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diff --git a/Documentation/networking/devlink/devlink-trap.rst b/Documentation/networking/devlink/devlink-trap.rst new file mode 100644 index 000000000..ef719ceac --- /dev/null +++ b/Documentation/networking/devlink/devlink-trap.rst @@ -0,0 +1,617 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============ +Devlink Trap +============ + +Background +========== + +Devices capable of offloading the kernel's datapath and perform functions such +as bridging and routing must also be able to send specific packets to the +kernel (i.e., the CPU) for processing. + +For example, a device acting as a multicast-aware bridge must be able to send +IGMP membership reports to the kernel for processing by the bridge module. +Without processing such packets, the bridge module could never populate its +MDB. + +As another example, consider a device acting as router which has received an IP +packet with a TTL of 1. Upon routing the packet the device must send it to the +kernel so that it will route it as well and generate an ICMP Time Exceeded +error datagram. Without letting the kernel route such packets itself, utilities +such as ``traceroute`` could never work. + +The fundamental ability of sending certain packets to the kernel for processing +is called "packet trapping". + +Overview +======== + +The ``devlink-trap`` mechanism allows capable device drivers to register their +supported packet traps with ``devlink`` and report trapped packets to +``devlink`` for further analysis. + +Upon receiving trapped packets, ``devlink`` will perform a per-trap packets and +bytes accounting and potentially report the packet to user space via a netlink +event along with all the provided metadata (e.g., trap reason, timestamp, input +port). This is especially useful for drop traps (see :ref:`Trap-Types`) +as it allows users to obtain further visibility into packet drops that would +otherwise be invisible. + +The following diagram provides a general overview of ``devlink-trap``:: + + Netlink event: Packet w/ metadata + Or a summary of recent drops + ^ + | + Userspace | + +---------------------------------------------------+ + Kernel | + | + +-------+--------+ + | | + | drop_monitor | + | | + +-------^--------+ + | + | Non-control traps + | + +----+----+ + | | Kernel's Rx path + | devlink | (non-drop traps) + | | + +----^----+ ^ + | | + +-----------+ + | + +-------+-------+ + | | + | Device driver | + | | + +-------^-------+ + Kernel | + +---------------------------------------------------+ + Hardware | + | Trapped packet + | + +--+---+ + | | + | ASIC | + | | + +------+ + +.. _Trap-Types: + +Trap Types +========== + +The ``devlink-trap`` mechanism supports the following packet trap types: + + * ``drop``: Trapped packets were dropped by the underlying device. Packets + are only processed by ``devlink`` and not injected to the kernel's Rx path. + The trap action (see :ref:`Trap-Actions`) can be changed. + * ``exception``: Trapped packets were not forwarded as intended by the + underlying device due to an exception (e.g., TTL error, missing neighbour + entry) and trapped to the control plane for resolution. Packets are + processed by ``devlink`` and injected to the kernel's Rx path. Changing the + action of such traps is not allowed, as it can easily break the control + plane. + * ``control``: Trapped packets were trapped by the device because these are + control packets required for the correct functioning of the control plane. + For example, ARP request and IGMP query packets. Packets are injected to + the kernel's Rx path, but not reported to the kernel's drop monitor. + Changing the action of such traps is not allowed, as it can easily break + the control plane. + +.. _Trap-Actions: + +Trap Actions +============ + +The ``devlink-trap`` mechanism supports the following packet trap actions: + + * ``trap``: The sole copy of the packet is sent to the CPU. + * ``drop``: The packet is dropped by the underlying device and a copy is not + sent to the CPU. + * ``mirror``: The packet is forwarded by the underlying device and a copy is + sent to the CPU. + +Generic Packet Traps +==================== + +Generic packet traps are used to describe traps that trap well-defined packets +or packets that are trapped due to well-defined conditions (e.g., TTL error). +Such traps can be shared by multiple device drivers and their description must +be added to the following table: + +.. list-table:: List of Generic Packet Traps + :widths: 5 5 90 + + * - Name + - Type + - Description + * - ``source_mac_is_multicast`` + - ``drop`` + - Traps