On 25 Jan 2024, at 21:55, Aaron Conole wrote:
> From: Kevin Sprague <ksprague0...@gmail.com>
>
> During normal operations, it is useful to understand when a particular flow
> gets removed from the system. This can be useful when debugging performance
> issues tied to ofproto flow changes, trying to determine deployed traffic
> patterns, or while debugging dynamic systems where ports come and go.
>
> Prior to this change, there was a lack of visibility around flow expiration.
> The existing debugging infrastructure could tell us when a flow was added to
> the datapath, but not when it was removed or why.
>
> This change introduces a USDT probe at the point where the revalidator
> determines that the flow should be removed. Additionally, we track the
> reason for the flow eviction and provide that information as well. With
> this change, we can track the complete flow lifecycle for the netlink
> datapath by hooking the upcall tracepoint in kernel, the flow put USDT, and
> the revaldiator USDT, letting us watch as flows are added and removed from
> the kernel datapath.
>
> This change only enables this information via USDT probe, so it won't be
> possible to access this information any other way (see:
> Documentation/topics/usdt-probes.rst).
>
> Also included is a script (utilities/usdt-scripts/flow_reval_monitor.py)
> which serves as a demonstration of how the new USDT probe might be used
> going forward.
>
> Signed-off-by: Kevin Sprague <ksprague0...@gmail.com>
> Co-authored-by: Aaron Conole <acon...@redhat.com>
> Signed-off-by: Aaron Conole <acon...@redhat.com>
Thanks for following this up Aaron! See comments on this patch below. I have no
additional comments on patch 2.
Cheers,
Eelco
> ---
> Documentation/topics/usdt-probes.rst | 1 +
> ofproto/ofproto-dpif-upcall.c | 42 +-
> utilities/automake.mk | 3 +
> utilities/usdt-scripts/flow_reval_monitor.py | 653 +++++++++++++++++++
> 4 files changed, 693 insertions(+), 6 deletions(-)
> create mode 100755 utilities/usdt-scripts/flow_reval_monitor.py
>
> diff --git a/Documentation/topics/usdt-probes.rst
> b/Documentation/topics/usdt-probes.rst
> index e527f43bab..a8da9bb1f7 100644
> --- a/Documentation/topics/usdt-probes.rst
> +++ b/Documentation/topics/usdt-probes.rst
> @@ -214,6 +214,7 @@ Available probes in ``ovs_vswitchd``:
> - dpif_recv:recv_upcall
> - main:poll_block
> - main:run_start
> +- revalidate:flow_result
> - revalidate_ukey\_\_:entry
> - revalidate_ukey\_\_:exit
> - udpif_revalidator:start_dump
You are missing the specific flow_result result section. This is from the
previous patch:
@@ -358,6 +360,27 @@ See also the ``main:run_start`` probe above.
- ``utilities/usdt-scripts/bridge_loop.bt``
+probe revalidate:flow_result
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+**Description**:
+This probe is triggered when the revalidator decides whether or not to
+revalidate a flow. ``reason`` is an enum that denotes that either the flow
+is being kept, or the reason why the flow is being deleted. The
+``flow_reval_monitor.py`` script uses this probe to notify users when flows
+matching user-provided criteria are deleted.
+
+**Arguments**:
+
+- *arg0*: ``(enum flow_del_reason) reason``
+- *arg1*: ``(struct udpif *) udpif``
+- *arg2*: ``(struct udpif_key *) ukey``
+
+**Script references**:
+
+- ``utilities/usdt-scripts/flow_reval_monitor.py``
+
+
Adding your own probes
----------------------
> diff --git a/ofproto/ofproto-dpif-upcall.c b/ofproto/ofproto-dpif-upcall.c
> index b5cbeed878..97d75833f7 100644
> --- a/ofproto/ofproto-dpif-upcall.c
> +++ b/ofproto/ofproto-dpif-upcall.c
> @@ -269,6 +269,18 @@ enum ukey_state {
> };
> #define N_UKEY_STATES (UKEY_DELETED + 1)
>
> +enum flow_del_reason {
> + FDR_REVALIDATE = 0, /* The flow was revalidated. */
It was called FDR_FLOW_LIVE before, which might make more sense. As the flow is
just NOT deleted. It might or might not have been revalidated. Thoughts?
> + FDR_FLOW_IDLE, /* The flow went unused and was deleted. */
> + FDR_TOO_EXPENSIVE, /* The flow was too expensive to revalidate. */
> + FDR_FLOW_WILDCARDED, /* The flow needed a narrower wildcard mask. */
> + FDR_BAD_ODP_FIT, /* The flow had a bad ODP flow fit. */
> + FDR_NO_OFPROTO, /* The flow didn't have an associated ofproto. */
> + FDR_XLATION_ERROR, /* There was an error translating the flow. */
> + FDR_AVOID_CACHING, /* Flow deleted to avoid caching. */
> + FDR_FLOW_LIMIT, /* All flows being killed. */
Looking at the comment from Han on FDR_PURGE, and this patch needing another
spin, we should probably add it.
