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Date: Fri, 28 Jun 2024 14:09:32 -0400
From: Aaron Conole <aconole@...hat.com>
To: Adrian Moreno <amorenoz@...hat.com>
Cc: netdev@...r.kernel.org, echaudro@...hat.com, horms@...nel.org,
i.maximets@....org, dev@...nvswitch.org, Donald Hunter
<donald.hunter@...il.com>, Jakub Kicinski <kuba@...nel.org>, "David S.
Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Paolo
Abeni <pabeni@...hat.com>, Pravin B Shelar <pshelar@....org>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v6 05/10] net: openvswitch: add psample action
Adrian Moreno <amorenoz@...hat.com> writes:
> Add support for a new action: psample.
>
> This action accepts a u32 group id and a variable-length cookie and uses
> the psample multicast group to make the packet available for
> observability.
>
> The maximum length of the user-defined cookie is set to 16, same as
> tc_cookie, to discourage using cookies that will not be offloadable.
>
> Signed-off-by: Adrian Moreno <amorenoz@...hat.com>
> ---
I didn't thoroughly review this, but just wanted to comment that I like
the idea of a psample action here specific to the actual action that is
being performed on the packet - psample. Much like we do for userspace
and other actions.
> Documentation/netlink/specs/ovs_flow.yaml | 17 ++++++++
> include/uapi/linux/openvswitch.h | 28 ++++++++++++++
> net/openvswitch/Kconfig | 1 +
> net/openvswitch/actions.c | 47 +++++++++++++++++++++++
> net/openvswitch/flow_netlink.c | 32 ++++++++++++++-
> 5 files changed, 124 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/netlink/specs/ovs_flow.yaml b/Documentation/netlink/specs/ovs_flow.yaml
> index 4fdfc6b5cae9..46f5d1cd8a5f 100644
> --- a/Documentation/netlink/specs/ovs_flow.yaml
> +++ b/Documentation/netlink/specs/ovs_flow.yaml
> @@ -727,6 +727,12 @@ attribute-sets:
> name: dec-ttl
> type: nest
> nested-attributes: dec-ttl-attrs
> + -
> + name: psample
> + type: nest
> + nested-attributes: psample-attrs
> + doc: |
> + Sends a packet sample to psample for external observation.
> -
> name: tunnel-key-attrs
> enum-name: ovs-tunnel-key-attr
> @@ -938,6 +944,17 @@ attribute-sets:
> -
> name: gbp
> type: u32
> + -
> + name: psample-attrs
> + enum-name: ovs-psample-attr
> + name-prefix: ovs-psample-attr-
> + attributes:
> + -
> + name: group
> + type: u32
> + -
> + name: cookie
> + type: binary
>
> operations:
> name-prefix: ovs-flow-cmd-
> diff --git a/include/uapi/linux/openvswitch.h b/include/uapi/linux/openvswitch.h
> index efc82c318fa2..07086759556b 100644
> --- a/include/uapi/linux/openvswitch.h
> +++ b/include/uapi/linux/openvswitch.h
> @@ -914,6 +914,31 @@ struct check_pkt_len_arg {
> };
> #endif
>
> +#define OVS_PSAMPLE_COOKIE_MAX_SIZE 16
> +/**
> + * enum ovs_pample_attr - Attributes for %OVS_ACTION_ATTR_PSAMPLE
> + * action.
> + *
> + * @OVS_PSAMPLE_ATTR_GROUP: 32-bit number to identify the source of the
> + * sample.
> + * @OVS_PSAMPLE_ATTR_COOKIE: An optional variable-length binary cookie that
> + * contains user-defined metadata. The maximum length is
> + * OVS_PSAMPLE_COOKIE_MAX_SIZE bytes.
> + *
> + * Sends the packet to the psample multicast group with the specified group and
> + * cookie. It is possible to combine this action with the
> + * %OVS_ACTION_ATTR_TRUNC action to limit the size of the sample.