incoming packets that the device decided to drop because of a + multicast source MAC + * - ``vlan_tag_mismatch`` + - ``drop`` + - Traps incoming packets that the device decided to drop in case of VLAN + tag mismatch: The ingress bridge port is not configured with a PVID and + the packet is untagged or prio-tagged + * - ``ingress_vlan_filter`` + - ``drop`` + - Traps incoming packets that the device decided to drop in case they are + tagged with a VLAN that is not configured on the ingress bridge port + * - ``ingress_spanning_tree_filter`` + - ``drop`` + - Traps incoming packets that the device decided to drop in case the STP + state of the ingress bridge port is not "forwarding" + * - ``port_list_is_empty`` + - ``drop`` + - Traps packets that the device decided to drop in case they need to be + flooded (e.g., unknown unicast, unregistered multicast) and there are + no ports the packets should be flooded to + * - ``port_loopback_filter`` + - ``drop`` + - Traps packets that the device decided to drop in case after layer 2 + forwarding the only port from which they should be transmitted through + is the port from which they were received + * - ``blackhole_route`` + - ``drop`` + - Traps packets that the device decided to drop in case they hit a + blackhole route + * - ``ttl_value_is_too_small`` + - ``exception`` + - Traps unicast packets that should be forwarded by the device whose TTL + was decremented to 0 or less + * - ``tail_drop`` + - ``drop`` + - Traps packets that the device decided to drop because they could not be + enqueued to a transmission queue which is full + * - ``non_ip`` + - ``drop`` + - Traps packets that the device decided to drop because they need to + undergo a layer 3 lookup, but are not IP or MPLS packets + * - ``uc_dip_over_mc_dmac`` + - ``drop`` + - Traps packets that the device decided to drop because they need to be + routed and they have a unicast destination IP and a multicast destination + MAC + * - ``dip_is_loopback_address`` + - ``drop`` + - Traps packets that the device decided to drop because they need to be + routed and their destination IP is the loopback address (i.e., 127.0.0.0/8 + and ::1/128) + * - ``sip_is_mc`` + - ``drop`` + - Traps packets that the device decided to drop because they need to be + routed and their source IP is multicast (i.e., 224.0.0.0/8 and ff::/8) + * - ``sip_is_loopback_address`` + - ``drop`` + - Traps packets that the device decided to drop because they need to be + routed and their source IP is the loopback address (i.e., 127.0.0.0/8 and ::1/128) + * - ``ip_header_corrupted`` + - ``drop`` + - Traps packets that the device decided to drop because they need to be + routed and their IP header is corrupted: wrong checksum, wrong IP version + or too short Internet Header Length (IHL) + * - ``ipv4_sip_is_limited_bc`` + - ``drop`` + - Traps packets that the device decided to drop because they need to be + routed and their source IP is limited broadcast (i.e., 255.255.255.255/32) + * - ``ipv6_mc_dip_reserved_scope`` + - ``drop`` + - Traps IPv6 packets that the device decided to drop because they need to + be routed and their IPv6 multicast destination IP has a reserved scope + (i.e., ffx0::/16) + * - ``ipv6_mc_dip_interface_local_scope`` + - ``drop`` + - Traps IPv6 packets that the device decided to drop because they need to + be routed and their IPv6 multicast destination IP has an interface-local scope + (i.e., ffx1::/16) + * - ``mtu_value_is_too_small`` + - ``exception`` + - Traps packets that should have been routed by the device, but were bigger + than the MTU of the egress interface + * - ``unresolved_neigh`` + - ``exception`` + - Traps packets that did not have a matching IP neighbour after routing + * - ``mc_reverse_path_forwarding`` + - ``exception`` + - Traps multicast IP packets that failed reverse-path forwarding (RPF) + check during multicast routing + * - ``reject_route`` + - ``exception`` + - Traps packets that hit reject routes (i.e., "unreachable", "prohibit") + * - ``ipv4_lpm_miss`` + - ``exception`` + - Traps unicast IPv4 packets that did not match any route + * - ``ipv6_lpm_miss`` + - ``exception`` + - Traps unicast IPv6 packets that did not match any route + * - ``non_routable_packet`` + - ``drop`` + - Traps packets that the device decided to drop because they are not + supposed to be routed. For example, IGMP queries can be flooded by the + device in layer 2 and reach the router. Such packets should not be + routed and instead dropped + * - ``decap_error`` + - ``exception`` + - Traps NVE and IPinIP packets that the device decided to drop