Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <20191217155102.46039-1-mcroce@redhat.com> <CAOrHB_BVf8mXuCUehMy0_Sbq=pgfg7Zu1ivPFT8Y9Zatdj1yPw@mail.gmail.com>
In-Reply-To: <CAOrHB_BVf8mXuCUehMy0_Sbq=pgfg7Zu1ivPFT8Y9Zatdj1yPw@mail.gmail.com>
From:   Matteo Croce <mcroce@redhat.com>
Date:   Thu, 19 Dec 2019 17:36:10 +0100
Message-ID: <CAGnkfhyojPg9ZxrR=NcNdsndxZpdpjgArzO+HHsVWnCKTBg1Tg@mail.gmail.com>
Subject: Re: [PATCH net-next v2] openvswitch: add TTL decrement action
To:     Pravin Shelar <pshelar@ovn.org>
Cc:     Linux Kernel Network Developers <netdev@vger.kernel.org>,
        ovs dev <dev@openvswitch.org>,
        LKML <linux-kernel@vger.kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Bindiya Kurle <bindiyakurle@gmail.com>,
        Simon Horman <simon.horman@netronome.com>,
        Ben Pfaff <blp@ovn.org>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Wed, Dec 18, 2019 at 4:06 AM Pravin Shelar <pshelar@ovn.org> wrote:
>
> On Tue, Dec 17, 2019 at 7:51 AM Matteo Croce <mcroce@redhat.com> wrote:
> >
> > New action to decrement TTL instead of setting it to a fixed value.
> > This action will decrement the TTL and, in case of expired TTL, drop it
> > or execute an action passed via a nested attribute.
> > The default TTL expired action is to drop the packet.
> >
> > Supports both IPv4 and IPv6 via the ttl and hop_limit fields, respectively.
> >
> > Tested with a corresponding change in the userspace:
> >
> >     # ovs-dpctl dump-flows
> >     in_port(2),eth(),eth_type(0x0800), packets:0, bytes:0, used:never, actions:dec_ttl{ttl<=1 action:(drop)},1,1
> >     in_port(1),eth(),eth_type(0x0800), packets:0, bytes:0, used:never, actions:dec_ttl{ttl<=1 action:(drop)},1,2
> >     in_port(1),eth(),eth_type(0x0806), packets:0, bytes:0, used:never, actions:2
> >     in_port(2),eth(),eth_type(0x0806), packets:0, bytes:0, used:never, actions:1
> >
> >     # ping -c1 192.168.0.2 -t 42
> >     IP (tos 0x0, ttl 41, id 61647, offset 0, flags [DF], proto ICMP (1), length 84)
> >         192.168.0.1 > 192.168.0.2: ICMP echo request, id 386, seq 1, length 64
> >     # ping -c1 192.168.0.2 -t 120
> >     IP (tos 0x0, ttl 119, id 62070, offset 0, flags [DF], proto ICMP (1), length 84)
> >         192.168.0.1 > 192.168.0.2: ICMP echo request, id 388, seq 1, length 64
> >     # ping -c1 192.168.0.2 -t 1
> >     #
> >
> > Co-authored-by: Bindiya Kurle <bindiyakurle@gmail.com>
> > Signed-off-by: Bindiya Kurle <bindiyakurle@gmail.com>
> > Signed-off-by: Matteo Croce <mcroce@redhat.com>
> > ---
> >  include/uapi/linux/openvswitch.h |  22 +++++++
> >  net/openvswitch/actions.c        |  71 +++++++++++++++++++++
> >  net/openvswitch/flow_netlink.c   | 105 +++++++++++++++++++++++++++++++
> >  3 files changed, 198 insertions(+)
> >
> > diff --git a/include/uapi/linux/openvswitch.h b/include/uapi/linux/openvswitch.h
> > index a87b44cd5590..b6684bc04883 100644
> > --- a/include/uapi/linux/openvswitch.h
> > +++ b/include/uapi/linux/openvswitch.h
> > @@ -927,6 +927,7 @@ enum ovs_action_attr {
> >         OVS_ACTION_ATTR_METER,        /* u32 meter ID. */
> >         OVS_ACTION_ATTR_CLONE,        /* Nested OVS_CLONE_ATTR_*.  */
> >         OVS_ACTION_ATTR_CHECK_PKT_LEN, /* Nested OVS_CHECK_PKT_LEN_ATTR_*. */
> > +       OVS_ACTION_ATTR_DEC_TTL,       /* Nested OVS_DEC_TTL_ATTR_*. */
> >
> >         __OVS_ACTION_ATTR_MAX,        /* Nothing past this will be accepted