> + */
> +enum ovs_psample_attr {
> + OVS_PSAMPLE_ATTR_GROUP = 1, /* u32 number. */
> + OVS_PSAMPLE_ATTR_COOKIE, /* Optional, user specified cookie. */
> +
> + /* private: */
> + __OVS_PSAMPLE_ATTR_MAX
> +};
> +
> +#define OVS_PSAMPLE_ATTR_MAX (__OVS_PSAMPLE_ATTR_MAX - 1)
> +
> /**
> * enum ovs_action_attr - Action types.
> *
> @@ -966,6 +991,8 @@ struct check_pkt_len_arg {
> * of l3 tunnel flag in the tun_flags field of OVS_ACTION_ATTR_ADD_MPLS
> * argument.
> * @OVS_ACTION_ATTR_DROP: Explicit drop action.
> + * @OVS_ACTION_ATTR_PSAMPLE: Send a sample of the packet to external observers
> + * via psample.
> *
> * Only a single header can be set with a single %OVS_ACTION_ATTR_SET. Not all
> * fields within a header are modifiable, e.g. the IPv4 protocol and fragment
> @@ -1004,6 +1031,7 @@ enum ovs_action_attr {
> OVS_ACTION_ATTR_ADD_MPLS, /* struct ovs_action_add_mpls. */
> OVS_ACTION_ATTR_DEC_TTL, /* Nested OVS_DEC_TTL_ATTR_*. */
> OVS_ACTION_ATTR_DROP, /* u32 error code. */
> + OVS_ACTION_ATTR_PSAMPLE, /* Nested OVS_PSAMPLE_ATTR_*. */
>
> __OVS_ACTION_ATTR_MAX, /* Nothing past this will be accepted
> * from userspace. */
> diff --git a/net/openvswitch/Kconfig b/net/openvswitch/Kconfig
> index 29a7081858cd..2535f3f9f462 100644
> --- a/net/openvswitch/Kconfig
> +++ b/net/openvswitch/Kconfig
> @@ -10,6 +10,7 @@ config OPENVSWITCH
> (NF_CONNTRACK && ((!NF_DEFRAG_IPV6 || NF_DEFRAG_IPV6) && \
> (!NF_NAT || NF_NAT) && \
> (!NETFILTER_CONNCOUNT || NETFILTER_CONNCOUNT)))
> + depends on PSAMPLE || !PSAMPLE
> select LIBCRC32C
> select MPLS
> select NET_MPLS_GSO
> diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
> index 964225580824..a035b7e677dd 100644
> --- a/net/openvswitch/actions.c
> +++ b/net/openvswitch/actions.c
> @@ -24,6 +24,11 @@
> #include <net/checksum.h>
> #include <net/dsfield.h>
> #include <net/mpls.h>
> +
> +#if IS_ENABLED(CONFIG_PSAMPLE)
> +#include <net/psample.h>
> +#endif
> +
> #include <net/sctp/checksum.h>
>
> #include "datapath.h"
> @@ -1299,6 +1304,39 @@ static int execute_dec_ttl(struct sk_buff *skb, struct sw_flow_key *key)
> return 0;
> }
>
> +#if IS_ENABLED(CONFIG_PSAMPLE)
> +static void execute_psample(struct datapath *dp, struct sk_buff *skb,
> + const struct nlattr *attr)
> +{
> + struct psample_group psample_group = {};
> + struct psample_metadata md = {};
> + const struct nlattr *a;
> + int rem;
> +
> + nla_for_each_attr(a, nla_data(attr), nla_len(attr), rem) {
> + switch (nla_type(a)) {
> + case OVS_PSAMPLE_ATTR_GROUP:
> + psample_group.group_num = nla_get_u32(a);
> + break;
> +
> + case OVS_PSAMPLE_ATTR_COOKIE:
> + md.user_cookie = nla_data(a);
> + md.user_cookie_len = nla_len(a);
> + break;
> + }
> + }
> +
> + psample_group.net = ovs_dp_get_net(dp);
> + md.in_ifindex = OVS_CB(skb)->input_vport->dev->ifindex;
> + md.trunc_size = skb->len - OVS_CB(skb)->cutlen;
> +
> + psample_sample_packet(&psample_group, skb, 0, &md);
> +}
> +#else