because of + failure during decapsulation (e.g., packet being too short, reserved + bits set in VXLAN header) + * - ``overlay_smac_is_mc`` + - ``drop`` + - Traps NVE packets that the device decided to drop because their overlay + source MAC is multicast + * - ``ingress_flow_action_drop`` + - ``drop`` + - Traps packets dropped during processing of ingress flow action drop + * - ``egress_flow_action_drop`` + - ``drop`` + - Traps packets dropped during processing of egress flow action drop + * - ``stp`` + - ``control`` + - Traps STP packets + * - ``lacp`` + - ``control`` + - Traps LACP packets + * - ``lldp`` + - ``control`` + - Traps LLDP packets + * - ``igmp_query`` + - ``control`` + - Traps IGMP Membership Query packets + * - ``igmp_v1_report`` + - ``control`` + - Traps IGMP Version 1 Membership Report packets + * - ``igmp_v2_report`` + - ``control`` + - Traps IGMP Version 2 Membership Report packets + * - ``igmp_v3_report`` + - ``control`` + - Traps IGMP Version 3 Membership Report packets + * - ``igmp_v2_leave`` + - ``control`` + - Traps IGMP Version 2 Leave Group packets + * - ``mld_query`` + - ``control`` + - Traps MLD Multicast Listener Query packets + * - ``mld_v1_report`` + - ``control`` + - Traps MLD Version 1 Multicast Listener Report packets + * - ``mld_v2_report`` + - ``control`` + - Traps MLD Version 2 Multicast Listener Report packets + * - ``mld_v1_done`` + - ``control`` + - Traps MLD Version 1 Multicast Listener Done packets + * - ``ipv4_dhcp`` + - ``control`` + - Traps IPv4 DHCP packets + * - ``ipv6_dhcp`` + - ``control`` + - Traps IPv6 DHCP packets + * - ``arp_request`` + - ``control`` + - Traps ARP request packets + * - ``arp_response`` + - ``control`` + - Traps ARP response packets + * - ``arp_overlay`` + - ``control`` + - Traps NVE-decapsulated ARP packets that reached the overlay network. + This is required, for example, when the address that needs to be + resolved is a local address + * - ``ipv6_neigh_solicit`` + - ``control`` + - Traps IPv6 Neighbour Solicitation packets + * - ``ipv6_neigh_advert`` + - ``control`` + - Traps IPv6 Neighbour Advertisement packets + * - ``ipv4_bfd`` + - ``control`` + - Traps IPv4 BFD packets + * - ``ipv6_bfd`` + - ``control`` + - Traps IPv6 BFD packets + * - ``ipv4_ospf`` + - ``control`` + - Traps IPv4 OSPF packets + * - ``ipv6_ospf`` + - ``control`` + - Traps IPv6 OSPF packets + * - ``ipv4_bgp`` + - ``control`` + - Traps IPv4 BGP packets + * - ``ipv6_bgp`` + - ``control`` + - Traps IPv6 BGP packets + * - ``ipv4_vrrp`` + - ``control`` + - Traps IPv4 VRRP packets + * - ``ipv6_vrrp`` + - ``control`` + - Traps IPv6 VRRP packets + * - ``ipv4_pim`` + - ``control`` + - Traps IPv4 PIM packets + * - ``ipv6_pim`` + - ``control`` + - Traps IPv6 PIM packets + * - ``uc_loopback`` + - ``control`` + - Traps unicast packets that need to be routed through the same layer 3 + interface from which they were received. Such packets are routed by the + kernel, but also cause it to potentially generate ICMP redirect packets + * - ``local_route`` + - ``control`` + - Traps unicast packets that hit a local route and need to be locally + delivered + * - ``external_route`` + - ``control`` + - Traps packets that should be routed through an external interface (e.g., + management interface) that does not belong to the same device (e.g., + switch ASIC) as the ingress interface + * - ``ipv6_uc_dip_link_local_scope`` + - ``control`` + - Traps unicast IPv6 packets that need to be routed and have a destination + IP address with a link-local scope (i.e., fe80::/10). The trap allows + device drivers to avoid programming link-local routes, but still receive + packets for local delivery + * - ``ipv6_dip_all_nodes`` + - ``control`` + - Traps IPv6 packets that their destination IP address is the "All Nodes + Address" (i.e., ff02::1) + * - ``ipv6_dip_all_routers`` + - ``control`` + - Traps IPv6 packets that their destination IP address is the "All Routers + Address" (i.e., ff02::2) + * - ``ipv6_router_solicit`` + - ``control`` + - Traps IPv6 Router Solicitation packets + * - ``ipv6_router_advert`` + - ``control`` + - Traps IPv6 Router Advertisement packets + * - ``ipv6_redirect`` + - ``control`` + - Traps IPv6 Redirect Message packets + * - ``ipv4_router_alert`` + - ``control`` + - Traps IPv4 packets that need to be routed and include the Router Alert + option. Such packets need to be locally delivered to raw sockets that + have the IP_ROUTER_ALERT socket option set + * - ``ipv6_router_alert`` + - ``control`` + - Traps IPv6 packets that need to be routed and include the Router Alert + option in their Hop-by-Hop extension