> >                                        * from userspace. */
> > @@ -939,6 +940,23 @@ enum ovs_action_attr {
> >  };
> >
> >  #define OVS_ACTION_ATTR_MAX (__OVS_ACTION_ATTR_MAX - 1)
> > +enum ovs_dec_ttl_attr {
> > +       OVS_DEC_TTL_ATTR_UNSPEC,
> > +       OVS_DEC_TTL_ATTR_ACTION_TYPE,    /* Action Type u32 */
> > +       OVS_DEC_TTL_ATTR_ACTION,         /* nested action */
> > +       __OVS_DEC_TTL_ATTR_MAX,
> > +#ifdef __KERNEL__
> > +       OVS_DEC_TTL_ATTR_ARG          /* struct sample_arg  */
> > +#endif
> > +};
> > +
>
> I do not see need for type or OVS_DEC_TTL_ACTION_DROP, if there are no
> nested action the datapath can drop the packet.
>
> > +#ifdef __KERNEL__
> > +struct dec_ttl_arg {
> > +       u32 action_type;            /* dec_ttl action type.*/
> > +};
> > +#endif
> > +
> > +#define OVS_DEC_TTL_ATTR_MAX (__OVS_DEC_TTL_ATTR_MAX - 1)
> >
> >  /* Meters. */
> >  #define OVS_METER_FAMILY  "ovs_meter"
> > @@ -1009,6 +1027,10 @@ enum ovs_ct_limit_attr {
> >         __OVS_CT_LIMIT_ATTR_MAX
> >  };
> >
> > +enum ovs_dec_ttl_action {            /*Actions supported by dec_ttl */
> > +       OVS_DEC_TTL_ACTION_DROP,
> > +       OVS_DEC_TTL_ACTION_USER_SPACE
> > +};
> >  #define OVS_CT_LIMIT_ATTR_MAX (__OVS_CT_LIMIT_ATTR_MAX - 1)
> >
> >  #define OVS_ZONE_LIMIT_DEFAULT_ZONE -1
> > diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
> > index 4c8395462303..5329668732b1 100644
> > --- a/net/openvswitch/actions.c
> > +++ b/net/openvswitch/actions.c
> > @@ -960,6 +960,31 @@ static int output_userspace(struct datapath *dp, struct sk_buff *skb,
> >         return ovs_dp_upcall(dp, skb, key, &upcall, cutlen);
> >  }
> >
> > +static int dec_ttl(struct datapath *dp, struct sk_buff *skb,
> > +                  struct sw_flow_key *fk, const struct nlattr *attr, bool last)
> > +{
> > +       struct nlattr *actions;
> > +       struct nlattr *dec_ttl_arg;
> > +       int rem = nla_len(attr);
> > +       const struct dec_ttl_arg *arg;
> > +
> > +       /* The first action is always OVS_DEC_TTL_ATTR_ARG. */
> > +       dec_ttl_arg = nla_data(attr);
> > +       arg = nla_data(dec_ttl_arg);
> > +       actions = nla_next(dec_ttl_arg, &rem);
> > +
> > +       switch (arg->action_type) {
> > +       case OVS_DEC_TTL_ACTION_DROP:
> > +               consume_skb(skb);
> > +               break;
> > +
> > +       case OVS_DEC_TTL_ACTION_USER_SPACE:
> > +               return clone_execute(dp, skb, fk, 0, actions, rem, last, false);
> > +       }
> > +
> > +       return 0;
> > +}
> > +
> >  /* When 'last' is true, sample() should always consume the 'skb'.
> >   * Otherwise, sample() should keep 'skb' intact regardless what
> >   * actions are executed within sample().
> > @@ -1176,6 +1201,44 @@ static int execute_check_pkt_len(struct datapath *dp, struct sk_buff *skb,
> >                              nla_len(actions), last, clone_flow_key);
> >  }
> >
> > +static int execute_dec_ttl(struct sk_buff *skb, struct sw_flow_key *key)
> > +{
> > +       int err;
> > +
> > +       if (skb->protocol == htons(ETH_P_IPV6)) {
> > +               struct ipv6hdr *nh = ipv6_hdr(skb);
> > +
> > +               err = skb_ensure_writable(skb, skb_network_offset(skb) +
> > +                                         sizeof(*nh));
> There is no need to initialize 'nh', just use 'struct ipv6hdr' to get the size.