> +};
> +
> /* 'udpif_key's are responsible for tracking the little bit of state udpif
> * needs to do flow expiration which can't be pulled directly from the
> * datapath. They may be created by any handler or revalidator thread at any
> @@ -2272,7 +2284,8 @@ populate_xcache(struct udpif *udpif, struct udpif_key
> *ukey,
> static enum reval_result
> revalidate_ukey__(struct udpif *udpif, const struct udpif_key *ukey,
> uint16_t tcp_flags, struct ofpbuf *odp_actions,
> - struct recirc_refs *recircs, struct xlate_cache *xcache)
> + struct recirc_refs *recircs, struct xlate_cache *xcache,
> + enum flow_del_reason *reason)
> {
> struct xlate_out *xoutp;
> struct netflow *netflow;
> @@ -2293,11 +2306,13 @@ revalidate_ukey__(struct udpif *udpif, const struct
> udpif_key *ukey,
> netflow = NULL;
>
> if (xlate_ukey(udpif, ukey, tcp_flags, &ctx)) {
> + *reason = FDR_XLATION_ERROR;
> goto exit;
> }
> xoutp = &ctx.xout;
>
> if (xoutp->avoid_caching) {
> + *reason = FDR_AVOID_CACHING;
> goto exit;
> }
>
> @@ -2311,6 +2326,7 @@ revalidate_ukey__(struct udpif *udpif, const struct
> udpif_key *ukey,
> ofpbuf_clear(odp_actions);
>
> if (!ofproto) {
> + *reason = FDR_NO_OFPROTO;
> goto exit;
> }
>
> @@ -2322,6 +2338,7 @@ revalidate_ukey__(struct udpif *udpif, const struct
> udpif_key *ukey,
> if (odp_flow_key_to_mask(ukey->mask, ukey->mask_len, &dp_mask, &ctx.flow,
> NULL)
> == ODP_FIT_ERROR) {
> + *reason = FDR_BAD_ODP_FIT;
> goto exit;
> }
>
> @@ -2331,6 +2348,7 @@ revalidate_ukey__(struct udpif *udpif, const struct
> udpif_key *ukey,
> * down. Note that we do not know if the datapath has ignored any of the
> * wildcarded bits, so we may be overly conservative here. */
> if (flow_wildcards_has_extra(&dp_mask, ctx.wc)) {
> + *reason = FDR_FLOW_WILDCARDED;
> goto exit;
> }
>
> @@ -2400,7 +2418,7 @@ static enum reval_result
> revalidate_ukey(struct udpif *udpif, struct udpif_key *ukey,
> const struct dpif_flow_stats *stats,
> struct ofpbuf *odp_actions, uint64_t reval_seq,
> - struct recirc_refs *recircs)
> + struct recirc_refs *recircs, enum flow_del_reason *reason)
> OVS_REQUIRES(ukey->mutex)
> {
> bool need_revalidate = ukey->reval_seq != reval_seq;
> @@ -2430,8 +2448,12 @@ revalidate_ukey(struct udpif *udpif, struct udpif_key
> *ukey,
> xlate_cache_clear(ukey->xcache);
> }
> result = revalidate_ukey__(udpif, ukey, push.tcp_flags,
> - odp_actions, recircs, ukey->xcache);
> - } /* else delete; too expensive to revalidate */
> + odp_actions, recircs, ukey->xcache,
> + reason);
> + } else {
> + /* delete; too expensive to revalidate */
> + *reason = FDR_TOO_EXPENSIVE;
> + }
> } else if (!push.n_packets || ukey->xcache
> || !populate_xcache(udpif, ukey, push.tcp_flags)) {
> result = UKEY_KEEP;
> @@ -2831,6 +2853,7 @@ revalidate(struct revalidator *revalidator)
> for (f = flows; f < &flows[n_dumped]; f++) {
> long long int used = f->stats.used;
> struct recirc_refs recircs = RECIRC_REFS_EMPTY_INITIALIZER;
> + enum flow_del_reason reason = FDR_REVALIDATE;
> struct dpif_flow_stats stats = f->stats;
> enum reval_result result;
> struct udpif_key *ukey;
> @@ -2905,9 +2928,14 @@ revalidate(struct revalidator *revalidator)
> }
> if (kill_them_all || (used && used < now - max_idle)) {
> result = UKEY_DELETE;
> + if (kill_them_all) {
> + reason = FDR_FLOW_LIMIT;
> + } else {
> + reason = FDR_FLOW_IDLE;
> + }
> } else {
> result = revalidate_ukey(udpif, ukey, &stats, &odp_actions,
> - reval_seq, &recircs);
> + reval_seq, &recircs, &reason);
> }
> ukey->dump_seq = dump_seq;
>
> @@ -2916,6 +2944,7 @@ revalidate(struct revalidator *revalidator)
> udpif_update_flow_pps(udpif, ukey, f);
> }
>
> + OVS_USDT_PROBE(revalidate, flow_result, reason, udpif, ukey);
> if (result != UKEY_KEEP) {
> /* Takes ownership of 'recircs'. */
> reval_op_init(&ops[n_ops++], result, udpif, ukey, &recircs,
> @@ -2962,6 +2991,7 @@ revalidator_sweep__(struct revalidator *revalidator,