header. Such packets need to be + locally delivered to raw sockets that have the IPV6_ROUTER_ALERT socket + option set + * - ``ptp_event`` + - ``control`` + - Traps PTP time-critical event messages (Sync, Delay_req, Pdelay_Req and + Pdelay_Resp) + * - ``ptp_general`` + - ``control`` + - Traps PTP general messages (Announce, Follow_Up, Delay_Resp, + Pdelay_Resp_Follow_Up, management and signaling) + * - ``flow_action_sample`` + - ``control`` + - Traps packets sampled during processing of flow action sample (e.g., via + tc's sample action) + * - ``flow_action_trap`` + - ``control`` + - Traps packets logged during processing of flow action trap (e.g., via + tc's trap action) + * - ``early_drop`` + - ``drop`` + - Traps packets dropped due to the RED (Random Early Detection) algorithm + (i.e., early drops) + * - ``vxlan_parsing`` + - ``drop`` + - Traps packets dropped due to an error in the VXLAN header parsing which + might be because of packet truncation or the I flag is not set. + * - ``llc_snap_parsing`` + - ``drop`` + - Traps packets dropped due to an error in the LLC+SNAP header parsing + * - ``vlan_parsing`` + - ``drop`` + - Traps packets dropped due to an error in the VLAN header parsing. Could + include unexpected packet truncation. + * - ``pppoe_ppp_parsing`` + - ``drop`` + - Traps packets dropped due to an error in the PPPoE+PPP header parsing. + This could include finding a session ID of 0xFFFF (which is reserved and + not for use), a PPPoE length which is larger than the frame received or + any common error on this type of header + * - ``mpls_parsing`` + - ``drop`` + - Traps packets dropped due to an error in the MPLS header parsing which + could include unexpected header truncation + * - ``arp_parsing`` + - ``drop`` + - Traps packets dropped due to an error in the ARP header parsing + * - ``ip_1_parsing`` + - ``drop`` + - Traps packets dropped due to an error in the first IP header parsing. + This packet trap could include packets which do not pass an IP checksum + check, a header length check (a minimum of 20 bytes), which might suffer + from packet truncation thus the total length field exceeds the received + packet length etc + * - ``ip_n_parsing`` + - ``drop`` + - Traps packets dropped due to an error in the parsing of the last IP + header (the inner one in case of an IP over IP tunnel). The same common + error checking is performed here as for the ip_1_parsing trap + * - ``gre_parsing`` + - ``drop`` + - Traps packets dropped due to an error in the GRE header parsing + * - ``udp_parsing`` + - ``drop`` + - Traps packets dropped due to an error in the UDP header parsing. + This packet trap could include checksum errorrs, an improper UDP + length detected (smaller than 8 bytes) or detection of header + truncation. + * - ``tcp_parsing`` + - ``drop`` + - Traps packets dropped due to an error in the TCP header parsing. + This could include TCP checksum errors, improper combination of SYN, FIN + and/or RESET etc. + * - ``ipsec_parsing`` + - ``drop`` + - Traps packets dropped due to an error in the IPSEC header parsing + * - ``sctp_parsing`` + - ``drop`` + - Traps packets dropped due to an error in the SCTP header parsing. + This would mean that port number 0 was used or that the header is + truncated. + * - ``dccp_parsing`` + - ``drop`` + - Traps packets dropped due to an error in the DCCP header parsing + * - ``gtp_parsing`` + - ``drop`` + - Traps packets dropped due to an error in the GTP header parsing + * - ``esp_parsing`` + - ``drop`` + - Traps packets dropped due to an error in the ESP header parsing + +Driver-specific Packet Traps +============================ + +Device drivers can register driver-specific packet traps, but these must be +clearly documented. Such traps can correspond to device-specific exceptions and +help debug packet drops caused by these exceptions. The following list includes +links to the description of driver-specific traps registered by various device +drivers: + + * :doc:`netdevsim` + * :doc:`mlxsw` + +.. _Generic-Packet-Trap-Groups: + +Generic Packet Trap Groups +========================== + +Generic packet trap groups are used to aggregate logically related packet +traps. These groups allow the user to batch operations such as setting the trap +action of all member traps. In addition, ``devlink-trap`` can report aggregated +per-group packets and bytes statistics, in case per-trap statistics are too +narrow. The description of these groups must be added to the following table: + +.. list-table:: List of Generic Packet Trap Groups + :widths: 10 90 + + * - Name + - Description + * - ``l2_drops`` + - Contains packet traps for packets that were dropped by the device during + layer 2 forwarding (i.e., bridge) + * - ``l3_drops`` + - Contains packet traps for packets that were dropped by the device during + layer 3 forwarding + * - ``l3_exceptions`` + - Contains packet traps for packets that hit an exception (e.g., TTL + error) during layer 3 forwarding + * - ``buffer_drops`` + - Contains packet traps for packets that were dropped by the device due to + an enqueue decision + * - ``tunnel_drops`` + - Contains packet traps for packets that were dropped by the device during + tunnel encapsulation / decapsulation + * - ``acl_drops`` + - Contains packet traps for packets that were dropped by the device during + ACL processing + * - ``stp`` + - Contains packet traps for STP packets + * - ``lacp`` + - Contains packet traps for LACP packets + * - ``lldp`` + - Contains packet traps for LLDP packets + * - ``mc_snooping`` + - Contains packet traps for IGMP and MLD packets required for multicast + snooping + * - ``dhcp`` + - Contains packet traps for DHCP packets + * - ``neigh_discovery`` + - Contains packet traps for neighbour discovery packets (e.g., ARP, IPv6 + ND) + * - ``bfd`` + - Contains packet traps for BFD packets + * - ``ospf`` + - Contains packet traps for OSPF packets + * - ``bgp`` + - Contains packet traps for BGP packets + * - ``vrrp`` + - Contains packet traps for VRRP packets + * - ``pim`` + - Contains packet traps for PIM packets + * - ``uc_loopback`` + - Contains a packet trap for unicast loopback packets (i.e., + ``uc_loopback``). This trap is singled-out because in cases such as + one-armed router it will be constantly triggered. To limit the impact on + the CPU usage, a packet trap policer with a low rate can be bound to the + group without affecting other traps + * - ``local_delivery`` + - Contains packet traps for packets that should be locally delivered after + routing, but do not match more specific packet traps (e.g., + ``ipv4_bgp``) + * - ``external_delivery`` + - Contains packet traps for packets that should be routed through an + external interface (e.g., management interface) that does not belong to + the same device (e.g., switch ASIC) as the ingress interface + * - ``ipv6`` + - Contains packet traps for various IPv6 control packets (e.g., Router + Advertisements) + * - ``ptp_event`` + - Contains packet traps for PTP time-critical event messages (Sync, + Delay_req, Pdelay_Req and Pdelay_Resp) + * - ``ptp_general`` + - Contains packet traps for PTP general messages (Announce, Follow_Up, + Delay_Resp, Pdelay_Resp_Follow_Up, management and signaling) + * - ``acl_sample`` + - Contains packet traps for packets that were sampled by the device during + ACL processing + * - ``acl_trap`` + - Contains packet traps for packets that were trapped (logged) by the + device during ACL processing + * - ``parser_error_drops`` + - Contains packet traps for packets that were marked by the device during + parsing as erroneous + +Packet Trap Policers +==================== + +As previously explained, the underlying device can trap certain packets to the +CPU for processing. In most cases, the underlying device is capable of handling +packet rates that are several orders of magnitude higher compared to those that +can be handled by the CPU. + +Therefore, in order to prevent the underlying device from overwhelming the CPU, +devices usually include packet trap policers that are able to police the +trapped packets to rates that can be handled by the CPU. + +The ``devlink-trap`` mechanism allows capable device drivers to register their +supported packet trap policers with ``devlink``. The device driver can choose +to associate these policers with supported packet trap groups (see +:ref:`Generic-Packet-Trap-Groups`) during its initialization, thereby exposing +its default control plane policy to user space. + +Device drivers should allow user space to change the parameters of the policers +(e.g., rate, burst size) as well as the association between the policers and +trap groups by implementing the relevant callbacks. + +If possible, device drivers should implement a callback that allows user space +to retrieve the number of packets that were dropped by the policer because its +configured policy was violated. + +Testing +======= + +See ``tools/testing/selftests/drivers/net/netdevsim/devlink_trap.sh`` for a +test covering the core infrastructure. Test cases should be added for any new +functionality. + +Device drivers should focus their tests on device-specific functionality, such +as the triggering of supported packet traps. |