But I have to set it later to have nh->hop_limit.
Do you mean to assign it before the skb_ensure_writable check?
What differs sizeof(*nh) and sizeof(struct ipv6hdr)? The former will
work also after a refactor.

> > +               if (unlikely(err))
> > +                       return err;
> > +
> > +               if (nh->hop_limit <= 1)
> > +                       return -EHOSTUNREACH;
> > +
> > +               key->ip.ttl = --nh->hop_limit;
> > +       } else {
> > +               struct iphdr *nh = ip_hdr(skb);
> > +               u8 old_ttl;
> > +
> > +               err = skb_ensure_writable(skb, skb_network_offset(skb) +
> > +                                         sizeof(*nh));
> same as above.
> > +               if (unlikely(err))
> > +                       return err;
> > +
> > +               nh = ip_hdr(skb);
> > +               if (nh->ttl <= 1)
> > +                       return -EHOSTUNREACH;
> > +
> > +               old_ttl = nh->ttl--;
> > +               csum_replace2(&nh->check, htons(old_ttl << 8),
> > +                             htons(nh->ttl << 8));
> > +               key->ip.ttl = nh->ttl;
> > +       }
> > +
> > +       return 0;
> > +}
> > +
> >  /* Execute a list of actions against 'skb'. */
> >  static int do_execute_actions(struct datapath *dp, struct sk_buff *skb,
> >                               struct sw_flow_key *key,
> > @@ -1347,6 +1410,14 @@ static int do_execute_actions(struct datapath *dp, struct sk_buff *skb,
> >
> >                         break;
> >                 }
> > +
> > +               case OVS_ACTION_ATTR_DEC_TTL:
> > +                       err = execute_dec_ttl(skb, key);
> > +                       if (err == -EHOSTUNREACH) {
> Can you use unlikely().
>

sure

> > +                               err = dec_ttl(dp, skb, key, a, true);
> > +                               return err;
> > +                       }
> > +                       break;
> >                 }
> >
> >                 if (unlikely(err)) {
> > diff --git a/net/openvswitch/flow_netlink.c b/net/openvswitch/flow_netlink.c
> > index 65c2e3458ff5..a9eea2ffb8b0 100644
> > --- a/net/openvswitch/flow_netlink.c
> > +++ b/net/openvswitch/flow_netlink.c
> > @@ -61,6 +61,7 @@ static bool actions_may_change_flow(const struct nlattr *actions)
> >                 case OVS_ACTION_ATTR_RECIRC:
> >                 case OVS_ACTION_ATTR_TRUNC:
> >                 case OVS_ACTION_ATTR_USERSPACE:
> > +               case OVS_ACTION_ATTR_DEC_TTL:
> >                         break;
> >
> >                 case OVS_ACTION_ATTR_CT:
> > @@ -2494,6 +2495,59 @@ static int validate_and_copy_sample(struct net *net, const struct nlattr *attr,
> >         return 0;
> >  }
> >
> > +static int validate_and_copy_dec_ttl(struct net *net, const struct nlattr *attr,
> > +                                    const struct sw_flow_key *key,
> > +                                    struct sw_flow_actions **sfa,
> > +                                    __be16 eth_type, __be16 vlan_tci,
> > +                                    u32 mpls_label_count, bool log)
> > +{
> > +       struct nlattr *attrs[OVS_DEC_TTL_ATTR_MAX + 1] = { 0 };
> > +       const struct nlattr *action_type, *action;
> > +       struct nlattr *a;
> > +       int rem, start, err;
> > +       struct dec_ttl_arg arg;
> > +
> Here we need to validate if eth_type is IPv4 or IPv6.
>
>

check for ETH_P_IP or ETH_P_IPV6 and return -EINVAL?