> bool purge)
> uint64_t odp_actions_stub[1024 / 8];
> struct ofpbuf odp_actions =
> OFPBUF_STUB_INITIALIZER(odp_actions_stub);
>
> + enum flow_del_reason reason = FDR_REVALIDATE;
> struct ukey_op ops[REVALIDATE_MAX_BATCH];
> struct udpif_key *ukey;
> struct umap *umap = &udpif->ukeys[i];
> @@ -2993,7 +3023,7 @@ revalidator_sweep__(struct revalidator *revalidator,
> bool purge)
> COVERAGE_INC(revalidate_missed_dp_flow);
> memcpy(&stats, &ukey->stats, sizeof stats);
> result = revalidate_ukey(udpif, ukey, &stats,
> &odp_actions,
> - reval_seq, &recircs);
> + reval_seq, &recircs, &reason);
> }
> if (result != UKEY_KEEP) {
> /* Clears 'recircs' if filled by revalidate_ukey(). */
> diff --git a/utilities/automake.mk b/utilities/automake.mk
> index 9a2114df40..146b8c37fb 100644
> --- a/utilities/automake.mk
> +++ b/utilities/automake.mk
> @@ -23,6 +23,7 @@ scripts_DATA += utilities/ovs-lib
> usdt_SCRIPTS += \
> utilities/usdt-scripts/bridge_loop.bt \
> utilities/usdt-scripts/dpif_nl_exec_monitor.py \
> + utilities/usdt-scripts/flow_reval_monitor.py \
> utilities/usdt-scripts/kernel_delay.py \
> utilities/usdt-scripts/kernel_delay.rst \
> utilities/usdt-scripts/reval_monitor.py \
> @@ -72,6 +73,7 @@ EXTRA_DIST += \
> utilities/docker/debian/build-kernel-modules.sh \
> utilities/usdt-scripts/bridge_loop.bt \
> utilities/usdt-scripts/dpif_nl_exec_monitor.py \
> + utilities/usdt-scripts/flow_reval_monitor.py \
> utilities/usdt-scripts/kernel_delay.py \
> utilities/usdt-scripts/kernel_delay.rst \
> utilities/usdt-scripts/reval_monitor.py \
> @@ -146,6 +148,7 @@ FLAKE8_PYFILES += utilities/ovs-pcap.in \
> utilities/ovs-tcpdump.in \
> utilities/ovs-pipegen.py \
> utilities/usdt-scripts/dpif_nl_exec_monitor.py \
> + utilities/usdt-scripts/flow_reval_monitor.py \
> utilities/usdt-scripts/upcall_monitor.py \
> utilities/usdt-scripts/upcall_cost.py
>
> diff --git a/utilities/usdt-scripts/flow_reval_monitor.py
> b/utilities/usdt-scripts/flow_reval_monitor.py
> new file mode 100755
> index 0000000000..e808020bb5
> --- /dev/null
> +++ b/utilities/usdt-scripts/flow_reval_monitor.py
> @@ -0,0 +1,653 @@
> +#!/usr/bin/env python3
> +#
> +# Copyright (c) 2022 Redhat, Inc.
> +#
> +# Licensed under the Apache License, Version 2.0 (the "License");
> +# you may not use this file except in compliance with the License.
> +# You may obtain a copy of the License at:
> +#
> +# http://www.apache.org/licenses/LICENSE-2.0
> +#
> +# Unless required by applicable law or agreed to in writing, software
> +# distributed under the License is distributed on an "AS IS" BASIS,
> +# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
> +# See the License for the specific language governing permissions and
> +# limitations under the License.
> +#
> +# Script information:
> +# -------------------
> +# flow_reval_monitor.py uses the dpif_netlink_operate:flow_put and
> +# revalidator:flow_result USDT probes to monitor flow lifetimes and
> +# expiration events. By default, this will show all flow_put and flow
> +# expiration events, along with their reasons. This will look like so:
> +#
> +# TIME UFID EVENT/REASON
> +# 101536.226986736 ufid:f76fc899-376d-466b-bc74-0000b933eb97 flow_put
> +# 101536.227196214 ufid:d08472b6-110e-46cb-a9e4-00008f46838e flow_put
> +# 101541.516610178 ufid:fc5cc4a2-39e7-4a2d-bbce-000019665b32 flow_put
> +# 101541.516967303 ufid:fddd6510-26dc-4c87-8f7a-0000fc0c2c3a flow_put
> +# 101551.688050747 ufid:fddd6510-26dc-4c87-8f7a-0000fc0c2c3a flow timed
> out
> +# 101551.688077175 ufid:fc5cc4a2-39e7-4a2d-bbce-000019665b32 flow timed
> out
> +# 101557.695391371 ufid:f76fc899-376d-466b-bc74-0000b933eb97 flow timed
> out
> +# 101557.695408909 ufid:d08472b6-110e-46cb-a9e4-00008f46838e flow timed
> out
> +#
> +# flow key data can be printed using the --flow-keys option. This will
> +# print the equivalent datapath flow string.
