am I missing something?
>
> Regards,
> Lorenzo
>

Re: [PATCH net] openvswitch: take into account de-fragmentation in execute_check_pkt_len

[Lorenzo Bianconi]

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> On Mon, Jun 22, 2020 at 5:02 AM Lorenzo Bianconi <lorenzo@kernel.org> wrote:
> >
> > > On Fri, Jun 19, 2020 at 4:48 AM Lorenzo Bianconi <lorenzo@kernel.org> wrote:
> > > >
> > > > ovs connection tracking module performs de-fragmentation on incoming
> > > > fragmented traffic. Take info account if traffic has been de-fragmented
> > > > in execute_check_pkt_len action otherwise we will perform the wrong
> > > > nested action considering the original packet size. This issue typically
> > > > occurs if ovs-vswitchd adds a rule in the pipeline that requires connection
> > > > tracking (e.g. OVN stateful ACLs) before execute_check_pkt_len action.
> > > >
> > > > Fixes: 4d5ec89fc8d14 ("net: openvswitch: Add a new action check_pkt_len")
> > > > Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
> > > > ---
> > > >  net/openvswitch/actions.c | 6 ++++--
> > > >  1 file changed, 4 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
> > > > index fc0efd8833c8..9f4dd64e53bb 100644
> > > > --- a/net/openvswitch/actions.c
> > > > +++ b/net/openvswitch/actions.c
> > > > @@ -1169,9 +1169,10 @@ static int execute_check_pkt_len(struct datapath *dp, struct sk_buff *skb,
> > > >                                  struct sw_flow_key *key,
> > > >                                  const struct nlattr *attr, bool last)
> > > >  {
> > > > +       struct ovs_skb_cb *ovs_cb = OVS_CB(skb);
> > > >         const struct nlattr *actions, *cpl_arg;
> > > >         const struct check_pkt_len_arg *arg;
> > > > -       int rem = nla_len(attr);
> > > > +       int len, rem = nla_len(attr);
> > > >         bool clone_flow_key;
> > > >
> > > >         /* The first netlink attribute in 'attr' is always
> > > > @@ -1180,7 +1181,8 @@ static int execute_check_pkt_len(struct datapath *dp, struct sk_buff *skb,
> > > >         cpl_arg = nla_data(attr);
> > > >         arg = nla_data(cpl_arg);
> > > >
> > > > -       if (skb->len <= arg->pkt_len) {
> > > > +       len = ovs_cb->mru ? ovs_cb->mru : skb->len;
> > > > +       if (len <= arg->pkt_len) {
> > >
> > > We could also check for the segmented packet and use  segment length
> > > for this check.
> >
> > Hi Pravin,
> >
> > thx for review.
> > By 'segmented packet' and 'segment length', do you mean 'fragment' and
> > 'fragment length'?
> 
> I am actually talking about GSO packets.

ack. IIUC you mean to add a check for gso packets as well taking into account
gso_size. I will fix in v2.

Regards,
Lorenzo

> 
> Thanks.
> 
> > If so I guess we can't retrieve the original fragment length if we exec
> > OVS_ACTION_ATTR_CT before OVS_ACTION_ATTR_CHECK_PKT_LEN (e.g if we have a
> > stateful ACL in the ingress pipeline) since handle_fragments() will reconstruct
> > the whole IP datagram and it will store frag_max_size in OVS_CB(skb)->mru.
> > Am I missing something?
> >
> > Regards,
> > Lorenzo
> >
> 

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