> +static inline void execute_psample(struct datapath *dp, struct sk_buff *skb,
> + const struct nlattr *attr) {}
> +#endif
> +
> /* Execute a list of actions against 'skb'. */
> static int do_execute_actions(struct datapath *dp, struct sk_buff *skb,
> struct sw_flow_key *key,
> @@ -1502,6 +1540,15 @@ static int do_execute_actions(struct datapath *dp, struct sk_buff *skb,
> ovs_kfree_skb_reason(skb, reason);
> return 0;
> }
> +
> + case OVS_ACTION_ATTR_PSAMPLE:
> + execute_psample(dp, skb, a);
> + OVS_CB(skb)->cutlen = 0;
> + if (nla_is_last(a, rem)) {
> + consume_skb(skb);
> + return 0;
> + }
> + break;
> }
>
> if (unlikely(err)) {
> diff --git a/net/openvswitch/flow_netlink.c b/net/openvswitch/flow_netlink.c
> index f224d9bcea5e..c92bdc4dfe19 100644
> --- a/net/openvswitch/flow_netlink.c
> +++ b/net/openvswitch/flow_netlink.c
> @@ -64,6 +64,7 @@ static bool actions_may_change_flow(const struct nlattr *actions)
> case OVS_ACTION_ATTR_TRUNC:
> case OVS_ACTION_ATTR_USERSPACE:
> case OVS_ACTION_ATTR_DROP:
> + case OVS_ACTION_ATTR_PSAMPLE:
> break;
>
> case OVS_ACTION_ATTR_CT:
> @@ -2409,7 +2410,7 @@ static void ovs_nla_free_nested_actions(const struct nlattr *actions, int len)
> /* Whenever new actions are added, the need to update this
> * function should be considered.
> */
> - BUILD_BUG_ON(OVS_ACTION_ATTR_MAX != 24);
> + BUILD_BUG_ON(OVS_ACTION_ATTR_MAX != 25);
>
> if (!actions)
> return;
> @@ -3157,6 +3158,28 @@ static int validate_and_copy_check_pkt_len(struct net *net,
> return 0;
> }
>
> +static int validate_psample(const struct nlattr *attr)
> +{
> + static const struct nla_policy policy[OVS_PSAMPLE_ATTR_MAX + 1] = {
> + [OVS_PSAMPLE_ATTR_GROUP] = { .type = NLA_U32 },
> + [OVS_PSAMPLE_ATTR_COOKIE] = {
> + .type = NLA_BINARY,
> + .len = OVS_PSAMPLE_COOKIE_MAX_SIZE,
> + },
> + };
> + struct nlattr *a[OVS_PSAMPLE_ATTR_MAX + 1];
> + int err;
> +
> + if (!IS_ENABLED(CONFIG_PSAMPLE))
> + return -EOPNOTSUPP;
> +
> + err = nla_parse_nested(a, OVS_PSAMPLE_ATTR_MAX, attr, policy, NULL);
> + if (err)
> + return err;
> +
> + return a[OVS_PSAMPLE_ATTR_GROUP] ? 0 : -EINVAL;
> +}
> +
> static int copy_action(const struct nlattr *from,
> struct sw_flow_actions **sfa, bool log)
> {
> @@ -3212,6 +3235,7 @@ static int __ovs_nla_copy_actions(struct net *net, const struct nlattr *attr,
> [OVS_ACTION_ATTR_ADD_MPLS] = sizeof(struct ovs_action_add_mpls),
> [OVS_ACTION_ATTR_DEC_TTL] = (u32)-1,
> [OVS_ACTION_ATTR_DROP] = sizeof(u32),
> + [OVS_ACTION_ATTR_PSAMPLE] = (u32)-1,
> };
> const struct ovs_action_push_vlan *vlan;
> int type = nla_type(a);
> @@ -3490,6 +3514,12 @@ static int __ovs_nla_copy_actions(struct net *net, const struct nlattr *attr,
> return -EINVAL;
> break;
>
> + case OVS_ACTION_ATTR_PSAMPLE:
> + err = validate_psample(a);
> + if (err)
> + return err;
> + break;
> +
> default:
> OVS_NLERR(log, "Unknown Action type %d", type);
> return -EINVAL;
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