> +#
> +# When filtering flows, the syntax is the same as used by
> +# `ovs-appctl dpctl/add-flow`.
> +#
> +# The following options are available:
> +#
> +# usage: flow_reval_monitor.py [-h] [--buffer-page-count NUMBER]
> +# [-k [FLOW_KEYS]] [-p VSWITCHD_PID]
> +# [-D [DEBUG]] [-f [FLOW STRING ...]]
# usage: flow_reval_monitor.py [-h] [--buffer-page-count NUMBER]
[-f [64-2048]] [-k] [-l [FLOW_STRING ...]]
[-p VSWITCHD_PID] [-D [DEBUG]]
> +#
> +# optional arguments:
> +# -h, --help show this help message and exit
> +# --buffer-page-count NUMBER
> +# Number of BPF ring buffer pages, default 1024
> +# -f <64..2048>, --flow-key-size=<64..2048>
> +# Set the size of the flow key, default 64
> +# -k, --flow-keys Print flow keys as flow strings
> +# -l [FLOW_STRING ...], --filter-flows [FLOW_STRING ...]
> +# Filter flows that match the specified ODP-like flow
We do not filter on the flow itself but on the packet content/keys creating the
flow.
We might want to clarify this as the actual DP flow might not include., for
example, the IP fields.
> +# -p VSWITCHD_PID, --pid VSWITCHD_PID
> +# ovs-vswitchd's PID
> +# -D [DEBUG], --debug [DEBUG]
> +# Enable eBPF debugging
> +#
> +# Examples:
> +#
> +# To use the script on a running ovs-vswitchd to see flow keys and expiration
> +# events for flows with an ipv4 source of 192.168.10.10:
> +# $ ./flow_reval_monitor.py --flow-keys --filter-flows \
> +# "ipv4(src=192.168.10.10)"
Can we add some details on what kind of filters/format is supported? For
example no mask support.
> +# TIME UFID
> EVENT/REASON
> +# 105082.457322742 ufid:f76fc899-376d-466b-bc74-0000b933eb97 flow_put
> +# ufid:f76fc899-376d-466b-bc74-0000b933eb97 has the following flow
> information:
> +# in_port(2),
> +# eth(src=0e:04:47:fc:74:51, dst=da:dc:c5:69:05:d7), \
> +# eth_type(0x800), \
> +# ipv4(src=192.168.10.10, dst=192.168.10.30, proto=1, tos=0,
> ttl=64,[...]),
> +# icmp(type=8, code=0)
> +# 105092.635450202 ufid:f76fc899-376d-466b-bc74-0000b933eb97 Flow timed
> out
> +#
> +# Notes:
> +# 1) No options are needed to attach when there is a single running
> instance
> +# of ovs-vswitchd.
> +# 2) If you're using the flow filtering option, it will only track flows
> that
> +# have been upcalled since the script began running.
> +# 3) When using the flow filtering option, the key size will likely need to
> +# be expanded to match on all the fields in the message. The default is
> +# kept small to keep the buffer copy sizes down when displaying
> +# flows (-k), but is hardcoded to 2048 when an actual filter (-l) is
> +# applied
We should add a note that the flow_put part is not included when HW offload
(TC) is used for the kernel datapath, or if DPDK is used.
> +
> +try:
> + from bcc import BPF
> + from bcc import USDT
> + from bcc import USDTException
> +except ModuleNotFoundError:
> + print("ERROR: Can't find the BPF Compiler Collection Tools.")
> + print("Please install them before running this script.")
> + exit(1)
> +
> +import argparse
> +from ipaddress import IPv4Address, IPv6Address
> +import psutil
> +import struct
> +import sys
> +import time
> +
> +#
> +# eBPF source code
> +#
> +bpf_src = """
> +#include <linux/sched.h>
> +#include <uapi/linux/ptrace.h>
> +
> +#define MAX_KEY <MAX_KEY_VAL>
> +#define FLOW_FILTER <FILTER_BOOL>
> +
> +enum probe { OP_FLOW_PUT, FLOW_RESULT };
> +
> +typedef union ovs_u128 {
> + unsigned int ufid32[4];
> + unsigned long long ufid64[2];
> +} ovs_u128;
> +
> +struct dpif_flow_put {
> + int flags;
> + void *key_ptr;
> + size_t key_len;
> + void *mask_ptr;
> + size_t mask_len;
> + u64 action_ptr;
> + size_t action_len;
> + void *ufid_ptr;
> +};
> +
> +struct udpif_key {
> + void *cmap_node;
> + void *key_ptr;
> + size_t key_len;
> + void *mask_ptr;
> + size_t mask_len;
> + ovs_u128 ufid;
> +};
> +
> +struct event_t {
> + u64 ts;
> + u32 reason;
> + u32 ufid[4]; /* Can't seem to make the ovs_u128 pass to python side. */
Is this still true?
