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Date: Wed, 26 Jun 2024 15:07:00 -0500
From: Adrián Moreno <amorenoz@...hat.com>
To: Ilya Maximets <i.maximets@....org>
Cc: netdev@...r.kernel.org, aconole@...hat.com, echaudro@...hat.com,
horms@...nel.org, dev@...nvswitch.org,
"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Donald Hunter <donald.hunter@...il.com>, Pravin B Shelar <pshelar@....org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v5 05/10] net: openvswitch: add emit_sample action
On Wed, Jun 26, 2024 at 12:51:19PM GMT, Ilya Maximets wrote:
> On 6/25/24 22:51, Adrian Moreno wrote:
> > Add support for a new action: emit_sample.
> >
> > 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>
> > ---
> > Documentation/netlink/specs/ovs_flow.yaml | 17 +++++++++
> > include/uapi/linux/openvswitch.h | 28 ++++++++++++++
> > net/openvswitch/Kconfig | 1 +
> > net/openvswitch/actions.c | 45 +++++++++++++++++++++++
> > net/openvswitch/flow_netlink.c | 33 ++++++++++++++++-
> > 5 files changed, 123 insertions(+), 1 deletion(-)
> >
> > diff --git a/Documentation/netlink/specs/ovs_flow.yaml b/Documentation/netlink/specs/ovs_flow.yaml
> > index 4fdfc6b5cae9..a7ab5593a24f 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: emit-sample
> > + type: nest
> > + nested-attributes: emit-sample-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: emit-sample-attrs
> > + enum-name: ovs-emit-sample-attr
> > + name-prefix: ovs-emit-sample-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..8cfa1b3f6b06 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_EMIT_SAMPLE_COOKIE_MAX_SIZE 16
> > +/**
> > + * enum ovs_emit_sample_attr - Attributes for %OVS_ACTION_ATTR_EMIT_SAMPLE
> > + * action.
> > + *
> > + * @OVS_EMIT_SAMPLE_ATTR_GROUP: 32-bit number to identify the source of the
> > + * sample.
> > + * @OVS_EMIT_SAMPLE_ATTR_COOKIE: A variable-length binary cookie that contains
> > + * user-defined metadata. The maximum length is OVS_EMIT_SAMPLE_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 packet being emitted.
> > + */
> > +enum ovs_emit_sample_attr {
> > + OVS_EMIT_SAMPLE_ATTR_GROUP = 1, /* u32 number. */
> > + OVS_EMIT_SAMPLE_ATTR_COOKIE, /* Optional, user specified cookie. */
> > +
> > + /* private: */
> > + __OVS_EMIT_SAMPLE_ATTR_MAX
> > +};
> > +
> > +#define OVS_EMIT_SAMPLE_ATTR_MAX (__OVS_EMIT_SAMPLE_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_EMIT_SAMPLE: 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_EMIT_SAMPLE, /* Nested OVS_EMIT_SAMPLE_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..1f555cbba312 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 +1304,37 @@ static int execute_dec_ttl(struct sk_buff *skb, struct sw_flow_key *key)
> > return 0;
> > }
> >
> > +static void execute_emit_sample(struct datapath *dp, struct sk_buff *skb,
> > + const struct sw_flow_key *key,
>
> The 'key' is not used in the function.
>
> > + const struct nlattr *attr)
> > +{
> > +#if IS_ENABLED(CONFIG_PSAMPLE)
>
> IIUC, the general coding style guideline is to compile out the whole
> function, instead of only the parts. i.e. something like:
>
> #if IS_ENABLED(CONFIG_PSAMPLE)
> static void execute_emit_sample(...) {
> <body>
> }
> #else
> #define execute_emit_sample(dp, skb, attr)
> #endif
>
>
> Otherwise, we'll also need to mark the arguments with __maybe_unused.
Thanks for the suggestion, will submit another version with this fix.
Adrián
>
> The rest of the patch looks good to me.
>
> Best regards, Ilya Maximets.
>
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