>
> > +       nla_for_each_nested(a, attr, rem) {
> > +               int type = nla_type(a);
> > +
> > +               if (!type || type > OVS_DEC_TTL_ATTR_MAX || attrs[type])
> > +                       return -EINVAL;
> > +
> > +               attrs[type] = a;
> > +       }
> > +       if (rem)
> > +               return -EINVAL;
> > +
> > +       action_type = attrs[OVS_DEC_TTL_ATTR_ACTION_TYPE];
> > +       if (!action_type || nla_len(action_type) != sizeof(u32))
> > +               return -EINVAL;
> > +
> > +       start = add_nested_action_start(sfa, OVS_ACTION_ATTR_DEC_TTL, log);
> > +       if (start < 0)
> > +               return start;
> > +
> > +       arg.action_type = nla_get_u32(action_type);
> > +       err = ovs_nla_add_action(sfa, OVS_DEC_TTL_ATTR_ARG,
> > +                                &arg, sizeof(arg), log);
> > +       if (err)
> > +               return err;
> > +
> > +       if (arg.action_type == OVS_DEC_TTL_ACTION_USER_SPACE) {
> > +               action = attrs[OVS_DEC_TTL_ATTR_ACTION];
> > +               if (!action || (nla_len(action) && nla_len(action) < NLA_HDRLEN))
> > +                       return -EINVAL;
> > +
> > +               err = __ovs_nla_copy_actions(net, action, key, sfa, eth_type,
> > +                                            vlan_tci, mpls_label_count, log);
> > +               if (err)
> > +                       return err;
> > +       }
> > +
> > +       add_nested_action_end(*sfa, start);
> > +
> > +       return 0;
> > +}
> > +
> >  static int validate_and_copy_clone(struct net *net,
> >                                    const struct nlattr *attr,
> >                                    const struct sw_flow_key *key,
> > @@ -3005,6 +3059,7 @@ static int __ovs_nla_copy_actions(struct net *net, const struct nlattr *attr,
> >                         [OVS_ACTION_ATTR_METER] = sizeof(u32),
> >                         [OVS_ACTION_ATTR_CLONE] = (u32)-1,
> >                         [OVS_ACTION_ATTR_CHECK_PKT_LEN] = (u32)-1,
> > +                       [OVS_ACTION_ATTR_DEC_TTL] = (u32)-1,
> >                 };
> >                 const struct ovs_action_push_vlan *vlan;
> >                 int type = nla_type(a);
> > @@ -3233,6 +3288,15 @@ static int __ovs_nla_copy_actions(struct net *net, const struct nlattr *attr,
> >                         break;
> >                 }
> >
> > +               case OVS_ACTION_ATTR_DEC_TTL:
> > +                       err = validate_and_copy_dec_ttl(net, a, key, sfa,
> > +                                                       eth_type, vlan_tci,
> > +                                                       mpls_label_count, log);
> > +                       if (err)
> > +                               return err;
> > +                       skip_copy = true;
> > +                       break;
> > +
> >                 default:
> >                         OVS_NLERR(log, "Unknown Action type %d", type);
> >                         return -EINVAL;
> > @@ -3404,6 +3468,41 @@ static int check_pkt_len_action_to_attr(const struct nlattr *attr,
> >         return err;
> >  }
> >
> > +static int dec_ttl_action_to_attr(const struct nlattr *att, struct sk_buff *skb)
> > +{
> > +       struct nlattr *start, *ac_start = NULL, *dec_ttl;
> > +       int err = 0, rem = nla_len(att);
> > +       const struct dec_ttl_arg *arg;
> > +       struct nlattr *actions;
> > +
> > +       start = nla_nest_start_noflag(skb, OVS_ACTION_ATTR_DEC_TTL);
> > +       if (!start)
> > +               return -EMSGSIZE;
> > +
> > +       dec_ttl = nla_data(att);
> > +       arg = nla_data(dec_ttl);
> > +       actions = nla_next(dec_ttl, &rem);
> > +
> > +       if (nla_put_u32(skb, OVS_DEC_TTL_ATTR_ACTION_TYPE, arg->action_type)) {
> > +               nla_nest_cancel(skb, start);
> > +               return -EMSGSIZE;
> > +       }
> > +
> > +       if (arg->action_type == OVS_DEC_TTL_ACTION_USER_SPACE) {
> > +               ac_start = nla_nest_start_noflag(skb, OVS_DEC_TTL_ATTR_ACTION);
> > +               if (!ac_start) {
> > +                       nla_nest_cancel(skb, ac_start);
> > +                       nla_nest_cancel(skb, start);
> > +                       return -EMSGSIZE;
> > +               }
> > +               err = ovs_nla_put_actions(actions, rem, skb);
> > +               nla_nest_end(skb, ac_start);
> > +       }
> > +       nla_nest_end(skb, start);
> > +
> > +       return err;
> > +}
> > +
> >  static int set_action_to_attr(const struct nlattr *a, struct sk_buff *skb)
> >  {
> >         const struct nlattr *ovs_key = nla_data(a);
> > @@ -3504,6 +3603,12 @@ int ovs_nla_put_actions(const struct nlattr *attr, int len, struct sk_buff *skb)
> >                                 return err;
> >                         break;
> >
> > +               case OVS_ACTION_ATTR_DEC_TTL:
> > +                       err = dec_ttl_action_to_attr(a, skb);
> > +                       if (err)
> > +                               return err;
> > +                       break;
> > +
> >                 default:
> >                         if (nla_put(skb, type, nla_len(a), nla_data(a)))
> >                                 return -EMSGSIZE;
> > --
> > 2.23.0
> >
>


-- 
Matteo Croce
per aspera ad upstream