> + u64 key_size;
> + u8 key[MAX_KEY];
> + enum probe probe;
> +};
> +
> +BPF_HASH(watchlist, ovs_u128);
> +BPF_RINGBUF_OUTPUT(events, <BUFFER_PAGE_COUNT>);
> +
> +int usdt__flow_result(struct pt_regs *ctx) {
> + u64 *ufid_present = NULL;
> + struct udpif_key ukey;
> +
> + bpf_usdt_readarg_p(3, ctx, &ukey, sizeof ukey);
> + ovs_u128 ufid = ukey.ufid;
> + ufid_present = watchlist.lookup(&ufid);
> + if(FLOW_FILTER && !ufid_present) {
> + return 0;
> + }
> +
> + struct event_t *event = events.ringbuf_reserve(sizeof(struct event_t));
> + if(!event) {
> + /* If we can't reserve the space in the ring buffer, return 1. */
See comments at the end regarding __sync_fetch_and_add().
> + return 1;
> + }
> +
> + event->probe = FLOW_RESULT;
> + event->ts = bpf_ktime_get_ns();
> + bpf_probe_read(&event->ufid, sizeof ufid, &ufid);
> + bpf_usdt_readarg(1, ctx, &event->reason);
> + events.ringbuf_submit(event, 0);
> +
> + return 0;
> +};
> +
> +
> +int usdt__op_flow_put(struct pt_regs *ctx) {
> + struct dpif_flow_put put;
> + ovs_u128 ufid;
> +
> + struct event_t *event = events.ringbuf_reserve(sizeof(struct event_t));
> + if(!event) {
> + /* If we can't reserve the space in the ring buffer, return 1. */
See comments at the end regarding __sync_fetch_and_add().
> + return 1;
> + }
> +
> + event->probe = OP_FLOW_PUT;
> + event->ts = bpf_ktime_get_ns();
> + bpf_usdt_readarg_p(2, ctx, &put, sizeof put);
> + bpf_probe_read(&event->ufid, sizeof event->ufid, put.ufid_ptr);
> + bpf_probe_read(&ufid, sizeof ufid, &event->ufid);
> + if (put.key_len > MAX_KEY) {
> + put.key_len = MAX_KEY;
> + }
> + event->key_size = put.key_len;
> + bpf_probe_read(&event->key, put.key_len, put.key_ptr);
> + event->reason = 0;
> + events.ringbuf_submit(event, 0);
> +
> + watchlist.increment(ufid);
> + return 0;
> +};
> +"""
> +
> +
> +#
> +# buffer_size_type()
> +#
> +def buffer_size_type(astr, min=64, max=2048):
> + value = int(astr)
> + if min <= value <= max:
> + return value
> + else:
> + raise argparse.ArgumentTypeError(
> + 'value not in range {}-{}'.format(min, max))
> +
> +
> +#
> +# format_ufid()
> +#
> +def format_ufid(ufid):
> + if ufid is None:
> + return "ufid:none"
> +
> + return "ufid:{:08x}-{:04x}-{:04x}-{:04x}-{:04x}{:08x}".format(
> + ufid[0], ufid[1] >> 16, ufid[1] & 0xffff,
> + ufid[2] >> 16, ufid[2] & 0, ufid[3])
> +
> +
> +#
> +# find_and_delete_from_watchlist()
> +#
> +def find_and_delete_from_watchlist(event):
> + for k, _ in b["watchlist"].items():
> + key_ufid = struct.unpack("=IIII", k)
> + if key_ufid == tuple(event.ufid):
> + key = (b["watchlist"].Key * 1)(k)
> + b["watchlist"].items_delete_batch(key)
> + break
> +
> +
> +#
> +# handle_flow_put()
> +#
> +def handle_flow_put(event):
> + if args.flow_keys or args.filter_flows is not None:
> + key = decode_key(bytes(event.key)[:event.key_size])
> + flow_dict, flow_str = parse_flow_dict(key)
> + # For each attribute that we're watching.
> + if args.filter_flows is not None:
> + if not compare_flow_to_target(args.filter_flows, flow_dict):
> + find_and_delete_from_watchlist(event)
> + return
> +
> + print("{:<18.9f} {:<45} {:<13}".format(event.ts / 1000000000,
> + format_ufid(event.ufid), "Insert (put) flow to kernel."))
Maybe change this to “Insert (put) flow to kernel module.” to valid missing tc
flow put?
> +
> + if args.flow_keys:
> + if len(flow_str) > 80:<
> + flow_str = " " + "),\n ".join(flow_str.split("), “))<<
> + else:
> + flow_str = " " + flow_str
> + print(" - It holds the following flow information:")
This is confusing as, it’s not the flow information, i.e. flow installed, but
the keys from the packet.
> + print(flow_str)
> +
> +
> +#
> +# compare_flow_to_target()
> +#
> +def compare_flow_to_target(target, flow):
> + for key in target:
> + if key not in flow:
> + return False
> + elif target[key] is True:
> + continue
> + elif target[key] == flow[key]:
> + continue
> + elif isinstance(target[key], dict) and isinstance(flow[key], dict):
> + return compare_flow_to_target(target[key], flow[key])
> + else:
> + return False
> + return True
> +
> +
> +#
> +# parse_flow_str()
> +#
> +def parse_flow_str(flow_str):
> + f_list = [i.strip(", ") for i in flow_str.split(")")]
> + if f_list[-1] == "":
> + f_list = f_list[:-1]
> + flow_dict = {}
> + for e in f_list:
> + split_list = e.split("(")
> + k = split_list[0]
> + if len(split_list) == 1:
> + flow_dict[k] = True
> + elif split_list[1].count("=") == 0:
> + flow_dict[k] = split_list[1]
> + else:
> + sub_dict = {}
> + sublist = [i.strip() for i in split_list[1].split(",")]
> + for subkey in sublist:
> + brk = subkey.find("=")
> + sub_dict[subkey[:brk]] = subkey[brk + 1:]
> + flow_dict[k] = sub_dict
> + return flow_dict
> +
> +
> +#
> +# print_expiration()
> +#
> +def print_expiration(event):
> + reasons = ["Unknown flow expiration reason!", "Flow timed out",
> + "Flow revalidation too expensive",
> + "Flow needs narrower wildcard mask",
> + "Bad ODP flow fit", "Flow with associated ofproto",
> + "Flow translation error", "Flow cache avoidance",
> + "Kill them all signal"]
Should we maybe define this with something like this:
Event = IntEnum("flow_del_reason", ["FDR_FLOW_LIVE",
"FDR_FLOW_TIME_OUT",
...], start=0)
If we do this, we can also use flow_del_reason.FDR_FLOW_LIVE below.
> + ufid_str = format_ufid(event.ufid)
> + reason = event.reason
> +
> + if reason not in range(0, len(reasons) - 1):
> + reason = 0
> + print("{:<18.9f} {:<45} {:<17}".
> + format(event.ts / 1000000000, ufid_str, reasons[reason]))
> +
> +
> +#
> +# decode_key()
> +#
> +def decode_key(msg):
> + bytes_left = len(msg)
> + result = {}
> + while bytes_left:
> + if bytes_left < 4:
> + break
> + nla_len, nla_type = struct.unpack("=HH", msg[:4])
> + if nla_len < 4:
> + break
> + nla_data = msg[4:nla_len]
> + trunc = False
> + if nla_len > bytes_left:
> + trunc = True
> + nla_data = nla_data[:(bytes_left - 4)]
Can we just not break out of this right away without doing the two
above lines?
> + else:
> + result[get_ovs_key_attr_str(nla_type)] = nla_data
> + if trunc:
> + break
> + next_offset = (nla_len + 3) & (~3)
> + msg = msg[next_offset:]
> + bytes_left -= next_offset
if bytes_left:
“Can we report that our buffer was truncated?!”
Not sure how to do this, but with 64 bytes being the default the -k option only
showed in_port() which took me a while to figure out. Maybe 128 would be better
when -k is configured?
> + return result
> +
> +
> +#
> +# get_ovs_key_attr_str()
> +#
> +def get_ovs_key_attr_str(attr):
> + ovs_key_attr = ["OVS_KEY_ATTR_UNSPEC",
> + "encap",
> + "skb_priority",
> + "in_port",
> + "eth",
> + "vlan",
> + "eth_type",
> + "ipv4",
> + "ipv6",
> + "tcp",
> + "udp",
> + "icmp",
> + "icmpv6",
> + "arp",
> + "nd",
> + "skb_mark",
> + "tunnel",
> + "sctp",
> + "tcp_flags",
> + "dp_hash",
> + "recirc_id",
> + "mpls",
> + "ct_state",
> + "ct_zone",
> + "ct_mark",
> + "ct_label",
> + "ct_tuple4",
> + "ct_tuple6",
> + "nsh"]
> +
> + if attr < 0 or attr > len(ovs_key_attr):
> + return "<UNKNOWN>: {}".format(attr)
> + return ovs_key_attr[attr]
> +
> +
> +#
> +# is_nonzero()
> +#
> +def is_nonzero(val):
> + if isinstance(val, int):
> + return (val != 0)
> +
> + if isinstance(val, str):
> + val = bytes(val, "utf-8")
> +
> + # If it's not a string or an int, it's bytes.
> + return (val.count(0) < len(val))
> +
> +
> +#
> +# parse_flow_dict()
> +#
> +def parse_flow_dict(key_dict, decode=True):
> + ret_str = ""
> + parseable = {}
> + skip = ["nsh", "tunnel", "mpls", "vlan"]
> + need_byte_swap = ["ct_label"]
> + ipv4addrs = ["ct_tuple4", "tunnel", "ipv4", "arp"]
> + ipv6addrs = ["ipv6", "nd", "ct_tuple6"]
> + macs = {"eth": [0, 1], "arp": [3, 4], "nd": [1, 2]}
> + fields = [("OVS_KEY_ATTR_UNSPEC"),
> + ("encap", ),
> + ("skb_priority", "<I"),
> + ("in_port", "<I"),
> + ("eth", "!6s6s", "src", "dst"),
> + ("vlan", ),
> + ("eth_type", "!H"),
> + ("ipv4", "!4s4s4B", "src", "dst", "proto", "tos", "ttl",
> "frag"),
> + ("ipv6", "!16s16s4s4B", "src", "dst",
> + "label", "proto", "tclass", "hlimit", "frag"),
> + ("tcp", "!2H", "src", "dst"),
> + ("udp", "!2H", "src", "dst"),
> + ("icmp", "!2B", "type", "code"),
> + ("icmpv6", "!2B", "type", "code"),
> + ("arp", "!4s4sH6s6s", "sip", "tip", "op", "sha", "tha"),
> + ("nd", "!16s6s6s", "target", "sll", "tll"),
> + ("skb_mark", "<I"),
> + ("tunnel", ),
> + ("sctp", "!2H", "src", "dst"),
> + ("tcp_flags", "!H"),
> + ("dp_hash", "<I"),
> + ("recirc_id", "<I"),
> + ("mpls", ),
> + ("ct_state", "<I"),
> + ("ct_zone", "<H"),
> + ("ct_mark", "<I"),
> + ("ct_label", "!16s"),
> + ("ct_tuple4",
> + "!4s4s2HB", "src", "dst", "tp_src", "tp_dst", "proto"),
> + ("ct_tuple6",
> + "!16s16sB2H", "src", "dst", "proto", "tp_src", "tp_dst"),
> + ("nsh", )]
> + for k, v in key_dict.items():
> + s = ""
> + if k in skip:
> + continue
> + if decode and int.from_bytes(v, "big") == 0:
> + parseable[k] = "0"
> + continue
> + if decode and k in need_byte_swap:
> + v = int.from_bytes(v, "little").to_bytes(len(v), "big")
> + attr = -1
> + found = False
> + for f in fields:
> + if k == f[0]:
> + attr = fields.index(f)
> + found = True
> + break
> + if not found:
> + raise KeyError("Invalid flow field '%s'" % k)
> + if decode and len(fields[attr]) > 1:
> + data = list(struct.unpack(fields[attr][1],
> + v[:struct.calcsize(fields[attr][1])]))
> + if k in ipv4addrs:
> + if data[0].count(0) < 4:
> + data[0] = str(IPv4Address(data[0]))
> + else:
> + data[0] = b"\x00"
> + if data[1].count(0) < 4:
> + data[1] = str(IPv4Address(data[1]))
> + else:
> + data[1] = b"\x00"
> + if k in ipv6addrs:
> + if data[0].count(0) < 16:
> + data[0] = str(IPv6Address(data[0]))
> + else:
> + data[0] = b"\x00"
> + if data[1].count(0) < len(data[1]):
> + data[1] = str(IPv6Address(data[1]))
> + else:
> + data[1] = b"\x00"
> + if k in macs.keys():
> + for e in macs[k]:
> + if data[e].count(0) == 6:
> + mac_str = b"\x00"
> + else:
> + mac_str = ":".join(["%02x" % i for i in data[e]])
> + data[e] = mac_str
> + if decode and len(fields[attr]) > 2:
> + field_dict = {field: d for field, d in zip(fields[attr][2:],
> data)}
> + s = ", ".join(k + "=" + str(v) for k, v in field_dict.items())
> + elif decode and k != "eth_type":
> + s = str(data[0])
> + field_dict = s
> + else:
> + if decode:
> + s = hex(data[0])
> + field_dict = s
> + ret_str += k + "(" + s + "), "
> + parseable[k] = field_dict
> + ret_str = ret_str[:-2]
> + return (parseable, ret_str)
> +
> +
> +#
> +# handle_event()
> +#
> +def handle_event(ctx, data, size):
> + # Once we grab the event, we have three cases.
> + # 1. It's a revalidator probe and the reason is nonzero: A flow is
> expiring
> + # 2. It's a revalidator probe and the reason is zero: flow revalidated
> + # 3. It's a flow_put probe.
> + #
> + # We will ignore case 2, and report all others.
> + #
> + event = b["events"].event(data)
> + if event.probe == 0: # OP_FLOW_PUT
Here we should also define an enum for the probe events, see ‘Event =
IntEnum("Event”...’ and ‘<EVENT_ENUM>’ in reval_monitor.py
> + handle_flow_put(event)<
> + elif event.probe == 1 and event.reason > 0: # FLOW_RESULT
Here we could do “event.reason > flow_del_reason.FDR_FLOW_LIVE”, see comment
above.
> + print_expiration(event)
> +
> +
> +def main():
> + #
> + # Don't like these globals, but ctx passing does not work with the
> existing
> + # open_ring_buffer() API :(
> + #
> + global b
> + global args
> +
> + #
> + # Argument parsing
> + #
> + parser = argparse.ArgumentParser()
> + parser.add_argument("--buffer-page-count",
> + help="Number of BPF ring buffer pages, default 1024",
> + type=int, default=1024, metavar="NUMBER")
> + parser.add_argument("-f", "--flow-key-size",
> + help="Set maximum flow key size to capture, "
> + "default 64 - see notes", type=buffer_size_type,
> + default=64, metavar="[64-2048]")
> + parser.add_argument("-k", "--flow-keys",
> + help="Print flow keys as flow strings",
> + action="store_true")
> + parser.add_argument("-l", "--filter-flows", metavar="FLOW_STRING",
> + help="Filter flows that match the specified "
> + "ODP-like flow",
> + type=str, default=None, nargs="*")
> + parser.add_argument("-p", "--pid", metavar="VSWITCHD_PID",
> + help="ovs-vswitchd's PID", type=int, default=None)
> + parser.add_argument("-D", "--debug", help="Enable eBPF debugging",
> + type=int, const=0x3f, default=0, nargs="?")
> + args = parser.parse_args()
> +
> + #
> + # Find the PID of the ovs-vswitchd daemon if not specified.
> + #
> + if args.pid is None:
> + for proc in psutil.process_iter():
> + if "ovs-vswitchd" in proc.name():
> + if args.pid is not None:
> + print("Error: Multiple ovs-vswitchd daemons running, "
> + "use the -p option!")
> + sys.exit(-1)
> +
> + args.pid = proc.pid
> + #
> + # Error checking on input parameters
> + #
> + if args.pid is None:
> + print("ERROR: Failed to find ovs-vswitchd's PID!")
> + sys.exit(-1)
> +
> + #
> + # Attach the USDT probes
> + #
> + u = USDT(pid=int(args.pid))
> + try:
> + u.enable_probe(probe="op_flow_put", fn_name="usdt__op_flow_put")
> + except USDTException as e:
> + print("Error attaching the dpif_netlink_operate__:op_flow_put
> probe.")
> + print(str(e))
> + sys.exit(-1)
> +
> + try:
> + u.enable_probe(probe="flow_result", fn_name="usdt__flow_result")
> + except USDTException as e:
> + print("Error attaching the revalidate:flow_result probe.")
> + print(str(e))
> + sys.exit(-1)
> +
> + #
> + # Attach the probes to the running process
> + #
> + source = bpf_src.replace("<BUFFER_PAGE_COUNT>",
> + str(args.buffer_page_count))
> +
> + if args.filter_flows is None:
> + filter_bool = 0
> +
> + # Set the key size based on what the user wanted
> + source = source.replace("<MAX_KEY_VAL>", str(args.flow_key_size))
> + else:
> + filter_bool = 1
> + args.filter_flows = parse_flow_str(args.filter_flows[0])
> +
> + # Run through the parser to make sure we only filter on fields we
> + # understand
> + parse_flow_dict(args.filter_flows, False)
> +
> + # This is hardcoded here because it doesn't make sense to shrink the
> + # size, since the flow key might be missing fields that are matched
> in
> + # the flow filter.
> + source = source.replace("<MAX_KEY_VAL>", "2048")
> +
> + source = source.replace("<FILTER_BOOL>", str(filter_bool))
> +
> + b = BPF(text=source, usdt_contexts=[u], debug=args.debug)
> +
> + #
> + # Print header
> + #
> + print("{:<18} {:<45} {:<17}".format("TIME", "UFID", "EVENT/REASON"))
> +
> + #
> + # Dump out all events.
> + #
> + b["events"].open_ring_buffer(handle_event)
> + while 1:
> + try:
> + b.ring_buffer_poll()
> + time.sleep(0.5)
I think we can remove this sleep.
> + except KeyboardInterrupt:
> + break
> +
> +
> +#
> +# Start main() as the default entry point
> +#<
> +if __name__ == "__main__":
> + main()
> --
> 2.41.0
Missing my previous comment on adding a check to make sure we do not lose
events:
“
Forgot to mention that you probably also want to add some checking to make sure
you do not lose events.
See __sync_fetch_and_add() below:
+BPF_TABLE("percpu_array", uint32_t, uint64_t, dropcnt, 1);
+
+static struct event_t *get_event(uint32_t id) {
+ struct event_t *event = events.ringbuf_reserve(sizeof(struct event_t));
+
+ if (!event) {
+ uint32_t type = 0;
+ uint64_t *value = dropcnt.lookup(&type);
+ if (value)
+ __sync_fetch_and_add(value, 1);
+
+ return NULL;
+ }
+
+ event->id = id;
+ event->ts = bpf_ktime_get_ns();
+ event->pid = bpf_get_current_pid_tgid();
+
+ return event;
+}
“
The other missing part is to include the PID/TID in the output so we can relate
to which revalidator thread did this (or add the comm with the name).
And finally, the part that got this patch delayed, not adding static OVS
structure definitions. Which is still the case in this version. For now, you
should probably copy the get_ovs_definitions() implementation from
reval_monitor.py.
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